The intelligentized management of the heating electric power supply for the HPHT Hydraulic Cubic Press is realized by introducing an intelligentized controlling system. This research addresses the status quo in domestic cubic hinge presses where the level of automation is low, leading to the production of middle-to-low level diamond products. The system aims to solve the problems of low automation and unstable temperature fields during production, thereby facilitating the improvement of diamond production and quality.1. Core Design Philosophy: Realizing Non-Constant Power "Curve Heating"Traditional domestic HPHT Hydraulic Cubic Presses commonly use the constant power heating method. However, the resistance inside the synthesis cavity continuously changes, and as the synthesis time lengthens, the temperature inside the cavity becomes increasingly high. This makes it difficult to ensure the stability of the temperature field within the cavity, which clearly restricts the improvement of diamond grade and output.Based on the practical experience of diamond synthesis, this research proposed a non-constant power heating scheme, meaning different power levels are applied according to different time segments during the entire synthesis process, thereby maintaining the relative stability of the temperature field within the synthesis cavity.Time-Segment Control: The intelligent controller can control the original heating power supply according to the best process curve selected by the user. It enables control over current changes in time segments, making the heating process more compliant with the process characteristics required for the growth of different diamonds.Controlled Temperature Field: During the production process, operators can raise or lower the current at any time according to actual needs, ensuring that the temperature field of the entire synthesis process is under a controlled status.2. Technical Implementation: Digital Control Replacing Manual AdjustmentThe core of intelligentized control involves replacing the traditional manual adjustment method with digital control.Replacing Manual Adjustment: The original heating power supply uses PID adjustment to achieve stable output via negative feedback control. However, the manual setting is achieved by a potentiometer, which makes it impossible to realize the non-constant power curve heating method. This traditional method also involves significant human factors and poor repeatability.Microprocessor Core: The intelligentized system takes a microprocessor (such as the AT89C51 single-chip microcomputer) as its core. The core handles program control, display, parameter input, data acquisition, D/A conversion, and switching quantities.Digital Control Loop: The system uses the single-chip microcomputer to digitally control the voltage, replacing the manual adjustment of the potentiometer's center point voltage. The single-chip microcomputer performs digital control based on the set process curve and outputs the corresponding analog voltage value via the D/A converter.Power Regulation: This analog voltage signal then drives the subsequent circuit through the power amplification circuit, regulating the output voltage of the heating power supply by changing the SCR (Silicon Controlled Rectifier) conduction angle.3. Program and Algorithm Design: Ensuring Control Precision and StabilityThe system utilizes precise program design and algorithms to ensure accuracy and anti-interference capability in harsh working environments.Modular Design: The application software adopts a modular design, consisting of the main program, the interrupt service program, and the control algorithm program.Timing Interrupt Control: The system uses the timing interrupt program (which generates an interrupt, for example, every 125ms) to complete control output and time accumulation. After the timing reaches 1s, the system decrements the set time value by one and determines whether to enter the control output of the next time segment.Control Algorithms: Algorithms used include comparison control, number system conversion, and multi-byte multiplication and division. The reasonable application of these algorithms satisfies the system's requirement for precision and simplifies the program structure.Anti-Interference Capability: Given the harsh working environment, the system uses a watchdog timer and voltage monitoring (such as the X5045 chip) to monitor the controller's operation status, preventing system abnormality or loss of control. Furthermore, "software trap" technology is set up in the application program. When the program loses control due to external interference, the trap processing program automatically restores the program, effectively improving the system's anti-interference ability.4. System Functions and CharacteristicsThe intelligentized control system, upon practical implementation, demonstrates the following functions and advantages:A. Mode Selection: The system can operate in manual or automatic control states as required.B. Multi-Segment Curve Control: In the automatic control mode, it features the arbitrary setting and controlling function for 8 segments of the heating curve.C. Real-time Fine-tuning: In automatic mode, it has the working curve translation fine-tuning function, allowing operators to fine-tune the working curve at any time according to need.D. Parameter Management: Parameter settings feature a password management function, ensuring that only authorized personnel can change parameters or passwords.E. Direct Display: Dynamic display technology is used to display the time segment, time value, and output value in real-time. The display is direct.F. Comprehensive Advantages: The system is characterized by high controlling precision, easy adjustment, good repeatability, and stability, facilitating the improvement of diamond production and quality.
read more+
The control system of the HPHT Hydraulic Cubic Presssignificantly reduces carbide anvil consumption by optimizing pressure regulation, fault protection, and process parameter matching. Below is a detailed analysis of the mechanisms and supporting data:1. Dynamic Pressure Compensation Reduces Pressure FluctuationsControl Method: A lower pressure threshold (e.g., activating a small pump when pressure drops 0.15 MPa below the set value) and an upper limit (e.g., stopping at 0.05 MPa above) maintain dynamic balance.Effect: Pressure fluctuations are confined to ±0.05 MPa, minimizing mechanical wear on anvils caused by abrupt pressure changes.2. Multi-Parameter Protection System Cuts Abnormal LossesAbsolute Protection: Immediate shutdown upon exceeding limits for pressure, current, or voltage prevents equipment failures (e.g., thyristor breakdown, hydraulic leaks) from damaging anvils.Relative Protection: Monitors pressure change rates and resistance deviations to preemptively flag material or system anomalies.Data Comparison:Relay-based control: Anvil consumption at 2 kg/10k carats, with 18% loss attributed to failures.Automated control with enhanced protection: Consumption drops to 0.5 kg/10k carats, failure-related losses reduced to 6.9%.3. Alarm System Mitigates Accident-Induced LossesElectrical Faults: Immediate shutdown for issues like burnt plugs or insulation cap damage prevents anvil overload.Hydraulic Faults: Pressure anomalies trigger停机 to address leaks or valve failures.Material Defects: Detects resistance/voltage abnormalities to reduce anvil impact from flawed synthesis blocks.4. Automated Process OptimizationT-P-t Coordination: Industrial computers precisely control temperature (T), pressure (P), and time (t) curves to avoid anvil overload or uneven wear from parameter mismatches.Result: One operator can manage four presses, reducing human-error-induced.5. Future Technical DirectionsElectro-Hydraulic Proportional Control: Enables precise adjustment of six-cylinder displacement and ultra-high pressure to further reduce mechanical shocks.Frequency Conversion Technology: Replaces small pumps to eliminate pressure surge during compensation, enabling fuzzy PID control.Summary: Upgrades in the HPHT Hydraulic Cubic Press control system (dynamic compensation, multi-parameter protection, automated process matching) reduced anvil consumption from 2 kg/10k carats to 0.5 kg/10k carats.
read more+
The HPHT Hydraulic Cubic Press is a high-tech product integrating machinery, electrics, and hydraulics, used primarily for synthesizing superhard materials such as diamond and cubic boron nitride. The hydraulic system's working pressure is 14 MPa.1. Excessive Hydraulic Pump Operating Noise and Rapid Wear of the Elastic Coupling Rubber PadPhenomenon/Cause Analysis The primary cause of the excessive noise from the hydraulic pump and the rapid wear of the elastic coupling rubber pad (with noticeable rubber powder flying out) is the large coaxiality error between the axis lines of the hydraulic pump and the electric motor. This error causes relative high-speed sliding between the coupling and the rubber pad, accelerating the wear.Solutions1. During assembly, the pump stand and the electric motor must be installed on the machine base simultaneously.2. Ensure that the coaxiality error between the electric motor's axis line and the pump stand's locating hole is maintained within 0.05.3. After installing the pump and the coupling, manually moving the assembly should allow free rotation without jamming.4. Use a feeler gauge to check that the clearance of the coupling is uniform.2. Failure of the Hydraulic Pump to Establish Working Pressure2.1 External and Pump Self-Checks1. Motor Direction: Check and ensure the rotation direction of the electric motor is consistent with the direction required by the pump.2. Displacement Setting: Since the machine uses an axial piston type manually variable displacement hydraulic pump, the displacement is manually adjusted. If the displacement indicator plate is at the zero point, the pump's displacement is zero, meaning it is running idle. During commissioning, the setting should be placed at around 6.5.3. Suction Pipe Sealing: Check the pump's oil suction port and pipe for sealing. If the suction pipe leaks air, the pump cannot draw in enough oil and cannot operate normally.4. Initial Oil Filling: Before the first start-up, sufficient hydraulic oil must be injected through the pump's cooling oil pipe to form a sealed cavity. Because the suction pipe enters the oil tank from the upper liquid level, without this initial seal, the pump cannot draw oil solely by its self-priming ability.2.2 Checking the Valve Working Position1. Overflow Valve (Relief Valve): Check if the overflow valve is in the working position. Rotating the valve handle should be met with resistance, confirming that the spring of the pilot valve is compressed and the overflow valve is active.2. YA15 Solenoid Valve Check: If pressure still fails to establish, check the YA15 solenoid directional valve. YA15 controls the remote control port of the overflow valve; only when YA15 is active (closing the remote control port) can the overflow valve establish system pressure. If the PC (Programmable Controller) output relay for YA15 is not conducting (indicator light off), use the programmer to check if the YA15 program content or input node status matches the requirements. Check the wiring continuity between the PC's YA15 output point and the electromagnet, including the neutral line and the 220V power line (including the fuse). Check if the YA15 electromagnet is intact. If all checks are clear, replace YA15 or the overflow valve to isolate the fault.2.3 Checking Pump Body or Manifold Issues If replacing the valves is unsuccessful, check the pump itself: connect a transparent plastic tube to the pump output and observe if the output oil is complete, continuous, and free of interruptions or air bubbles.The presence of interruptions or air bubbles indicates air leakage in the suction system, pointing to the pump body if the piping is sound. If pump output is normal, check the first valve plate to see if the inlet and outlet ports are connected (short-circuited).3. System Pressure Exists Immediately After StartupPhenomenon/Cause Analysis Pressure immediately upon startup means the pump is working, but a valve or pipeline is malfunctioning, as the system should not have pressure if valves are not actuated. First, check if the YA15 solenoid directional valve has actuated.Solutions1. If YA15 has actuated: Check the PC. If the YA15 output relay shows no output (indicator light off), the program is fine, but the fault is likely miswiring (input and output points directly connected). If so, rewire. If measurement shows direct continuity, it might be due to a quality issue where the PC’s output solid-state relay node is "cold-welded" together. Attempts can be made to restore it by repeatedly cycling the activating button; otherwise, the PC must be replaced or repaired.2. If YA15 has NOT actuated, but the system has pressure: Turn the overflow valve adjusting handle until it is completely disengaged. If pressure does not change: The pressure is established by resistance from an obstructed return oil line. Dismantle the return oil pipe from the first valve plate to the oil tank to check flow. This is often due to poor connection between the pipe joint and the steel pipe. If the piping is fine, the first valve plate is faulty. ◦If pressure changes with the handle and drops to zero when disengaged: The pressure is established by the overflow valve because its remote control port is closed. Check the YA15 valve itself (e.g., by applying 220V AC power to check passage). If YA15 is fine, check the flow path from YA15's input port to the overflow valve's remote control port, and the return oil line from YA15's output port to the oil tank.4. Failure of the Hydraulic System to Achieve Ultra-High Pressure4.1 Working pressure exists, but the booster indicator rod does not move.1. Check YA2/34DO: Check if the 34DO solenoid valve (YA2 directional valve) is actuated. If not, identify whether the fault lies between the PC and the valve, between the PC and the signal device, or within the PC program or the PC itself.2. Check YA13 and 34DO Installation: If YA2 is normal, check YA13. Dismantle 34DO, check its installation alignment (P port alignment), and check the valve itself. If realignment fails, and pressure remains, check the connecting steel pipe and passages between the 1st valve plate and the 5th valve plate (V-block) for obstructions. If the 34DO valve itself is faulty, replace or repair it.4.2 During pressurization, the booster indicator rod moves up, but there is no ultra-high pressure. This indicates that the low-pressure chamber of the booster has oil, but the high-pressure oil is not entering the main working cylinder.1. Check YA12: Check if the YA12 solenoid directional valve is actuated.2. Check Six Ultra-High Pressure Hydraulic Control Check Valves: Unscrew the upper plugs of the six check valves individually. If there is no hydraulic oil, the valve is unsealed. Remove the spool and check if the sealing oil line is complete and clear, and free of foreign matter. If the oil line is incomplete, re-lapping is required.3. Check Two-Position Seven-Way Valve (2/7 Valve): Feel the control oil pipe. If it is very hot, pressure oil is being relieved through the control oil circuit. Check the sealing performance of the 2/7 valve and inspect for damaged or missing seals.4.3 During pressurization, the booster indicator rod does not move, but system pressure reaches the set working pressure. This suggests that the high-pressure chamber (lower) and ultra-high pressure chamber (upper) have reached a force balance, or the 2/7 valve is in a closed state.1. Check YA13: Check the YA13 solenoid directional valve (the control valve for the 2/7 valve) and its piping.2. Check 2/7 Valve: If YA13 is fine, inspect the 2/7 valve itself. Check if the fit between the spool and the valve body is too tight or if there are impurities. If the fit is too tight, re-lapping according to the valve body's actual dimensions is required.4.4 No ultra-high pressure, and the high-pressure pump pressure gauge reads zero working pressure. This assumes normal function of the pump, overflow valve, and all six working cylinder actions (forward/retraction) in non-ultra-high pressure mode.1. Check Mechanical Unloading Valve: Check if the mechanical unloading valve is closed. Dismantle it, check for the conical spool, and confirm the contact oil line of the spool is complete and clear. Reinstall and tighten.2. Check Parallel Hydraulic Control Check Valve: If ultra-high pressure is still absent, check the parallel hydraulic control check valve. Dismantle it, inject oil into the inlet, and observe its sealing performance. If sealing is poor, replacement or repair is needed.3. Check Valve Plate: If all the above are ruled out, the fault is certainly caused by the valve plate itself.5. Screeching Sound and Violent Oscillation of the Pressure Gauge Needle During Booster DepressurizationPhenomenon Description When the booster depressurizes and the high-pressure pump pressure gauge reaches the set value, an occasional piercing screech occurs. The ultra-high pressure gauge pointer oscillates violently, and the oil pipe running from the overflow valve's remote control port to the YA15 solenoid directional valve becomes very hot, accompanied by strong, intense vibration.Cause Analysis This issue was identified by experts as being caused by the excessive volume of the remote pressure regulating capacity of the overflow valve.Solutions Two methods were proposed to eliminate this fault:1. Add a damping hole inside the inner diameter of the oil pipe connecting the overflow valve’s remote control port to the YA15 directional valve.2. Use an oil pipe with a smaller inner diameter to reduce the remote pressure regulating capacity. (In practice, replacing the oil pipe with one of a smaller inner diameter successfully eliminated the screeching and violent oscillation of the pressure gauge needle.)
read more+
The control system of the HPHT Hydraulic Cubic Press has an extremely important impact on the grade of synthetic diamonds. As industrial technology continuously advances, the demands for diamond grade are also increasing. The development and perfection of the control system are crucial factors for improving diamond quality.Here is a detailed explanation of how the HPHT Hydraulic Cubic Press control system affects diamond grade:1. Overcoming Limitations of Traditional Control SystemsTraditional electrical control systems for diamond presses used a logic control circuit composed of a large number of low-voltage electrical appliances, such as intermediate relays, time relays, and contactors. These traditional systems had several limitations that restricted the development of diamond grade to higher levels:Low Control Precision: The control over pressure and temperature was imprecise.Outdated Technology: The control effect was undesirable, hindering the development of high-level diamond grades.Maintenance Issues: They also suffered from a high failure rate and were inconvenient to repair.The severity of market competition demands that companies rely on advanced automated control systems to improve grade.2. Achieving Precise Control of Process ParametersPrecise pressure control and temperature control are the two crucial elements that guarantee the accurate implementation of the synthesis process and thus ensure the quality of diamond synthesis. Advanced automated control systems, such as those adopting industrial computers and advanced PID control, have greatly improved the grade of synthetic diamonds.Temperature Control (Current Control): HPHT Hydraulic Cubic Presses (like those used at Henan Jinqu Gold Limited Company Super Hard Material Sub-Company) use current control. This is considered the most ideal control method because it directly reflects the heat within the cavity. The system utilizes closed-loop PID control to effectively and automatically control the heating power. By controlling the conduction angle ($\alpha$) of the SCR phase shift trigger, the system ensures that the current magnitude strictly follows the preset current curve.Pressure Control: Pressure control mainly uses a switch control mode, which involves setting a pressure lower limit and a pressure compensation upper limit. The system achieves dynamic pressure compensation (dynamic补压) using a small pump. This mechanism ensures the stability of the pressure environment during the diamond generation process to the maximum extent.Parameter Matching: The decisive condition for obtaining ideal diamonds is the reasonable matching of temperature (T), pressure (P), and time (t). Achieving precise control of temperature and pressure through industrial computer automation, alongside research into reasonable T, P, t matching processes, is necessary to meet the stringent requirements for growing high-grade diamonds.3. Enhancing System Stability and SafetyAdvanced control systems increase protection parameters, allowing the press to operate more stably. The system continuously monitors the changes in various parameters during operation.Protection Parameters: Industrial computer control systems can set numerous absolute protection parameters (e.g., maximum pressure protection, maximum current protection) and relative protection parameters (e.g., pressure sudden change protection, voltage sudden change protection, current sudden change protection).Stable Operation: When a parameter exceeds the set protection value, the system can promptly trigger an alarm and stop the machine. This stability reduces the occurrence of accidents and has a highly important impact on diamond grade. The alarm system also helps avoid carbide anvil consumption caused by equipment faults (like SCR breakdown, burnout, or hydraulic issues).
read more+
The formation process of diamond is closely related to key parameters such as pressure, temperature, and synthesis time.1. Pressure Determines the number and size of crystal grains: Within the diamond phase region, the number and size of diamond crystal grains are primarily determined by pressure. As pressure increases, the number of diamond crystal grains rapidly increases, and their particle size also becomes larger. Affects nucleation and conversion rate: When pressure is low or temperature is high, the critical radius for diamond crystal grains is larger, making nucleation difficult and resulting in a low conversion rate. Conversely, when pressure is high or temperature is low, the critical radius is smaller, crystal grains form easily, are numerous and dense, and the conversion rate is high. Role in secondary pressurization: Secondary pressurization experiments showed that when the oil pressure increase amplitude is small (e.g., from 67MPa to 69MPa, an amplitude of 3%), the number of crystal grains basically does not increase. However, when the pressure increase amplitude is larger (e.g., from 67MPa to 71MPa, an amplitude of 7%), the number of crystal grains significantly increases. If the pressure increase amplitude is too large (exceeding 12%), even with high heating power, the number of crystal grains remains high, and their color turns black. Impact on crystal grain size: Whether in primary or secondary pressurization, crystal grain size changes significantly only within the first few minutes after the pressure stabilizes (about 6 minutes); even if the synthesis time is extended afterwards, the increase in grain size is not obvious. Used for controlling crystal grain quality: When the pressure increase amplitude is small, the increase in crystal grains is minimal, thus allowing control over the number and quality of crystal grains, providing a possible way to grow high-quality coarse-grained diamonds.2. Temperature Determines the color of diamond: The color of diamond is largely related to temperature. Yellow diamonds are typically distributed in higher temperature regions. When the second heating power is high, the resulting crystal grains are yellower. Affects the number and size of crystal grains: At the same pressure, when the temperature increases from low to high, the number and size of crystal grains will change from zero to a maximum, and then decrease again until no diamond appears. Affects nucleation and conversion rate: When temperature is high or pressure is low, nucleation is difficult, and the conversion rate is low. Choosing growth temperature: Although at lower temperatures the conversion rate is low and nucleation is sparse, impurities are not easily excluded from the crystal. Therefore, it is more appropriate to choose to grow diamonds at higher temperatures to control the growth rate, which can yield high-quality crystal grains grown in the so-called diamond "optimal crystal region". Combined effect with pressurization: When the second heating power (W2') is high, even if the pressure increase amplitude is large, the increase in the number of crystal grains is not significant, and the crystal grains are yellower. If only pressure is increased without increasing power, the resulting crystal grains will be black and mostly clustered.3. Synthesis Time Affects crystal grain size: Crystal grain size changes significantly only within the first few minutes after the pressure stabilizes (about 6 minutes); even if the synthesis time is extended afterwards, the increase in grain size is not obvious. Potential impact: The sources indicate that extending synthesis time may contribute to the synthesis of high-quality large-grained diamonds.In addition to the above main parameters, the research also involves the following factors:Catalyst: The study used Ni~oMn2sCos catalyst. The catalyst promotes the rapid formation of diamond crystal grains by distorting the graphite lattice through electron attraction. After diamond formation, the crystal grains are surrounded by the catalyst melt, and their continued growth depends on the diffusion and deposition of carbon atoms or atomic groups.Synthesis Method and Materials: The direct-heating static pressure catalyst method was adopted. Specific experimental methods included sheet-layered direct-heating assembly. Measures such as graphite pretreatment, improved sample assembly, or the use of new catalysts have also been explored to increase diamond grain size.Pressurization Process: Experiments were conducted using two processes: primary pressurization and secondary pressurization. By selecting pressure and temperature conditions, segmenting pressure and temperature increases, and strictly controlling the amplitude, high-quality coarse-grained diamonds can be obtained in a relatively short time.Diamond Formation Region: Diamond only forms within specific pressure and temperature ranges. The left boundary of this region is parallel to the catalyst melting curve, and the lower boundary is parallel to the graphite-diamond phase equilibrium curve.In summary, given specific materials such as graphite, catalyst, and pressure-transmitting medium, pressure and temperature are the decisive factors in the formation and growth process of diamond. A deep understanding of their relationships, roles, and mechanisms will be crucial for guiding research and production practices for growing high-quality large-grained diamonds.
read more+
The main repair steps for the HPHT Hydraulic Cubic Press are as follows:1. Problem Analysis and Repair Strategy Formulation: First, it is necessary to analyze the causes of press failure, such as the phenomenon of all 32-M24 connecting screws of the piston being pulled off. This could be due to the piston's segmented structure, O-ring seal failure allowing hydraulic oil to enter the contact surfaces, loose screws, and poor coaxiality between the upper and lower cylinder sections. To address these issues, the repair strategy involves welding the upper and lower cylinder sections together to prevent hydraulic oil ingress, improve coaxiality, and increase connecting force. It is necessary to consider that welding thermal deformation can lead to increased geometric tolerance, thus machining of the piston's upper cylinder section and the guide sleeve is required after welding to ensure their fit tolerance and geometric tolerance. The piston material is 40Cr quenched and tempered steel, which has poor weldability. Special attention must be paid to issues such as cracks, embrittlement, and softening in the heat-affected zone.2. Alignment: On a vertical lathe, the upper and lower cylinder sections are aligned using the lower cylinder section as a reference. They are pressed evenly with short pressure plates in sections to ensure that the coaxiality of the piston's upper and lower cylinder sections is less than or equal to 0.03mm.3. Welding Process: Based on the company's welding equipment, the characteristics of various welding methods, and the welder's technical status, shielded metal arc welding is selected. First, the root of the welding groove is spot-welded symmetrically to fix it, which reduces deformation after welding. Then, the welding groove is filled using a multi-layer welding method. During welding, two people must operate symmetrically, maintaining consistent current, speed, and electrode thickness, and keeping the temperature of the welding area constant. Different types of electrodes are selected for layered welding. For example, E6016—D1 electrodes are used for the first and second layers, E8515—G electrodes for the third and fourth layers, and E4303 electrodes for the cover layer. Strict control of welding parameters is required, including electrode diameter, welding current, and welding polarity. Strict welding precautions must be followed: electrodes must be baked before welding, workpieces must be cleaned of impurities, and short-arc, narrow-pass welding should be used. When welding in the quenched and tempered state, in addition to preventing cracks, the embrittlement and softening of the heat-affected zone must be considered. Welding methods with concentrated heat and high energy density can reduce the degree and range of softening. The weld seam must be thoroughly cleaned to remove pores, spatter, weld beads, and slag, thereby clearing both slag and some stress. Preheating is performed, with the preheating temperature and interpass temperature controlled between 200～250℃. Smaller heat input should be chosen to reduce softening and embrittlement in the heat-affected zone. Post-weld tempering treatment should be performed immediately. The tempering temperature should avoid the steel's temper brittleness range and be controlled to be 50℃ lower than the original tempering temperature of the base metal, held for 2.5 hours, then naturally cooled to room temperature with the furnace. This also serves as hydrogen removal. The part is then left to stand for 48 hours to relieve stress. After welding, the welding zone is inspected with ultrasonic testing to ensure it meets requirements.4. Alignment and Machining: On a horizontal or vertical lathe, alignment is performed using the lower cylinder section as a reference. The welded area is leveled by turning, and then the outer circle of the upper cylinder section is machined, controlling the surface roughness to Ra≤1.6μm. The upper end face of the upper cylinder section is also machined, achieving a surface roughness of Ra≤1.6μm.5. Matching and Machining of Guide Sleeve Inner Hole: The upper end of the guide sleeve's inner hole is machined to create a stepped hole. A wear ring made of QT500—7 material is fitted into the stepped hole with an interference fit (interference amount of 0.2 ± 0.02mm) and hot-fitted. After hot fitting, alignment is performed using the outer diameter of the guide sleeve that mates with the working cylinder as a reference. Using the machined outer diameter of the upper cylinder section as the actual dimension, the inner hole of the wear ring is machined to form an H7/g6 fit with the upper cylinder section's outer diameter. Finally, a pressure ring is pressed on, and 32 screws are installed to enhance the connecting force, concluding all repair work.These steps collectively ensure that after repair, the piston's operational resistance is reduced, its coaxiality is improved, and the return pressure is significantly lowered, allowing the equipment to operate stably for many years.
read more+
The sulfur additive in powder catalysts affects synthetic diamonds in the following detailed ways:Changes in Catalyst Characteristics and Impact on Growth Process Sulfur, as a trace element additive, is incorporated into powder catalysts (such as Fe-Ni catalysts). This additive can significantly alter the characteristics of the catalyst, thereby influencing its catalytic action to a certain extent. This, in turn, changes the growth conditions, mechanism, and process of diamond, ultimately affecting various properties of the diamond, including its morphology, color, strength, and internal inclusion distribution.Impact on Diamond Morphology Overall Crystal Shape: When synthesized using Fe-Ni catalysts with sulfur additive in a domestic cubic anvil high-pressure apparatus, most diamond crystals are cubo-octahedral and possess a complete crystal shape. Appearance of Etch Pits on Faces: This is one of the most significant morphological features of diamonds synthesized with sulfur-containing catalysts. Etch pits typically appear on the faces of most diamond crystals synthesized with sulfur-added Fe-Ni catalysts, a phenomenon absent in diamonds synthesized without the sulfur additive. Both optical microscopy and electron microscopy observations confirm this. These etch pits usually manifest as many irregular indentations aggregated in a specific area. Integrity of Faces: In contrast, the faces of diamond crystals containing the sulfur additive are relatively complete.impact on Diamond Growth Mechanism Disruption of Crystal Lattice Arrangement: The appearance of etch pits indicates that the addition of sulfur elements disrupts the lattice arrangement of the {100} crystal faces during diamond growth. Selective Adsorption Effect: Research speculates that this disruption and the etch pit phenomenon are caused by the selective adsorption of sulfur or sulfides on the faces of the diamond. The influence of impurities on crystal growth morphology is often due to the selective adsorption of impurities on crystal faces, and this adsorption alters the relative growth rates of the crystal faces, thereby contributing to changes in crystal morphology.Impact on Diamond Internal Structure and Properties Significantly Reduced Inclusion Content: The inclusion content in diamond crystals synthesized with sulfur-added Fe-Ni catalysts is remarkably lower than that in diamonds synthesized without the sulfur additive. Inhibition of Inclusion Entry: Optical microscopy observations reveal that this phenomenon suggests that the addition of an appropriate amount of sulfur plays a certain inhibitory role in the entry of inclusions during diamond growth. Diamond Color Change: Due to the difference in internal inclusion content, diamonds synthesized with sulfur-added catalysts appear light yellow, while those synthesized without the sulfur additive exhibit a dark yellow color. Control of Inclusion Distribution: Overall, adding an appropriate amount of sulfur to the mixed system of Fe-Ni catalyst and graphite helps control the content of inclusions in diamond.
read more+
Regarding the hydraulic control modes of the HPHT Hydraulic Cubic Press, the sources provide a detailed analysis and discussion. With the widespread application of large-tonnage cubic hydraulic presses and large-cavity synthesis processes like 38mm and 40mm, the state of the pressure and temperature fields within the synthesis cavity has changed. Therefore, optimizing control modes, especially pressure control modes, has become a crucial task for diamond manufacturers and equipment suppliers.Below are the main hydraulic (pressure) control modes for the HPHT Hydraulic Cubic Press:Ideal Pressure Control ModeTo reduce the increased pressure gradient caused by pressure loss and phase change in large-cavity processes, and to meet the stable pressure conditions required for the growth of high-quality single-crystal diamonds, an ideal pressure control mode should have the following characteristics: Controllable pressure increase curve: This allows for coordination with the heating curve to improve pressure transmission effects and reduce the generation of pressure gradients. Gradually increasing pressure curve during the holding stage: This helps reduce the increased pressure gradient caused by the deterioration of pressure transmission performance due to pyrophyllite phase change. Controllable pressure release speed: To accommodate different requirements for pressure release speed at high and low pressures.Currently Applied Pressure Control ModesThe sources introduce several pressure control modes currently in use:1. Traditional Pressure Control Mode Characteristics: In this mode, pressure fluctuations are significant, representing a crude control method. Applicability: It is not suitable for large-cavity synthesis processes.2. Variable Frequency Pressure Holding Control Mode Characteristics: This mode maintains constant pressure during the holding stage. Drawback: It neglects to compensate for the pressure gradient caused by synthesis phase changes.3. Passive Incremental Pressure Supplement Mode Principle: This mode supplements pressure by a set increment after the holding pressure drops to a certain set value. Nature: This is a passive pressure supplementation mode. Drawback: In reality, the number of pressure supplements during the holding stage of the press is limited and related to the failure of the high-pressure seal of the press. Therefore, this mode does not truly achieve the goal of compensating for the pressure gradient through incremental pressure supplementation.4. Active Incremental Pressure Holding Mode Principle: This mode achieves incremental pressure supplementation by setting pressure increments and time intervals (i.e., number of pressure supplements). Nature: This is an active incremental pressure supplementation mode. Optimization: Using a variable frequency pressure holding method can minimize the pressure drop within each set time interval, although typically, press pressure-holding performance is good, and this pressure drop can be ignored. Importance: Possessing active incremental pressure holding functionality is one of the important features for a cubic hydraulic press to effectively reduce pressure gradients and provide pressure conditions suitable for the growth of high-quality single-crystal diamonds in large cavities.5. Pressure Control Mode Using Proportional Valves Principle: Proportional valves control the thrust and displacement of electromagnets continuously and proportionally by controlling current or voltage according to a set curve, thereby achieving control over system pressure and flow. Advantages: Pressure holding stage: It can achieve continuous incremental system pressure during the pressure holding stage. Pressure increase stage: It can achieve continuously controllable pressure increase speed during the pressure increase stage. Pressure release stage: Through program-controlled pressure release actions, the pressure release speed is controllable. Full-process control: Therefore, this mode achieves full-process curve control of pressure. Assessment: The pressure control mode using proportional valves is considered the closest to the ideal control mode currently possible and is a relatively ideal hydraulic control system.In summary, to provide pressure conditions suitable for the growth of high-quality single-crystal diamonds in large cavities, the cubic hydraulic press should at least possess active incremental pressure holding functionality to effectively reduce pressure gradients. Among these, the pressure control mode using proportional valves is a relatively ideal hydraulic control system. Additionally, the large-cavity synthesis process requires a synthesis tonnage of at least 1800T to meet its pressure conditions.
read more+
Powder catalyst, as one of the raw materials for synthesizing diamonds, significantly impacts the overall quality and yield of synthetic diamonds. It can be said that powder catalyst is the catalyst for diamond synthesis, and its characteristics directly affect the yield and quality of diamonds.The key characteristics of powder catalyst influence the yield and quality of synthetic diamonds in the following aspects:Oxygen Content As the oxygen content of the powder catalyst continuously increases, the single-batch yield (i.e., production quantity) will gradually decrease. The color of the synthesized single crystal will also gradually turn grayish. Its particle size and peak value will gradually decrease. During the manufacturing process, powder catalysts have a relatively large surface area, making them prone to adsorbing oxygen or moisture, thereby increasing their reaction potential. When some substances react, they produce corresponding oxides. These oxides are difficult to remove and cannot effectively facilitate carbon dissolution and catalytic action during the synthesis process, thus damaging the stability of synthesized diamonds and significantly affecting their quality.Nickel (Ni) Content As the Ni content of the powder catalyst increases, the metal will possess a certain electronic or geometric structure under catalytic action. Generally, under relatively high-temperature conditions, elemental Ni and carbon do not easily form stable compounds. Cobalt (Co) achieves a relatively moderate condition for carbon solubility. The fewer electrons it exhibits, the stronger its carbon-dissolving ability. If the iron content relatively increases, the growth rate of diamond single crystals will increase. Differences in the nickel content of the powder catalyst will affect the quality of synthesized diamonds.Particle Size (Granularity) If the particle size of the powder catalyst is coarse and unevenly distributed, it will lead to a lack of overall uniformity when mixed with graphite powder. This will prevent the "diamond film" from providing a relatively stable state for the synthesized single crystal, thereby affecting the quality of the synthesized diamond. To produce higher quality synthetic diamonds, the "diamond film" must ensure its thickness and physical properties remain unchanged during the synthesis process.In summary, the oxygen content, nickel content, and particle size of the powder catalyst all have a certain impact on the subsequent yield and quality of synthesized diamonds. Therefore, in production, close attention must be paid to the control of these three factors.
read more+
The application of pressure compensated variable pumps in HPHT Hydraulic Cubic Press machines primarily lies in their ability to meet the higher demands for pressure control and compensation in modern diamond synthesis processes, significantly enhancing production efficiency and product quality.Here is a detailed explanation of its application in HPHT Hydraulic Cubic Press machines: Replacing Traditional Pump Types and Adapting to Diversified Processes The HPHT Hydraulic Cubic Press machine has a history of over 40 years of development and application in China. For a long time, the hydraulic system of six-sided top hydraulic presses has consistently used SCY series axial piston pumps as the power source. However, SCY series axial piston pumps primarily provide a constant flow, resulting in a constant system pressurization speed. This step-wise curve is inconsistent with improved diamond synthesis processes. In recent years, with the improvement of synthesis technology and the diversification of HPHT Hydraulic Cubic Press machine applications, such as the synthesis of fine diamond particles, diamond composite sheets (PCD), cBN, etc., there is a need for a pressurization method that matches their growth curve. Pressure compensated variable pumps precisely meet this demand, becoming an effective way to replace SCY series axial piston pumps. Working Principle and Matching with Synthesis Process The unique aspect of the pressure compensated variable pump is that its output flow decreases as the working pressure increases, which is precisely what modern diamond synthesis processes require. The main body of the oil pump (refer to Figure 1 in source) is driven by a transmission shaft, causing the cylinder block to rotate. The plungers are pressed against the variable head (or swash plate) by a central spring. This causes the plungers to reciprocate as the cylinder block rotates, completing the oil suction and oil pressure actions. When the spring force is greater than the hydraulic thrust acting on the annular area at the lower end of the servo piston, the oil pushes the variable piston downwards, increasing the pump's flow. Conversely, when the oil pressure is greater than the spring force, the servo piston moves upwards, blocking the channel, causing the oil in the chamber to be unloaded. At this point, the variable piston moves up, the swash plate angle decreases, and thus the pump's flow decreases. This design ensures that the pump's outlet flow changes approximately according to a constant power curve within a certain range. Actual Application Effects and Advantages Provides a curve that matches new diamond synthesis processes: The pressure compensated variable pump can achieve a pressure curve that matches new diamond synthesis processes, ensuring that the synthesis process meets requirements. Improves work efficiency: During the piston's idle forward stroke and rapid return stroke, the pressure compensated variable pump operates in a no-load large flow output state, which accelerates the piston's speed during these two work steps. This overcomes the defect of constant oil supply by the original SCY series axial piston pump, reducing the piston's unnecessary travel time. According to calculations, in the same working time, using a pressure compensated variable pump results in two more pieces of diamond synthesized per shift on average compared to using an SCY series axial piston pump. Improves product quality: The quality of synthesized diamond is generally improved by 5% compared to when using SCY series axial piston pumps. Application Example (Φ500mm Press Machine) For example, when synthesizing Φ34.5mm cavity diamonds on a Φ500mm press machine, the pressurization ratio of the press's intensifier is 1∶7.7. The diamond synthesis parameters are set as: temperature delivery pressure 45MPa, first stop pressure 60MPa, and final pressure 75MPa. It is also required that the overpressure speed begins to slow down after the first stop pressure. Pump adjustment method: First, adjust the limit screw to the maximum position, then adjust the spring sleeve. When the system pressure is observed to be 7.8MPa, lock the spring sleeve. Then, screw the limit screw to the position where the final pressure is 75MPa and the system pressure is 12MPa. Through such adjustments, the pressurization speed during synthesis will operate according to the desired process curve (Figure 2 in source). Preparation and Precautions Before Use Noise issue: Besides misalignment of the coupling and motor, attention must be paid to the matching of the oil outlet pipe and connector body inner diameter with the oil pump flow. When the motor is unloaded, the oil output of the pressure compensated variable pump is at full flow. Therefore, the inner diameter of the oil outlet pipe and connector body must have sufficient space to accommodate the full flow of oil. Otherwise, an excessively small inner diameter will create fluid resistance, leading to severe vibration of the oil pipe and pump noise. Pump body overheating issue: If an excessively small connector body or oil outlet pipe inner diameter causes a large amount of lubricating oil from the pump's swash plate to be trapped in the oil chamber instead of being discharged from the drain port, it will lead to pump body overheating. Serious consequences include increased oil temperature, affecting the sealing effect of the main machine. Solution: Effective oil drainage is necessary. The screw plug at the bottom of the pump body can also be turned into an oil drainage channel through the connector body, thereby completely solving the pump overheating problem through multi-channel oil drainage.In summary, the pressure compensated variable pump, through its unique flow-pressure matching characteristics and efficient operating mode, greatly enhances the performance of HPHT Hydraulic Cubic Press machines in the synthesis of artificial diamonds and other superhard materials, holding significant value for promotion and application.
read more+
the energy-saving modification for the HPHT Hydraulic Cubic Press is mainly achieved by not starting the oil pump (motor) during the pressure intensifier depressurization stage. This increases the non-working time of the oil pump motor, thereby reducing energy consumption.Modification Rationale and PrinciplesProblem Statement: The HPHT Hydraulic Cubic Press operates continuously during the synthetic diamond production cycle, and its power source (oil pump motor) is in a continuous working state. With the trend towards larger equipment, motor power is typically 7.5kW, 11kW, or even higher, leading to alarming energy consumption, especially electricity. Therefore, reducing energy consumption, particularly electricity consumption, has become an urgent issue that needs to be addressed.Solution Approach: The entry point for the modification is to increase the non-working time of the oil pump motor to reduce its loss. After analyzing the working principles, structure, and synthetic process of the press, the decision was made to focus on "not starting the oil pump (motor) during the pressure intensifier depressurization".Problem with the Old System: Before the modification, to depressurize the pressure intensifier, an oil pump had to be started to generate pressurized oil. This pressurized oil would pass through check valve 14 and solenoid valve 48, eventually pushing open pilot-operated check valve 22, placing it in an open state. Only then could the high-pressure oil return to the oil tank via one-way throttle valve 21, pilot-operated check valve 22, and solenoid valve 10, completing the pressure intensifier depressurization. This process required starting the oil pump motor as the power source and took about 30-60 seconds.Modification of the New System: The modified plan involves using the high-pressure oil retained in the pressure chamber after pressure-holding to replace the oil pump motor as the power source for depressurizing the pressure intensifier. The specific changes are as follows:When the work program proceeds to the pressure intensifier depressurization, the solenoid YV14 is energized.The high-pressure oil inside the intensifier cylinder is then used to open valve 21 through valve 19.The hydraulic oil from the intensifier cylinder then returns to the oil tank through valve 21, valve 48, and filter 16, thereby achieving depressurization of the pressure intensifier.Analysis of Benefits After ModificationEconomic Benefits:Modification Cost: The increase in cost for each modified hydraulic press is approximately 90 yuan.Electricity Savings Calculation: Using a 15-minute synthesis process as an example, the pressure intensifier depressurization time is calculated as 40 seconds. A single 6x1300 ton HPHT Hydraulic Cubic Press working 340 days a year can save approximately 3989.33 kilowatt-hours of electricity annually.Electricity Bill Savings: Based on an average electricity price of 0.60 yuan/kWh, the annual electricity cost savings for one modified press is about 2393.6 yuan. If a medium-sized factory with 50 large-tonnage HPHT Hydraulic Cubic Presses (assuming 11kW motor power) adopts this modification, the annual electricity savings alone could amount to 119,680 yuan. The economic benefits are undoubtedly considerable.Environmental and Other Benefits:Noise and Vibration: Before the modification, the workshop was filled with the roaring sound of the oil pump motor starting and stopping, and the vibration of oil pipes and the hydraulic station door panel caused by it. After the modification, the workshop is noticeably "quieter," significantly reducing the noise and vibration generated during the depressurization process.Equipment Lifespan and Maintenance: The modification reduces the number of daily starts of the oil pump motor, which helps to extend its service life. It also greatly mitigates issues such as loose connections and oil leaks that can result from long-term pipe vibration, thereby reducing potential maintenance costs.Working Environment: The equipment modification also significantly improved the working environment for the staff.The modification to the HPHT Hydraulic Cubic Press, which enables depressurization without starting the oil pump (motor), is a technical upgrade that is low in investment, quick to show results, and highly effective. For manufacturers of the presses, this technology enhances the overall technical content and increases the added value of the product. For users of the presses, the greatest benefits are energy savings, reduced consumption, and an improved working environment.
read more+
Servo control technology, by constructing a closed-loop servo control system, enables precise control of the ultra-high pressure relief process in cubic presses, overcoming issues such as discontinuous pressure relief and poor linearity found in traditional control methods (e.g., solenoid valve on-off control, stepping motor control). This addresses the higher demands for equipment performance and synthesis stability in high-performance super-hard material synthesis.Core Control Principle: Dynamic and precise control of the gap between the conical valve core and the valve seat.The ultra-high pressure relief valve of a cubic press primarily consists of a servo motor, relief valve body, conical valve core, conical valve seat, ultra-high pressure oil inlet, and low-pressure oil outlet. The most critical components are the conical valve core and the valve seat.The fundamental way to control the pressure relief speed is by controlling the size of the gap between the conical valve core and the valve seat: a larger gap results in faster pressure relief, and vice versa.However, in practical applications, the relationship between pressure relief speed and the gap is not a fixed linear one. As pressure decreases, a larger gap is required to maintain the pressure relief speed. Therefore, dynamically and precisely controlling this gap is the key technology.Servo control technology innovatively uses a servo motor to replace the stepping motor to drive the ultra-high pressure relief valve mechanism. A servo motor is a high-precision executive component. When configured with servo control technology, it can convert voltage signals into angular displacement or angular velocity output on the motor shaft, thereby precisely adjusting torque or speed to achieve accurate control of speed and position parameters. Advantages of servo motors compared to stepping motors include: Constant torque output, where the output torque is largely unaffected by the pressure relief speed, solving the problem of stepping motors where output torque is inversely proportional to speed, often leading to valve core jamming. Much better high-speed response performance than stepping motors. Closed-loop control with high precision, ensuring accurate valve reset. This avoids the disadvantage of stepping motors' open-loop control, which is prone to losing steps. The servo controller drives the servo motor to rotate, dynamically and precisely adjusting the opening gap between the conical valve core and the valve seat, meeting the requirements for smooth and linear ultra-high pressure relief. Its adjustable torque characteristic allows setting different torque values for closing and opening the relief valve, ensuring safe closing and timely opening. Its fast response capability can quickly reset the valve core in case of abnormal pressure relief, preventing accidents caused by sudden pressure drops.Construction of a Closed-Loop Servo Control System. The system consists of a Programmable Logic Controller (PLC), a servo control system (including a servo motor and servo drive), and a high-precision pressure sensor. An OMRON CP1H series PLC (CP1H-XA40DT-D) and a Siemens V90 servo control system (servo motor 1FL6042-1AC61-0AB1, servo drive 6SL3210-5FE10-4UA0) are used. Hardware Design: The PLC acts as the lower machine, collecting data from the pressure sensor and uploading it in real-time to the human-machine interface (HMI), which consists of an industrial computer and a display. The HMI converts pressure data into production pressure curves to monitor the pressure relief process in real-time. The servo controller is selected for position control mode, providing precise pulses. Communication between the HMI and the PLC uses the RS485 communication protocol. Software Design: An intelligent PID control algorithm is introduced. This algorithm library combines theoretical design with experimental data to establish a safe pressure relief algorithm that relates pressure relief speed to control parameters.Control Implementation Process. During the pressure relief phase, the PID control software automatically matches empirical pressure relief control parameters from the algorithm library based on the process-set pressure relief speed (SV(t)), ensuring safe initiation of the pressure relief process. The PID control software continuously calculates the measured pressure relief speed (PV(t)) and compares it with SV(t). If a deviation exists, the PID control software automatically adjusts the pressure relief control parameters based on the trend and deviation of PV(t), and outputs control pulses to the servo controller, driving the servo motor to open the pressure relief valve mechanism. It also records the pulse amount, thereby achieving closed-loop control and linear pressure relief. For different super-hard material synthesis processes (e.g., significant differences in pressure control, frequent changes in pressure relief speed, uncertainty in pressure relief parameters), the intelligent pressure control software can solve these problems without manual intervention. Full-process segmented pressure relief and inflection point handling: When synthesizing similar super-hard materials, the pressure relief speed varies across different pressure segments, typically divided into 2-3 segments of slow, medium, or fast pressure relief curves. The software includes an inflection point judgment program. When an inflection point is encountered, it recalculates the process pressure relief speed and adjusts control parameters in a timely manner, achieving a smooth transition of the pressure relief process curve and preventing instability or accidents. Pressure relief to return stroke determination and valve reset: When the pressure is relieved to the process-set safe return pressure (usually below 5 MPa), the system stops pressure relief, and the cubic press switches to the fast return stroke process. To ensure continuous production and execution of the next process, the ultra-high pressure relief valve must close. The software records the output pulse amount during pressure relief. When switching from pressure relief to return stroke, it controls the servo motor to reverse, outputting the recorded pulse amount to the servo controller to achieve precise reset of the ultra-high pressure relief valve. This prevents valve core jamming or failure to open again, creating conditions for precise control in the next ultra-high pressure servo relief process.Actual Application Results. The servo control system has successfully undergone trial acceptance on DZ1000 and DZ800 forging cubic presses. Test results show that during the process of ultra-high pressure relief from 100 MPa to a safe pressure of 3 MPa, the coincidence rate between the actual pressure relief speed curve and the process pressure relief speed curve reached over 95%, achieving smooth, linear, safe, and precise control of ultra-high pressure relief. In terms of pressure relief speed, servo control technology can achieve linear control in a wide range of 0.01~0.5 MPa/s, which is particularly suitable for the slow pressure relief processes required for high-end super-hard material synthesis. Although the application cost of servo control technology increased by 20% compared to stepping motors, its performance improved by more than double. It is also safer and more reliable, facilitating the synthesis of high-performance super-hard materials.
read more+Intersection of Jingjin Road and Weiyi Road,Luoxin Park, Xin
+86 0379-6068-6876 |
