Addressing frequent problem of "direct replication of injection pressure across machines for same product leading to material shortage/flash/dimensional fluctuations," this section breaks down differences in pressure system hardware, control algorithms, and external configurations of FANUC/Sumitomo/Haitian machines. It establishes a penetrating analysis model of "pressure setting → transmission loss → effective effect," helping machine commissioning engineers master "pressure compensation strategies based on equipment characteristics" and solve problem of "setting pressure meets standards but process results are unstable."

 

Pressure is "power engine" of injection molding—it drives melt to fill mold, compensate for shrinkage, and transmit clamping force. However, due to differences in hydraulic/servo system design, control algorithms, and external configuration limitations, three pressure testing machines exhibit significant differences throughout the entire pressure chain (setting → transmission → action), resulting in drastically different actual effects for same pressure setpoint on different machines.
1. Pressure Hardware: Inherent Difference Between Power Source and Transmission System
- FANUC (ROBOSHOT series): Employs a high-response servo valve (response time ±0.1ms) + precision hydraulic cylinder (internal leakage rate <0.1mL/min), paired with a closed-loop pressure sensor (accuracy ±0.5bar). Its pressure transmission efficiency is over 95%, and injection pressure fluctuations can be stably controlled within ±1bar.
- Sumitomo (DE series): Standard configuration includes a proportional servo valve (response time ±0.3ms) + standard hydraulic cylinder (internal leakage rate ≈0.3mL/min), sensor accuracy ±1bar. Its advantage lies in fine pressure gradient control (supporting 0.1bar-level adjustment), but due to a slightly slower valve response, there is a significant pressure lag (approximately 50ms) in high-pressure section (>20MPa).
- Haitian (MA series): Employs a standard electromagnetic directional valve (response time ±1ms) + a high-flow hydraulic cylinder (internal leakage rate ≈0.5mL/min), with a sensor accuracy of ±2bar. While possessing strong load-bearing capacity (pressure upper limit 35MPa), its pressure transmission efficiency is only 85%~90%, with significant fluctuations (±3bar) in low-pressure range (<10MPa).
Key contradiction: Hardware differences determine "pressure sensitive range" of three machines—Fanuc needs to withstand minor fluctuations (e.g., a ±1bar deviation affects thin-walled component filling), Sumitomo needs to compensate for high-pressure lag (e.g., pressure not keeping up during end-filling), and Haitian needs to withstand system losses (e.g., pipeline pressure drop leading to insufficient actual pressure).
2. Control Logic: Differences in "Precise-Coarse" Pressure Regulation Modes
- Fanuc: Employs "position-pressure dual closed-loop" control. During injection stage, it prioritizes tracking position curve, switching to pressure control when approaching V/P switching point, and adjusting holding pressure through real-time feedback. For example, when holding pressure is set to 16MPa, system dynamically compensates for pressure drop caused by melt cooling and contraction, ensuring mold cavity pressure remains stable at 14~16MPa.
- Sumitomo: Based on a "speed-pressure gradient" algorithm. Injection stage proceeds at a preset speed range, with pressure dynamically adjusted according to melt resistance, making it more suitable for filling complex structures. For example, when filling deep cavities, Sumitomo actively reduces end speed and simultaneously increases pressure (e.g., from 10MPa to 12MPa) to avoid flash due to excessive speed.
- Haitian: Simplified to a coarse-tuned "pressure-time" logic. Injection stage proceeds with constant pressure, and time is set empirically. This logic relies on "pressure coverage." For example, if injection pressure is set to 18MPa, only 15MPa may actually act on melt due to system losses, requiring an extended holding time to compensate for insufficient filling.
Key contradiction: For same product's "filling target" (e.g., no flash, no missing material), three machines need to achieve it through different logics—FANUC relies on precise pressure control with a dual closed-loop system, Sumitomo relies on speed-pressure linkage for pressure adjustment, and Haitian relies on time-based pressure loss compensation.
3. External Configuration: Differences in "Pressure Loss" Between Piping and Molds
- FANUC: Standard factory configuration includes high-pressure piping (8mm inner diameter) + quick couplings (pressure drop < 0.5 bar), and good mold interface sealing (leakage rate < 0.05 mL/min). Engineers routinely check for piping aging (quarterly) to reduce pressure loss.
- Sumitomo: Piping inner diameter 6mm (cost optimization), pressure drop approximately 1~1.5 bar/meter, couplings are prone to loosening after long-term use (pressure drop increases to 2~3 bar). Couplings need to be tightened regularly (monthly) to prevent pressure decay.
- Haitian: Pipeline inner diameter is 10mm (anti-clogging design), but due to high viscosity of hydraulic oil (46# hydraulic oil), viscosity increases at low temperatures (e.g., 30cSt at 20℃ vs. 15cSt at 30℃), leading to increased pump outlet pressure loss (approximately 2-4 bar). Preheating hydraulic oil (to above 40℃) is required before production.
Key contradiction: External configuration amplifies deviation between "set pressure" and "actual pressure in mold cavity"—Fanuc needs to prevent pipeline aging, Sumitomo needs to prevent joint loosening, Haitian needs to control oil temperature and viscosity.

 

Background and Known Conditions
- Product: ABS air conditioning vent for a certain car model (size 200×100×50mm, average wall thickness 2.5mm, multi-slider + submerged injection);
- Material: ABS (melt flow index 20g/10min, recommended injection pressure 15~20MPa);
- Objective: All three injection machines must achieve "no missing material, no flash, and a CPK ≥ 1.33".
Case 1: FANUC → Sumitomo: "Pressure Lag Trap" of Frequent Flash
FANUC Initial Parameters (Stable Production):
- Injection Pressure: 18MPa (Segmented: 80% Fill → 60% Holding Pressure);
- V/P Switching Position: 98mm (Screw Diameter 45mm);
- Result: 800 molds produced continuously, no flash, no material shortage, stable dimensions (critical dimension φ8mm hole tolerance ±0.06mm).
Problems when directly copied to Sumitomo DE-60:
- After producing 300 molds, flash appeared on slider parting surface (thickness 0.2mm, out of tolerance 0.1mm);
- Mold cavity end pressure was only 12MPa (FANUC is stable at 14~16MPa).
Engineer Analysis and Adjustments: Sumitomo servo valve had a slow response (±0.3ms vs. FANUC ±0.1ms). Original 18MPa injection pressure caused flash due to the lag in filling speed at the end. Therefore, injection pressure was increased to 20MPa (to cover lag loss), and Sumitomo's "pressure gradient compensation" function was enabled, adding an extra 2MPa pressure during end-fill stage (total pressure 22MPa).
Simultaneously, Sumitomo pipeline pressure drop was high (due to slightly loose connections), and actual mold cavity pressure was 1.5 bar lower than setting. Therefore, connections were tightened and pressure sensor was calibrated, correcting set pressure to 21MPa (to compensate for pressure drop).
After adjustments, 800 molds were produced, flash disappeared, mold cavity pressure stabilized at 14~16MPa, and dimension CPK=1.42 met standard.
Case 2: FANUC → Haitian: "Pressure Loss and Time Compensation" Trap of Material Shortage
FANUC initial parameters (same as above stable parameters).
Issues encountered when directly copying design to Haitian MA3000:
- Shortage of material at the end of product (away from gate) (approximately 8% of area lacking material);
- Actual mold cavity pressure is only 10MPa (Fanuc is stable at 14~16MPa).
Engineer Analysis and Adjustments: Haitian hydraulic system has significant pressure loss (approximately 3 bar pressure drop across pipelines and connectors). Original 18MPa setting only applies 15MPa to melt, requiring an increase in set pressure to 21MPa (to compensate for loss).
Simultaneously, Haitian's "pressure-time" logic relies on holding time for shrinkage compensation, and original holding time of 200ms is insufficient. Therefore, holding time is extended to 300ms (to ensure sufficient melt shrinkage compensation).
Furthermore, Haitian oil temperature is too low (25℃), and high viscosity of hydraulic oil causes unstable pump output pressure. Therefore, preheating to 45℃ before production stabilizes system pressure.
After adjustments, 800 molds were produced, material shortage disappeared, mold cavity pressure stabilized at 13-15 MPa, dimensional shortness decreased to 0.05 mm, and CPK=1.38 met standard.

 

Core Conclusions
Essence of pressure parameter failure across machines is:
- Pressure characteristics determine sensitivity range: Fanuc is sensitive to small fluctuations (±1 bar is sensitive), Sumitomo is sensitive to high-pressure lag (gradient compensation is required), and Haitian is sensitive to system losses (setup value needs to be increased + time extended);
- Control logic determines adjustment direction: Dual closed-loop systems require precise matching of position-pressure switching, gradient control requires linkage of speed-pressure, and coarse adjustment logic requires time compensation for pressure loss;
- External configuration amplifies deviations: "Small problems" such as pipe aging, loose joints, and oil temperature and viscosity can directly lead to insufficient pressure.
Core Competency Requirements for Machine Adjustment Engineers:
1. Pressure Sensitive Area Identification: Ability to quickly identify pressure pain points on machine (e.g., FANUC's terminal pressure, Sumitomo's high-pressure lag, Haitian's system losses);
2. End-to-End Loss Calculation: Thoroughly investigate each link from "pump outlet pressure → pipeline pressure drop → joint loss → actual mold cavity pressure," quantifying compensation values (e.g., setting pressure +1 bar for every 1 bar pressure drop per meter of pipeline);
3. Proficiency with Verification Tools: Mastery of tools such as hydraulic pressure gauges (for measuring pump outlet pressure), mold cavity pressure sensors (for measuring actual operating pressure), and infrared thermometers (for monitoring oil temperature), achieving three-dimensional verification of "setting-transmission-operation."