For previous reading, please refer to Solutions and Practical Guide to Sticking Problems on Injection Molding Machines Under 800T.
FANUC Electric Injection Molding Machine In-Depth Optimization Guide for Injection Speed ​​and Process Parameters (Models Under 1000T)
(Focusing on FANUC ROBOSHOT series control systems, covering screw diameters from 18-54mm and machines from 30-1000T, including material commissioning, troubleshooting, and application of system-specific functions)

 

Injection speed control of FANUC electric injection molding machines is based on a closed-loop algorithm based on "servo motor torque-screw displacement." Core principle is to infer speed rationality from "melt filling quality." A qualified filling process requires "no cold slug marks, controllable weld marks, and low internal stress (part deformation <0.2%)." Furthermore, FANUC system's "injection pressure-speed curve" must exhibit a "smooth rise, steady-state filling, and linear pressure drop" pattern (peak pressure fluctuation within ±5%, and no oscillation at V/P switching point).

- Initial Stage: Establishing a Basic Speed Framework (to Ensure Filling Integrity). Set initial speed based on part wall thickness: 80-120 mm/s for thin-walled parts (<2 mm), and 30-50 mm/s for thick-walled parts (>5 mm). Manually inject one mold and observe following on FANUC "Real-time Process Monitoring" interface:
- Cold Slug Spot Determination: If a whitish or dark area appears at the front end of part (within 5mm of slug tip), this indicates that injection speed is too slow, causing premature melt cooling. In FANUC "Injection Speed Segment Settings," increase the first segment speed by 10-15 mm/s (e.g., from 80 mm/s to 90 mm/s). Also, check nozzle temperature (it should be 5℃ higher than front section of barrel. FANUC system allows for individual nozzle parameter adjustments in "Temperature Module").
- End Material Shortage Determination: If edge of part is not fully filled and FANUC "Melted Volume Display" indicates "Actual Shot Volume < 95% of Set Value," this indicates that injection speed is too fast, causing increased melt shear viscosity (especially for high-viscosity materials such as PC). Reduce injection speed by 10 mm/s and check barrel temperature distribution (FANUC "Temperature Curve" function displays temperature difference between each segment. If rear segment is >8℃ lower than front segment, adjust heater power).
- Intermediate: Mold and Pressure Collaboration Verification (Controlling Weld Marks and Internal Stress) Perform a test shot with mold, monitoring pressure at weld mark using FANUC "Cavity Pressure Sensor" (if equipped):
- Excessive pressure peak (>20% of set value): For example, if target is 100 bar and actual value is 120 bar, this indicates that speed is too high, causing frictional heating of melt and a sudden drop in viscosity. Limit upper pressure limit in high-speed section using FANUC "Speed-Pressure Linkage Curve" (e.g., when shot speed is >90 mm/s, force pressure to ≤110 bar). Simultaneously, monitor mold venting (FANUC system can be linked to "Mold Venting Analysis" function, indicating that vent groove depth must be >0.04 mm).
- White weld mark (e.g., thin-walled ABS parts): Slow speed is causing melt to cool at weld. Increase speed by 15 mm/s and utilize FANUC "Mold Temperature Gradient Control" (front mold temperature 10℃ higher than rear mold temperature, e.g., front mold 85℃, rear mold 75℃) to ensure smoother melt flow at weld.
- Final Stage: Mass Production Stability Calibration (to ensure consistency). Run 30 molds continuously and analyze using FANUC "Production Data Recording" function:
- Speed Fluctuation > ±5%: If FANUC system displays "Injection Speed CV Value" > 5%, check injection servo valve response (check valve current fluctuation on "Servo Diagnosis" screen. If > 10%, clean valve core) or calibrate ball screw clearance (test injection axis repeatability in "Mechanical Calibration" module. If error > 0.02mm, adjust ball screw).
- Product Weight Deviation > 0.5%: Unstable speed is causing fill volume fluctuations. Check barrel temperature (if FANUC "Heater Coil Load Rate" shows > 80% in a certain range, it indicates low heating efficiency and requires replacement of heater coil). Avoid changes in melt viscosity affecting flow rate.

Injection speed of a FANUC electric injection molding machine needs to be adjusted based on screw's material storage capacity and servo response characteristics:
- Small-tonnage machines (30-200 tons) + small screws (18/22 mm): Upper limit of injection speed is low (recommended <100 mm/s). Due to small plasticizing capacity of screw, high speeds can easily lead to insufficient mixing of the melt. FANUC system can increase back pressure by 10-15 bar through "Dynamic Back Pressure Compensation" function (enabled in "Melt Parameters") to compensate for insufficient mixing.
- Large-tonnage machines (500-1000T) + large screws (44/54mm): Injection speeds can be increased to 120-150 mm/s, and screw has a large material storage capacity (FANUC "Shot Size Estimation" function shows a single storage capacity of >800g). However, V/P switching point must be controlled (FANUC "Switching Point Accuracy" is set to ±0.1mm) to avoid high-pressure impact on mold. (FANUC "Mold Protection" function allows you to set a pressure threshold, automatically interrupting injection if it exceeds the limit).

FANUC system uses patented features such as "i-Melt Melt Optimization" and "V/P Switching Optimization" to achieve a balance between speed and internal stress/shear heat. Ideal speed = maximum allowable shear rate of material x 0.7 (FANUC's "Material Database" automatically adjusts this factor). Avoid excessive speeds that could cause molecular chain breakage (material brittleness) or mold wear (flash/strain).

- Speed identification by listening to sounds and correlating them with system parameters: Normal speed: A uniform "puffing" sound is heard during injection, and FANUC "Injection Motor Current" is stable (e.g., for a 22mm screw with ABS, current is approximately 12A). Excessive speed: A sharp "whistling" sound is heard, current surges (>18A), and FANUC "Barrel Temperature Real-Time Curve" indicates actual value is 3-5℃ higher than set value (shear heating). In this case, speed should be reduced by 10-15 mm/s in "Speed Segment Settings" setting, and FANUC "Cooling Water Flow Monitoring" should be enabled (ensuring cooling water flow is >5 L/min to reduce barrel heat accumulation). Excessive speed: A dull "gurgling" sound is heard, injection time is excessive (>2 seconds), and FANUC "Part Weight Fluctuation" indicates >1%. In this case, speed should be increased and melt volume should be checked (FANUC "Melting End Position" should be 1-2 mm higher than theoretical value, and mixing time should be increased).
- Quick Verification of Internal Stress and System Tools: After demolding, test with a FANUC Polarized Light Stress Tester (optional) or Solvent Method (whitening of edge of an acetone drop after 30 seconds indicates high internal stress). This indicates excessive molecular chain orientation due to excessive injection speed. In this case, reduce injection speed by 10-20 mm/s in FANUC Post-Processing Parameters settings and extend holding time by 2 seconds (FANUC Holding Time Segment setting allows for multiple holding times, such as 80 bar/2 seconds for the first stage and 60 bar/3 seconds for the second stage).

- For high-viscosity materials (PC, PMMA): FANUC Material Database indicates that PC has a viscosity >10⁵Pa·s. Therefore, injection speed should be 20% higher than for standard materials (80-100 mm/s). Additionally, increase barrel temperature by 10℃ in Temperature Parameters settings to reduce melt viscosity. FANUC "Melt Profile" function monitors melt temperature distribution, ensuring temperatures of 280℃ in the front section and 260℃ in the middle section (to prevent overheating and decomposition in the middle section).
- Fiber-reinforced materials (30% GF-PP): FANUC "Fiber Length Retention" function indicates that fibers are susceptible to breakage due to high-speed shearing (strength drops by 40% when length < 0.5mm). Therefore, an upper limit of 40-50 mm/s should be set in "Injection Speed Limit" setting, combined with "low back pressure + high screw speed" (FANUC "Screw Speed" is set to 60 rpm, 10% higher than pure PP, to ensure fiber dispersion).
- Decomposable materials (PVC): FANUC "Safe Injection Speed Window" function automatically calculates (injection speed * barrel temperature ≤ 12000). For example, if material temperature is 180℃, injection speed should be ≤ 66 mm/s. At the same time, enable "staged cooling firing rate" (set FANUC "firing rate curve" to 60 mm/s/material temperature 165℃ for front section and 50 mm/s/material temperature 160℃ for rear section), and set "screw cleaning" module to automatically clean nozzle every 2 hours (to prevent accumulation of PVC decomposition products).

 

- Symptom: Weld mark on air conditioner panel (2.5mm thickness) exhibits wavy patterns, and adhesion strength on 100-grid test is less than 4B.
- Special solutions for FANUC system: ① Segmented injection speed + mold temperature linkage: Define two segments in FANUC "Injection Speed Segment Settings"—the first at 70 mm/s (filling runner to 80% of cavity), and second at 95 mm/s (filling remaining portion). Simultaneously, set mold temperature for second segment to 85℃ in "Mold Temperature Control" setting (FANUC's "Local Mold Temperature Adjustment" function is implemented through water channel zoning). ② Shift V/P switching point forward: Set FANUC "Switching Point Accuracy" to 0.1 mm, advancing it from original 12 mm to 9 mm (reducing high-pressure filling time and preventing excessive shearing and cooling of melt at the weld). ③ Check ring clearance calibration: Due to strong ABS adhesion, FANUC "Screw Assembly Diagnosis" function indicates that check ring clearance is >0.2 mm. After disassembly and replacement, clearance is restored to 0.15 mm. (System automatically records a 12% decrease in melt torque and improved injection speed stability after replacement).

- Symptom: Edge of a mobile phone middle frame (1.2mm thick) cracked after three days of storage. Stress testing showed >80MPa (standard <60MPa).
- FANUC system-specific solutions: ① Injection rate-temperature matching formula: Call FANUC "Material Process Assistant" and enter PC parameters (melting point 220℃). System automatically recommends an injection rate of (material temperature - 260℃) * 1.5 + 50 (e.g., material temperature 280℃, injection rate = 80 mm/s). This avoids excessive shear heating caused by excessive injection speed at low temperatures. ② Mold temperature gradient control: FANUC's "Multi-zone Mold Temperature Control" setting is set to 85℃ for front mold and 75℃ for rear mold (high front mold temperature reduces melt cooling rate, while low rear mold temperature reduces internal stress accumulation). System monitors mold temperature fluctuations in real time to within ±1℃. ③ Holding pressure speed ramp switching: Set FANUC "Speed Switching Curve" to "500ms linear speed reduction" (from 80 mm/s to 30 mm/s) to avoid stress concentration caused by sudden pressure changes (stress test down to 55 MPa).

- Symptom: Sink marks on the back of a car bumper (4mm thick) are 0.3mm deep (standard <0.1mm).
- FANUC system-specific solutions: ① Segmented injection speed feeding: FANUC's "three-stage injection speed setting"—first stage is 55 mm/s (high-speed filling), second stage is 45 mm/s (medium-speed feeding to prevent rapid surface solidification), and third stage is 30 mm/s (low-speed compaction); ② Holding pressure speed linkage: When injection speed drops to 30 mm/s, FANUC's "holding pressure automatic increase" function is triggered (holding pressure increases from 60 bar to 80 bar, 20% higher than injection pressure) to compensate for melt cooling shrinkage; ③ Conformal cooling optimization: FANUC system is linked to mold temperature controller, increasing cooling water flow rate in thick-walled areas (>6 mm) to 1.0 m/s (water temperature 15℃), shortening cooling time by 30% (sink mark depth reduced to 0.08 mm).

- Symptom: Gearbox housing (projected area 0.8m²) still exhibits flash at a clamping force of 1500 bar. Flash thickness is 0.1mm (standard <0.05mm).
- Special solutions for FANUC system: ① Linked calculation of injection speed and clamping force: FANUC "Clamping Force Verification" function shows that actual clamping force required is = Projected Area * Material Pressure (PA is 300 bar/cm²) ÷ 100 = 2400 bar (original 1500 bar was insufficient). However, due to excessive injection speed, melt pressure peak reached 200 bar, so injection speed was reduced by 15 mm/s (injection speed from 60 mm/s to 45 mm/s), and V/P switching point was advanced to 10 mm (pressure peak dropped to 150 bar, eliminating flash). ② Parting surface gap compensation: FANUC "Mold Protection" function scans parting surface and indicates that corner gap is greater than 0.06 mm. It automatically adjusts clamping force distribution (increasing pressure in local area by 10%), or sets a virtual "elastic sealing strip" in system to compensate (reducing flash by 0.03 mm). ③ Injection speed torque monitoring: FANUC "Servo Torque Limit" is set to 15A (22 mm screw), and injection speed is automatically reduced if limit is exceeded (to avoid flash caused by a surge in melt pressure).

- Symptom: HDPE barrels (6mm thickness) exhibited radial warpage of 1.5mm after cooling (standard: <0.8mm).
- FANUC system-specific solutions: ① Segmented injection speed temperature control: FANUC's "injection speed-temperature linkage" setting—first segment is 25mm/s (high-temperature filling, promoting outer layer crystallization), and second segment is 20mm/s (low-temperature feeding, slowing inner layer crystallization)—to avoid differences in inner and outer layer crystallization rates. ② Mold temperature synchronization adjustment: FANUC's "outer layer mold temperature 40℃/inner layer mold temperature 30℃" zoned control (accelerates outer layer crystallization, delays inner layer crystallization) improves crystallization synchronization to 90% (reducing warp to 0.6mm). ③ Injection speed fluctuation control: FANUC's "injection speed servo gain adjustment" (increased from the default 50% to 70%) improves response speed and reduces injection speed fluctuation to ±3mm/s (improving melt density uniformity).

- Symptom: Radial air marks appeared on the surface of a transparent lampshade (3mm thick), resulting in a 15% decrease in light transmittance.
- FANUC System-Specific Solutions: ① Injection Rate-Exhaust Groove Matching: FANUC "Exhaust Analysis" function indicates that exhaust groove depth at air mark location is less than 0.03mm and needs to be deepened to 0.05mm. Simultaneously, at an injection rate of 80mm/s, FANUC "Vacuum Exhaust" module is activated (with an exhaust rate of 0.2m³/h) to reduce residual gas. ② Melt Temperature Uniformity: FANUC "Heater Load Balancing" function adjusts power of each stage (temperature difference controlled within ±2℃) to avoid air marks caused by melt density fluctuations. ③ Pre-fill strategy: FANUC's "Injection Pre-fill" setting—first fill 50% of material at a low speed of 50 mm/s, then fill at a high speed of 80 mm/s (to avoid high-speed impact on mold, which can delay gas discharge and eliminate gas lines).

- Symptom: Black spots on the surface of PVC pipes (2mm thickness) and a noticeable sour odor on starting material.
- Special solutions for FANUC system: ① Injection speed and temperature safety window: FANUC's "Material Safety Parameters" automatically limit (injection speed * material temperature ≤ 12000). For example, if material temperature is 180℃, injection speed should be ≤ 66 mm/s (system forcibly locks out-of-limit parameters). ② Segmented cooling injection speed: FANUC "Injection Speed-Temperature Curve" is set for low-temperature injection (material temperature 165℃, injection speed 60 mm/s), while simultaneously enabling "water jacket cooling" at the rear end of barrel (water temperature 20℃, FANUC "Cooling Water Temperature Control" accuracy ±1℃). ③ Screw anti-retention cleaning: FANUC "Automatic Cleaning Cycle" is set to clean nozzle every 2 hours (copper brush automatically operates), and "nozzle temperature is set 5℃ lower than barrel" (to reduce accumulation of decomposition products and eliminate black spots at material head).

- Symptom: Ejection resistance of shoe sole (10mm thickness) exceeded 50kN (standard <30kN), causing deformation during forced ejection.
- FANUC System-Specific Solutions: ① Injection Speed-Internal Stress Control: FANUC "Ejection Force Prediction" function indicates that injection speed needs to be less than 25mm/s (current 30mm/s results in high internal stress). After reducing speed, ejection resistance is reduced to 35kN. ② Ejector Follow-Up: FANUC "Ejector Synchronous Control" setting pre-retracts ejector by 0.5mm when injection speed exceeds 25mm/s (reducing ejection resistance), and fully retracts when injection speed is less than 20mm/s. ③ Silicone Masterbatch Injection: FANUC "Material Additive System" injects 0.3% silicone masterbatch (compatible with TPU) into front end of barrel, reducing ejection resistance to below 25kN (no oil spots).

 

- Symptom: Cross-section of an electronic housing (2mm thick) exhibits "black and white delamination," resulting in a 25% decrease in impact strength.
- FANUC system-specific solution: ① Segmented firing speed matching melting point: PC melting point 220℃, ABS melting point 210℃. FANUC's "segmented firing speed and temperature" setting: 65mm/s/240℃ for front section (PC phase) (to ensure PC melting), 75mm/s/220℃ for back section (ABS phase) (to prevent ABS overheating); ② Firing speed-pressure coordination: 80 bar pressure at a firing speed of 65mm/s for front section (to compact the PC phase), increasing to 100 bar pressure at a firing speed of 75mm/s for back section (to promote interface fusion and reduce delamination rate to 8%); ③ Mold temperature gradient compensation: FANUC's "85℃ PC phase mold temperature/75℃ ABS phase mold temperature" setting (to reduce interfacial cooling differences, further reducing delamination rate to 3%).

- Symptom: POM gears (20% glass fiber) exhibit chipping on tooth surface, with a 30% decrease in bending strength (fiber breakage).
- FANUC system-specific solutions: ① Injection speed-fiber length control: FANUC "Fiber Breakage Warning" function indicates that injection speed must be less than 35 mm/s. A gradual injection speed setting (30 mm/s in the front section, 35 mm/s in the back section) was used to maintain a fiber length of 0.8-1.2 mm (increasing bending strength by 25%). ② Screw mixing section optimization: FANUC "Screw Assembly Design" function recommended deepening mixing section screw groove (from 3 mm to 4 mm). Combined with an injection speed of 35 mm/s, this reduced shear rate to a safe range (reducing fiber breakage). ③ Gate shear control: FANUC "Gate Speed Simulation" function indicated that shear rate at fan-shaped gate was greater than 5000 s⁻¹. Adjustment to a trapezoidal gate was made (reducing shear rate to 4000 s⁻¹, resulting in more uniform fiber orientation).

1. i-Melt Melt Optimization: Enter material grade, and FANUC system automatically matches melt temperature profile, screw speed, and back pressure (e.g., for PC material, it automatically recommends a melt temperature of 280℃, a screw speed of 60 rpm, and a back pressure of 100 bar), reducing manual debugging time by 50%.
2. Injection Speed Fine-Tuning Interface: FANUC Process Editor supports step-by-step injection speed fine-tuning (accuracy of ±1 mm/s). Combined with real-time pressure curve display, this allows precise control of filling process (e.g., increasing injection speed by 5 mm/s at weld line location).
3. Abnormal Diagnosis Assistant: When injection speed fluctuations occur, FANUC Fault Tree Analysis function automatically indicates cause (e.g., "servo valve response delay," "uneven barrel temperature," "screw wear") and provides solutions (e.g., "clean servo valve," "calibrate heater coil," "replace check ring").

1. Material Compatibility: Check material viscosity and shear sensitivity in FANUC "Material Database" (e.g., whether PVC has entered decomposition window due to excessive speed);
2. System Parameter Validity: Check whether speed matches FANUC recommended "material, wall thickness, and mold" combination (e.g., whether high-speed mode is enabled for thin-walled parts);
3. Equipment Status: Check FANUC "Servo Diagnostics" (response speed) and "Screw Wear Detection" (if clearance > 0.3mm, replacement is required);
4. Mold Issues: FANUC "Mold Analysis" function indicates design flaws in vent groove, parting surface, or gate (e.g., air marks caused by insufficient venting).
Summary: Core of injection speed tuning for FANUC electric injection molding machines is to "leverage system closed-loop control and proprietary functions to achieve precise energy transfer for melt filling." By combining "segmented speed-pressure linkage," "material database matching," and "real-time data monitoring," combined with dynamic adjustments based on mold feedback, stable, defect-free, and low-stress production can be achieved. After each speed parameter is adjusted, it is necessary to pass FANUC's "production data verification" (50 consecutive mold dimensions, appearance, and internal stress meet standards) to solidify parameters and avoid batch problems caused by "parameter drift."