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Home / How to Adjust Clamping Force on a 220-ton injection molding machine for Thick-Wall Plastic Parts？

How to Adjust Clamping Force on a 220-ton injection molding machine for Thick-Wall Plastic Parts？

2025/11/24 By le zhan

How to Adjust Clamping Force on a 220-ton injection molding machine for Thick-Wall Plastic Parts

A customer told us they were using a 220-ton injection molding machine to produce 10mm thick electric vehicle battery casings, but 27% of the parts were defective: some had flash (thin plastic seeping from between the mold halves), and some were severely deformed and failed quality inspection. To prevent flash, they increased the clamping force to the machine’s maximum of 220 tons, but this caused part deformation.

Thick-walled plastic parts place higher demands on a 220-ton injection molding machine. The molten plastic must flow deeper into the denser cavity, requiring an injection pressure 15% to 25% higher than for thin-walled parts. Clamping force plays a balancing role: too little leads to flash in the mold; too much leads to part deformation or excessive stress on the mold. Therefore, this operating guide will show you how to calculate, adjust, and verify the clamping force.

The Importance of Clamping Force in a 220-Ton Injection Molding Machine for Thick-Walled Parts

To effectively adjust the clamping force, it is essential to understand why thick-walled parts (such as PVC pipes over 5mm thick, HDPE packaging boxes over 8mm thick, and automotive bodies over 12mm thick) have specific requirements for a 220-ton injection molding machine. The core challenge lies in balancing injection pressure and mold stability.

Thick-walled cavities require higher injection pressures (1200-1800 bar) to inject the molten plastic into every corner before it cools. This pressure exerts an outward force on the mold—the clamping force acts like a “lid” keeping the box closed. Insufficient clamping force can lead to the following:

  • Molten plastic seeps between the two halves of the mold, creating flash that requires costly finishing.
  • Misalignment of the two halves of the mold causes parts to exceed dimensional tolerances.
  • Repeated bending of the mold weakens guide pins and cavities, reducing mold life by 30-40%.

Excessive clamping force can lead to the following:

  • Excessive pressure can deform cooling components, causing warping. – The mold surface is compressed, leaving dents or “shrinkage marks” on the part surface.
  • Injection molding machine energy consumption increases by 15-20%, driving up operating costs.
The Importance of Clamping Force in a 220-Ton Injection Molding Machine for Thick-Walled Parts

Accurately Calculating the Clamping Force for a 220-Ton Injection Molding Machine

The most common operator mistake is setting the clamping force to the injection molding machine’s maximum value “for safety reasons.” The correct clamping force depends on three variables: the projected area of ​​the part, the injection pressure of the plastic, and the safety factor.

Calculation Formula: Clamping Force (tons) = (Projected Area × Injection Pressure) ÷ 2,000 × Safety Factor

Let’s illustrate each component with a practical example (a 10mm thick ABS car body):

  1. Projected Area: The area of ​​the most significant cross-section of the part. For irregular shapes, please use CAD software or draw the part on graph paper. Our ABS body has a projected area of ​​18.6 square inches.
  2. Injection Pressure: Thick-walled ABS requires 1400 bar (20305 psi). Please refer to the relevant material data sheet; rigid plastics (PC, ABS) require higher pressure than soft plastics (PP, PE).
  3. Conversion Factor (2000): Converts psi to tons.
  4. Safety Factor (1.2-1.3): Provides cushioning for thick-walled parts to withstand pressure spikes during filling.

Based on the example above, the calculation is: (18.6 × 20305) ÷ 2000 × 1.3 = Approximately 247 tons. After adjusting the safety factor to 1.15 and optimizing the injection pressure, the final target is 215 tons.

220-ton Injection Molding Machine

Detailed Clamping Force Adjustment Steps

After determining the target clamping force, follow these steps to adjust your 220-ton injection molding machine. We will use a Topstar TMll 220-ton injection molding machine as an example to show you the specific steps.

First, perform an LOTO operation on the injection molding machine to prevent accidental start-up. Clean the mold parting line (remove old plastic or debris) and check that the guide pins are lubricated—debris or dry guide pins can cause uneven force distribution. Confirm that the mold is properly clamped onto the platen. Next, navigate to the “Clamping” menu on the touchscreen. Select “Force Adjustment” to enter the target force (215 tons). For toggle-type injection molding machines, the force is adjusted by changing the closing angle; the smaller the angle, the greater the force.

For a 220-ton injection molding machine, locate the clamping pressure relief valve. Use a pressure gauge to monitor the force. Turn the valve clockwise to increase the force and counterclockwise to decrease it. Typically, each rotation will adjust the force by 5-10 tons. Then unlock the injection molding machine and run 5-10 trial cycles with an empty mold. Check the machine’s force monitor to see if the target force (215 tons) is reached during the clamping phase. If not, fine-tune the control force by 5 tons and test again.

Next, run 10 cycles with a thick-walled mold. Check the specific condition of each part:

  • Flash = Increase pressure by 5-10 tons: Molten plastic is escaping – increase pressure to seal the mold.
  • Warp/Sinkmark = Reduce pressure by 5 tons: Excessive pressure is causing part deformation – slightly reduce the pressure.
  • Perfect Part = Lock Settings: Saves the adjustment values ​​to the machine’s formula to match the mold/material combination.

Common Adjustment Mistakes and How to Avoid Them

Even with a correct formula, minor errors can lead to the failure to produce thick-walled parts. Therefore, we need to avoid the following five pitfalls:

  1. Confusing Projected Area with Actual Volume: Projected area determines the required pressure. A 10mm thick part with a larger flat surface requires more pressure than a heavier but narrower part.
  2. Setting the pressure of a 220-ton injection molding machine to maximum “just in case”: Running at 220 tons of pressure puts excessive stress on the toggle or hydraulic system, leading to premature wear.
  3. Ignoring Material Temperature: Lower-temperature plastics are thicker and require higher injection pressure, and therefore also higher clamping force. If the material temperature drops by 20 degrees Fahrenheit, an increase of 5-8 tons of pressure is needed.
  4. Ignoring Post-Adjustment Checks: Run the machine for more than 50 cycles after adjustment, then check for part consistency. Pressure may shift slightly as the machine heats up.
  5. Ignore mold wear: Worn molds require 5-10 tons more pressure than new molds. Check mold wear monthly.

Topstar’s Secrets to Successful Injection Molding of Thick-Walled Parts

Ignore the wear of injection molding machine molds

Topstar’s TMll 220-ton injection molding machines distribute pressure more evenly across the mold, reducing warpage in thick-walled parts by 40%. They also adjust the injection force, applying a higher force during filling (at the pressure peak) and a lower force during cooling (to prevent warpage). Furthermore, they trigger an alarm when the set force deviation exceeds 5%, allowing for timely detection and resolution before problems lead to scrap. Additionally, force needs to be matched to injection speed; reducing injection speed reduces pressure peaks, and reducing the filling speed by 10% can reduce clamping force by 5 tons without generating flash.

Precise Clamping Force Control for Thick-Walled Plastic Parts

Adjusting the clamping force of a 220-ton injection molding machine to produce thick-walled parts is not a matter of guesswork, but a precise process of calculation, testing, and fine-tuning. Errors can be extremely costly. For thick-walled parts, the first step is to develop a formula, conduct small-scale testing, and utilize all the machine’s functions to ensure consistency, thus reducing costs.

 

 

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