SERVTEK Services offers you the capability to convert your injection molding machine to a larger or smaller injection capacity to accommodate a wider range of parts production with the same machine.  This flexibility can be accomplished by Upsizing or Downsizing your injection unit.

SERVTEK Services can help you obtain maximum flexibility with optimum performance.

Upsizing

Do you have a need for a larger shot size capacity on your injection molding machine?

It is possible to economically modify your injection unit to increase its shot capacity without replacing the entire injection unit. There are certain controlling factors which need to be considered to determine upsizing feasibility, including:

• Capacity of hydraulic system of the machine
• Resins to be processed
• Barrel design
• Feed Screw design

A 25% increase in shot size capacity can be achieved with the following modifications to the injection unit:

• The barrel is replaced with another barrel with a larger inner diameter (ID). The outer diameter (OD) remains the same to allow for use of the same mounting and flange configuration, the same heater bands, etc.
• The feed screw is replaced with another having a larger flight OD. The spline bushing and retainer are also replaced to accommodate for the new feed screw.
• The end cap and shut-off / check valves are also changed to fit the new barrel and feed screw.
• RESULT – Same injection unit...different shot size!

Downsizing

Do you need to decrease the shot size capacity on your injection molding machine?

If your products are showing surface defects, loss of impact strength, or similar problems, the cause could lie within the residence time of the material. The residence time is the time that the resin remains in the barrel before being injected. Whenever a process uses less than 25% of the shot capacity of the injection unit, a longer than recommended residence time may result, leading to the problems mentioned above.

Some corrective measures to adjust for long residence time could include:

• Decreasing barrel temperatures in the feed zone (reduces the heat applied to the resin).
• Decreasing feed screw RPM (decreases frictional heat).
• Decreasing back pressure (decreases shear heat).

However, when the above measures do not improve the process, the recommended solution is to downsize the Injection Unit. Downsizing is the modification of the injection unit to reduce it's shot capacity:

• The barrel is replaced with another barrel with a smaller inner diameter (ID).
• The outer diameter (OD), in most cases, remains the same to allow for the use of the same mounting and flange and the same heater bands.
• The feed screw is changed by another with smaller OD.
• The spline bushing and retainer are also changed to accommodate for the new screw.
• The end cap and shut-off/check valves are also changed to fit the new barrel and feed screw.
• If necessary, relief valves are adapted to the hydraulic system to limit the pressure.

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