Parting Line Steel Preload Calculation for Multi Cavity Injection Moulds
Calculate multi cavity parting line preload by balancing machine clamp force against internal hydraulic separation force to maintain positive shut-off land sealing stress.
Insert Shimming
Meaning
Manual adjustment techniques involve placing thin strips of metal behind mould components to change their height. Performing insert shimming allows a toolmaker to fine tune the shutoff surfaces and eliminate flash on a moulded part. These shims are often made of stainless steel or brass and come in precise thicknesses starting at 0.01 millimeters.
This process is common during the initial trial phase of a new mould.
Height Adjustment
Small variations in the machining of cavity inserts can lead to gaps at the parting line. Using insert shimming raises the lower insert to meet the upper half of the tool with the correct pressure. This fix is faster than re-machining the entire plate or welding the steel.
Flash Prevention
Gaps as small as 0.02 millimeters allow molten plastic to escape the cavity and form a thin skin on the part. Proper insert shimming closes these gaps and ensures a clean break at the gate. This technique is especially useful for resins with low viscosity that flow easily into tiny cracks.
Tolerance Stack
Cumulative errors in a large tool assembly can move a part out of its dimensional specification. When insert shimming is used to correct these errors, the technician must document the location and thickness of every shim. Losing a shim during a routine cleaning can result in the production of thousands of defective parts.