Thursday, April 7, 2011


Factors to be considered to obtain maximum efficiency in the process are:
1. Use a uniform wall thickness, avoid stamping over ribs and bosses because they tend to cause shrinks in parts.
2. Raised patterns, numbers, or letters should be at least 0.5 mm high and preferably 0.75 mm or more to minimize over stamping in adjacent areas.
3. Edges of patterns and letters should be rounded rather than being sharp. This will minimize cutting of the silicone pad, thus insuring a longer life to the die.
4. Areas to be stamped should as flat and parallel as possible.
5. Dimensions must not vary from cavity to cavity in multi cavity moulds because variation of even 0.025mm can cause difficulty in stamping.
6. Very short moulding cycle, not allowing the part to cool properly, will result in excessive shrinkage and warp.
7. When several moulds are made by different moulders, the base pattern should be the same i.e. the hob used should be same.
8. In multi cavity moulds, the runners and gates should be positioned in such a way that all the parts are ejected from the mould at the same temperature.
9. Compatibility of the substrate with the hot stamping and heat transfer process should be considered while choosing the substrate.
10. Sufficient draft on the parts should be allowed to prevent distortion during ejection.
11. All the tool marks, in the areas to be decorated, should be polished because any imperfection will be magnified when high lustre metallics or colours are used.
12. When angular or spherical borders are coated, the angle from the horizontal should not exceed 400. A step surface of at least 1.25 mm from the adjacent area should be provided.
13. When raised areas are located in a deep recess, a minimum clearance of 1.5 mm from the edge of the wall of recess should be provided. This minimises the wrinkling of leaf and prevents the heated die from marring (spoiling or damaging) the side wall.

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