What will the mold designer tell the product designer?
When a new plastic part was designed and sent to the injection molding company to review, what will the injection molding engineers discuss with the product designers? We make a summary of what the mold designer will feed back the product designer. However, the battle between the product designer and injection molding engineer will continue till we make the perfect product.
1. Reasonable and uniform wall thickness
Wall thickness is the first thing the mold designer will check when receiving a new project drawings. The wall thickness can’t be too think or too thick, about 2 to 3 mm will be a favorable range for the mold designer. Thick wall thickness will cause sink mark, and thin wall thickness is easy to be broken and warp.
The other suggestion mold engineers would like to tell product designers is the uniform wall thickness. The inconsistent wall thickness will bring a lot of defects. If the molten plastic flowed from thin wall area to the thick, it may not be able to fully pack the thick area. The mold designer could adjust the gate placement to make molten plastic flow from thick area to the thin. However, the thick area cools slower, which will cause the sinking or warping issue. If the thick area is necessary, the mold designer will suggest to make it hollowed and add ribs.
2. Adding ribs
For the long and wide plastic housing, the molten plastic has to take a relative long time to fill all space. The cooling rate will be different along the long and wide part, which will produce the internal stress inside the plastic molded part. After the internal stress released, the plastic injection molded part get warped. In order to resist the internal stress, it is necessary to add ribs on the long and wide plastic part to avoid warping issue.
3. Draft
The injection molded part is ejected from the mold, the side wall, ribs and bosses must have a small draft angle for the part to be ejected smoothly. We can reduce the material on the top or increase the material on the bottom to add the draft angle, it depends on the real product.
4. Gate, ejector, slider, parting line
Mold designer would tell product designer where the gate, ejector, slider and parting line locate. All there things will leave marks on the product. Generally we will locate gate mark and ejector mark on the inner surface. Sometimes the slider mark will appear on the outer surface, for cosmetic need, we will try to optimize the mark by adding the groove or changing the geometry a little bitter.
Parting line mark appears on the outer surface of the injection molded part. If the part has a high cosmetic requirement, the parting line should be made as invisible as possible. The injection mold should be made very precision to reach the requirement.
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