The cost of injection mold is dependent on the shape or geometry of the molded part, mold steel cost including standard components, and engineering cost (labor cost). It is important to note that labor and material cost greatly varies on geographical location. Labor cost from US, EU, or Japan can be 10 to 20 times more than that of China, India or Philippines but the quality is almost same. Yes, almost same quality. Well, slightly lower but sometimes better.
Putting out the geographic factor, the mold can be classified by its precision type and usage factor. Precision types are explained below:
- High Grade (HG) molded parts are parts with all features having important functionality. The product drawings are completely detailed showing all features being dimensioned with a very tight dimensional tolerances. The general part tolerance is (+/-)0.15mm while specified tolerances are as tight as (+/-)0.02mm. Every part dimensions will be computed individually and must be remodeled into CAD to ensure accuracy and fit. The precision level of every mold part is very high because it involve a lot of fits and shut-offs. A typical example of these parts are wiring harness connectors.
- Medium Grade (MG) molded parts are parts with fewer important functional parts than HG. The general dimensional tolerance are usually (+/-)0.25mm, specified and non-specified. Functional shapes such as clip locks does not go tighter than (+/-)0.05mm. Critical parts does not exceed 50% of the total specified dimensions. A typical example of these are auto fuse box and insulators.
- Shape Parts (SP) are part where only a few shapes are functional. 3D CAD file from customer can be used directly with minimal modification for mold making. Examples are caps and covers.
Classification by usage are as follows:
|Cycles||1M and up||500K to 1M||100K to 500K||500 to 100K||Lower than 500|
|Mold base min hardness||28 HRC||28 HRC||8 HRC||mild steel or AL||mild steel or AL|
|CAV and CORE min hardness||58 HRC||48 HRC||38 HRC||30 HRC||mild steel or AL|
Molds are made differently so mold shops should have their own quotation standards. Very busy shops tend to quote higher than shops with very few jobs. The simpler mold, the better and cheaper.
Mold type and classification chart was referenced from EMAMOLD.