Design Rule for Injection Molding
The products using injection molding technology are around us, which nearly can be found everywhere.
The most common materials for injection molding are PP, ABS, PE, PS, PU, PA6, PC, POM, PEEK
Injection molding is a formative manufacturing technology which can be the most cost-saving method used in mass production.
The benefits of the injection molding are summarized as below:
1. Mass production of plastic-Injection molding is the most cost-saving technology for manufacturing large volume same plastic parts, compared to CNC machining.
2. Wide range of materials can be used. Many variety of plastic materials can be used for injection molding. Therefore, the parts can meet a lot of physical properties of materials.
3. High productivity-Injection molding can production a number of parts in a very short time, compared to CNC machining and 3D printing.
4. Great repeatability and tolerance - Injection molding process have relatively repeatability with capability of producing totally identical parts. Some injection mold even have 300,000-1000,000 cycles. Injection molding is able to produce parts with tolerance from 0.1-0.05mm.
5.Nice appearance - The parts manufactured by injection molding can be with mirror-like effect or textured surface and don't need extra finishing.
Injection molding have a lot of advantages but the limitations can't be avoided.
The limitation of injection mold
1. High cost for starting up a mold - Every part need custom mold for mass production and the start-up cost is very high.
2. It is costly to change the design of mold. If the design of mold is not properly at the first time, the changing cost is relatively high.
3. Having longer lead time - The time for making a mold is usually 30-40 days and there will be extra time for mass production depending on the quantity.
Though it is the most cheap way for manufacturing volume products, the expense of the mold making is pretty high.
What's more, some common defects in injection molding will occur. The defects are included as below:
1.uneven wall thickness will cause warping.
2. Sink marks may appear on surface.
3. Scratch will occur when demolding.
4. Air in the mold will result in short shots.
Therefore, acknowledging the rules for right injection molding design is essential.
Below are some useful methods for designing the injection mold to avoid defects. Taking the below design tips for reference and following them can help you avoid some mistakes in making mold.
1. Choose even and smooth wall thickness.
Customizing the wall thickness in 1-3 mm to avoid warping and sinking.
2. Add chamfer or round edge on transition areas.
When there is different thickness section in a part, chamfer can be used to make transitions flexible and smooth. Adding round edges can have constant wall thickness as well.
3. Add draft angle.
Daft angle will make easy for demolding and prevent scratch during ejection, for parts taller than 50 mm, increasing the draft by 1° for every 25 mm, for parts with a textured finish, increasing the draft by an extra 1°-2°
In order to optimize your budget, the keys below maybe useful for you to decrease your expense on starting up your mold.
Keys to cutting the cost of injection molding.
1. Using straight-pull mold.
2. Minimize the part volume by reducing the wall thickness.
3. Use the same mold for parts in same material.
Above are the guide and tip for designing mold, hope it can be helpful for you.
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