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Design Guidelines of
Plastic Injection Molded Parts
Vicky LiuRespon Plastic Industrial Co.,Ltd.
Add: NO 509 Wulv Road, Tong’an Industrial Zone, Tong’an, Xiamen, ChinaZip Code:361100
Cell: 008615985829163Email: sales01@rpimoulding.comWebsite: www.rpimoulding.com
Skype: rpimoulding
Core & Cavity
Box designed through core-cavity method. Can get to features with bigger, faster cutter. Easier and faster to polish.
Coring Out
Coring out is a technique where you remove material from a plastic part, leaving distinct walls and ribs which provide enough strength and mating surfaces for other parts in the assembly to avoid shrinkage.
Radius Corners
part corners should be with a radius rather than a sharp edge to avoid being scratched.
Draft
Here are some rough guidelines to follow: We strongly advise using at least 0.5 degrees on all “vertical” faces.2 degrees works very well in most situations.3 degrees is minimum for a shutoff (metal sliding on metal).3 degrees is required for light texture (PM-T1).5 or more degrees is required for heavy texture (PM-T2).
Ejector Pins
ejector pins of various sizes are used to push the plastic part out of the mold after it has solidified.
Ribs
Deep and thin ribs should be avoided if possible. Deep ribs require draft and clearance in order to allow the milling tool access.
Deep, thin ribs tend to increase the mold milling time and make hand polishing difficult and time consuming.
Size Limitations
Size limitations are due to mold base size,injection molding machines, CNC, and other equipments.
Straight Pulls and Through Holes
A mold costs less if it is a straight pull, i.e. it doesn’t have undercuts.
A part that can be made with a straight-pull mold has all its features designed so that when the two halves of the mold pull straight away from each other, there is no mold metal that wants to pass through part plastic. Undercuts on the part require mold pieces to pull out sideways, perpendicular to the direction of pull.
Surface FinishesList of available standard finishes
PM-F0: Non-cosmetic: finish to Protomold discretionPM-F1: Low-cosmetic: most toolmarks removedPM-F2: Non-cosmetic: Protomold discretion, EDM finish and/or toolmarks permissibleSPI-C1: 600 grit stone, 10-12 RaPM-T1: Protomold texture, SPI-C1 followed by light bead blastPM-T2: Protomold texture, SPI-C1 followed by medium bead blastSPI-B1: 600 grit paper, 2-3 RaSPI-A2: Grade #2 Diamond Buff, 1-2 Ra
Higher Cost
Polishing: Smoother part surfaces are achieved using manual mold polishing techniques.
Texturing: Given the line-of-sight nature of bead blasting. To avoid “drag marks” , bigger draft shoud be applied.
Undercuts
Side-Action Support is usually used for unavoidable Simple Undercuts. i.e. Angle Lifters, Sliders.
Wall thickness uniform
Maintain consistent wall thickness can avoid sink marks and part wrapage.
Thicker and non-uniform wall thicknesses can often result in sinks in the material
Gussets provide additional support to reduce warpage
Thin ribs on thicker walls may provide stiffness but also can result in sinking on the outside of the wall. To prevent sink, the thickness of the rib should be about half of the thickness of the wall.
Recommended Wall Thickness by Resin Type
For helps, pls get in touch with us:• Vicky Liu• Respon Plastic Industrial Co.,Ltd.• Add: NO 509 Wulv Road, Tong’an Industrial Zone, Tong’an, Xiamen,
China• Zip Code:361100• Cell: 008615985829163• Email: sales01@rpimoulding.com• Website: www.rpimoulding.com • Skype: rpimoulding
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