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