Design Guidelines

Injection Molding Cost Calculator
Online Quotes in 30 Seconds
  • The world’s only 30-second injection molding quote
  • Parts shipped in as little as 15 days

Get your 30 second quote now

Used by 10,000 companies. Save 30-50% on molds.
By Jeremy Losek, Sep 14th, 2021

Injection Molded Plastic Part Design Guidelines

For design engineers who are new to designing for plastic injection molding, there can be a knowledge gap in making sure the CAD model is properly designed for this manufacturing process. There are certain, very specific design features that must be considered in the design stage in order to avoid moldability issues that can produce undesirable results in the molded parts. If they’re not considered from the beginning of the design process, and they’re not discovered until the Design For Manufacturability (DFM) review, design changes can add time and cost to an injection molding project.

Draft angle is one example. If a part does not have draft angle designed into it where needed, it may not eject from the mold cleanly and smoothly, and the part will have to be redesigned with proper draft angle.

To help avoid costly and time-consuming design mistakes, we created a plastic injection molding design guide. It provides information on the most important design requirements so they can be incorporated at the initial design stage. The sample tips below illustrate the type of information provided in the complete guide. Download the complete design guide by filling out the form below.

plastic injection molding basic injection molding design guidelines


Plastic Injection Molding Part Guidelines
Proper Design of Bosses
Plastic Injection Molding Part Guidelines

Bosses find use in many part designs as points for attachment and assembly. The most common variety consists of cylindrical projections with holes designed to receive screws, threaded inserts, or other types of fastening hardware. Generally, the outside diameter of bosses should remain within 2.0 to 2.4 times the outside diameter of the screw or insert

It is suggested avoiding bosses that merge into sidewalls because they can form thick sections that lead to sink. Proper bosses should be positioned away from the sidewall, and if needed, use connecting ribs for support. Try using open boss designs for bosses near a standing wall.


Plastic Injection Molding Part Guidelines
Plastic Injection Molding Part Guidelines

Normally, the boss hole should extend to the base-wall level, even if the full depth is not needed for assembly. Shallower holes can leave thick sections, resulting in sink. Deeper holes reduce the base wall thickness, leading to filling problems, knit lines, or surface blemishes. Because of the required draft, tall bosses (those greater than five times their outside diameter) can create a filling problem at their top or a thick section at their base.

Plastic Injection Molding Part Guidelines

ICOMold is a Leader in Plastic
Injection Molding for US Companies

Manufacturing Locations Across National Time Zones
The Fathom Advanced Manufacturing Platform
HEADQUARTERS

1050 Walnut Ridge Drive
Hartland, WI 53029
ISO 9001:2015
AS9100:2016
ITAR

ARIZONA

444 W. 21st St. Ste. 101
Tempe, AZ 85282
ISO 9001:2015
NIST800-171 Compliant
ITAR

COLORADO

7770 Washington St.
Denver, CO 80229
ISO 9001:2015
ITAR

MINNESOTA

13758 Johnson Street NE
Ham Lake, MN 55304

TEXAS

1801 Rowe Lane
Pflugerville, TX 78660
ISO 9001:2015
AS9100:2016

1513 Sam Bass Rd
Round Rock, TX 78681
ISO 9001:2015
ISO 13485:2016

CALIFORNIA

620 3rd Street
Oakland, CA 94607
ISO 9001:2015 Design Certified
NIST 800-171 Compliant
ITAR

FLORIDA

14000 N.W. 58th Court
Miami Lakes, FL 33014
ISO 9001:2015 Design Certified
ISO 13485:2016


 

NEW YORK

1920 Slaterville Rd
Ithaca, NY 14850
ITAR

401 W. Shore Blvd.
Newark, NY 14513
AS9100:2016
ISO 9001:2015
ITAR

ILLINOIS

1207 Adams Drive
McHenry, IL 60051
ISO 9001:2015

1401 Brummel Ave
Elk Grove, IL 60007
ISO 9001:2015 Design Certified