Plastic part design rules or design guides

It is essential to have a plastic part that is designed by design guides of injection moulding.

Before we start the tooling process, we will check your product parts if they are feasible and producible for tooling; Hereunder is a list of part structure aspects that we will check..

  1. Draft angles: Does your part have draft angles?

Your part must have at least 0.5 degrees of draft angles parallel at the parting direction (in the direction of the mould opening) to facilitate easy withdrawal from the mold . Better is to have a draft angle of 1-2 degrees to eject the part easily out of the mould. When the product has a texture add 1.5 degree for each 0.025 mm texture-depth.

  1. Uniform Wall thickness, is your part of the same thickness at all areas?

An uniform wall thickness will ensure uniform cooling and reduce defects, like warping . Also make sure the wall thickness isn't too thick and can be decreased where necessary. Core out thick sections. When you feel the part needs to be stiff, use ribs instead of thick walls. also, it injection time is shorter when using parts with smaller wall thicknesses. (short cycle times)

  1. Sprue-point or gate location: where is your gate location positioned?

The best position of your gate location is on a thick part, so the shrinkage will be more uniform.

  1. Radius/Radii

Make sure there are no sharp corners, make round corners to prevent stress concentration. The inside corner radius should be a minimum of one material thickness.

  1. Ribs

Consider the use of ribs instead of making a part thicker. Use ribs to make parts stiffer, make sure base thickness of Ribs should be 60% of the nominal wall thickness or less. The height of the ribs should be not more than 3 times the wall thickness

  1. Bosses.

The wall thickness of a boss should also not be more than 60% of the wall thickness of the attached wall

Other Concerns:

  • Lettering
  • T-junctions

  • Wall thickness material strength

  • transitions

    All holes will create a weld line. (Quality concern)
    Any depression that passes 2/3 of the way through the wall will create a weld line.
    Irregularly shaped or square holes are not recommended.
    The space between two holes should be the greater of two times the wall thickness or two times the hole diameter.

  • In the text above you have read some plastic design guides or rules, if you know another design rule, please let us know. and if you wish a plastic part designer and mold design team please visit or mouldplastic web