When you need technical support - free guidelines

Written by: Rutland Plastics Ltd | Published:

Taking your design through to production requires the part to undergo ‘Design for Manufacture’. A free electronic Design Guide and accompanying Design Checklist can help anyone involved in or considering a product or part that will be injection moulded.

“We at Rutland Plastics are frequently asked questions about basic design rules for plastic moulded parts”, explains Simon Grainger, Design and Project Engineering Manager. “Whilst there are several books on the subject, the majority of people do not have time to read through them.It is hoped that much of our written advice we share online and in our design guides answers the most frequently asked questions quickly and simply”.

The following is taken from Rutland Plastics Design Checklist and forms part of a series of articles that offer help and advice in a number of areas.

Wall Thickness Uniform section where possible

Too thin = structural failure, poor insulation

Too thick = appearance defects, over weight/ over engineered, extra cost.

Thin uniform wall with ribs is generally better than a thick wall.

Coring should be employed wherever possible to reduce material content and reduce thick sections.

Any changes in section should ideally be from thick to thin. Increase in thickness should be <25%.

For any transition, sharp corners should be avoided.

Rib Guidelines

Component section = S Draft per Rib Side = A = 0.5°


Rib thickness <50% of adjoining wall thickness

Rib height < 3x adjoining wall thickness

More ribs are preferable to higher ribs

Minimum radius of 25% of adjoining wall thickness at the base of the ribs.

Spacing between ribs > 2x nominal wall thickness.

Draft of > 0.5 deg each side.

Consider texture on the surface where ribs are used to improve the appearance of the finished part.

To request your Free Design Guide and accompanying Design Checklist are supplied in electronic format, both publications are useful design tools for anyone involved in or considering a product or part that will be injection moulded.

To request your copy complete the form via the link below:


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One-off usage is permitted but bulk copying is not. For multiple copies contact the sales team.

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