Design Guide for PETG Pressure Formed Precision Parts in automotive and mobility: Draft, Radii and Draw Ratio

Thermoforming rewards designs that respect how a heated sheet stretches. These rules prevent most tooling rework and most thickness complaints.

Use it as a working checklist when you write your next enquiry.

Product Overview

This category covers a family of products rather than a single item. In practice a buyer defines pressure formed precision parts by three things: the base resin, the format or dimension, and the performance or certification level it has to meet. Typical options in this category include textured in-tool surfaces; sharp detail and crisp radii; gauge 1.0 to 6.0 mm. Materials most often specified are Polypropylene, PC/ABS Alloy, Polyethylene Terephthalate Glycol, Acrylonitrile Butadiene Styrene, and the choice between them changes stiffness, temperature resistance, chemical behaviour and price.

In the automotive and mobility sector the decision is usually driven by dimensional stability and heat resistance, with impact strength as a secondary requirement. Typical end uses include commercial vehicle trim, line side trays, interior panels.

Key Material Properties

The table below summarises the values that usually decide the material choice.

Polyethylene Terephthalate Glycol is frequently the default selection here: PETG forms at lower temperatures and holds detail well, which is why it dominates medical trays.

Design Rules for Thermoformed Parts

Thermoforming rewards designs that respect how the sheet stretches. These rules prevent most tooling rework.

• Design uniform wall thickness by avoiding abrupt depth changes in the same cavity.
• Use a draft angle of at least 3 degrees per side so the part releases without vacuum locks.
• Leave a flat sealing flange of at least 6 mm when the pack has to be heat sealed or lidded.
• Add ribs, steps or kiss-offs instead of increasing overall gauge to gain stiffness.
• Avoid undercuts unless the tool has moving sections, which adds cost to every cycle.
• Keep the draw ratio moderate: deep cavities thin the sheet and force you to start with a thicker gauge.

Send these rules to your designer together with the sheet gauge and the target cycle time; most tooling modifications come from ignoring draft and corner radii.

Common Grades and Variants

• Polypropylene based: lowest density among commodity plastics
• PC/ABS Alloy based: balances PC toughness with ABS processability
• Polycarbonate based: outstanding impact strength (250x glass)
• Polyethylene Terephthalate Glycol based: excellent clarity with no stress whitening

Beyond the base resin, most suppliers offer UV stabilised, food contact, flame retardant, anti-static and recycled content versions of the same product. Ask which additive package is included, because it is often the difference between a part that lasts three years and one that lasts ten.

Processing and Finishing Options

Processing method drives both cost and performance, so it should be fixed early in the design.

• Texturing
• Painting
• Cnc trimming
• Pressure forming

Secondary operations such as printing, welding, machining and assembly are often cheaper to do in the same factory, and they reduce the risk of mismatch between components.

How to Specify Pressure formed precision parts Correctly

Use this checklist when comparing two or three supplier quotations.

1. plan CNC trimming for critical features
2. confirm the achievable tolerance in writing
3. validate the paint or coating adhesion
4. use pressure forming when crisp detail is required
5. check texture uniformity on vertical walls

Send this list to your supplier with the drawing and you will receive comparable quotations from every factory you contact.

Frequently Asked Questions

Do you offer samples?

Yes. Standard samples are normally free of charge and shipped within three working days; custom samples are charged at cost and credited against the first production order.

What is the minimum order quantity for pressure formed precision parts?

For standard sizes and colours the minimum is usually one pallet or one production run; for custom tooling the economic minimum depends on the tooling cost amortised over the expected volume. Send us your annual volume and we will calculate the break even point.

Which certifications can you provide?

We can provide ISO 9001 quality system documentation, material certificates, RoHS and REACH statements, and where applicable food contact, flame retardancy or drinking water approvals. Tell us your target market and we will match the document set.

What tolerance can be achieved?

Standard production tolerance follows the relevant ISO or DIN tolerance class for the process; tighter tolerances are possible after machining or grinding, but they add cost. Define the tolerance only on the functional dimensions.

How do you control colour consistency?

Colour is controlled with a masterbatch reference approved by the customer, and every production lot is checked against the approved sample under standard lighting before shipment.

Conclusion

Share your specification and quantity with us and we will recommend the most cost effective material, tooling route and packing method for your market.