Design Guide for PP Twin Sheet Thermoformed Products in industrial equipment: 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.

This guide is written for engineers, purchasers and project managers who need a practical answer, not a resin data sheet.

Product Overview

This category covers a family of products rather than a single item. In practice a buyer defines twin sheet thermoformed products 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 both sides; gauge 2.0 to 8.0 mm; hollow double wall structures. Materials most often specified are High Density Polyethylene, Polypropylene, Polycarbonate, PC/ABS Alloy, and the choice between them changes stiffness, temperature resistance, chemical behaviour and price.

In the industrial equipment sector the decision is usually driven by thick gauge capability and flare and fire rating, with paintability as a secondary requirement. Typical end uses include kiosk shells, machine housings, twin sheet panels.

Key Material Properties

Typical values for a general purpose grade are listed below; filled, stabilised and speciality compounds will differ.

Polypropylene is frequently the default selection here: PP is the lightest mainstream packaging resin and keeps its shape under repeated flexing.

Design Rules for Thermoformed Parts

Apply these points before the tool is cut; after that every change costs tooling and time.

• Make corner radii at least equal to the sheet thickness; sharp corners are where holes start.
• 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.
• Confirm the trim method early: steel rule die, CNC router or press tool each have different tolerances.
• Use a draft angle of at least 3 degrees per side so the part releases without vacuum locks.
• Design uniform wall thickness by avoiding abrupt depth changes in the same cavity.

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

• PC/ABS Alloy based: balances PC toughness with ABS processability
• Polypropylene based: lowest density among commodity plastics
• High Density Polyethylene based: high impact strength even at low temperature
• Polycarbonate based: outstanding impact strength (250x glass)

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

The route below is the one most factories use for this type of part.

• Twin sheet forming
• Assembly
• Pressure forming
• Welding

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 Twin sheet thermoformed products Correctly

These are the criteria that actually predict whether the part will perform in service.

1. confirm the pinch-off design with your moulder
2. check flatness of large panels
3. specify wall thickness on both sheets
4. validate the weld strength with a burst or drop test
5. design mounting features into the twin sheet structure

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

Frequently Asked Questions

What is the minimum order quantity for twin sheet thermoformed products?

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.

Can you produce twin sheet thermoformed products in Polypropylene?

Yes. {mat1} is one of our regular materials for this item, and we can supply virgin, modified and certified grades with full traceability. Material certificates and test reports are issued per batch.

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.

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.

What packing and shipping options are available?

Standard packing is export cartons on fumigation-free pallets, with custom labelling, barcode and retail packing available. We also handle consolidated containers and door to door delivery.

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.