Design Guide for PET Clamshell Blister Packaging in hardware and tools: 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 clamshell blister packaging 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 gauge 0.30 to 0.80 mm; full colour printed inserts; hinged single piece designs. Materials most often specified are Polypropylene, Polyvinyl Chloride, Polystyrene, Recycled PET, and the choice between them changes stiffness, temperature resistance, chemical behaviour and price.

In the hardware and tools sector the decision is usually driven by puncture resistance and hanging strength, with visibility as a secondary requirement. Typical end uses include plumbing blisters, fixing packs, hand tool clamshells.

Key Material Properties

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

Polyethylene Terephthalate is frequently the default selection here: High IV PET resin is the reason a 1.5 L bottle can be light yet hold carbonation pressure.

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.
• Confirm the trim method early: steel rule die, CNC router or press tool each have different tolerances.
• Leave a flat sealing flange of at least 6 mm when the pack has to be heat sealed or lidded.
• Avoid undercuts unless the tool has moving sections, which adds cost to every cycle.
• 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

• Polystyrene based: rigid and glossy
• Polyethylene Terephthalate based: excellent barrier to CO2 and moisture
• Polypropylene based: lowest density among commodity plastics
• Polyvinyl Chloride based: inherently flame retardant

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

Each step below has its own control points, and skipping one of them is where most defects start.

• Vacuum forming
• Twin sheet forming
• Pressure forming
• Die cutting

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 Clamshell blister packaging Correctly

Use this checklist when comparing two or three supplier quotations.

1. test the hinge for at least 20 open-close cycles
2. check the pack passes the retail drop test
3. specify the closure type and tamper evidence level
4. avoid sharp internal corners at the hinge
5. confirm the trim method to avoid sharp edges

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

Frequently Asked Questions

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 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.

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 long does tooling and sampling take?

A new tool typically takes 25 to 45 days depending on cavity count and complexity, followed by T1 samples within one week. Existing tools can usually start production within 10 to 15 days of order confirmation.

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.

Conclusion

If you are planning a new hardware and tools project, send us your drawing, annual volume and target properties, and we will come back with a material proposal, a tooling plan and a budget quotation.