Design Guide for rPET 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; tamper evident tear strips; full colour printed inserts. Materials most often specified are Polyvinyl Chloride, Polystyrene, Recycled PET, Polypropylene, 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, garden tool packs, drill bit cards.

Key Material Properties

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

Recycled PET is frequently the default selection here: Food-grade rPET requires a recognised recycling process plus solid-state polycondensation.

Design Rules for Thermoformed Parts

A few geometry decisions made on the drawing save weeks of tooling adjustment later.

• Confirm the trim method early: steel rule die, CNC router or press tool each have different tolerances.
• 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.
• Leave a flat sealing flange of at least 6 mm when the pack has to be heat sealed or lidded.
• Use a draft angle of at least 3 degrees per side so the part releases without vacuum locks.

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
• Recycled PET based: lower carbon footprint than virgin resin
• Polyvinyl Chloride based: inherently flame retardant
• Polypropylene based: lowest density among commodity plastics

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
• Rf sealing
• Die cutting
• Twin sheet 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 Clamshell blister packaging Correctly

Use this checklist when comparing two or three supplier quotations.

1. check the pack passes the retail drop test
2. specify the closure type and tamper evidence level
3. test the hinge for at least 20 open-close cycles
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 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.

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.

What is the minimum order quantity for clamshell blister packaging?

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.

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.