Design Guide for PP Clamshell Blister Packaging in retail and merchandising: 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.

The notes below come from day to day production and export work with overseas buyers.

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; snap lock, button lock and RF seal closures; tamper evident tear strips. Materials most often specified are Recycled PET, Polystyrene, Polypropylene, Polyvinyl Chloride, and the choice between them changes stiffness, temperature resistance, chemical behaviour and price.

In the retail and merchandising sector the decision is usually driven by shelf presentation and print quality, with stack strength as a secondary requirement. Typical end uses include promotional packs, dump bins, shelf trays.

Key Material Properties

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

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

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

• Make corner radii at least equal to the sheet thickness; sharp corners are where holes start.
• 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.
• Keep the draw ratio moderate: deep cavities thin the sheet and force you to start with a thicker gauge.
• 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.

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

• Recycled PET based: lower carbon footprint than virgin resin
• Polyvinyl Chloride based: inherently flame retardant
• Polyethylene Terephthalate based: excellent barrier to CO2 and moisture
• Polystyrene based: rigid and glossy

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.

• Die cutting
• Vacuum forming
• Twin sheet forming
• Rf sealing

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

Work through these points in order and most specification mistakes disappear.

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

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.

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.

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 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.

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.

Conclusion

Our team supplies clamshell blister packaging to retail and merchandising customers worldwide, with samples, material certificates and full inspection reports available before mass production.