Custom Tank Covers Thermoforming in food grade polypropylene for Food Processing at 6 mm

Vacuum formed tank covers are used across food processing because they can be produced without the tooling spend of injection moulding and without the weight of sheet metal. This page covers how 6 mm food grade polypropylene sheet is formed for food processing, what tolerances are realistic, and what has to be on the drawing before tooling starts.

The route below is the one used for most of the tank covers shipped from this plant: sheet is heated on the forming machine, drawn over an aluminium or composite mould, cooled on a jig, then trimmed on a 5-axis router. For tank covers the sheet gauge is selected from the load case rather than from habit, and food grade polypropylene is the material most often specified for this combination.

Typical specification

Where these parts are used

• conveyor guards for food processing
• mixer covers for food processing
• product trays for food processing
• washdown panels for food processing
• tank covers in general food processing builds

How the part is made

1. Drawings are reviewed and a manufacturability report is issued with wall thickness, draft and radii marked up.
2. Tooling is cut: aluminium for production volumes, composite or printed moulds for samples and first articles.
3. Sheet is dried when the material needs it, then heated to forming temperature on the machine.
4. The sheet is formed over the mould with vacuum and, where the draw is deep, with plug assist.
5. The part cools on a jig so the shape is held while the material stabilises.
6. Trimming is done on 5-axis routers or with a dedicated trim fixture to meet the drawing.
7. Parts are inspected, fitted with inserts or hardware if required, packed and shipped.

Material notes: food grade polypropylene

Food grade polypropylene is used for trays, hoppers and liners that touch product, and it can be washed with caustic cleaners.

Design tips for this part

• hold the draw ratio near 1:1 for deep parts, or specify plug assist
• keep a draft angle of at least 3 degrees on vertical walls so the part releases cleanly
• call out the finish on the drawing: mould texture, paint, or as-formed gloss
• plan the trim line on a flat face so the router can hold tolerance
• add ribs or returns instead of increasing sheet thickness to save weight and cycle time

Quality and inspection

Moulds, trim fixtures and programmes are stored against the part number, so a repeat order matches the first batch. Batch releases carry a dimensional report, material certificate and, where agreed, PPAP or ISIR documentation.

Cost and lead time

Tooling is the main cost driver at low volume, so a 6 mm tank covers for food processing is usually quoted with a composite or printed mould first and the aluminium tool cut once the design is frozen. That keeps the first article cost low and gives a real part to test before the production tool exists. The result is lighter weight compared with the alternatives, and a piece price that stays stable across repeat releases.

• Sample tooling: 7–15 working days
• Production tooling: 3–4 weeks
• Repeat orders run on stored tooling with no new proving run

Frequently asked questions

What do you need to quote?

A 3D file or drawing, the material if it is fixed, the annual quantity and the finish. Photos of the current part are enough for a first estimate.

What quantities make sense?

Vacuum forming pays off from roughly 25 pieces up to several thousand a year. Below that, printed or composite tooling keeps the setup cost low.

Do you supply certificates?

Material certificates, dimensional reports and flame retardancy or food contact declarations are issued with the shipment where the specification requires them.

Getting started

Send the drawing or a photo of the current tank covers with the quantity and the finish. The first reply is a manufacturability review with the wall thickness, material and a quotation, so the decision is made on facts rather than on a price alone.