Thick Gauge Vacuum Forming of Hoppers in Agricultural Machinery at 6 mm

Vacuum formed hoppers are used across agricultural machinery 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 LDPE sheet is formed for agricultural machinery, 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 hoppers 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 hoppers the sheet gauge is selected from the load case rather than from habit, and LDPE is the material most often specified for this combination.

Typical specification

Where these parts are used

• hopper liners for agricultural machinery
• tractor hood panels for agricultural machinery
• cab interior trim for agricultural machinery
• fertiliser tank covers for agricultural machinery
• hoppers in general agricultural machinery 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: LDPE

LDPE is flexible and tough in thin section, used for liners and protective covers that have to bend during fitting.

Design tips for this part

• keep a draft angle of at least 3 degrees on vertical walls so the part releases cleanly
• avoid sharp steps in the mould, which show as chill marks on the finished surface
• use corner radii of at least three times the sheet thickness to avoid thinning
• add ribs or returns instead of increasing sheet thickness to save weight and cycle time
• hold the draw ratio near 1:1 for deep parts, or specify plug assist

Quality and inspection

Sheet thickness is checked on the formed part at the points shown on the drawing, and the readings go into the report. First article inspection covers critical dimensions, wall thickness, colour and texture against the approved sample.

Cost and lead time

Tooling is the main cost driver at low volume, so a 6 mm hoppers for agricultural machinery 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 repeatable quality 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 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.

Can you match an existing part?

Yes. Send a sample or scan and the part can be reverse engineered, with the wall thickness and material measured from the sample.

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.

Getting started

Send the drawing or a photo of the current hoppers 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.