Thick Gauge Vacuum Forming of Ventilation Shrouds in Truck And Bus at 6 mm

Vacuum formed ventilation shrouds are used across truck and bus 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 UV stabilised HDPE sheet is formed for truck and bus, 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 ventilation shrouds 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 ventilation shrouds the sheet gauge is selected from the load case rather than from habit, and UV stabilised HDPE is the material most often specified for this combination.

Typical specification

Where these parts are used

• engine tunnel covers for truck and bus
• stepwell panels for truck and bus
• interior trim panels for truck and bus
• bunk liners for truck and bus
• ventilation shrouds in general truck and bus 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: UV stabilised HDPE

UV stabilised HDPE is the standard answer for outdoor tanks, agricultural hoppers and marine hardware that see direct sun.

Design tips for this part

• 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
• avoid sharp steps in the mould, which show as chill marks on the finished surface
• keep a draft angle of at least 3 degrees on vertical walls so the part releases cleanly
• 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. Moulds, trim fixtures and programmes are stored against the part number, so a repeat order matches the first batch.

Cost and lead time

Tooling is the main cost driver at low volume, so a 6 mm ventilation shrouds for truck and bus 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 lower tooling cost 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

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.

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.

How long does tooling take?

Sample and first article tooling is usually cut in 7 to 15 working days. Production aluminium tools take 3 to 4 weeks depending on size and cooling layout.

Getting started

Send the drawing or a photo of the current ventilation shrouds 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.