Vacuum forming explained

Here another video of how vacuum formed parts get created.

My late dad used to build a lot of vacu-formed kits in the 1980`s, but they were never satisfing to me.


Still a very useful technique for some scratch-building parts and not just aircraft canopies.

The vacuum form machine that Micro-Mark sells really does work as advertised:

Micro-Mark:: Compact Vacuum Forming Machine

I actually use mine quite a bit more than I expected.


Hi Michael, how sharp of detail will it replicate? I made some space-filler - not foreground quality - “radios” with Grandt Line bolts, washers, etc. Think it can reproduce the sharp edges of small bits and pieces? Thanks, Fred

Hi Fred you have to consider that the sharpness of the details is dictated by the thickness of the plastic. tthe thicker the plate is, the less detail you get.Tht may be the reason why mostly ship hull and aircraft kits come vacu-formed. I have only little experice with vacu-formed kit and I remember a Spähpanzer Luchs kit that I had. They didn´t even get the Continental tires right.

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As Hermann says, vacuum forming is very good for general shapes, especially complex, compound curved shapes. Any shape that will have undercuts will be problematic because the undercut will create a “key” that locks the new vacuum formed shape with the form it’s made over or into.

Sharpe edges are best made by vacuuming the plastic into the form as a “negative” mold, whereas shapes formed over the form as “positives” tend to have rounded edges.

I use my vacuum form machine to make complex basic shapes that would otherwise be difficult to hand master. It’s good for shapes like fenders, body work, or other parts that you want to have as final parts with thin, formed sheet appearances.

Here’s a series of photos showing the vacuum forming of the matching funnel-shaped pieces that make up the cooling fan for a Churchill tank. The photos are slightly out of sequence, but I’m sure you can get the general idea. The funnels or cones were made on the vacuum form machine, they were then cut out, and the details added using traditional scratch-building techniques.

These basic shapes, though, would have been very difficult to make using some other technique (maybe stretch-forming would have worked, but vacuum forming was ideal).


Hi Michael, thank you for this exceptional demonstration and explanation,. I may have more questions soon, All my best, Fred

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Happy to add my .02! I’m no expert, but I have stayed in a Holiday Inn Express at least once! LOL!

That excellent master making! Did you make the brass parts on a CNC machine? And hoy big are the parts.

I turned the brass forms on a lathe. The holes are drilled to vent air as the hot styrene is vacuumed down over the forms. This is necessary for the vacuum to suck the plastic down into areas that would create airtight pockets. (Another part design consideration for vacuum forming.

Here’re a couple of pics of the parts installed in the model, an AFV Club Churchill III:

Overall diameter of the cooling fan was around 1" (25.4mm). The pill-shaped fuel strainer cups and caps to either side of the compartment were also vacuum formed for this project.