I found a Thule Motion XT cargo box that has a large dent and crack in it. I learned from a documentary manufacturing video on how Thule cargo boxes are made that they are essentially

utility grade all-purpose acrylic. The acrylic pieces are heated in a massive rotary oven the...where the material is heated to roughly 340 degrees. After being heated in the oven the acrylic has gone from sturdy to pliable perfect for vacuum molding

I'm wondering if a standard heat gun could focus enough hot air into a corner of the cargo box to make it pliable enough to push out a dent with. It looks like 340 degrees is the target spec. Might be tough to achieve that with outdoor temperatures and a breeze I'd imagine. Anyone know what's possible with a heat gun for making plastic pliable again, specifically acrylic?

Worth sharing the following details on acrylic for others who may come across this

What are the Characteristics of Acrylic (PMMA)?

Now that we know what it is used for, let’s examine some of the key properties of Acrylic. PMMA is classified as a “thermoplastic” (as opposed to “thermoset”), and the name has to do with the way the plastic responds to heat. Thermoplastic materials become liquid at their melting point (160 degrees Celsius in the case of Acrylic). A major useful attribute about thermoplastics is that they can be heated to their melting point, cooled, and reheated again without significant degradation. https://www.creativemechanisms.com/blog/injection-mold-3d-print-cnc-acrylic-plastic-pmma

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    Just because they made it that way, doesn't mean you can alter it. Some plastics are thermoset, meaning heating them once cures them for good. Others are thermoplastic, meaning they can be reshaped more than once. – Harper - Reinstate Monica Dec 7 '19 at 20:16

YES a common "garage" type heat gun will heat up the material enough to reshape it. In fact, I know from experience that many household heat guns will heat up plastic enough to melt it, so be very careful.

You say the dent is "large" but with no detail. I would say you could, with a helper, probably un-dent a fairly large area by pusing/shaping while simultaneously heating. But I am sure there are limits so it would depend on your "large".

P.S.-There is no such thing as a "standard heat gun"; they come in all sorts of wattage/heat level configurations.


As it turns out heat guns can have a tremendous temperature range. I bought a used Wagner Furno 500 Heat Gun and found some very explicit details worth sharing here. The unit has a variable temperature and fan range and boasts a temperature range of 150°F - 1200°F using 1500 Watts of power across 6 heat settings and 3 fan settings.

Wagner Furno 500 Box Front face close up of technical data

An interesting feature of this specific unit is the recommended settings for different applications as well as the actual temperatures corresponding to the different setting levels. I overlaid the temperature range sticker from the power cord over the image of the unit itself

Level 1     200°F
Level 2     400°F
Level 3     500°F
Level 4     800°F
Level 5    1000°F
Level 6    1200°F

Temperature Setting Buttons and indicators

Application temperature setting guide


I had a major dent in my plastic bumper and rather than buy another one, I tried that trick after hearing about it somewhere else. It does work SOMEWHAT. You can still see that it is misshapen, it never goes back to the exact same shape, but it looks better than it did. But as said, some heat guns can get hot enough to melt it or make the paint bubble. I used one that said it got to 650 deg. F, I held it about 8 inches away and moved it fast back and forth, it popped out after about only 30 seconds.

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