Softening plastic with heat - what should I use?

[TallTony]

Hi, I hope this is an appropriate place to ask - for a work project I need to soften a stick of plastic (polypropylene, 2mm think) and stick onto another piece of plastic at an angle.

So I need a heat source that does not use a flame and can be repeatable/controllable.

I was thinking a simple hot-plate would suffice but ideally I want something small so that risk of my staff burning themselves is small. a lot of modelling is delicate and micro, I was wondering if anyone could make any suggestions

Thanks, Tony

[Eric Mc]

Hair drier?

[dr_gn]

If I understand what you're doing (plastic welding), you'd be better applying heat directly to the joint with something like a thermostatic controlled soldering iron. The technique can be used for scale models - you could buy a modelling welding kit back in the 70's, but never caught on for fine work.

There are videos on welding polypropylene online if you do a search.

[sunbeam alpine]

Hot air paint stripper?

[dr_gn]

If the o/p wants to join a rod to a plate using heat (I think that's what he wants to do), both parts need to be melted locally within the join.

[dr_gn]

Here's a modelling plastic welder (Airfix Magazine Feb '77!)

[TallTony]

Thanks for the replies everyone.

A little more detail...

This is for a project at work which will involve making many thousands of this part, so it needs to be a quick repeatable process. It is a project and at this stage I'm not looking to spend a huge amount, just have something that will get past H&S and be easily used. What I think would be perfect is a small desk-mounted heat source such as a mini hotplate or small hotair blower than I can rest the plastic stick against to soften. I have seen small portable single-ring ones with ceramic glass top which is perfect but the size of the heating element is whatever a cooker ring size is (20cm?). I can see there being a risk of burning oneself plus the volume of heat will be big. A 1" plate would be great.

I do like the idea of a hotair blower, I know it's handheld but can quickly be switched on and off. Shall research that one, we safely use soldering irons so it's a similar process.

[blue van]

Ultrasonic welding may do it

[CubanPete]

blue van said:

Ultrasonic welding may do it

Beat me to it! This would be my suggestion also.



Something like a hot knife used for cutting / sealing rope might work.

For a production process you need to think about fume extraction too.

[mcdjl]

Id have said laser welder but that wouldn't be cheap and would be fussy about the plastics used. Could you use a small induction hob, with a 1" bit of iron held in position. That'd get hot, but the rest stay cold and be cheap.

[Murph7355]

How big are the pieces?

If you're making "many thousands" might it be better to 3d print it or mould it as one part?

[bmw320ci]

soldering iron?

[Mr Pointy]

Here's a few options:

https://www.amazon.co.uk/Draper-78775-Flameless-He...

https://www.amazon.co.uk/Heat-Shrink-Tubing-Mini-C...

https://www.amazon.co.uk/Laser-Tools-6848-Flameles...

[Yertis]

Mr Pointy said:

Here's a few options:

https://www.amazon.co.uk/Draper-78775-Flameless-He...

https://www.amazon.co.uk/Heat-Shrink-Tubing-Mini-C...

https://www.amazon.co.uk/Laser-Tools-6848-Flameles...

I've got one of those and while great for heat shrink I don't think they would be precise enough for this job.

[Yertis]

But this is of interest to me having recently botched up a piece of trim on the TR when I'd just finished putting a whole bunch of stuff back together, and have found a whole family of new tools to fascinate me on eBay – plastic welding rod? Never knew such a thing existed.