Controlling heating elements in a heat tunnel

Oh, there won't be any bristles in the brush at the time of the bend.

Oh, there won't be any bristles in the brush at the time of the bend. [/quote]

Put a hole in the side or top of an oven and just stick the bristle end inside. It looks thicker where the bristles will go, so the handle will soften first. Pick a temperature somewhat above the softening temp of the plastic, then experiment with how long to leave it in the heat before you pull it out and bend it. Use an air blast or even a water spray to quench after the bend to freeze it into shape faster. Anything from a toaster oven to a surplus home oven depending on how hot and how many you want to heat at once. Convection oven would be even better, more uniform and faster heating. Or make a hinged heated block kind of like a waffle maker, with a channel where you want the bend. Open, insert, close, count to ten, open, remove, bend, quench. For that matter, dig out the waffle maker you have somewhere in a cabinet and never use, and modify that :-).

----- Regards, Carl Ijames

I wonder if one of the flexible acrylic bending heat strips would work for you. What temperature are you after? From what plastic are the handles made?

What kind of speed/daily qty are you looking for? That might drive answers more into the realm of your wishlist.

Would directed hot air be quicker?

Might be easier to generate & control too.

If 212 degrees does it, I'd use boiling water, your choice of heater. water transfers heat 50X faster than air.

Karl

Amazon sells temperature controllers at a hobbyist price (and quality??).

I heven't tried them, my collection is pre-owned Omron and Omega.

-jsw

I would use a stream of hot water. This is probably your cheapest solution and something that is safe and has no fire or environmental concerns. You would obviously recirculate the water.

Well for repeatability I'd opt for simplicity. Make up 2-3 removable forms using some light steel. U shaped channel with a pin to go through the hole. At the point you need the bend, bend the sheet metal to the correct angle. For the bending, use two heat guns with heat directors to spread the heat around the handle in the area of the bend.

Connect the guns up to a simple speed controller so you can control the heat.

In use the handle gets stuck in the form, form and handle go into air blast between guns. Heat softens the plastic enough that it bends down to match the form. Once it bends into place the operator pulls the form/handle out of the blast and sets it onto a cooling rack. Then it's simply a matter of repeating the process as needed.

Not MY waffle maker! It gets used at least once a month. I have a great recipe for waffles with flavor and just the right texture. But maybe a trip to Salvation Army...

New product, don't know. They are PVC...I think.

Yep, used a heat gun for prototypes.

Well, shit...there they are. Thanks!

And the recipe is.......

share please.

Unlikely, but possible, I guess.

I recycle all my old toothbrushes into crevice brushes by bending an angle on the whole head or half the bristles. My trusty HF butane torch leaves a nice black residue on them. That's why I didn't suggest it for your use, Tawm.

A heat gun and a spinner, then a jiggy rack to lay them on at the right angles, might be the ticket.

You make it sound so simple....

Could be. I've bent some plastics over the years...

I had to do 5 samples today, they took 3 minutes apiece to heat with my good heat gun. I can see how to do it better now.

Make up a U shaped deflector to contain and direct the heat. One gun feeding from each side OR if you don't want hot air grab some nextflex heating element, Bend it into a series of U shapes with guards and use that.