Heat bending without a Heat strip bender


#1

Hi,

any idea of how to bend the main body without buying a Heat strip bender and without building one?

I was thinking of heating and oven metal sheet to 150C (300F) and then place it over the plastic on the spot we want to bend it.

I don't have plastic to test at the moment, but do you think it might work?


#2

Not sure about in the EU but you can get these pretty cheap in the US: http://www.amazon.com/Craftics-24-Plastic-Strip-Heater/dp/B003GUPFPG/ref=sr_1_1?s=hi&ie=UTF8&qid=1343083427&sr=1-1&keywords=strip+heater

I know that Eric and David have used the ones at TechShop but I've ordered one like this for testing as it can heat and bends Acrylic materials up to 1/4" thick

-t


#3

Thank you. I was frightened by the price of the tool suggested by Eric and David in the assembly instructions :slight_smile:
This one for 40USD is pretty cheap indeed. Now have to find one in Europe as Amazon doesn’t ship to EU these products, and the EU Amazons don’t have DIY products.
Simo


#4

Wow... that's crazy.

I think in Europe (or at least in Italy) they have no idea of the existence of such tools: all the guides (also professional hobbists) explain various randoms method of bending, like putting it in the oven, heating with heat guns, place on top of the heat produced by a bonfire, and so on...

I guess I'll go with a heat gun, that might also come of use in other circumstances (like desoldering)


#5

Yeah I was looking into options here too- what came to mind for me was putting two wood blocks over the acrylic with a narrow slit between them over the area to bend. The blocks would insulate the parts you want to stay flat so that if you heat across the slot with a heat gun it would bend along that line. Let us know what you find in your experimentation!


#6

Hey there,

Did some test bending today. Worked pretty good.
http://www.code-with-passion.com/2012/08/05/bending-acrylic-the-dyi-way/

I used a soldering torch.

Going to bend the real body probably this week.


#7

Glad it works out even without the strip bender. I’ve read that you have not to melt the plastic, as when melting it changes physical characteristics and, furthermore, the melting produces toxic fumes.
Maybe you can lower a bit the temperature of the torch.

Simo


#8

Rather than trying to custom build a box shape, wouldn't it be easier to base the design around some kind of standard heavy duty plastic box which is readily available, cheap and easy to obtain worldwide? Any DIYer could then just cut sections out of that box to make it the right shape using basic hand tools.

These boxes spring to mind as the right sort of thing:

http://www.solveneeds.com/LinBins.php


#9

See answer to the same comment in the blog post :slight_smile:
Cross posting is never a good thing :slight_smile:


#10

I used a setup similar to many other home-bulit acrylic benders and foam cutters on the internet with nichrome wire.

The design is simple, requires some wood, nichrome wire, spring/screws, and a 30-40W 12 Volt power supply (you could use a computer power supply).

The wire then runs 2-3 mm below the plastic which is supported by wooden platforms on either side. The nichrome wire then heats to ~1100F which then nicely slowly softens the plastic above. The heating step requires approximately 6 minutes.


Total cost if you have the power supply at home is roughly ~8$+shipping on ebay for the nichrome wire and a few bucks for spring/odds and ends.

For rough calculations there is a nice nichrome heat/power calculator here:

http://www.jacobs-online.biz/nichrome/NichromeCalc.html


#11

Christopher, what gauge/diameter is your nichrome wire?

It looks quite thick!? And how much change in length does it have? is the spring really required?

Thanks for the link btw!

Cheers

Dominik


#12

I used 28 gauge wire, approximately 12 inches in length. I just used the spring as many people have commented on the length change, but you can’t see it visually while it heats… It would probably work without it.


#13

Thanks,

got some smaller gauge, so will have to go for a shorter length. But I need it just for the ROV anyway :)

Cheers


#14

Hey all-


I noticed a lot of interest in this so I decided to try the two-wood-block idea this morning and it worked great! Here's how to do it:

Parts needed:

1) Two wood blocks (here in the US, I used 2" x 4" cross section wood, but anything close to that should work). Ideally the blocks will have hard, unrounded edges so that hot air does not escape under the blocks.

2) A heat gun that can go to a temperature of 950 degrees F (or around 500 degrees C if you use real units)

3) A piece of scrap cardboard

4) A test piece of acrylic (you'll want to try this out first to see what wood spacing, temperature setting, and exposure time work best for your conditions)


Step 1:

Place the piece of acrylic on top of the cardboard with the face you want to be on the outside of the bend facing up and position the two wood blocks on top of the acrylic so that a slit with a width of about 3mm goes over the area you want to bend. If you have additional 3mm thick acrylic, you can use it to separate the blocks and assure they are parallel.


I realized I needed to take a photo of this afterward, so a different piece of scrap acrylic is shown in the image above


Step 2:

Turn on the heat gun and set it to around 500 degrees C. Actually, I never tried another setting- this just seemed "about right" but hotter or colder may work better. Hold the heat gun nozzle about 2 cm above the opening of the slit and move back and forward across the entire length (actually go a bit beyond entire length) of acrylic underneath the slit at a rate of no less then about 2cm/ sec. The silt will duct the hot air across the acrylic, but it will still be hottest directly below the nozzle, and you'll want the plastic to be heated evenly. Do this for about 3 minuets (again, I haven't really experimented with this so more time might work better).


Step 3:
Once you've sufficiently heated the acrylic, set the heat gun down, remove the blocks of wood, and pick up the acrylic. An early sign that it is ready to bend is that the acrylic will look a bit distorted where you heated it. Pick up the acrylic and slowly bend it away from the side you heated (the plastic will stretch to make an outer radius more easily on the hotter side). If heated properly, the plastic should be easily bendable by hand without much more effort needed then it would take to bend a coat hanger. Bend a few degrees past square since there will be some elasticity and it's nicer if the sides spring in toward the ROV structure anyway.

Step 4:
Smile at what a wonderful job you've done and get some ice cream to celebrate. Since this way of bending is not extreamly precise, the slots on the shell may not line up perfectly with the tabs on the structure. This can be remedied by using a shop file to extend the slots appropriately, and it is no cause to cancel your ice cream celebration!



#15

That’s a great instructional, should be in the wiki too :slight_smile:


#16

Done!

http://wiki.openrov.com/index.php/Assembly#Bending_the_Outer_Shell


#17

Used your approach to bend my ROV. THANK you!

http://www.code-with-passion.com/2012/08/30/say-hello-to-the-openrov-054-body/

Soon on the OpenROV blog and wiki


#18

Maybe it’s better if we reorganize the wiki a bit :slight_smile:
Will do that today


#19

Hi Simone
Video


#20

I do not understand German: what is he using as heating in the first example?