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Advice designing plastic bender using 0.035 nichrome coil?

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  • #16
    Originally posted by nickel-city-fab View Post

    Battery charger transformer will work, or even a variac -- I've seen fosm cutting machines setup that way. All a filament transformer is, is about 6v at several amps.
    You mean like a 12v 10A car battery charger? I guess that's not bad as a "kit spec", better than specifying a variac! But I though most of them are "smart" at this point, and might not take kindly to being put on a PWM dimmer if 12v isn't exactly right.
    Location: Jersey City NJ USA

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    • #17
      Originally posted by gellfex View Post

      You mean like a 12v 10A car battery charger? I guess that's not bad as a "kit spec", better than specifying a variac! But I though most of them are "smart" at this point, and might not take kindly to being put on a PWM dimmer if 12v isn't exactly right.
      Yep, thats why I avoid the smart chargers like the plague that they are. Straight up old school transformer models are just fine. The mechanic at my old job swears by this one: https://www.harborfreight.com/210402...art-63423.html

      Says its the best thing because it isn't smart (he does a lot of European cars with electronics)
      25 miles north of Buffalo NY, USA

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      • #18
        If you live anywhere near a Signmaker's business, then trot along and ask him to show you the gizmo that is used widely with-in that industry for bending ANY plastics.

        They use this heat source for bending big sheets of Acrylic, or as you lot call it - Perspex, works like a charm too.

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        • #19
          Originally posted by greenie View Post
          If you live anywhere near a Signmaker's business, then trot along and ask him to show you the gizmo that is used widely with-in that industry for bending ANY plastics.

          They use this heat source for bending big sheets of Acrylic, or as you lot call it - Perspex, works like a charm too.
          I know how it works, I've used them, but I want to make a simple, cheap 2" one, not an expensive one to bend a 48" wide sheet 1/4" thick! I've run a vac-former that took 48x96x 0.25 sheets heated hanging in a vertical gas oven, been around.

          And it's the Brits that call it Perspex, we call it Plexiglas.
          Last edited by gellfex; 04-07-2020, 12:31 AM.
          Location: Jersey City NJ USA

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          • #20
            Depending on the kind of radius you need, how about just sticking several hundred watts of light bulbs inside an old pipe, or even a chunk of curved sheetmetal with the bulbs underneath? Curve up a chunk of aluminum flashing and tack it onto the edges of some plywood forms, stick lightbulbs underneath...
            25 miles north of Buffalo NY, USA

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            • #21
              I wonder if you could make use of a halogen work light- the one with the straight glass tube. They get pretty hot, and the filament is protected. Maybe not long enough though. I have (or had) one that came out of a printer- that was about 10 inches long or so. The main drawback to these is that you have to put up with the blinding light. And chances are if it's long enough, it's probably a 500 watt tube. That's probably more heating power than you need- though you can always dim it.

              As far as stove top elements, they can be straightened without damaging them. I've done that a few times. Oven elements are even easier to straighten, and those can give you enough length to heat the full width of a sheet. They are 220 but you run them on 110 and that's just about the right heat level.

              Whether you use a nichrome wire or a halogen tube or stove element, you can't get too close to the plastic with it. Let the element heat the air, then let the hot air rise through a gap to heat the plastic. That seems to work about the best from my experience.
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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              • #22
                Would the heat gun from a plastic welder be of use? HF has a cheap welding kit.

                -js
                There are no stupid questions. But there are lots of stupid answers. This is the internet.

                Location: SF Bay Area

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                • #23
                  Originally posted by Jim Stewart View Post
                  Would the heat gun from a plastic welder be of use? HF has a cheap welding kit.

                  -js
                  I have that plastic welder, but it's no better solution than the heat pen. I may just stay with that method, one of my neighborhood recruits already has one anyway.
                  Location: Jersey City NJ USA

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                  • #24
                    Seems to me you want a heated infra red lamp set up in a jig for restricting light-heat to roughly the area you wish to heat. The timing would have to be adjusted through trial and error. Thermal plastic will allow bending and keep the material pliable for the time required again through trial and error,something like this all cutting to shape before applying heat or trying to bend.Too warm of course it will end up a disastor too hot you could or would make a real mess and also most likely burn your fingers and mark the job with tool marks finger prints.This type of cutting bending is done all the time by printers ask there for exact details or look on the web. I once made a deal with a friend of mine when buying a new van from him he is a car salesman,he wanted clocks made with his company name etc .I already had clocks a plenty which I bought from an auction (kitchen type clocks) we removed all the front plastic covers and the hands etc and removing the existing ads i.e paper clock faces simply by peeling them off. What amazed me was the printer also a friend of a friend bought a special cutter which was a simple circular blade and once the printing and colouring was selected he printed all placed them under the cutter one at a time and churned out two hundred easily enough we sat one evening round the fire and with the help of my kids put them all back together. The kids loved it. I was not expensive the circular cutter cost about twelve pounds and printing around thirty so under fifty pounds all was ready to deliver about thity years ago.Alltogether the clocks cost me aroung one fifty pounds plus and I got about four hundred to five off the new van. Definitely check with a printer's company, any good company could cut them into any shape automatically these days, even adding a company logo your's or theirs. Let me know how it goes Alistair
                    Please excuse my typing as I have a form of parkinsons disease

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                    • #25
                      Originally posted by Alistair Hosie View Post
                      Seems to me you want a heated infra red lamp set up in a jig for restricting light-heat to roughly the area you wish to heat.
                      That is more or less a description of the above wire coil in a ceramic channel! It's funny how everyone kinda shoots right past the simple actual requirements of this idea, I guess it's too simple? A sharp bend in 1" wide 1/16 thick plastic is all it is. Less than 10 seconds with the heat pen, 5 with the coil on a variac.

                      Location: Jersey City NJ USA

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                      • #26
                        How sharp of a bend? You could turn up a piece of steel, polish it, and chuck it into a soldering iron to do that job..... Put it on a lamp dimmer for greater control if need be.
                        25 miles north of Buffalo NY, USA

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                        • #27
                          I did a small experiment. I took a piece of pvc pipe of 2 inch diameter and cut it into strips to simulate the straps for the face shield. I then heated up some cooking oil and when my wife wasnt watching dipped the pvc into the oil. It takes six seconds and is soft enough to bend. I suspect it doesnt even need six seconds. You can then bend it by hand and dip it in water to freeze in its required position. On an industrial scale it would be easy to strap a few of these straps to a jig and pull them off as needed and place them in a bending jig .The oil doesnt damage the pvc at all. I am unfamilier with the product being used for the straps but I am sure it would be within the heat range of the oil. .
                          video, sharing, camera phone, video phone, free, upload
                          Last edited by plunger; 04-08-2020, 04:56 AM.

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                          • #28
                            Originally posted by nickel-city-fab View Post
                            How sharp of a bend? You could turn up a piece of steel, polish it, and chuck it into a soldering iron to do that job..... Put it on a lamp dimmer for greater control if need be.
                            As said above I already tried that with a HD soldering iron, it wasn't as good as the coil.
                            Location: Jersey City NJ USA

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                            • #29
                              GF - can you just create a different mask design and forgo the whole bending process to begin with?

                              Im looking at that mask and the only place im seeing where there might be a sharp bend is at the head strap in the back?

                              If that's the case there's plenty of different ways to come up with an anchor point other than bending the material,

                              of course I may be way off and that's not where it's at? just trying to figure it out, good on you for helping people out in this time of need...

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                              • #30
                                I'm a little late but here's my simple setup for clean sharp bends in plastic. This works very well for my needs. I'm usually bending 0.125" polycarbonate, but can
                                do thicker no problem.

                                I'm using 0.025" Nichrome wire.

                                It's powered by my LiPo battery charge, which has special "Foam Cutting" mode. I used to use my 12V 6A dumb charger, but prefer the LiPo charger as it displays
                                current and voltage. It runs 4V 7A in this configuration. It also has an Auto Off mode in the event I forget to turn it off.

                                Two key features;

                                The spring. The Nichrome stretches a bit when hot, so this helps keep decent tension. Don't run any current thru the spring or it will anneal real fast!

                                The screws for wire retainers, the threads make for real nice wire height adjusters.

                                Thank you for helping out!

                                P.S., I think the 0.035" Nichrome will be fine, just use a short length.

                                Click image for larger version  Name:	IMG_4197.jpg Views:	0 Size:	1.70 MB ID:	1867234Click image for larger version  Name:	IMG_4199.jpg Views:	0 Size:	1.70 MB ID:	1867235Click image for larger version  Name:	IMG_4201.jpg Views:	0 Size:	1.86 MB ID:	1867236Click image for larger version  Name:	IMG_4203.jpg Views:	0 Size:	2.33 MB ID:	1867237

                                Last edited by C_M_H; 04-08-2020, 01:30 PM. Reason: Removed the big pics.

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