Page 1 of 2 12 LastLast
Results 1 to 10 of 14

Thread: How to: Build a heater strip to bend acrylic for 30 bucks or less!

  1. #1
    FLAC greatwhite's Avatar
    Join Date
    May 2007
    Location
    Top o' the world Ma!
    Posts
    1,282

    How to: Build a heater strip to bend acrylic for 30 bucks or less!

    Here's my little contribution to mp3car.com, hopefully someone finds it useful:


    So you want to bend acrylic to make that "gucci" computer case or amp mount, but don’t want to fork out a lot of dough to have someone with the equipment do it.

    Understandable, and with proper units costing anywhere from 200 bucks to a couple thousand, what's a guy with the customizing bug to do?
    I didn’t want to spend that much either so I started digging around and finally ended up building my own acrylic bending rig.

    And it only cost about 30 bucks total! (Could be free if you're a good "dumpster diver" or have lots of junk hanging around)


    So, here we go:


    Tools:
    Saw (table saw, circular saw, or if you’re really energetic a hand saw)
    Drill and bits
    Pencil
    Measuring tools (tape measure, etc)
    Hammer, screwdrivers, etc, etc…………the basic stuff.


    Materials:
    Old hair dryer
    16 gauge wire
    Crimp on ring terminals
    Wood nuts #10
    Bolts #10 about 2” in length (adjust as required)
    ” sheet of mdf (2’x8’ is more than enough)
    Wood glue (optional)
    Deck screws or MDF screws (you only need 10 or so)
    “aluminum channel
    Smal spring
    12 V power source capable of at least a 10 amp supply (I use a battery charger)

    The how to:

    (This is going to be kind of long, so settle in! You may want to print it if you're going to build one......)

    What you will be building is this:



    Making the heater strip:

    Start by taking apart a hair dryer. I had an old one lying around, but you can pic one up anywhere for a couple bucks. What we’re after is the coiled wire in the nozzle of the dryer, this is the heating element. It's made of Nichrome and that's what we're after. It has a high resistance and that's what makes the heat when an electrical curent is passed throuh it. Same stuff is in toasters, toaster ovens, etc. Snip the end where it’s attached to the form and unwind it from the heat proof cardboard (mica or something like that) or whatever it is.



    You want the biggest of the coils. Put the others away for another project (small ones are good for heater plastic cutters). I also saved the motor as it’s a 12v motor that can move a lot of air (never know where you’ll use one of those!).

    Head out to the shop and clamp one end of the wire in the vice and use a pair of pliers to hold the other. Carefully pull the wire to straighten it as much as possible. Don’t pull too hard or you might break it. You’ll also be quite surprised about how long that sucker actually is!

    Once you get it mostly straight (it will always have a twist in it so don’t sweat it if it isn’t bone straight), take the two ends and double the wire up.

    Now take the two ends (or the looped end, doesn’t matter which) and clamp it in the vice again. We’re now going to twist the wires together. Take the free end and chuck it up in your cordless drill. Slowly turn the drill on and twist the whole length of the wire.

    Congratulations, you just made your first “heater” strip!

    Determining the heater strip length:

    Once that is done, we need to know what length of the wire you can heat with the power supply you have on hand. The length of the wire you can heat depends on the thickness and resistance of the heating wire and the amps your PS can produce so everyone is going to be different. Mine is about 2 feet long which is just right for about any project you would want to do yourself.

    Take one of your un-insulated ring terminals and insert the heater wire into it the normal way. Take a piece of your 16 gauge wire (about 10 feet we’ll cut it later), strip the end, and insert it into the ring terminal backwards. Crimp it down nice and tight. It should look like this when done:

    *lost the pic somenow, I'll get another soon*

    Clip your power supply to one end of your newly twisted wire.

    *BE CAREFUL WITH THIS NEXT STEP. THE WIRE WILL GET HOT, POSSIBLY RED HOT, AND BURN YOUR TABLE OR YOU! NO FOOLING AROUND HERE GUYS. THE HEATED WIRE WILL CUT RIGHT INTO YOUR SKIN (AND DEEP) IN A BLINK IF YOU TOUCH IT!*

    Turn on your power supply and touch the other end of the circuit (positive or negative ends if you prefer that terminology) to the heating element. Watch for the wire to get hot or even glow red hot. What you want here is to find a length that allows the wire to just barely get that “dull red” glow (It's so faint, you won't be able to see it unless the wire is in a slight shadow, it'll look pretty much normal in regular light). Any hotter and it may burn the acrylic, any less and it may not get hot enough to let it bend without cracking. As I said, mine is about 24 inches long. But if you find you want yours shorter, just clip your PS to the 16 gauge wire at different lengths (remember the 10 foot length?) until you find the right resistance. Look for that “dull red” color.
    Now that you’ve determined the optimum length, cut your wire to length and crimp another ring terminal on it in the normal fashion.

    Set your heater strip aside for now.

    Construct your base:

    Obviously, this is dependant on the length of your heater strip. You will want to cut your MDF at least 3 inches wider than the length of your strip.

    Now cut a second piece of MDF the same size as your first.

    Mark a centre line across your first piece. This is where your aluminum channel will go. Cut your channel a little bit shorter than the total length of your heater strip.

    You can see the length here:



    This will protect the MDF from the heat and direct the heat up to the desired bending area of your acrylic.

    Now you need to cut your second piece of MDF in half. Place the aluminum channel on your center line and sandwich it between the two cut pieces of MDF. Make it nice and snug. You want the channel either flush with the top pieces or slightly recessed. You can use some wood glue to hold the halves to the base, but I just put a screw in each corner to hold it together.

    Take another piece of 16 gauge wire and crimp a ring terminal on it. Drill a hole into the Mdf base, slip the ring terminal over the wood nut and insert the wood nut from below.



    You can hammer it into the wood if you wish (recommended).

    At the other end of the channel, drill another hole and insert another wood nut from below.

    Your base is now done and it’s time for final assembly.

    Final Assembly:

    Take one of your #10 bolts and spin a nut on it. Slip the ring terminal on your heater strip on (the end without the 16 gauge wire). Spin 2 more nuts on the bolt. Push the bolt into the hole in the MDF at the end of the channel (the end with the wire on the wood nut) and spin it into the wood nut. Tighten the bottom nut down to tighten the bolt and keep it from turning.



    Now take your small spring and attach it to the other ring terminal.

    *lost pic, I'll get another soon*

    The purpose of the spring is to keep the heater wire taught as it will get longer as it heats and not carry any of the electrical load (that’s why you crimped the 16 gauge wire backwards into this ring terminal). So you will want to have a little tension on the spring when you install it. It doesn’t take much! Spin a bolt into the wood nut (put a regular nut on the bolt first to secure it afterwards) at the end of the channel and slip the spring over the bolt.

    Now adjust the height of the ring terminals on your bolts to have the heater strip below the top of the aluminum channel but not touching the sides or bottom. Once you get the height right, tighten the two nuts together on the plain ring terminal end to hold it there.



    You can adjust the length of the spring also if needed (you may have to adjust the tension after you heat the wire also, remember it will get longer as it heats).

    YOU’RE ALMOST DONE. STAY WITH ME NOW!

    You want to mark some reference lines on you base so you can keep your acrylic lined up while heating. Use a tape measure and mark lines on the base parallel to the aluminum channel (I marked it every inch, but do as you wish).



    Whew! The assembly part is done! A few adjustments and we’re ready to go.

    Now, let’s give ‘er a test run.

    Clip your power supply on either end of the heater strip by the 16 gauge wire. Again, you’re looking for that dull red glow. Make sure the heater wire doesn’t sag enough to touch the channel. If it does, shorten your spring slightly and try again until you get it just right.

    Now take a piece of scrap plexi (or lexan, or whatever you need). Place it on the heater, line it up to where you want the bend and turn on the power supply.



    Wait for about a minute or so, and then try to slowly bend up one side of the plexi. If it’s warm enough, it will bend in a perfectly straight line along the heated part. If it doesn’t move easily, let it warm a bit more.

    With enough practice you can bend plexi to any angle you need. Here’s a scrap piece I bent to make sure the strip works:




    As you can see, 90 degree bend and perfectly straight with a nice tight radius and no cracking!
    Took me about 1.5 minutes.
    You can bend to whatever angle you want or need.
    You can make boxes, covers, etc. Clear, smoked, plexi, lexan - You’re only limited by your own imagination.

    You can also light these things with led’s. Leave the plexi clear and it will appear “edge lit” or you can lightly sandblast the plexi to have the whole thing glow. You can get really fancy by sticking a logo on the plexi, sand blasting it, pull the logo off and it will glow around the logo!


    Now, start creating some stuff out of acrylic! It’s marvelous stuff!

    Cheers

    *Just so there's no confusion, the bulk of the "technical info" came out of a magazine I read recently, car audio something, but I can't rememeber which*
    For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return.
    Leonardo Da Vinci

  2. #2
    Variable Bitrate
    Join Date
    Jan 2007
    Location
    East Central FLA
    Posts
    241
    Thank you.

  3. #3
    Variable Bitrate walstib's Avatar
    Join Date
    Jul 2005
    Location
    Atlanta, GA
    Posts
    362
    Thanks for the great write up!

    A long time ago, I used to use nichrome to cut foam cores for model airplane wings. One thing I found back then was using a power supply from a train set allowed you to adjust the heat with the potentiometer instead of having a fixed heat based on wire length. Just something to possibly try.

    I also thought about having a piano hinge between the two pieces of MDF and mount the heating element just above the hinge. You could then clamp the acrylic to one side, turn the unit on and tilt up the other side after heating. Maybe even mounting a protractor at the joint would allow you to get precise bends. You would need to clamp it down using this configuration so the acrylic would not lift up and hit the wire when bending it.
    Carputer Project Status:
    0% - Mobo died on 2/17/08
    Check out the worklog for my '01 Pathfinder.

  4. #4
    Low Bitrate
    Join Date
    Jul 2005
    Location
    Missouri
    Posts
    61
    Looks good. One thing i've seen on homemade strip heaters is sheetrock instead of aluminum.
    William Surritte, Technician
    No Limit Technologies
    1931 U.S. HWY. 160, Caulfield, MO 65626
    http://home.centurytel.net/nolimititech/
    Planning: |++++ |
    Software Development: |++++ |
    Hardware Development: |++ |

  5. #5
    FLAC greatwhite's Avatar
    Join Date
    May 2007
    Location
    Top o' the world Ma!
    Posts
    1,282
    Quote Originally Posted by walstib View Post
    Thanks for the great write up!

    A long time ago, I used to use nichrome to cut foam cores for model airplane wings. One thing I found back then was using a power supply from a train set allowed you to adjust the heat with the potentiometer instead of having a fixed heat based on wire length. Just something to possibly try.

    I also thought about having a piano hinge between the two pieces of MDF and mount the heating element just above the hinge. You could then clamp the acrylic to one side, turn the unit on and tilt up the other side after heating. Maybe even mounting a protractor at the joint would allow you to get precise bends. You would need to clamp it down using this configuration so the acrylic would not lift up and hit the wire when bending it.
    I also thought about hinging the unit, much like you would with a metal brake. The only problem with that is that the plastic has to bend directly over the heat element in this configuration. In truth, you usually remove the plexi from the heat and bend it right away. The lines and Al channel are there to heat only the "bending line". This way the only part of the plexi that is flexible is the bend line which gives you your straight line. You'd also have to have your hinge directly below the element and this would allow the heat to disperse as opposed to the channel which gives you a nice tight bend because it only heats the plexi in the spot it will bend. the plexi would also have to slide on one side or the other if it is clamped or you will end up "thinning out" the joint area (pulling it apart) or forcing it down into the bend area (neither is good for a clean radius). The main reason for not clamping or hinging the unit is the way the plexi bends in the corner, you want it to pull up and away from the outside curve in the bend. Clamping it to a hinged table won't allow it to do this. If you force the bend too tight, the plexi will craze, crack, bulge out or fail.

    Besides, the plexi gets so soft, bending it is as easy as falling off a log..........

    I have used a protractor and carpenters square before for 90 and 45 degree bends.

    If it I were to build a rig for precise bends, I'd build a second table hinged in the middle with a gauge on it. I''d heat the plexi and tranfer it to the table (talble already set to desired angle), place the plexi on it to to bend and support it (the plexi will still bend in just the heated area) and wait for it to cool. This would give you a nice long, straight, controlled bend without worrying about the heater strip issues and it will cool faster, thus minimizing your chance of disturbing the angle.

    I was also going to add a potentiometer to control the heat, but it just seemed simpler to make a fixed unit as it will never be any longer or shorter. More heat just messes up the plexi (burning, discolor, bubbles, etc) and not enough heat can cause cracking and crazing when bending. If you're thinking of bending thicker materials (this is good up to about 1/4 inch or so) with more heat, you'll just end up burning it. To bend thicker materials, ust flip the project over in the same spot after heating one side.

    All good thoughts and considerations though...................

    Cheers
    For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and there you will long to return.
    Leonardo Da Vinci

  6. #6
    Newbie copter's Avatar
    Join Date
    Dec 2007
    Location
    Nor★Cal
    Posts
    55
    Good write up.. I used a dishwasher heating element to bend mine.
    _____________________________
    06 BLACKTIE LBZ | GRAYSTONE METALLIC | MBRP 4" | AMP STEPS | KMC DIESELS | TOYO M/T'S | NCT/COGNITO 4-6" | BILSTEIN 5100'S | MAG-HYTEC DIFF COVER | HID'S | PPE XCELLERTOR |
    ______________________________________

  7. #7
    Newbie
    Join Date
    Nov 2001
    Posts
    31
    Thanks for the post! Were you able to take pictures or find the missing pictures to include in your post?

  8. #8
    Low Bitrate 20mg's Avatar
    Join Date
    Oct 2007
    Location
    chico ca
    Posts
    71
    awsome writeup.

  9. #9
    Constant Bitrate
    Join Date
    Mar 2007
    Location
    Central Florida
    Posts
    156
    Just out of curiosity, why didn't you make it AC powered, since the blow dryer is AC?

  10. #10
    Newbie
    Join Date
    Jun 2008
    Posts
    1
    hi can you post those pictures that are missing??? it would be a great help... thanks!!!

Page 1 of 2 12 LastLast

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •