HomeWork Day Two

Please post your Homework for Day Two
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  • I have a lot to say in this update.  Some of it is a warning!

    First, I'm happy to report that my vacuum forming machine is complete and functional.  Yeah!  I experimented with two things right off.  The first being just random shapes to understand the nature of the process.  The other was to see how many shapes I could pull in one attempt.  The results were mixed.  I think if I had only place 2 or 3 of these items on the platen they would have come out better.  That said, I still ended up with a couple of useable pieces.  In the first picture below are the pieces I pulled.  I put the originals next to the vacuum formed copies for reference.

    Fon, the piece in the lower right corner of the photo is actually two pieces nested; a plumbing end cap set inside a ring from a failed 3D print.  The vacuum formed copy has a lot of webbing and none of the styrene was drawn into the negative space between the plug and the ring.  To get better results, what would suggest that I try?  My first thought was to pull them separately and glue them together.

    Here's the warning part:
    All - I had a pretty sad experience with my maiden voyage.  The results you see below were technically my second attempt.  The first attempt really was a non-starter.  The heating elements never got hot enough!  I let the machine run for 40 minutes to no avail.  I deduced that the issue was running all of my heating elements in series.  Looking at the controller from the original oven from which the elements came, I realized that there were two sets of elements, each set was wired in series.  However, the sets themselves were wired in parallel.  So, I rewired the elements in my "hot box" so that I had two sets of elements running in parallel.  Instant improvement.  It heated the plastic up in about 2-3 minutes.

    I know that, Wolf, this description probably means nothing to you.  You mentioned, though, that you had enlisted some assistance from a friend more familiar with electricity.  S/He would understand (I think) what I mean so it might be worth mentioning it.

    Fon, you'll probably have the same problem as we used the same toaster oven for the elements.

    If anyone wants, I can draw a diagram of my wiring.

    And finally, the part I'm really ticked about...  My solution to the magnetic strip.  The second two images below show how I modified the handles on the clamping frame.  The solution is pretty easy and works well (so far).  Simply twist the handles to engage the "hooks" onto the horizontal rail.  The hooks hold the frame in place during the heating cycle.  To move the frame down to the vacuum, just twist the handles out again to disengage the hooks.  The biggest trick is fiddling with shape of the hooks to get them to grab the rail snugly without being too difficult to unhook.  I ended up using wire that I twisted [using the cordless drill - Rowen ;)] to effectively double its thickness (and remove that annoying curvature from spooled wire).  The twisting gave the wire sort of a tooth with helps the hooks "snap" onto the rail.

    Next up...  I'll be carving some foam for helmet forms.

    -Dave

  • Dave!!!! I love your handle design. That is a fantastic idea.

  • ...and great solution for the heating issue.  I will review that in the class this Saturday.

  • Thanks.  I'm glad you like it.  If I had to redo this, though, I would bend the hook part of the handle wires after installing the handles themselves.  Originally, I bent everything to shape then installed them.  Well...  Not all of my parts lined exactly so I ended up having to man-handle the wires into a workable shape.  It would have been easier to just do the hook bends directly onto the rail.  If you wanted to get super fancy, you could bend the hooks with a radius to match the arc of the handles, but that's probably not worth the effort.

    Another change I would consider is the type of wire.  I would use something a touch stiffer.  One side of this contraptions works like a charm.  The other is fiddly.  When I try to disengage the hook, the wire flexes just a hint which causes it to bite even harder onto the rail.  It's easy to manage, though.  I just unhook that side and hold it in place while switching the machine to vacuum.  Then I unhook the other side and drop the frame onto the platen.

    By the way, in my original post, I meant to say that I was "tickled" about my solution, not "ticked".  :)

  • Well, without having to rewire a whole unit for my heater, and with an out of the box vacuum cleaner for the suction, I am patiently waiting for all the silicone to cure til tomorrow and then create something to hold the frame up and do some test pulls finally.

    I really hope this will work. I am quiet chuffed with my efforts atm. Of course Mini had to inspect the minute I put it up indoors. I will deffinetely make some big button switches on the front for the heater and the vacuum.

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  • Nice job, Wolf.
  • well I couldnt wait and managed to get everything together. Did the first pulls aaaaaand they all went bad. I am thinking I will need to canabalize a toaster oven after all. I seem to have too much heat in the middle and do not get a uniform heat distribution. Or maybe I did something wrong with the construction of the plate. Possibly both.  :D
  • Wolf, since I have no idea how familiar you are with this process, please excuse me if I ask something obvious.  How long did you wait for the plastic to warm?  I wonder if you tried to do a pull too soon.  The plastic goes through three phases before it is ready...  In the first the plastic gets all warped and goofy looking.  In the second phase it goes taunt and smooth again.  The final phase is where you get a nice uniform drooping.
  • Another thought...  Since you did not rip apart your heat source, can you just dial back the temperature on it?  Or...  Don't bring the plastic quite as close to the heat while it is warming?
  • Thank you Dave. Here´s what I have:

    When I heat the plastic it warps first. then goes limb and wobly. Then starts drooping in the middle.
    I did a second pass with a bigger distance to the heater. Same result. It basically starts melting from the middle. That is why I think that maybe the heater is too directional?

    Dialing back only does kill one of the two heater rods. So heating would only happen on one side.
    I also figured after checking Fon´s video that I made a construction error with the Platten. (facepalm moment 4me)

    So i will change that and do another test with the existing heater but in a different configuration.
    But I think making a uniform heater with heating wire should help.


  • I adjusted the heater unit, bend the reflectors for a more uniform heat distribution and got me first really decent pull.

    I bought a toaster oven too to create a better heating unit eventually. I will fix the Platte tomorrow


  • Definitely better.
  • Well, I believe I have FINALLY assembled a working machine... the vacuum makes a ton of noise, the heating elements have a range of temperatures that they function through, and it looks like the first image "you" will have to cock your head sideways to see the picture I intended to take. I attempted Dave's idea of linking pairs of the heating elements in parallel, and it feels like it's warming up uniformly. I will attempt my first set of pulls tomorrow, to see what else can go wrong. I know this machine is very rough, but I'm treating it as sort-of a "mark 1", so now I know what to do differently for my better model in the future.
  • Nice!  Soon, you'll have all manner of vacuum formed parts.  :)
  • I thought I'd post a shot of the helmet I'm attempting to make. It will be a total of four parts, and it is my interpretation of what a Kashyyyk Scout helmet looks like. I'm not entirely done with the faceplate sculpt, and I have two more parts to complete, but that shouldn't take me too long. These parts only took about an hour and a half today, between baseball practice, removing tumbleweeds before the fire hazard season hits, and getting ready for tomorrow's Cub Scout pinewood derby. I think I'm a little overbooked. (You'd never imagine how many tumbleweeds there are around here... :P)
  • I bet it feels good to get a couple of molds done.
  • hi guys, just trying to catch up on everything!  heres my machine
  • inside the heat box
  • the heater would switch off if i tilted it so i had to open it and tape the tilt lever.
  • heater on
  • and my first pull
  • here's the plans for the two helmets and hands im making
  • Hey, Alan!

    I like the helmet designs.  The second one, though, (the one with the more angular features) has undercuts around it.  Were you planning on vacuuming forming that as two pieces and joining them?  The only other way I can think to solve that problem is to make a form that you can disassemble.

    -Dave

  • first helmet sculpted with resin and car body filler, then sanded and detail with different strength sand paper and a dermel. Then i covered my sculpt in coats of rebound 25 rubber and made a shell from plasti-paste to support the rubber mould. then ran the moulds in smooth cast 300 as i need to make different variations of the helmets.
  • more pulls
  • i spray painted the vacuum formed visor with a few coats of tail light tint so i could still see out of the helmet. i sprayed with a grey base primer then wet sanded and a coat of gold chrome.
  • and finally i added EL wire to the outside
  • On the visor, do you get a lot of distortion after painting it?  I had a good bit of trouble with that on mine.
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