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Foam Cutter......need double sided V-rail

Discussion in 'Other Builds' started by Wayne Webb, Jul 10, 2015.

  1. Wayne Webb

    Wayne Webb Well-Known
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    Hi all.
    I'm a graphic designer/sheep farmer/bluegrass musician in Florida and am just getting into CNC. I have been reading up on it for quite awhile but this is my first project. The 5 -axis controller is built, tested and ready. I basically just have to finish the Y axis, mount the drag chains, run the wires and load the software. I plan to try it with Mach3 to begin with, then later upgrade to something else if needed.

    All of this is made from 8020 15 series except the trusses in the center of the bed are steel. I machined the guides for the x axis out of cold rolled steel but wanted lighter ones for the Y to reduce mass and g-forces so tried to use aluminum. Problem is, when I began to machine the 90° bevel on the first aluminum one, it warped from the heat. Would the "open rail" work if I doubled it (two v's), bolted it down to the extrusion at every hole with a 9mm standoff and used the little "gantry plate"? It's just going to be under a little tension from the spring-tensioned resistance wire pulling from the opposite side and carrying the weight of a small drag chain. The main forces on it will be the tension of the tiny wire.

    Thanks for your help. :)
    Wayne
     
    #1 Wayne Webb, Jul 10, 2015
    Last edited: Jul 10, 2015
  2. Wayne Webb

    Wayne Webb Well-Known
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    I didn't get any replies so, I decided to try the open rail and some 6mm spacers. I couldn't get a workable clearance with the Delrin wheels and the plate so, I will be using the "plate" or "truck" I already designed along with the smaller wheels I have.. May have to modify it a little but it should work fine. I will tap some 5mm holes down the center of my extrusions to mount the rail. I will be using my foam cutter design to make monument signs. 3D letters, and architectural moldings.
     
  3. Joe Santarsiero

    Joe Santarsiero OB addict
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    Hello Wayne. Welcome to the forums!!
    We would love to see your build and frankly, pics are worth a thousand...:)

    If possible, please take some snapshots for the community and show us what your working with. Sometimes pictures will invoke the response you require.

    Joe
     
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  4. rcKeith

    rcKeith Well-Known
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    Hi Wayne
    I've built a 4 axis hot wire foam cutter and use it to make wings and fuselages for Radio Control planes. Mine is built from MDF and uses drawer slides but I am starting to do some work with www.robbocutter.co.uk to produce one using standard openbuild parts. My build details are on my website www.rckeith.co.uk. If you can put some pictures up I may be able to help

    Keith
     
  5. Wayne Webb

    Wayne Webb Well-Known
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    Here are couple of shots of the little Y axis "carriage" I designed for it. (front and back views ). As you may be able to see, I'm going to try snugging the wheels with set screws. If that doesn't work well, I'll just design another one which uses eccentric bushings. I'm going to rig both carriages with onboard limit switches so that, if the hot wire breaks or snags, it will e-stop the machine.
    I couldn't get the OpenBuilds plate and wheels to work in the design without changing a bunch of stuff. If my carriage doesn't fit the width of the openrail, I will either have to modify it or design and make another one. The rails are scheduled to be delivered tomorrow morning. Instead of using a T-slot, I intend to drill holes down the center of the upright extrusion to mount them, and stand them off with 6mm spacers.
     

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    #5 Wayne Webb, Jul 16, 2015
    Last edited: Jul 16, 2015
  6. rcKeith

    rcKeith Well-Known
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    That's a big machine, nice work. Tensioning the hot wire may be tricky with it being quite long especially if the axis move independently. What are you intending to cut.

    Keith
     
  7. Wayne Webb

    Wayne Webb Well-Known
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    Thanks
    I hope to cut monument signs and architectural moldings out of EPS foam. The axes will be slaved together most of the time but it will also have a removable 'crossbar' which will connect the tops of the two uprights if needed. That should allow maximum tension capability. But I'm hoping it can do taper cuts as well in independent mode.
     
  8. Wayne Webb

    Wayne Webb Well-Known
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    This is a drag chain mounting bracket I just finished designing. This will mount to the narrow side of the t-slot and carry the drag chain on the Y axis .[​IMG]
     
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  9. Wayne Webb

    Wayne Webb Well-Known
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    hotwire carriage on rail.jpg
    What are the odds? The Open rails fit my home made carriage and it clears the low-head mounting screws by about 1.3mm. That's a blessing!
     
    #9 Wayne Webb, Jul 17, 2015
    Last edited: Jul 17, 2015
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  10. Joe Santarsiero

    Joe Santarsiero OB addict
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    This is a very cool build Wayne and an ambitious first CNC project. You're cruising right along.
    You have my attention!
    I can't wait to see it in action.

    Joe
     
  11. Wayne Webb

    Wayne Webb Well-Known
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    Thanks Joe! I'm having a blast with this.
     
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  12. Wayne Webb

    Wayne Webb Well-Known
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    One of the two carriages mounted to the open rail.
    [​IMG]
     
  13. Wayne Webb

    Wayne Webb Well-Known
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  14. Wayne Webb

    Wayne Webb Well-Known
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    These are the little brackets, for mounting the timing belt and limit switches to the y axis carriage.
    They were cut on the CNC router and bent on a box brake.
    [​IMG]
     
  15. Mark Carew

    Mark Carew OpenBuilds Team
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    Coming along nicely :thumbsup:
     
  16. Wayne Webb

    Wayne Webb Well-Known
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    This is one of the two insulator assemblies for the foam cutter. They will hold the nichrome wire at both ends. I designed it for adequate strength with minimal weight so that the wire will not sag. The insulator/wire attachment assembly weighs only 9 grams.
    I have a question for anyone who has built a foam cutter: When I connect the feeder wire to the nichrome and turn it on, will the heat conduct back through into the feeder wire and melt the insulation off it? If so, how do I go about preventing this? Also, I will be heating about 9' of wire. What gauge of feeder wire do I need? 18? 16? 14? Thanks
     

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    #16 Wayne Webb, Aug 18, 2015
    Last edited: Aug 18, 2015
  17. JustinTime

    JustinTime Master
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    None of my foam cutting bows that I made had the lead wire ever melt. I used mostly speaker wire for it. The last time I did one I went all out and used a #10 speaker wire but in the past I used #14 and #16.
     
  18. Wayne Webb

    Wayne Webb Well-Known
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  19. Rustem Asadulin

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    l
    looks like a heavy load?do the stepper motors manage that weight? and what size of v groove bearings you used on vertical axis?
     
  20. Wayne Webb

    Wayne Webb Well-Known
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    All of the weight rests on the v rail so, it's only a lateral load the motor has to move since the v bearings roll very easily.. Very small G forces as well because of low working velocity; so backlash is almost nonexistent. Actually, I think the motors may need MORE resistance like a gearbox or something to help with motor resonance. I used very small v bearings on the Y; 1/2" diameter I believe.
     
  21. Wayne Webb

    Wayne Webb Well-Known
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    Got my power supply in this morning; can't wait to try it out. :)
     
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  22. Wayne Webb

    Wayne Webb Well-Known
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    Ok,
    I had the power supply turned up to 62.4V (double-checked @ 62.7v with a meter) and 4.75A but it was cutting extremely slow with a very thin kerf, even though the wire was glowing bright orange. Both feed wires, coming from the power supply to the nichrome, were 18 gauge and about 26' long each. that's a total of 52' of 18 gauge wire. I will have to pull one of the wires off and measure for voltage drop because, according to my calculations, that setup should have been generating a temp of 1240F on the nichrome wire. The only remedy available at this point, if there is voltage drop, is to go to a heavier gauge wire because I had the new power supply turned all the way up.
    In summary:
    Nichrome wire size- 24 gauge
    Nichrome wire length- 83"
    Feed wire size- 18 gauge
    Feed wire length- 2x26=52'
    DC Voltage- 62.4v
    Amps- 4.75A
     
  23. Wayne Webb

    Wayne Webb Well-Known
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    Ok, I disconnected one wire from the end of the nichrome and checked the voltage; it's reading 62.8v across the ends of the two 26', 18 gauge wires. that's no voltage drop at all. Again, the wire glows bright orange. I'll post a video later.
     
  24. Mark Carew

    Mark Carew OpenBuilds Team
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  25. Wayne Webb

    Wayne Webb Well-Known
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    Ok, I have the feed rate set too low; going to try doubling it. Also, the Mach 3 stopped processing code about the time the centers of the letters were done. Is this because it's the trial version? Anyway, I'm using Aspire to generate the toolpaths and send them to Mach 3. Problem is, that Aspire thinks it's a router, where it can lift the "tool" to safe height and traverse the cuts, which causes the wire to cut through the letters. Either I will have to find a way to work around this or find another program.
    https://www.facebook.com/4515689450.../512283505598305/?type=2&theater&notif_t=like
     
  26. Mark Carew

    Mark Carew OpenBuilds Team
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  27. Wayne Webb

    Wayne Webb Well-Known
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    Designed some safety/warning decals for the foam cutter.
     

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  28. Wayne Webb

    Wayne Webb Well-Known
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    little sample "monument sign" cut on the new foam cutter...
    [​IMG]
     
  29. Tweakie

    Tweakie OpenBuilds Team
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    Excellent :thumbsup:

    Tweakie.
     
  30. Wayne Webb

    Wayne Webb Well-Known
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