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Melting foam

Discussion in 'Trouble Shooting - Support - Help Section' started by cptdragn, Aug 27, 2010.

  1. cptdragn

    cptdragn Member

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    While waiting on my board to get back I thought I'd throw this out.

    Have any of you run into this problem.

    Background: I have the MK1 with the belt upgrade as well as a few of the other mods that have been posted here. Mostly the bearings and zero nut on the gantry. I'm running from 100-250 depending on how the cut files were set up. While I had a few problems with the cal settings I finally worked though them and got it to where I was happy with the results. I am using the stock 1/8 bit that comes with the MK1. The current bit has cut less than 15 sheets of foam. At least 10 of these were PBIII.

    While cutting PBIII foam I have no issues and no melting of foam. Doesn't seem to matter as to what speed I'm running.

    However, while cutting 2 sided actual BlueCor, The first 1 or 2 sheets cut ok and then the bit starts loading up and melting the foam. You can clean off the bit and it is warm to cool to the touch but it will still load up right after you start into the next sheet. I have tried the following.
    Slowed down the dremel to its lowest speed.
    Result: Loaded up even worse.
    Ran at high speed ( dremel ) but slowed down the cutting speed to 50
    Result: no difference. still loads up the bit with melted foam.
    Ran dremel at slowest speed with cutting at 25
    Result: bit still loaded up.

    It seems that for some reason, The bit is melting the foam regardless of the speed of the dremel or the cut speed. This is a new bit that was replaced less than 15 sheets ago. Again, it doesn't happen with PBIII, only BlueCor.
    Is there another bit that I can try that will not melt foam? I don't mind any dust if it stops the melting.
     
  2. Brother Pain

    Brother Pain New Member

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    I was just getting ready to post about this same thing. Just over the past week, my bit has started doing this. My bit, however, is the original bit and has eaten through 7 - 8 bundles of foam. I had assumed my issue was just a worn bit, and wanted to validate. I am also running a RotoZip mod on mine.

    Greg
     
  3. Anonymous

    Anonymous New Member

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    I had a similar problem when cutting EPP foam, and solved the problem by running the Dremel at the low-speed setting while running the pp at 80 or 100 ips. Essentially, the cutter needs to rip larger chips off, instead of making powder.
    It's been a long time since I was dealing with that problem, but that's what I remember. I hope it helps. I'll look for the cut-file of the model I was making to see if I left any notes in that file, and if I learn any more I'll add another post or revise this one.
    (OK I checked - I remembered correctly.) ;)
     
  4. Flashsolutions

    Flashsolutions Active Member

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    I have had this problem from time to time... worse with Depron and smaller bit sizes.

    I replaced my 2 speed Dremel with a variable speed unit.

    I cut at 130 ipm. Make sure both x and y axis are set to the same velocity.

    When you are cutting at the right speed, you can hear the difference. It is a more crisp sound.

    If ANY of the shaft is touching the foam instead of the cutting flutes, it will heat up and melt foam, so make sure your Z axis does not push the bit too far into the foam as to hit the exposed shaft.

    I have at times resorted to using an airbrush to spray cool air on the bit as it cuts, but if you get the Dremel speed matched to the cut speed you generally won't have to cool the bit as it will be chipping out material rather than forcing itself thru the foam.
     
  5. cptdragn

    cptdragn Member

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    Well, if I go though the trouble of replacing the dremel, I’ll just go the rotozip route myself. Kill two birds. Still, I don’t think the dremel is the problem. It works fine as long as you’re using PBIII. It’s when your trying to go thought that extra layer of plastic film that BlueCor has that I run into a problem with the bit melting the foam. Or more to the point, I think it’s melting that top plastic layer which sticks to the bit and causes it to load up that much more. While it will throw some of it off, it just loads up again. It’s a vicious cycle. I have tried using a wood dowel to know it off as it starts laying but that only works to a point and then only so long as I hold it against it.

    I do have the X and Y set to the same speed. And as I stated, I’m actually cutting at a slower speed then you state above but still have the problem. At least on this machine, running the dremel at its lowest setting causes more problems with bit load up than it does using its highest setting. I understand the theory, it’s just not working out that way in practice. Using a viable speed router cord proved to be a mistake as well. Either it would not run at all or it ran at full speed. There was no adjustment.
     
  6. Jnida63

    Jnida63 Member

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    Hhmm, I never had a problem with blucore, I did do the rotozip with the variable speed controller and run it at it's lowest rpm and cut at about 150ipm.
    The only time I ever have a problem is when the bit gets dull or the shaft of the bit is touching the material being cut.
    You want the fastest feed rate possible in my experience
     
  7. 3DMON

    3DMON Moderator Staff Member

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    Hey Tony,
    Try a bit with a fish tail point instead of the ballnose like the stock bit. It sounds like the plastic is getting stuck on the tip which doesn't allow the tips cutting surface to cut the foam which cases the melting.
     
  8. cptdragn

    cptdragn Member

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    Shawn,

    Thanks, I'll try that idea. At worse, I spent money on a bit I can't use.

    Jeff,

    I would have thought so as well but its not working out that way for me. While I may end up with the rotozip, I'd like to see if something simpler would resolve this problem.

    As a side note, those of you that have done the rotozip mod, what are the pro's and con's of doing the mod?
     
  9. cptdragn

    cptdragn Member

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  10. Jnida63

    Jnida63 Member

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    can you post a picture of the melted bit? Might help diagnose looking at it
     
  11. Thewz

    Thewz Moderator

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    Did this ever get solved? Mine just started to do this today.... :fugly: of course right when I needed it the most. I too assumed that the bit was dull but I guess now. I may try a fluted style rather than the rasp stock bit. I too have the belt mod and am running at about 100IPM with the stock 2 speed router on high.
     
  12. Tweakie

    Tweakie Member

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    Has anyone tried spraying the bit with dry PTFE (similar to the stuff used with heli gears) in an attempt to stop the cuttings from sticking and causing the overheating ??

    Just a thought.

    Tweakie.
     
  13. kram242

    kram242 Administrator Staff Member

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    Once in a while when my bit gets dull, I can extend the life a little more by spraying silicone lubrication on the bit. To be honest I find the melting only seems to happen on occasion few a far between and I have always attributed it to a dull bit or of course going past the cutting flutes which results in instant melting.
    Mark and Trish
     
  14. Thewz

    Thewz Moderator

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    I got a 1/8 "drywall" bit. It makes a lot more foam dust than the grinder but makes a very smooth cut. I've been able to get my feeds to 100IPM (X&Y) without any issues now. It also seems to plunge through the foam better now.

    Thanks Mark
     
  15. kram242

    kram242 Administrator Staff Member

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    Good tip wz thank you for sharing.
    Mark and Trish
     

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