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Destroying your Rotozip

Discussion in 'General Phlatprinter Stuff' started by ToxicToast, May 25, 2010.

  1. ToxicToast

    ToxicToast Down in the weeds. Staff Member

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    Shredded my rotozip attachment tonight :oops:



    Was having a blast cutting MDF today with my new improved drive roller (thanks M&T!). Unfortunately, I got carried away and ran a job that took 2.5 hrs with lots of complex shaping and depth changes. Guess I was pushing it at 25ipm... Attached files [​IMG]
     
    ToxicToast, May 25, 2010
    #1
  2. kram242

    kram242 Administrator Staff Member

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    :D We did the same thing when we were trying to cut MDF back before the days of the multipass. We tried to cut in a single pass! :D

    Mark and Trish
     
    kram242, May 25, 2010
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  3. cncmachineguy

    cncmachineguy Member

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    I think what we are learning here is heat IS our enemy! Even if the spindle can be on all day with no problem, when we start cutting stuff, anything, the tool will get hot. this heat transfers to the shaft, then to the bearing, cooks the greese, heats the bearig more and the plastic melts. And flex shaft death occurs.

    Maybe its time for me to make the all metal spindle mod. :)
     
    cncmachineguy, May 25, 2010
    #3
  4. ToxicToast

    ToxicToast Down in the weeds. Staff Member

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    Believe it or not! Multipass was on. It milled everything out perfectly, but the failure point was in the drill-plunges. I think the plunges went into the material too quickly, possibly the material was slipping so each successive depth plunge was hitting adjacent material?

    Thanks for the excellent explanation of the heat failure, Bert!
     
    ToxicToast, May 25, 2010
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  5. rcav8r

    rcav8r Moderator Staff Member

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    When I was cutting my balsa kit, I would wait between sheets as the shaft felt rather warm after cutting a sheet of balsa (typically 48x4x1/16"). It wasn't so hot I couldn't hold it, but still warmer than I thought it should have been. I'm not sure what type of duty cycle these things are rated, but at around $25.00, I'm guessing not much.

    So has anyone lubricated the flex shaft yet? I know I have no where near the time that a lot of these guys/gals here have, but I'm still thinking it wouldn't be a bad idea to lubricate it here soon.
     
    rcav8r, May 25, 2010
    #5
  6. ToxicToast

    ToxicToast Down in the weeds. Staff Member

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    Since I have the guts open, I'm breaking out the Teflon lube on all the metals and bearings anyway. I did lube the flex shaft torque line about 3 weeks ago with the Teflon.
     
    ToxicToast, May 25, 2010
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  7. Gefahren

    Gefahren Member

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    As a possible alternative to those who have fried there flex shaft, I've got an older dremel flex shaft that has a metal hand piece with it. The actual flex shaft looks to be the same size as the rotozip ones (mines under the craftsman name, same part number however) so if you can find these dremel flex shafts then you could put the hand piece on the end of the rotozip shaft and have a hopefully more robust and heat dissipating part. I don't know if dremel still make these this way or not, mine is at least 10 years old now.

    I've never done any heavy cutting with my craftsman(rotozip) , just light stuff with the flex shaft, but I do keep it lubricated with spray silicone and it seems to work fine. I'll see if I can take the dremel shaft apart and fit it to a spare rotozip flex shaft I have.
     
    Gefahren, May 27, 2010
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  8. ToxicToast

    ToxicToast Down in the weeds. Staff Member

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    Let us know how that works out (with the dremel head)
     
    ToxicToast, May 28, 2010
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  9. slick8086

    slick8086 New Member

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    Hi folks,
    I think this is my first post, but I wanted to chime in my experience working with flex shaft and CNC tools.

    At my previous company we worked with Foredoms for grinding stainless steel. We used variable foot controls, but we would run these for long stretches (3 and 4 hours at a time). The amount of bend in the flex cable makes a difference. The less the better.

    But in this case it doesn't look like it was the cable that caused the failure more like too much side pressure. That bit looks dull but that could just be the picture.

    If your bit wasn't cutting up to snuff, then is it possible that it was pushing your material out of line, then you next cut would be even harder which would push the material out of alignment and the process would snowball. Of course this is just speculation on my part.
    Also is that the right cutting tool for MDF? I'd think a sabre bit would be better, but that is an inexperienced guess.

    On my CNC lathe I learned it is better to replace the tool even if it still has a little life than to run it till it fails.
     
    slick8086, Sep 27, 2010
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  10. ToxicToast

    ToxicToast Down in the weeds. Staff Member

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    Hey Slick, you may be right in that it might've not been the right bit for the task. It was brand new when I started this, so I don't think dulling was the cause. It was probably overstressed. I had it set for multipass on this job, but subtle slippage in the position of the material meant that later passes were actually digging into more material and putting much more strain on it. I could hear it but since the MK2 cuts from the underside, I didn't want to risk aborting the run until it cut more. Then I heard the noise get much worse so I aborted it then. The slippage was noticeable and you could see where the later passes were starting to have to go through more material. So your theory is pretty much spot-on.

    Thanks!
     
    ToxicToast, Sep 30, 2010
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