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X axis belt tension question

Discussion in 'Troubleshooting and Build Support' started by gben, Mar 28, 2011.

  1. gben

    gben Member

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    Hey guys. I finished installing my new rollers this weekend and did a few test cuts. I cut the escher lizard file out as a test cut and it was cutting great until about halfway through the file. I lost quite a few steps in the x direction. There was an audible sound that I believe was the belt slipping on the stepper pulley when x issues occurred. I loosened the x stepper and checked the set screw on the pulley shaft coupling but it still seemed tight. I tightened everything up again and manually rotated the rollers. Every 3/4 turn of the rollers I would hear what sounded like the belt teeth briefly disengaging from the stepper pulley. I drove the x axis with the stepper at a feedrate of 150 ipm and everything sounded fine until I put some drag on the rollers then I would hear the brief "skipping" sound. I ran the circle test file and lost about 2 inches in X. I'm thinking I have an issue with belt tension but wanted to get some feedback. I would normally think that more tension was necessary on the belt but both installs had what I though was a fair amount of tension on the belt. Thoughts or suggestions on this would be appreciated.
     
  2. scraighamilton

    scraighamilton Member

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    Ben, funny you post this now. I have been chasing this problem all weekend. I have noticed that not enough tension on the belt the belt will skip but to much tension the belt will also skip, do to stretch.
    I learned a few things that might help. You need to make sure that the belt stays in the middle of the stepper pulley, the roller pulleys are not as critical (imho). You also need to tension the belt so that it is tight enough that the teeth on the belt won't jump on the pulley. I do my belt tensioning with the motors on and locked. That is as tight as I go. So far in my testing, everything seems to be going well.

    Hope this helps.
     
  3. rcav8r

    rcav8r Moderator Staff Member

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    FWIW, my X-belt is rather tight. That is I made it as tight as I could by hand. I didn't use a tool for leverage to rock the stepper, just pulled by hand as tight as I could and tightened the stepper mounting screws. If I push down on the belt between the roller pulleys, there is about 1/16" play. The belt is centered on all 3 pulleys. So far mines been rock solid.
     
  4. gben

    gben Member

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    Craig & rcav8r, thanks for the info. I'll tighten the belt up a bit and try it out like that.
     
  5. SlowBipe

    SlowBipe Member

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    Ben,

    Early on I was havin a lot of trouble with my x axis. It missed steps even though it didn't seem like the belt could be slipping. I hav since replaced my x stepper motor with a new larger stepper. Seems to have resolved all of the issues for me. I do cut a lot of wood with mine and I use a laminate trimmer for cutting.

    SlowBipe
     
  6. gben

    gben Member

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    Slowbipe. I may pick up a larger stepper if I continue to have problems. I'd like to cut wood on mine as well so maybe that is a good option regardless. Thanks for the suggestion.
     
  7. pezzer2003

    pezzer2003 Member

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    SlowBipe,
    Could I ask what size stepper you installed for the X axis?
    Thanks..
     
  8. SlowBipe

    SlowBipe Member

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    I put this motor on my x axis and am very happy with the results. I was skipping many steps on the motor while just cutting 1" dow foam at 80 ipm in one pass. I say just, but that is probably one of the hardest things I have cut so far.

    http://www.mpja.com/prodinfo.asp?number=18189+MS

    It is the same size, but just longer and heavier. I thought there might have been something wrong with my original motor, as I could easily stop the rollers with one finger before switching out to the new rollers. I think I may have had my belts too tight in the beginning as well. Either way the replacement motor was cheap and well worth the change. Mark suggested this motor in the following post:

    http://www.phlatforum.com/viewtopic.php?f=270&t=2548

    Since then I have swapped out my z axis motor for the one that I thought was defective on my x-axis and it is working fine there.

    Just remember that when you get the new motor that the wire colors probably won't be the same as the ones you are taking off. Mine weren't and the heat sinks on the driver got pretty hot before I realized my mistake. Just read up on the online wiring documentation for the new motor before you install. If you get one and want to know how I wired my colors let me know.

    SlowBipe
     
  9. robhsmit

    robhsmit New Member

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    I'm having the same problem with my X axis. I just put in my third roller and trying to get things running. Tried a test circle file that I created, and I keep loosing steps on the x.

    I'll try loosening the belt as I thought tighter was better.

    Thanks,
    Rob
     
  10. Watt_the?

    Watt_the? Member

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    Well, you guyz are right... despite the fact that I don't have yet the rollers, so I did not run the PP at all with foam, I went ahead and order two steppers, one for X axis and one for Y axis. Because the space available for stepper on Y axis is just 80mm I had to go with a 16 Kg torque, 76mm length, and for X axis I went with a 20 Kg torque, 80mm length motors. I got them from the same site SlowBipe bought his from. It may be an overkill but... let's see how will be when I have the first cut.
     
  11. rcav8r

    rcav8r Moderator Staff Member

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    Just my $0.02 on larger steppers. Remember this is just my opinion based on what I have seen with my experience with my Phaltprinter MK1 and I am by no means an expert in this motion control stuff, but the Phlatprinters sure have been great learning tools...

    If the stock steppers aren't performing well then there is more than likely a mechanical issue somewhere. I tried fixing the issues I had with my earlier PP MK1 with bigger steppers. Yea it fixed some problems, but it didn't actually resolve the issue, just worked around it so to speak. And later the issue cropped up again in a different form. In my case with the MK1 it was the Z axis. When it was all said and done, there was a spot where it was binding that I didn't notice before. Once THAT was resolved, the stock stepper was just fine.

    I am running my PP with all stock steppers. I had to swap the Z pulleys as it was skipping steps like crazy when they were in their stock locations. I tore it down, and found the anti-backlash nut is binding. Not sure why, probably a manufacture defect. I chose not to replace it, as simply swapping the pulleys was a work around....for now. I could have easily put a bigger stepper (OK, not easily for the Z-axis due to space), but I'm sure I'll be replacing the anti-backlash nut eventually for a real fix.

    If you are trying to push a tool through material faster than it is capable of a bigger stepper will help....in a way. But this is harder on the cutting tool, and you run the risk of pushing the part around on the table. I have made many a cut on my MK1 in 1/4" aircraft ply with no problems, and I'm sure my PP will handle it just fine as it cuts 1/8" aircraft ply fine , but I haven't tried yet.

    I also had a problem with my freshly built PP's X-axis. It kept loosing steps. Here all it was, was the current setting on the stepper board. I took the board out of my MKI, and didn't double check the settings. It was set for the old stock steppers. It's been working like a dream since...

    I know some guys hate the stock steppers, but the ones in the pp are light years ahead of the old stock ones in the MK1. Those older ones were 2nds, and it was easy enough to get a bad one. The only problem I had with the original stock steppers was when I over drove the channel trying to overcome a mechanical issue, and it burned up the stepper (that learning thing again) The replacement was what has now become the stock stepper for the PP
     
  12. SlowBipe

    SlowBipe Member

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    I agree with rcav.

    That learning thing got me over and over as well. The PP III is my first and I had a lot to learn. My x axis is as smooth as butter now, and I am fairly certain that if I had the stock stepper it would work just fine. It has taken me a while to get here though.

    Regardless, I am happy with the overpowered upgrade which seems to be working well. I probably am over driving the phlatprinter with my cutting 1" foam, as I am stuck between a couple of problems. I want to make the cut in one pass to avoid any steps on the material. My bit is a 3 fluted mill and spins on my router at 20,000 rpm minimum. If I move to slowly through the material, the foam melts to the end of the bit and makes a big mess. I am thinking about putting the Harbor Freight tool back on to cut this foam so that I can move at a slower speed. If I could order again, I think I would have gone for the 2 fluted mill. That might reduce some of the problem with the foam melting to the end of the bit.

    Anyway, don't expect the motor I posted above to solve all of your problems, but it is a good replacement motor that drops into the x axis pretty well. If you think your motor might actually be damaged as I thought mine was (leaning curve) then you might want to try this. I couldn't find the motor Mark supplies for a price lower than this one, but that doesn't mean that it couldn't be found.

    Besides that, it adds a little more weight to the base of the PP to keep it from sliding off the table :D

    SlowBipe
     
  13. Jnida63

    Jnida63 Member

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  14. gben

    gben Member

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    Hey guys. I played around with the belt tension on my axis more today and couldn't quite find a tension that prevented skipping. It seems worse when I rotate the rollers backward versus forwards which has me somewhat puzzled. The belt also seemed to translate over to one side of the pulley flange even when it started centered. One potential cause of some belt related issues could be the fact that my idlers are slightly off axis as I tapped the stepper housing holes a bit crooked quite some time ago. It didn't seem to cause problems with the old rollers so I wasn't expecting any issues during this new install.

    After my 10th adjustment the flange on my stepper pulley sheared off as I manually rotated the rollers.


    [​IMG]

    So now I'm a bit frustrated as I felt like I was so close to having a fully functional machine now I'm totally out of commission. I'm guessing excessive belt tension put a sizeable axial load on the stepper pulley flange and eventually broke it off when I was trying to find the magic tension. I looked up the stepper pulley part number tonight (6T16-018DF2508??) on SDSPI and it looks like it is out of stock there as well as the phlatstore.

    My gameplan now will likely be some combination of getting a new stepper pulley, a new belt and either repairing or replacing my stepper so that I can correct the off axis idlers (if they are even related to this issue). I'm still really jazzed about the P3 and look forward to getting this fixed and dialed in. Attached files [​IMG]
     
  15. Gefahren

    Gefahren Member

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    I had the same problem with my X-axis pulley after tightening it up too much. Lucky for me I had a slightly larger all metal pulley laying around from another project. Now my machine will feed a 2x4' 1/4" piece of MDF without skipping. I don't remember the exact SDSPI part #, but I can look up my order history if you are interested.

    Attached files [​IMG]
     
  16. kram242

    kram242 Administrator Staff Member

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    Gefahren,
    That would be great if you could find the part number. I think this may be a good solution to the x pulley problem.
    Thank you
    Mark and Trish
     
  17. Gefahren

    Gefahren Member

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    Ok, I looked it up and narrowed it down to two different pulleys, just don't remember which belt pitch it is, I'm sure Mark could clear that up.

    A 6A16-025DF3708 .080 (MXL) Pitch, 25 Teeth, Aluminum Alloy Timing Pulley

    or

    A 6A 6-21DF03108 .0816 (40DP) Pitch, 21 Teeth, Aluminum Alloy Timing Pulley

    I'm pretty sure it's the second one, looks like they are about $10 now. but they are in stock.
    actually, now I'm really sure its the second one.
     
  18. gben

    gben Member

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    Thanks Gefahren.

    I went and counted the grooves on the P3 stepper pulley and got 18. Looking at the timing pulley on the Phlatstore (if it is the same one used on the P3) it looks like we should be looking for the following parameters:

    Pitch 0.080" (MXL)
    Number of grooves 18
    Belt width 0.250"
    Bore size 0.250"
    2 Flanges with hub
    Pitch dia. 0.458"

    With these parameters on sdp-si.com I found the following two timing pulleys in aluminum.

    A 6A16-018DF2508 (this one has a conventional hub with a set screw)
    A 6D16-018DF2508 (this one has a "fairloc hub")

    I've had mixed results with the "fairloc hub" type shaft coupling in the past. They usually clamp well if the OD of the shaft and ID of the bore are reasonably close but they do slip if not tightened enough. I do like them better than set screws though. The 6D16 is out of stock right now though so I'm planning to order a 6A16 and will try that.
     
  19. Gefahren

    Gefahren Member

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    I'd check with mark about it being a MXL pitch pulley, I'm positive mine is a 40DP pitch.
    Also with it being alittle bigger (21 vs 18 teeth) I get another tooth engaged with the belt so there is less chance it will skip. I was trying to feed a 2x4' sheet of MDF and it kept skipping teeth is why I tightened it up in the first place, now it doesn't skip at all. My steps per inch only changed down to 372. :02cents:



    Edit, now that I think about it, there's not much difference between MXL(0.08) and 40DP(0.0816) so I have no idea what the belt and drive pulleys are in the PPIII. I didn't even look at the store before opening my mouth, heh. :oops:
     
  20. kram242

    kram242 Administrator Staff Member

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    Hey guys this is the one we have been using from stock drive
    https://sdp-si.com/eStore/PartDetail.as ... roupID=218
    Part Number A 6T16-018DF2508
    Unit Inch
    Pitch .080" (MXL)
    No. Of Grooves 18
    Material Polycarbonate
    Belt Width 0.25"
    Bore Size 0.250"
    Bore Configuration Aluminum "T"-Insert
    Flange Configuration 2 Flanges / With Hub
    Pitch Diameter 0.458"
    Outside Diameter 0.438"
    Overall Length 0.688"
     
  21. dugd1013

    dugd1013 Member

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    A 6A16-018DF2508 is the aluminum version of the stock pulley from the same company. I blew apart my stock pulley about a month into running files. This pulley has double set screws and is a direct replacement piece. No problems since the change out.


    Description
    .080 (MXL) Pitch, 18 Teeth, Aluminum Alloy Timing Pulley


    Product Details
    Part Number A 6A16-018DF2508
    Unit Inch
    Pitch .080" (MXL)
    No. Of Grooves 18
    Material Aluminum Alloy
    Belt Width 0.25
    Bore Size 0.250"
    Flange & Hub Configuration 2 Flanges / With Hub
    Pitch Diameter 0.458"
    Outside Diameter 0.438"
    Overall Length 0.563"
    Hub Diameter 0.64"

    Price Information
    Quantity Price
    1 to 24 $8.68
    25 to 49 $5.89
    50 and up $5.25
    Availability In Stock
    Sell Unit Each
    Quantity

    Phone: (800) 819-8900X491 Fax: (516) 326-8827 Email: support@sdp-si.com
     
  22. gben

    gben Member

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    Dugd,

    Thanks for the confirmation on the part number. That's the exact one I picked so that is good. Should be delivered tomorrow so I'll try it out this weekend.
     
  23. gben

    gben Member

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    The new aluminum pulley arrived this Thursday from sdp-si. I was able to get it installed on the stepper yesterday. If anyone buys these as a replacement part in the future note that the set screw threads appear to be a different pitch than is used in the stock P3 pulley. I just used the set screws that came with the part and they seem to be working fine.

    [​IMG]


    With everything installed I tested the x axis with a moderate belt tension. The belt was still ratcheting pretty badly. I gave up for the day after that result as I didn't feel like playing the guess the perfect tension game.

    This afternoon I decided to take a fresh look at the drive and inspect the belt for any visible damage. The belt looked fine but in the process of inspecting it I noticed that the black idler rollers were not rotating so the belt was just dragging across them. I'm surprised I didn't notice such an obvious thing before but they are black and usually shadowed in the installed location. I backed off the two stepper screws until the idlers rotated freely and decided to check the axis again. Everything worked fine, no ratcheting, no issues. Everything was tracking well. Woohoo. Apparently that was the problem. I must have been torquing the stepper screws up tighter during this install than in previous installations and preventing the idlers from rotating properly.

    I ran a few test files and everything appears to be working well. I still need to tweak a few settings but I'm back in action. Attached files [​IMG]
     
  24. kram242

    kram242 Administrator Staff Member

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    Good job troubleshooting Ben! :good: Glad to hear your up and running
    Thank you for the set screw thread tip as well
    Mark and Trish
     
  25. isrdriver

    isrdriver New Member

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    I just got my machine and haven't really used it yet, but I discovered the same problem with the X-axis right off. I used a very thin sheet of foam to do the X-axis calibration and it was working fine. Later, with a 3/4 thick foam, I had the problem, which seemed to me to be a stalled motor. When I lifted the pressure rollers slightly, the problem went away. So I cut a short block of scrap MDF and put it under the pressure roller lever on each side to take some of the tension off and it didn't do it again (stall or drop steps) despite a number of trails. Not an elegant fix, but if this turns out to be the cause, I suggest a slightly weaker spring on the pressure rollers. It only required a 1/4" of lift under the handle to stop the motor from stalling and no friction was lost on the drive. Might not work on slicker materials.
     

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