Can't Machine a Simple Circle with a Probotix Fireball


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Thread: Can't Machine a Simple Circle with a Probotix Fireball

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    Default Can't Machine a Simple Circle with a Probotix Fireball

    For the last two weeks I have been working against degrading operational characteristics of my good old dependable Probotix V90 Fireball. It started with non-circular rings cut out of 1/8" aircraft plywood. It has now gotten so bad that I can't cut concentric circles, let alone hold tolerances to within acceptable levels.

    I'm using Vectric Cut 2D CAM and Planet CNC USB controller. The router is a Ridgid R2401. I checked for backlash, loose rods and guides, and TIR on the router. Everything seems to be fine. I have changed cutting speeds, feed rates, cutters, and even stock hold-down methods.

    I'm using Haas, Hurco, and Bridgeport milling machines at work, so it's not exactly foreign territory. But this problem has me bamboozled.

    Any ideas (besides getting another machine)?

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    Last edited by JPX2000; 11-24-2018 at 01:01 AM.


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    Registered Jim Dawson's Avatar
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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    Motor power supply maybe? Is it cutting correctly in one axis and not the other?

    Last edited by Jim Dawson; 11-24-2018 at 10:23 AM.
    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    Jim, it's not really consistent. and ID's and OD's are usually oversized. X or Y axis doesn't seem to matter. I'm not sure how to check the power supply going into the motors. Guess I was looking at a mechanical reason for the problem.



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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    Grab the collet and push and pull on it. If it moves, or feels loose, find out what's loose.

    Gerry

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    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    Quote Originally Posted by JPX2000 View Post
    Jim, it's not really consistent. and ID's and OD's are usually oversized. X or Y axis doesn't seem to matter. I'm not sure how to check the power supply going into the motors. Guess I was looking at a mechanical reason for the problem.
    Per your first post, you seemed to have checked the mechanical, so that would lead me to the electrical side. The reason I suggested the motor power supply voltage is that it is common to all axes and your problem seems to be at least on both the X & Y axis.

    That voltage is easy to check. Using a multimeter and with the motors enabled, check the output of the 24VDC power supply, it should be about 24VDC. Also check with the machine running a job. I would expect it to maintain an output of about 24VDC. If it's is sagging to 20VDC or so, then you may have a power supply problem.

    Also take a look at the electrical connections in general in the control box. With the machine disconnected from power, go through and re-tighten each screw terminal, look for corrosion at the terminals and any evidence of heating at the terminals. Also unplug and reconnect each ribbon cable, this ''cleans'' the connections.

    One mechanical thing to check is the couplings between the motors and the lead screws.

    Jim Dawson
    Sandy, Oregon, USA


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    Quote Originally Posted by ger21 View Post
    Grab the collet and push and pull on it. If it moves, or feels loose, find out what's loose.
    I already checked that out. I put an indicator on a dowel pin and spun the collet, and got less than 0.0005” TIR.



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    Quote Originally Posted by Jim Dawson View Post
    Per your first post, you seemed to have checked the mechanical, so that would lead me to the electrical side. The reason I suggested the motor power supply voltage is that it is common to all axes and your problem seems to be at least on both the X & Y axis.

    That voltage is easy to check. Using a multimeter and with the motors enabled, check the output of the 24VDC power supply, it should be about 24VDC. Also check with the machine running a job. I would expect it to maintain an output of about 24VDC. If it's is sagging to 20VDC or so, then you may have a power supply problem.

    Also take a look at the electrical connections in general in the control box. With the machine disconnected from power, go through and re-tighten each screw terminal, look for corrosion at the terminals and any evidence of heating at the terminals. Also unplug and reconnect each ribbon cable, this ''cleans'' the connections.

    One mechanical thing to check is the couplings between the motors and the lead screws.
    Thanks, Jim, I was going to go that direction next. I was also wondering if I was using the wrong post processor, since there are dozens to choose from in the list. Manual programming seems to work a little better but I’m not gonna go there.



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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    Quote Originally Posted by JPX2000 View Post
    Thanks, Jim, I was going to go that direction next. I was also wondering if I was using the wrong post processor, since there are dozens to choose from in the list. Manual programming seems to work a little better but I’m not gonna go there.
    Given that the machine has been running well for some time, I would suggest the the post processor you have been using would work fine. The problem seems to have developed recently so think back and see if you can find a point in time that things changed. Because the problem is getting worse over time, that would indicate a mechanical or electrical problem.

    One of the first things that I do when going out to troubleshoot a machine for a customer is to have a chat with the operator to try to understand what happened just before the problem occured.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    OK, Jim, the only anomaly occurred about 2 months ago when a 1/4" cutter fed right down through 1/2" of plywood into the spoil board. The feed rate was set way too high, causing the spindle holder to flex, resulting in the cutter being pulled down out of the collet about 1/2". I don't think that did any damage, because after checking the program, resetting the feed rate, and cleaning up the boo-boo, the part was cut out nearly as programmed.

    I've no idea how to check for the proper output voltages to the motors. If I don't wire up something myself, I usually don't mess with it. I haven't found a pin-out diagram for this PBX USB board, but I'm still looking. Could I check the voltage outputs without taking off the controller cover? I already did that to make sure that screws were tight on the terminals (they were) and to unplug and replug the headers. That cover is a real PITA to deal with.

    Whatever this is, it's not something obvious. I may have changed some sort of setting in the controller software.

    I do appreciate the time you're taking to help with this. My free time is limited and building season is upon us. If you've any suggestions on measuring the output V that would be great.



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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    There should be a silver box with a several terminals on it, that is the power supply, according to the one pdf I read it should be a 24V supply.

    Should look something like this

    https://ae01.alicdn.com/kf/HTB1KN83L...driver-and.jpg

    Set the multimeter for DC volts and check the voltage across the + and - terminals. Stay away from the L and N terminals, they have line voltage (120VAC?) on them.

    Jim Dawson
    Sandy, Oregon, USA


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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    Quote Originally Posted by Jim Dawson View Post
    There should be a silver box with a several terminals on it, that is the power supply, according to the one pdf I read it should be a 24V supply.

    Should look something like this

    https://ae01.alicdn.com/kf/HTB1KN83L...driver-and.jpg

    Set the multimeter for DC volts and check the voltage across the + and - terminals. Stay away from the L and N terminals, they have line voltage (120VAC?) on them.
    The rear of my control box is pretty well closed up. There are 4 connectors, one for the X,Y, and Z, plus an A axis for revolving surfaces to be machined, I don't have any exposed terminal screws. the rear of the box looks like the attached photo (not mine, somebody's similar enclosure). There are 5 pins on the connectors, and this is what I'm trying to find. I want to know what each pin powers so that I don't go sticking meter probes onto the wrong ones.

    Can't Machine a Simple Circle with a Probotix Fireball-damage1-jpg

    Opening the enclosure, holding the halves apart, and finding voltage values is not gonna be easy. I'll have to recruit my technophobic spouse to help. Fun.

    One last thought... should I perhaps be thinking about whether the step per unit values are still correct?



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    Default Re: Can't Machine a Simple Circle with a Probotix Fireball

    Yeah, if your parts are off size but consistent then that would be a symptom of your step unit values being off.

    That box in the pic looks like it had a hard life

    The power supply should be inside of the box. There must be some screws in that box somewhere to take it apart. I just looked at some pictures, it looks like there are screws in the bottom of the box, then the bottom just pulls off. At that point you should be able flip it over and pull the top off and get to everything.

    EDIT: Doing a bit more research, it looks like the power supply might be integrated into the main power board in the box. The other picture I saw with the seperate power supply may have been an upgrade or some kind of mod.

    Last edited by Jim Dawson; 11-25-2018 at 10:38 AM.
    Jim Dawson
    Sandy, Oregon, USA


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