Y axis issues?

tm america
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Y axis issues?

Post by tm america » Wed Jul 30, 2014 12:37 am

I got my machine altogether and i am having issues with the y axis.. it seems the left side motor is loosing steps.. I checked all my connections they looked good.. i thought maybe it is doing it cuz the wire going to the left motor is longer- more resistance?So i cut another length of wire and installed it so the right and left wires are the same length from the point of splice.Still seems to be doing it..Seems like after i run a larger test file when i run the y axis all the way back to the zero position the right side will be touching and the left side will be about a half inch away .. When both started with touching..The test file i am running is roughly 600 inches of cutting.. I'm wondering if i have a weak motor ?or if it is somehow a wiring problem..I am gonna test the resistance of the wires next to see if they read the same .Has anyone else had similar issues or found a solution to this problem

WillAdams
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Re: Y axis issues?

Post by WillAdams » Wed Jul 30, 2014 2:07 am

You shouldn't have that much racking on the gantry.

The extra length of wire is a good idea, but shouldn't be necessary (the pulses aren't fast enough that the difference in length would matter).

Standard mechanical things to check:

- belt tension --- one negative of the new belt anchors is that it's difficult to get equal tension on the Y-axis --- fiddle w/ that until both belts have the same tension / play the same note when plucked
- pulleys --- make certain that the set screws are all tight and that they're not slipping
- idler wheels --- make certain that they're tight

And of course, adjust the motor current if need be.
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tm america
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Re: Y axis issues?

Post by tm america » Wed Jul 30, 2014 2:16 am

I went over everything.. pulley's are the two screw type with one going into the flat spot on the shaft both are tight. belt tension is very close on both sides.But shouldnt effect it unless it jumped a tooth.I am running a tb6560 controller with mach3 and i have both motors tied into the same drive.. then the wire splits and goes to both motors..so in therory they are both getting the same power .. only thing i could think is high resistance in a wire,bad connections or a weak motor ?I am gonna swap the motors from side to side and see if it reverses the issue ..If it does i know it is the motor. If not it has to be a wire..Pnly other thing i can think of is if there was some kind of inference going to the one wire?

tm america
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Re: Y axis issues?

Post by tm america » Wed Jul 30, 2014 2:56 am

Ok i swapped the motors from side to side and it still does the same thing after running the program the left side ends up about 1/4 inch from the 0 position .so i'm guessing it is either a wire or somehow it is getting fed current form outside sources...I'm gonna swap the wires now and if that doent fix it i will reroute the wire i have running down one of the slots in the maker slide on the gantry.. maybe it is getting static back feeding it?..maybe it is something with how i have it wired?when i origonally wired it i wired both y axis motors the same ..I soon relized i needed them to run opposite of eachother so on the left side i hooked red to blue,yellow to green,green to yellow,and blue to red..This made it run in the correct dirrection but maybe somehow the pairs should be switched differently?Also this is a fairly big machine it has 56 inch x axis travel and 54 inch y axis travel with 5 inches in the z axis..

WillAdams
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Re: Y axis issues?

Post by WillAdams » Wed Jul 30, 2014 3:20 am

I don't believe that there's an effectual difference between any of the possible ways of swapping a motor's direction of rotation by altering the wiring.

I would suggest swapping the motors around to see if some pair of them works better together --- at a guess it's possible for motors to be slightly different.

It might be that you'll need to re-wire the machine so that each motor is controlled individually and you can have the micro-controller adjust for this sort of thing --- maybe --- have someone who actually knows about the electronics advise you on that --- as Catalin has noted I'm (sort of) mechanically inclined, so my preference here is for a driveshaft, but electronics are not something I know much about, hence my efforts on the wiki.
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tm america
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Re: Y axis issues?

Post by tm america » Wed Jul 30, 2014 3:32 am

I did swap motors from side to side.i suppose i could try swapping the pairs on one of the motors.I tried running at different speeds and it didnt have any effect.i ran it everywhere from 40 ipm to 400ipm no change.I do have a 4 axis controller .. worst case i will just wire one side to the y axis and the other to the a axis and just slave them together .. but i'm thinking it will still have the same result?

tm america
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Re: Y axis issues?

Post by tm america » Wed Jul 30, 2014 3:58 am

I switch the pairs on one side and it made no change.I switched the way i had the wires on the side where the wires y off to the two sides. Still no change.. only thing i can try from here is changing the wires on the left side..there must be a short in the wire or a place with high resistance..I moved the gantry thru its full movement with the belts off no binding ..So i am really not seeing where this issue is coming from...

cvoinescu
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Re: Y axis issues?

Post by cvoinescu » Wed Jul 30, 2014 8:25 am

Indeed, it sounds like one of the wires may be bad -- or you may have a mechanical problem on the left side.

Will, it's not a matter of pulse timing (not by many orders of magnitude), but of resistance. The impedance of the motors is very low, compared to the loads we're used to, so an extra meter of wire makes a significant difference in how the current gets split between the two motors. So yes, it can be a concern.
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WillAdams
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Re: Y axis issues?

Post by WillAdams » Wed Jul 30, 2014 9:49 am

Thanks!

That makes sense. I added your explanation as a note on ``Wire Length'' on the Electronics page.
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tm america
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Re: Y axis issues?

Post by tm america » Wed Jul 30, 2014 3:56 pm

I added wire to the right side motor and repleced the left side motor still no change.the left side of the gantry still does not end where it started it is about 3/8 to 1/2 away..I measured the makerslide down both sides ..everything looked good..right now I am thinking I'm gonna wire the motors into two different drivers and just slave them in mach3.I will use equal lentgh wires ..hoping this fixes it..otherwise I'm gonna swap out the v wheels and maker slide on the left side to make sure I'm not getting unwanted resistance.....I even went as far as pushing and plulling the gantry byy the exact center to see if it racked..when I pushed it showed more resistance on the right side then when pulled I got the opposite result..so I'm not gonna take that to seriously..I might end up making something more accurate to test this..maybe put a eyelet dead center and use a spring with a fishing scale to measure and monitor the results.then use the same set up on both sides ..So I can see if one take more force to move then the other?

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