Motion madness - how to determine source of problem?

[Mayo]

PRT 48x96 with 4G and PK296A1A SG7.2 motors

I recently had one of my X motors start to fail and I had it rebuilt locally. I installed it and it works good - allowing me to finish a deadline job.

On a different job a couple days later, the bot lost steps and cut through already cut sections and ruined the job.

In using the keyboard or MX (any distance) the gantry shudders or shakes like it has Parkinsons. It's less noticeable when doing a Jog move but it's still there. There is some uniformity or regularity to the shakiness if that makes any sense.

Thinking maybe a Gecko drive was causing it, I took the Y and Z Gecko drives and put them into the X drive locations on the board, and the X Geckos in the Y and Z locations. This didn't fix the problem so I ruled out the drivers.

I checked my unit values, they're what I normally use.
I tightened and loosened the turnbuckles but this made no difference.

Now I'm wondering if one of the resistors near the Geckos might be bad or something else on the board - or the power supply? I don't know what the resistors should read...

Could anyone having had similar problems give suggestions what to check next?

[Mayo]

OK in further testing, it's looking like turnbuckle tension may be the problem.
When I make the X turnbuckles to the almost loose stage, the shuddering and the clattering noise disappears or becomes practically unnoticeable.
Does this mean the turnbuckles are just magnifying an underlying problem, or are they causing the problem?

I always ran the machine with the recommended number of turns on the turnbuckles and I always had clattering sounds like it was on a train track.
But I thought that's just the way it is for these machines.

At one time I thought maybe the X racks were not lined up to each other and I ran a string from the first X2 rack "groove" to the matching X1 rack groove. I then checked with a square against the rails and the string was square to the rails.

I'm going to run another job now and see if everything is back to better than normal...

[srwtlc]

When is the last time you checked/replaced/greased the pinions?

[Mayo]

Pinions were replaced in Feb. of 2015 and I cut EPS foam for about 90% of my work - which is only averaging 2-3 days a week at most.
When I put the new pinions on, and greased the rack, there was no difference in the clackety clack sound I have always heard since day one.
I'm now thinking either the recommended 4 turns of the turnbuckles is way too tight or that my motors have always had sloppy gear boxes.

When the pinions are not engaged in the rack, or when I have the turnbuckles only tight enough to start moving the spring, there is no clacking sound when I move or jog in the X direction.

When they are at the recommended tightness, one motor will make noise while moving in the positive X direction and the other motor will make noise when moving in the negative X direction. Never are both noisy at the same time.

[Gary Campbell]

Mayo...
Mag a dial indicator onto the frame and set the point against the X car. Push pull to see how much, if any, play is in the system. Try both sides and check both variations of your spring tension to see if there is a difference. Also doesn't hurt to do the Y... on the motor side

[Mayo]

I ran one small job with no problems. Today I started another small job and while cutting the 2nd piece, the X car once again jumped off the rails.
I'm now thinking maybe something is running in the background that's interrupting the file and causing lost steps.
I stopped the machine, opened task manager and did some screen captures of applications and processes.
Will post those as soon as I transfer them to this computer.
Gary - I will have to get a dial indicator - never used one before.

[Chuck Keysor]

Mayo, you can borrow my dial indicator. It is an "A-Line-It Deluxe". But it does not have a magnetic base, which Gary said you will need. (Maybe I should have bought the "Ultra-Deluxe" model........ :)) Chuck

[Mayo]

This morning I made changes based on the Black Viper "tweaked" settings for the Windows 7 Pro Service pack 1.
Initial results seem that the computer is faster responding.
I ran one job of 20 pieces and so far so good. Maybe I shut off whatever was interrupting the bot... time will tell.

[Mayo]

Continuing to have problems with motors not acting as they should... updated info -
When I first got my 4g board, I was able to jog at 6 inches per second.
After dealing with steps or ridges in cuts I decided to lower the jog speed to 5. This worked for some time and the missed steps seemed to be happening less frequently. It didn't eliminate the ridges completely though.

Yesterday the motors missing steps started happening again for no obvious reason.
So I dropped the X motors away from the rack and when I did a jog move the motor(s) would make a higher pitched sound after about 24 inches of travel, based on the numerical readout since they weren't actually moving the gantry. I then experimented with changing the jog speed and found a speed of 4.99 did not stall the motors but 5.0 does stall them or make them out of sync. The sound of the motors after traveling approx. 20 to 24 inches in X distinctly changes to a higher pitch and then looses steps when my jog speed is 5 or higher.

Incidentally, when I ran the speed test program, the result was over 73%.


Why would a jog speed of 6 have worked for some time but now I'm only able to jog at 4.99 ?
Has some other setting been changed inadvertently that I'm not aware of?
The only thing I changed (today) was making the slow corner speed from 60 down to 50.
I don't even know what else to check at this point.

[bleeth]

pinions, proper tension on motor springs, grease on rack, tightness of gantry bolts and squareness of gantry.

[Gary Campbell]

Add to Dave's list:
Age of components
Number of heat cycles they have endured
Gearbox lubrication

[bob_dodd]

Mayo
In you first couple of post you say when you loosen turn buckle it may be better , also you cut a lot of EPS foam , I had a problem like this once and it was EPS foam packed in the rack gear , try a sharp hook tool in between rack teeth just a thought

[Gary Campbell]

Mayo...
If you find that there are no mechanical reasons for the erratic actions and you can't diagnose the electronics, you might consider a modern upgrade:

http://gcncservices.com/product/rezurrection-control/

Custom built with the functional and safety features you desire