[dwessels]

Hi,

I have an X3 that I added a CNCFusion deluxe ballscrew kit with helical couplers and have been having some issues with backlash.

Backlash I have measured is as follows:
X - 0.0135 in
Y - 0.006 in
Z - 0.006 in

Does anyone have any ideas on what I can look for?

I have also tried backlash compensation in Mach3, but when I have it turned on, the steppers will lock / lose steps randomly when they change directions. I have the backlash accel setting set to 30% and the shuttle accel set to 0.005.
Any ideas?

Thanks!

Denzil

[SScnc]

I don't use b/l comp but it seems like Hoss said that you have to set it at 100% to get it to work correctly. But again, I don't know that for sure.

Can't hurt to try it though

HTH

[dwessels]

I tried 100% as well, it had the same issues. I wouldn't even use backlash compensation except for my X backlash being 0.0135, which causes me some headaches.

If you are jogging both the X and Y, when it has issues, the stepper just stops moving and makes a noise, it doesn't move again until you stop it and start it moving again.

Thanks,

Denzil

[Stepper Monkey]

Backlash comp generally sucks. It isn't implemented that well on Mach either. Between those two things I don't know if anybody does use it truly successfully.

That being said, you can get it to work, but since it gets very conflicty with a lot of other very useful settings and comps in Mach, it involves shutting all of them off entirely. All in all not a very good tradeoff. You have to really cripple Mach to get the Backlash comp running smoothly, and even then only most of the time, and it slows your cuts WAY down doing so.

You shouldn't worry too much about it really. Just get your machine tuned as close mechanically as you can, within 2 or 3 thou, and then use good coding practice from there. Just because a machine has 3 thou backlash doesn't mean you can't cut accurate parts to under a thou all day long. You just need to pay attention to how you code it.

You should look at your bearings on X, not just the nut, with that huge of slop. A little tuning should take it a long way towards where you need to be.
Backlash comp just isn't the answer you are looking for.

[dwessels]

I did a little more troubleshooting tonight and what I worked out is that it only happens when I am moving 2 axis at the same time.
In other words, it doesn't happen when I only shuttle the X back and forth, it happens when I move something else at the same time. ie. Moving Y and then changing directions with X. X or Y will freeze and make a noise. If I restart the movement it will go again.

Thanks,

Denzil

[MrWild]

Stalling your steppers. Slow it down,check for stiction, and what kind of motor controllers are you using? It sounds like midband resonance. If so, there are several ways to go about a cure. Gexckos with electronic damping, or mechanical dampers. What kind of motors, and what kind of power supply? I think you have multiple problems, not just your lash.

[dwessels]

The motors, controllers and power supply are from Keling:
*KL-6050 Stepper rated 60V/5.0A
*Z - NEMA34 KL34H280-45-8A, 640 oz-in
*X,Y - NEMA23 KL23H86-20-8B, 425 oz-in
*54V/13A Power Supply 115V/230V toroidal transformer with bridge rectifier.

[Stepper Monkey]

If there is a direct cause and effect between moving multiple axes at once and the stalling, but they move fine independently, then it really is going to be in your software config with the backlash comp. I know generically things like stiction or resonance are very common gremlins but they just don't sound like they are at all relevant here, as you have not described the stalling either upon start or at given speeds when moving an axis independently, only when moving them together.
You really don't want to be using the comp feature, really, but if you must try it out then read up on the Artsoft site about configuring it and turn off the other listed features in Mach you likely have running that are known to interfere with it. Especially the CV mode. Turning on constant velocity and backlash comp at the same time is a guaranteed nightmare.

[dwessels]

Thanks Stepper Monkey.
I read section 5.6.3 in the manual and it didn't say much about backlash compensation. I also tried changing the general config option "Motion Mode" from Constant Velocity to Exact stop, but no difference.

Just to clarify. They do NOT stall when moving both axis if I have backlash compensation turned off. As soon as I turn on backlash compensation, one of the axis will stall when I change jog direction.

Thanks!

[cyclestart]

I think you have multiple problems, not just your lash.

For sure. .0135 backlash is not acceptable from that deluxe kit, neither is .006. Get that sorted before even thinking about backlash comp.

Double (then triple) check the mechanical assembly, alignment and adjustments.
Lower the acceleration to be sure steps aren't being lost that way.
Getting weird results when moving axis simultaneously? No idea. Could be software settings as Stepper Monkey suggests.

Edit/ Mach has a routine to check the performance of each axis during setup? Pretty sure (don't use Mach myself). Did these problems not show up during initial setup?
Word in bold edited

[ataxy]

definitely none of those backlash are acceptable and are definitely abnormal for ballscrew unless they are used, it may be normal to see anything from 0.002 to 0.004 on cheap single nut ballscrew

[dwessels]

Are there places backlash can hide in an X3?
I have double checked everything and all the screws/bolts are all pretty tight.

Is there a correct way to set the gib screw for the table?

[Stepper Monkey]

I had to pretty much completely dismantle my X3 when I first got it. I had to not only clean and adjust it but to do some minor filing, lapping, retapping, alignment, and even replacement of a couple of small bolts. There was a lot of swarf jammed in between parts that should have been bolted together flush.
Nothing difficult, but the machine really did look like it was thrown together hastily by someone who really didn't give a crap, which is very likely the case. The machine was a good design, just assembled badly. Spend a long dirty afternoon doing that right and you should no complaints after that.

I never put ballscrews on mine. I'm actually the only one on here that I can find still running stock screws. I just tuned it stock and it still keeps better accuracy than most ballscrew setups, its just that so few people try that first before replacing parts.

Unfortunately, there are generally 3 steps to X3 ownership;

Step 1: "The backlash is horrible, what do I do?" Advice - get ballscrews.

Step 2: "Ok, I installed ballscrews, and the backlash is still horrible, what do I do?" Advice - set up the machine right, particularly the bearing blocks.

Step 3: Actually dismantle and tune the machine, solve the problem.

Hint: You can entirely skip steps one and two if you want to! Some people will say otherwise - that the installation of the ballscrew kit fixed thier problem. I'd say those people had to take apart thier machine to install them and made enough changes in putting it back together again to have accomplished step three while they were in there. The screws didn't do it though, as cheap single nut ballscrews actually can ADD some backlash, it was just that they were the cause for the owners to have done the needed disassembly.

The backlash really is going to be in your bearing blocks (and gibs and the like), as no screw has that much backlash. Just a long afternoon of alignments and assembly of the machine by someone who cares is going to be the cure.

The ballscrews have many great advantages and you won't ever be sorry for having purchased them, but attempting to use them to solve backlash problems is a misapplication of them. That they simply cannot do.

[ataxy]

I had to pretty much completely dismantle my X3 when I first got it. I had to not only clean and adjust it but to do some minor filing, lapping, retapping, alignment, and even replacement of a couple of small bolts. There was a lot of swarf jammed in between parts that should have been bolted together flush.
Nothing difficult, but the machine really did look like it was thrown together hastily by someone who really didn't give a crap, which is very likely the case. The machine was a good design, just assembled badly. Spend a long dirty afternoon doing that right and you should no complaints after that.

I never put ballscrews on mine. I'm actually the only one on here that I can find still running stock screws. I just tuned it stock and it still keeps better accuracy than most ballscrew setups, its just that so few people try that first before replacing parts.

Unfortunately, there are generally 3 steps to X3 ownership;

Step 1: "The backlash is horrible, what do I do?" Advice - get ballscrews.

Step 2: "Ok, I installed ballscrews, and the backlash is still horrible, what do I do?" Advice - set up the machine right, particularly the bearing blocks.

Step 3: Actually dismantle and tune the machine, solve the problem.

Hint: You can entirely skip steps one and two if you want to! Some people will say otherwise - that the installation of the ballscrew kit fixed thier problem. I'd say those people had to take apart thier machine to install them and made enough changes in putting it back together again to have accomplished step three while they were in there. The screws didn't do it though, as cheap single nut ballscrews actually can ADD some backlash, it was just that they were the cause for the owners to have done the needed disassembly.

The backlash really is going to be in your bearing blocks (and gibs and the like), as no screw has that much backlash. Just a long afternoon of alignments and assembly of the machine by someone who cares is going to be the cure.

The ballscrews have many great advantages and you won't ever be sorry for having purchased them, but attempting to use them to solve backlash problems is a misapplication of them. That they simply cannot do.

i would actually agree with you in a certain way, definitely people should start at step three those machine are most of the time made by people who have less then what people would agree to work for here, so its kind of normal that there attention to detail and quality craftsmanship goes with it anybody who buy one of those machine should definitely start by cleaning and regreasing and oiling the machine and if there knowledge gives them the capacity to do it lap,file,grind any little detail that where left unfinished and that are often interfering with the quality of those product ounce this done those machine are often pretty precise, of course dont expect to build things that are in the +/- 0.0001 range but you can definitly get +/-0.001 ounce they are well adjusted

[dwessels]

Thanks guys.

I am still very new to this machining, so I am still learning as I go. Hopefully I will start at step 3. If I could get +/- 0.001 out of this machine, I would be really happy. That was why I bought nice ballscrew and helical couplings... but I didn't end up there.

When I put the new ballscrews in, I completely disassembled the table and cleaned everything. I will do it again, but I am not to sure how to lap or adjust the gib screws. I just tightened them so that it took out the play in the table as much as possible without binding the movement. Any special tricks to adjusting the gibs?

What spots did you have to grind / file?

[HackMax]

I never put ballscrews on mine. I'm actually the only one on here that I can find still running stock screws.

Well here's another one that hasn't converted to ballscrews. :-) I figured I give the original screws their chance to shine and when they
wear out I would put the ballscrews in. I get somewhere around .003 backlash from all axes and I haven't bothered to adjust them since I got the machine from grizzly. The only thing I had to do was to remove all the goop and oil it up and then of course CNC it. Mach3 takes care of the backlash for me so far.

Rick

[philbur]

I can't see that anybody has mentioned checking the preload on the ballscrew thrust bearings. I think this is one of the major sources of excessive backlash

Phil

Thanks guys.

I am still very new to this machining, so I am still learning as I go. Hopefully I will start at step 3. If I could get +/- 0.001 out of this machine, I would be really happy. That was why I bought nice ballscrew and helical couplings... but I didn't end up there.

When I put the new ballscrews in, I completely disassembled the table and cleaned everything. I will do it again, but I am not to sure how to lap or adjust the gib screws. I just tightened them so that it took out the play in the table as much as possible without binding the movement. Any special tricks to adjusting the gibs?

What spots did you have to grind / file?

[Stepper Monkey]

Awesome. Glad to see there is another stock one out there. Mine is a Grizzly too, and it gets a consistent .0025-.003 now as well. I think that's likely about as good at it is going to get, but that's more than accurate enough.

Other than cleaning it up and of course replacing that crappy contactor in the head that always fails with a proper US-made one, it has been a real trooper.

[HackMax]

Other than cleaning it up and of course replacing that crappy contactor in the head that always fails with a proper US-made one, it has been a real trooper.

What is a contactor? Something I should be aware of?

[ataxy]

Awesome. Glad to see there is another stock one out there. Mine is a Grizzly too, and it gets a consistent .0025-.003 now as well. I think that's likely about as good at it is going to get, but that's more than accurate enough.

Other than cleaning it up and of course replacing that crappy contactor in the head that always fails with a proper US-made one, it has been a real trooper.

for acme screw thats pretty good