Did my best to preload ballnut, but no success.

[alexccmeister]

Here's the thing. I have CNCFusion Kit #4 and I am getting around 0.2mm backlash for both X and Y. I took out the ballnut and ball bearings and measured them with my digital caliper. The stock balls are roughly 0.124".

One ballnut I got from Homeshopcnc has ball bearings of size 0.125". So I installed the ballnut on my Y axis hoping to get rid of the backlash. It didn't but dropped the backlash down to 0.06mm which is good enough. But the Y axis would bind up when I tightened the gib screws until there is no play.

Another thing I noticed is that there is a lot of crunching noise coming from the ballnut when I turn the ballscrew.

After a few more tries, I finally decided to switched back to the stock ballnuts and live with the backlash of 0.2mm. With backlash compensation, I hope I can make decent parts.

What's cnc X2 users' experience on this? CNCfusion is offering me a good deal for preloading balls for X and Y but now I am thinking is it worth to get them cos my initial trials created alot of problems for my mill.

Would this qualify for doing some lapping of the ways to try to get rid of the uneven way surfaces? Apart from misalignment of the cnc parts caused by inherent defects of X2 mill, I presume the uneven ways could be contributing to the table binding.

Any thoughts on this from the experts would be much appreciated. Thanks.

Alex

[alexccmeister]

Oh another thing I forgot to mention. I am using a 24V power supply from Keling Inc. If I were to use a 48V or higher power unit, would the stepper torgue increase at higher speed as compared to using the 24V power unit at the same high speed?

I get binding issue when my stepper speed is around 2500mm/min. But when I reduce to 1000mm/min, the binding issue disappeared.

I would like to maintain a high speed if I could without binding issue. If this can be solved by using a higher voltage power supply, I would do this instead.

Alex

[kawazuki]

Why do people aim for such ridiculously fast rapids on a machine with an effective table work space of 200 x 100mm? So you can rapid from one side of the workpiece to the other in 5 secs! So what! Will the table inertia mean you miss where you're aiming for? If it all works smoothly at 1m/min will your life be so much worse waiting those additional 7.5 seconds for the same movement? These are supposed to be 'relaxing hobby' machines after all!

[alexccmeister]

LOL, thanks for the wake-up call. I am so into the zero backlash thing I have forgotten about the size of the table and the travel. I guess I am just a perfectionist and it would have been nice to see rapid movement without binding though.

Alex

[Jason3]

Alex, I'm sorry I can't help you with your original question.

But, I feel strongly that fast rapids are well worth shooting for, especially if you intend to do any amount of 3d work. You may only save 5 seconds on a single move, but multiply that over thousands of moves...

For me, it meant a part that took over 9 hours at 2500 mm/min takes 5 3/4 hours if I machine at 4000 mm/min. I've recently bumped rapids up to 7500 mm/min. If that proves ok - and I fully expect it will - I'll push it up some more. Obviously there are practical limits, and machines vary widely but I think a little optimization can go a long way.

There's nothing wrong with keeping things sane, if that's your style though. Personally I'd rather go car racing than play golf - I guess some people will accept the possibility of fiery death for some excitement... Perhaps it's like that with machine tools!

Best,

Jason

[alexccmeister]

Hi Jason,

Thanks for the encouragement. I am still trying to get the rapid movement work for me but as I mentioned in the first post, I don't want to pay money for a set of preload balls if the result will end the same as what I have now.

BTW, what's the machine you are using? I can only dream of 5000mm/min rapid move. 7500 is a huge number. Any advice on how you achieved this?

Alex

[spoiledbrat]

In order to have zero backlash, I recommend two ballnuts on each axis. For it to truly work, you need to use a spring mechanism that pushes the ballnuts either toward or away from each other. If your device is adjustable, set the pre-load (the pressure at which the ballnuts are pushing or pulling from one-another) to the upper side of your expected cutting forces.

With the spring in place, the nuts are able to travel past the small imperfections on the leadscrew (dust, basic screw tolerance) without smushing any metal.

Look for my post on this page: Anti backlash nut design

I have been using this design with great success for 3 years now.

Good luck tweaking your machine.

Rob

[CarbideBob]

Lots of things to mess you up reloading your own ballnuts.
Any noise on a ballscrew is bad.
I'm a bit confused on the ball sizes used. Where did you get them?

Preloaded nuts generally use 2 different size balls. Every other ball is slightly smaller. The second ball acts as a spacer and "floats" in the ball channel so that the balls aren't fighting against each other. You don't measure these kinds of balls with calipers.

Also of course everything must be super clean. Nuts, screws, and balls are usally cleaned in an ultrasonic before assembly.

I agree that high rapids are very desirable. I find anything that can't do 10000 mm/min like watching paint dry, but I'm spoiled as my CNCs run at 20000 mm/min.
Bob

[Jason3]

Originally Posted by alexccmeister Hi Jason, Thanks for the encouragement. I am still trying to get the rapid movement work for me but as I mentioned in the first post, I don't want to pay money for a set of preload balls if the result will end the same as what I have now. BTW, what's the machine you are using? I can only dream of 5000mm/min rapid move. 7500 is a huge number. Any advice on how you achieved this? Alex

Alex, I'll quickly admit not qualified to advise you with your machine as I have no experience with similar setups. I can only offer suggestions, there's lots of others with much more experience with these machines around here, I'm sure they'll contribute their knowledge to help you.


As far as my machine, I meant to illustrate my point rather than suggest you should aim for similar numbers - beyond being a vertical mill that machine is quite different to yours. It uses brushless servos, linear bearings and 10 mm pitch ground ballscrews. It's a lightweight machine, so no deep cuts or big cutters - I rely on a 40K rpm spindle and high feedrate to get an acceptable rate of metal removal. I have run it more than twice that fast (18,000 mm/min rapids), but I had some reservations about my G-code so slowed it down again. It's still pretty fast at 7500 mm/min for a metal cutting machine I think. It was my first machine, so there are few areas I think I can improve. I'll tear it down soon for some mods and upgrades, I have a nice 50K rpm spindle for it and I'm going to beef up the X and Z axis and make it look a little nicer... It needs limit switches too.

Regards,

Jason

[alexccmeister]

Originally Posted by spoiledbrat In order to have zero backlash, I recommend two ballnuts on each axis. For it to truly work, you need to use a spring mechanism that pushes the ballnuts either toward or away from each other. If your device is adjustable, set the pre-load (the pressure at which the ballnuts are pushing or pulling from one-another) to the upper side of your expected cutting forces. With the spring in place, the nuts are able to travel past the small imperfections on the leadscrew (dust, basic screw tolerance) without smushing any metal. Look for my post on this page: Anti backlash nut design I have been using this design with great success for 3 years now. Good luck tweaking your machine. Rob

Hi Rob,

I ordered 6 ballnuts from homeshop cnc hoping to build my own mill/router but the project never took off due to lack of material and resources. But I have these 6 ballnuts that I have tested with my cncfusion ballscrew and one in particular gives me a good fit with minimal backlash. I used that as a basis of measurement.

Putting 2 ballnuts in series will not be possible with my X2. I was intending to use double ballnut for my new mill/router. That's why I got six.

I would like to figure our where the misalignment is that causes the ball to grind so loudly. When I run the ballnut over the ballscrew when not installed on the mill, the ballnut ran smoothly. But once installed, the grinding starts. This has to be caused by misalignment issue.

Originally Posted by CarbideBob Lots of things to mess you up reloading your own ballnuts. Any noise on a ballscrew is bad. I'm a bit confused on the ball sizes used. Where did you get them? Preloaded nuts generally use 2 different size balls. Every other ball is slightly smaller. The second ball acts as a spacer and "floats" in the ball channel so that the balls aren't fighting against each other. You don't measure these kinds of balls with calipers. Also of course everything must be super clean. Nuts, screws, and balls are usally cleaned in an ultrasonic before assembly. I agree that high rapids are very desirable. I find anything that can't do 10000 mm/min like watching paint dry, but I'm spoiled as my CNCs run at 20000 mm/min. Bob

Hi Bob,

The ball bearings are from the ballnuts I got from homeshopcnc. I found out from the 9 ballnuts that I have so far (3 from thomson and 6 from nook) that the ball bearing sizes are slightly different from one ballnut to the next. Its not consistent.

I read up on ballscrews and ballnuts and I did the installation of the balls as per your advice. One small and one big (how much bigger or how much smaller I have no idea. More like trial and error), but nonetheless I am getting binding issue. To be honest, I am still getting binding issues with the stock ballnuts with backlash of 0.2mm. So I suspect its this alignment issue again that is the culprit.

I understand you use a micrometer to measure these things, but all I have is a caliper and I think I got the measurement quite close with it.

I will keep in mind to clean the ball and screw thoroughly the next time I take them apart. I admit they are not entirely clean when I install them into teh ballnut and then onto the ballscrew.

Originally Posted by Jason3 Alex, I'll quickly admit not qualified to advise you with your machine as I have no experience with similar setups. I can only offer suggestions, there's lots of others with much more experience with these machines around here, I'm sure they'll contribute their knowledge to help you. As far as my machine, I meant to illustrate my point rather than suggest you should aim for similar numbers - beyond being a vertical mill that machine is quite different to yours. It uses brushless servos, linear bearings and 10 mm pitch ground ballscrews. It's a lightweight machine, so no deep cuts or big cutters - I rely on a 40K rpm spindle and high feedrate to get an acceptable rate of metal removal. I have run it more than twice that fast (18,000 mm/min rapids), but I had some reservations about my G-code so slowed it down again. It's still pretty fast at 7500 mm/min for a metal cutting machine I think. It was my first machine, so there are few areas I think I can improve. I'll tear it down soon for some mods and upgrades, I have a nice 50K rpm spindle for it and I'm going to beef up the X and Z axis and make it look a little nicer... It needs limit switches too. Regards, Jason

Hi Jason,

Definitely make a lot of difference when using ground ballscrew. I am targeting 3m/min speed. If I can get this without binding, I am very happy.

Alex

[alexccmeister]

Hi guys,

After doing some checking on my motor, I thought about it and took the cncfusion kit off the mill and run the stepper motor without any load. And guess what? With no load and at 3000mm/min, the ballscrew stopped turning while the stepper was still going. I guess this is what you would call a mis-step? Anyway, this was the binding problem I was talking about. Turns out it wasn't the table causing the binding. It was the stepper torque just went south with high speed. I tested this by holding the ballscrew with my hand. No torque at all. In fact I could easily stop the stepper motor with my hand until I reduced the motor speed down to 500mm/min when my hand failed to stop it.

So this definitely has to do with my power supply. Its a 24V 6.3A power unit from Keling. I was warned before its not enough but I never thought its this bad. So now in the lookout for a good power unit to replace the current one. I am looking again at Keling's power supply. Specifically this one:

KL-600-48 48V/12.5A 115V /230V

What do you guys think? 48V and 12.5A is big enough? My Driver is 5056. Base on Keling spec please see below:

5: KL- 5056 Microstepping Driver
Features of this driver
* Supply voltage up to +50VDC, current output up to 5.6A peak
* Optically isolated input signals, pulse frequency up to 400 KHz
* Automatic idle-current reduction
* 3-state current control for less motor heating
* 16 selectable resolutions in decimal and binary
* Suitable for 4,6,8 lead motors
* Stepping on upward or downward pulse edge (selectable)
* DIP switch current setting with 8 different values
* Over-voltage and short-circuit protection

Or should I go with 80V or even 100V? Overkill for an X2? Thanks.

Alex

[alexccmeister]

Hi guys,

Abit of updates. I took some time to lap the ways for X and Y and now they are as smooth as a baby's butt. Almost. Also solved my binding problem. Turns out when I locked the ballnut to the saddle, it was lower than it should be and when I run the motor, it was binding as it was not turning at the correct axis. It was slightly turning a cone shape if you know what I mean.

I pulled the ballnut block up while tightening the bolt holding it to the saddle hence correcting the problem. The result is I could now rapid at 5000mm/min without binding issue. As mentioned before, I will max it at 3000 for cutting. Just glad to know its solved.

I haven't installed the X axis yet. Hopefully that will not affect the Y axis performance. Looks like my 24V is sufficient after all. Almost flattened my finger when I tried to slip it in to touch the ballscrew when it was running.

Alex