3 Axis CNC router

[JAZZCNC]

Clive, Jazz, thanks that makes sense - I remember reading but not understanding this in the ipm manual! I’ll give it a go and see. Could not understand how it could be loosing steps on such a light cut.... cheers guys


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99% sure it will be that Joe. (Provided nothings lose or falling off machine which knowng you sure it won't be..lol)
Happens 50% of the time with these controller/drive combo and it's something I check for has matter routine. Can happen on any controller really but with the IP-M or S happens randomly depending on how drives setup. Esp if not used tuning software to check Rising edge setting in drive.

Edit: For anyone else reading this that doesn't have Cslabs controller but as similair problem then the same can apply.
The test and fix is the same. Or if the the drives have option to change the leading edge setting use this. Both work same.

[Neale]

I saw exactly the same problem on my machine. X and Y were fine, but Z looked as if it were losing steps on complex 3D work. In my case, it didn't show up on single test runs; what seemed to happen was that you lost one step every time you changed direction. Fix was simple - as Jazz said, just change step polarity. I think this is more likely to happen with the CSMIO controllers as they have differential outputs - brilliant for noise rejection, but too easy to get the two wires swapped!

My only reservation about this diagnosis is that I wouldn't expect to see any significant error on a single movement, as the effect is cumulative with movement direction changes. But Jazz's test (I did exactly the same thing when I was chasing the error) will soon show the truth!

[JAZZCNC]

what seemed to happen was that you lost one step every time you changed direction.

That's exactly what happens because the last pulse gets sent after the next direction change happens so it gets dropped.

To be honest, can happen on any system. The reason it tends to happen on these is that of the flexibility both drives and controller give. Meaning it's easy for one or other to be set wrong. Majority of older or lesser drives only allow rising edge which is ok for most sytems until you get controller that use's the falling edge.!!

[JoeHarris]

Thanks Neale, on a single movement there is very little error, only when cutting a test pocket with changes in direction did i see the error so I'm hoping this is the explanation. Whilst I've taken care throughout the build and asked a lot of questions, I have made this machine with basic tools and basic skills, so I'm sure it's not just down to calibration!

[Desertboy]

I read sometimes the seals on the ballscrew can be tight when new so when you first run the machines they can stick a little, the solution run it up and down the full length of the travel a few times. Greasing can help to.

I had a sticky bit right at the end of my travel on one of my Y ballscrews kept firing a stall detect at me, after 10 to 15 running up and down the lengths occasionally stalling the problem disapeared. The area where it stalled is now part of my homing sequence so it gets travelled over regulary never stalled again.

[JAZZCNC]

I had a sticky bit right at the end of my travel on one of my Y ballscrews kept firing a stall detect at me, after 10 to 15 running up and down the lengths occasionally stalling the problem disapeared. The area where it stalled is now part of my homing sequence so it gets travelled over regulary never stalled again.

That's most likely to be alignment issue not sticky seals. To be honest I've fitted 100's ballscrews and never had sticky seal on the ballnut(presume you mean ballnut seal)

Now what can happen is often the spacers on the BK bearings are not long enough and the seal in BK bearing can rub on the screw.
This tends to happen mostly on cheap BK bearings. Also on cheap BK bearings, like what Chai Sells, the bearings are not always shimmed correctly or even in wrong way round so when tightening the nut they will bind.

Joe If BK's came from Fred at BST then you can tighten them fully and they won't bind. Fred BK bearings are light years better than Chai's.

[JoeHarris]

That's most likely to be alignment issue not sticky seals. To be honest I've fitted 100's ballscrews and never had sticky seal on the ballnut(presume you mean ballnut seal)

Now what can happen is often the spacers on the BK bearings are not long enough and the seal in BK bearing can rub on the screw.
This tends to happen mostly on cheap BK bearings. Also on cheap BK bearings, like what Chai Sells, the bearings are not always shimmed correctly or even in wrong way round so when tightening the nut they will bind.

Joe If BK's came from Fred at BST then you can tighten them fully and they won't bind. Fred BK bearings are light years better than Chai's.

My Hiwins came from Fred but ballscrews and bk/bf bearings from chai.... not wild about taking them apart especially now!

[Desertboy]

I hadn't squared the gantry up at this point so very possible it was alignment, if would be about the same time. It has taken me ages to get dual homing working.

Hmm interesting with the bearings will have a look, I have a spare BK12/BF12 fitting to strip down. But will make sure I buy my bearings from Fred next time I keep seeing his name mentioned.

[JoeHarris]

So starting up again, I got the spindle control from Mach set up last night. All seems to work OK, apart from the RPM readout on Mach reads 0 regardless of the spindle speed. Is that normal? The one setting I was not sure about was mach's "spindle pulley" settings. The IP-M manual was not much help on that front. Does anyone know what this should be set to for a 2.2KW chinese water-cooled spindle?

That's most likely to be alignment issue not sticky seals. To be honest I've fitted 100's ballscrews and never had sticky seal on the ballnut(presume you mean ballnut seal)

Now what can happen is often the spacers on the BK bearings are not long enough and the seal in BK bearing can rub on the screw.
This tends to happen mostly on cheap BK bearings. Also on cheap BK bearings, like what Chai Sells, the bearings are not always shimmed correctly or even in wrong way round so when tightening the nut they will bind.

Joe If BK's came from Fred at BST then you can tighten them fully and they won't bind. Fred BK bearings are light years better than Chai's.

Sadly I think I am going to have to strip down the machine and sort out the bearings as they are binding quite regularly and causing pretty major accuracy issues. You get what you pay for I guess, and I should have shimmed them before I assembled the machine - lesson learned!

[JoeHarris]

So starting up again, I got the spindle control from Mach set up last night. All seems to work OK, apart from the RPM readout on Mach reads 0 regardless of the spindle speed. Is that normal? The one setting I was not sure about was mach's "spindle pulley" settings. The IP-M manual was not much help on that front. Does anyone know what this should be set to for a 2.2KW chinese water-cooled spindle?

Sadly I think I am going to have to strip down the machine and sort out the bearings as they are binding quite regularly and causing pretty major accuracy issues. You get what you pay for I guess, and I should have shimmed them before I assembled the machine - lesson learned!

Strip down has commenced... feels good to be in it again!

and I have some mild steel tube on order to remake the undersized BK bearing spacers/shims.

14mm o/d with 1mm wall for the 16mm ballscrew bearings

and 18mm o/d with 1.5mm wall for the 20mm screws.

I guess mild steel is what the originals are made from?

The plan is to cut them from the tube slightly oversized and then neaten them up in my ancient lathe so they are nice and uniform in length all the way around. Does that sound reasonable to anyone who has done this before?!