[nikuk]

I have an issue with the design of the X2 or CNCFusion parts. I have the prototypical X2 mill conversion. The X2 CNC Fusion kit uses an aluminum block to mate the Y axis ballnut to the saddle. The block rises up through a slot in the saddle. The saddle has a 6mm set screw / bolt which will pinch the aluminum block.

My Fusion part is about 0.040" narrower then the saddle slot.
If I shim the front & back to be mechanically "snug" I get 0.0005 - 0.001 backlash (no table or fixturing, just the saddle & gibs strip on the machine) on the test indicator. Have tried repeated 3.0" Y moves and she repeats nicely.
As I thread the 6mm bolt in it eliminates the rear gap between the aluminum block & saddle. This results in ~0.035" backlash in Y movements.
I drilled & tapped (drill press) a 6mm thread halfway into the alum block, in the hopes that this would help. The bolt hole in the saddle is already threaded. I threaded the bolt through the saddle & bottomed it into the alum. This gets me ~0.048" backlash.

I am considering drilling & tapping completely through the aluminum and placing washer style shimming front & back. Before I do this I was wondering if anyone else had run into this. There are so many of these conversions out there but the threads I have found in the last two days have no mention of this particular issue.

• HF 44991.
• LMS Belt drive.
• LMS solid column & base.
• CNC Fusion preloaded ballnut kit.
• Keling/Automation Inc steppers,
• Gecko 540, USB100, Mach3, plenty of HP Dell laptop.

FWIW I worked in a mom & shop machine shop a few years and was involved in alot of machine repair & maintenance so I'm not a complete newb here.

[nikuk]

err, should add that with the saddle completely off and the test indicator on the aluminum block the backlash is roughly 0.00025.

And I am using CNC Fusion's "stock" lovejoy" couplers with rubber bushings. Not the heli-couplers.

[nikuk]

hmmm. sitting at the machine now (last effort to assess before bed)...

put the saddle on, setup a test indicator, set the gibs to firmly snug, ran this:

g0y0
g0y1.5
g0y-1.5
g0y0
g0y1.5
g0y-1.5
g0y0
g0y1.5
g0y-1.5
g0y0
g0y1.5
g0y-1.5
g0y0
g0y1.5
g0y-1.5

and she hits 0.0 (+/- a tenth) on every move but finishes at 0.0005 past.

Now I'm just tired and confused.

[arcticrain]

I had an issue with my CNC Fusion kit on the y axis. The pocket for the bearing wasn't deep enough and this caused it to protrude ever so slightly. I had to shim it so that when it was bolted down it wasn't being support on the bearing. I was having similar issues with backlash before I shimmed it. I brought this issue up with CNC Fusion and they had not realized the width of the bearings had changed. I am assuming this affected a lot of kits.

Attachment 290326

[kawazuki]

Are you really aiming for sub - thou backlash with an X2 ? The overloaded ballnuts are acknowledged to only achieve 0.002 - 0.005" at best so how you are getting a quarter thou backlash is strange?
And the std Fusion connectors are good but not as good as the helical's so there is some more built - in lash. Depends on what you want 0.001" accuracy or 0.050" - what do your manufactured parts demand?

[nikuk]

@Arcticrain - I am not having that issue with the mount. I have a different style of mount. Thank you though.

Are you really aiming for sub - thou backlash with an X2 ? The overloaded ballnuts are acknowledged to only achieve 0.002 - 0.005" at best so how you are getting a quarter thou backlash is strange?
And the std Fusion connectors are good but not as good as the helical's so there is some more built - in lash. Depends on what you want 0.001" accuracy or 0.050" - what do your manufactured parts demand?

I'm getting tenths of backlash on the nut itself - no table, no saddle, no load.

LOL, No. I'll be perfectly content if this machine holds 0.003-0.005 in steel and 6061 al. There is no way I can accept 0.05". Even for purely hobby level parts.

The machine freely repeats X+Y interps to 0.001 or less, but this is with no external load (no workholding, workpiece, or cutting forces). The fact that the Y axis carrier is free floating means there WILL be slop in actual cut parts. So do I:

1. Mechanically shim it and pray the shims dont work themselves out
2. Pinch the bolt and figure out how to deal with a mile of backlash
3. tap the bolt full through and hope the 0.05 comes down to something reasonable
4. something else altogether