After a loooong time mostly away from the shop (a job hunt, a new job…then another new job) I had been considering selling the mill and moving onto some other projects. After sitting down and really looking at the whole picture, I realized that the mill will help me complete these projects quicker, but it’s gotta work better than it does now. Holding a thou with this thing is basically impossible, so the question at this point is how much better can I get it. There are a few things that aren’t quite right:
- Backlash:
- X: 0.002″
- Y: 0.002″
- Z: 0.006″
- Spindle perpendicularity (to table): currently off by about 0.001″/1″ (about 1 mrad or 0.000017°). This doesn’t sound like much, but with a 2.5″ face mill it’s very noticeable on a single pass.
- Z-axis perpendicularity (to table): unknown at the moment.
The testing looks like this:
- Put indicators on X-,Y-,Z-axes and ballscrews simultaneously (one axis at a time)
- Determine if screw is able to move independently of axis structure.
- If so, need to pull screw and repack with larger balls, or order new ballscrew and nut.
- Determine if mounting block is moving relative to saddle.
- Need to reinstall screws with Loctite.
- Determine if screw is able to move independently of axis structure.
- Measure Z-axis perpendicularity
- Put indicator in spindle and 123 block on table, determine if movement is perpendicular.
- Shim column or rotate head to achieve best perpendicularity.
- Put indicator in spindle and 123 block on table, determine if movement is perpendicular.
- Measure spindle runout
- Measure runout of taper
- Measure stack-up by installing TTS holder with ground rod in it
- Test higher spindle speeds, up to 10k RPM
- Measure top bearing temperature and noise, compare to previous values
So the first step is to resolve these, then do some further testing. This will not only give me a more useful machine, but also is helping me think through issues on one of the projects I’m working on.
In addition, I’m working on upgrading to LinuxCNC. I have a computer which is being setup with it now (slowly but surely), using Mesa hardware (7i76 and 6i25). I’ll note here my comparison of control upgrade options:
- Upgrade to LinuxCNC ($300)
- Buy Mesa 7i76+6i25
- With steppers including encoders ($720+):
- New steppers (~$50 each)
- New encoders (~$65 each)
- Design and manufacture or buy mounting bracket ($??)
- Convert to LinuxCNC using Mesa 7i76+6i25+7i52 (~$370)
- With direct servos ($1780+)
- New servos ($240 each)
- New servo drivers ($218 each)
- New mounting adapters for motors ($??)
- Convert to LinuxCNC using Mesa 7i77+6i25 (~$300)
- With servos and pulleys (1:3 or 1:4) ($1200+)
- New servos ($150 each)
- New servo drivers ($138 each)
- New mounting adapters for motors ($??)
- Pulleys and belts ($??)
- Convert to LinuxCNC using Mesa 7i77+6i25 (~$300)
Finally, I’m whipping up an oil mist eliminator because of the crazy amount of oil mist that comes from using the minimum quantity lubricant system. This seems easier than completing the modifications I made to get flood coolant (and will probably be valuable with that system should I go to it, anyway).