PNC-3000 part 8

I wrote earlier that Roland usually doesn't produce junk, this is also still my belief.. But someone had a really bad day in the workshop, the day the table for my mill was line bored.

I had decided that I wanted a vacuum fixture for engraving, so after some manual workshop-time I only needed some cutouts for a O-ring and fixpoints, problem was I couldn't get the fixture clamped down without the dial indicator showed over 0.02mm height difference across 50mm, which is a bit too much for my likening. No amount of cleaning the vice and table could fix this.
Then it stuck me that I had not yet indicated the table, and so I did.. This was a saddening experience..  approx 0.08mm across the 180mm X travel.. this had to be fixed or at least investigated, before anything useful work could be made on the mill.
Removing the table was surprisingly simple, remove the X motor, remove the nut and the thrust bearings for the leadscrew, losen the grubscrews for the rods, move the table all the way to the left, tab out the rods with a brass rods, until there is enough room to slide the table out of the bearings. Be careful not to hit the bearing seals with the rod, it should not be necessary to tab through the bearings, if the table is moved all the way to the left.
With the table off I could mike the rod distance relatively to the table top,  and this matched beautiful with my observations when the table was on the mill, meaning that there is no doubt that the problem is that the table top isn't lined up with the linear rods the table is sliding on, which should be a relatively simple fix.

The difference in height on the worst rod was a chocking 0.19mm!
With the table off I also discovered an adjustment grubscrew for the leadscrew.. Win.. :D

In the garage I learned that though the theory behind fix may be simple, the execution was tricky. After having spent 2 evenings in the garage trying to mount the table without any success, partly because my mill is quite worn, and partly because there is very few places where you can clamp down the table, I decided on another strategy.
My mill has a detachable vertical head, that when removed turns the mill into a horizontal mill. This eliminate the effect of the worn table ways, and gives plenty of options to clamp down the table, relatively speaking, though it was still tricky to line up things.


I choose my 25mm carbide insert mill, instead of a fly cutter this was more work, but easier to control and I didn't had enough travel in my mill to get all the way past both ends of the table. After the first attempt I wasn't really satisfied, the finish was fine, but I still had 0.06mm in difference, and a bit of a popeller shape.

So I gave it another go, and after having buffed it up with 1200 grit and brasso, I was within 0.035mm end to end on the rods. I's possible that another turn measuring and milling would have gotten me closer, but in practice this has no noticeable effect.

When the table was mounted in the mill, the total difference over the full working area was about 0.01mm. This is good enough for me.

In the meanwhile I have also got a new drive belt, which has quiet down things considerable, and almost removed all vibration and resonance.