Warco mini mill cnc conversion

[irving2008]

This one?



The question is how the table attaches to the Y-axis. On my bigger one the table is machined with integral dovetails that run on ways machined in the Y-saddle, similar to this one of an X2 If so its hard to see how they could get misaligned. All the pictures I can find of the mini-mill (X2 clone) seem to suggest its much the same unless the saddle is in two parts? Are the gibs tightened up? A loose gib could allow the table to twist on the saddle, or the saddle to twist on the y-ways.

[buster]

Thats' the one.
The X/Y saddle has dovetails machined presumably!! at 90 degrees same as the X2.
I am trying very hard to see how the X and Y can be out of square, it's also very difficult to do an actual
measurement of the complementary dovetails on the saddle to check their squareness.

The gibs were nice and tight and threadlocked and the steppers had an easy life moving the table (3Nm) . Table also had
no more than 0.08mm play with the X extended to far right/left.

I should of noticed this problem about 10 months ago.

[irving2008]

when you did the test did you lock the gibs on the stationary axis?

The other thing i would do is put the base of the engineers square in the vice but proud of the top and indicate along that in the X to make sure its still aligned that way - it should be. with the Y-gib locked. Then move to the other leg of the square, lock X and release y and then indicate Y. that way you haven't got any disassembly between tests... or do the same things with a 123 block on the 3+2 sides.

If the ways are not machined square I suppose it would be possible to have them recut and fit a wider gib-strip (if need be). You could remove the table then indicate the Y axis movement relative to a square clamped to the x-way... that would give a clue as to which way is mis-aligned

[buster]

I visited the garage about 45 mins ago to recheck everything again and
it's true the Y is not square to the X and again I got >0.3mm over about 60mm along the engineers square. I even checked the engineers square and its fine.

Tomorrow I will try you idea of indicating the Y movement relative to the X.

Let you know the result.

[buster]

I did another test tonight with the table removed and checked with a square
how true the Y movement was. The results show a 0.4mm error over about 65mm.

I repeated yesterdays test and set the dial to +-0.03 over 140mm on the X axis. A 6inch square held in the vice as before and I get 0.62mm error over a Y movement of 120mm. From this I can work out the angle error between the saddle X and Y dovetails.

I now have two choices, either get someone to machine the X/Y channels true
or possibly get software to compensate. Can mach3 auto compensate for non true XY axis!!!

[BillTodd]

I would strip the table and saddle off to check there's not swarf or other crap trapped in the dovetails. I would not expect these little machines to have tapered gibs, so any foreign body on the fixed side could cause the problem with giving a tell-tail loose gib on the other.

Bill

[buster]

BillTodd,
I just removed the saddle and examined the LHS dovetails and indeed the machining was not good. At the top of the dovetail was a small (0.1mm) of unmachined
ramp shaped metal 2/3 thirds the length of the channel. I scraped most of it away with a thin file and finished with off with 600 grit.
If I keep up this scraping process I will of course do two things - ruin the dovetail or get no near perfection!!!

I will reassemble the lot tomorrow and retry the previous laborious calibration setup again.