My sizes are out

[dazp1976]

I ran Gcode to move X to 10mm then back to 0, 1000 times and same with Y and checked position everything seemed good.
http://www.mycncuk.com/threads/13525...399#post115399

I would have seen backlash with that check right?

Not really no. Even if it has backlash it will still follow the same pattern back and forth so you wouldn't notice.
Have a look at some vids that show how to properly check it.

If your sizes are out by more than say 0.2mm I'd say it wasn't a backlash issue. I've never really seen backlash values of more than 0.08mm which would make a circle smaller by only 0.16mm.

[JAZZCNC]

If you had 1mm of backlash you'd feel it by shaking each axis, it would feel like it's falling off.!

[dazp1976]

If you had 1mm of backlash you'd feel it by shaking each axis, it would feel like it's falling off.!

Tell me about it!!
1 thing I'd say as well is I often use cheap nasty Chinese cutters for roughing through then swap a decent cutter for a finish.
Those Chinese ones can vary in size a chunk.
I can rough a new 6mm 3flute bit using it to finish as well and I won't fit a bearing in the hole.
Then next I'll leave 0.5mm on with the same cutter, swap it for a 4flute Cobalt bit for finishing and be able to just get the bearing in.
That's with my drawings modified where a circle is set 0.1mm lager than I actually want it.

My Benchtop only has 3000rpm at the spindle so I find Cobalt work better for me as I can hog it a tiny bit.
Those Carbide bits are designed for higher rpm and I've shattered a few so there used for finishing only too.

[pippin88]

I ran Gcode to move X to 10mm then back to 0, 1000 times and same with Y and checked position everything seemed good.
http://www.mycncuk.com/threads/13525...399#post115399

I would have seen backlash with that check right?

No, that will not show backlash.

Look up what it is and how to check it.

You need a proper measuring instrument, e.g a dial indicator. You move the axis in one direction into the dial indicator, zero the dial indicator then move the axis in the opposite direction a defined amount. You then check the dial indicator reading and compare to what it should be.

[Doddy]

A couple of experiments for you to try.

*** CAUTION: Hand coded G-Code and un-tested. Sit next to your E-Stop!!! ***

test2.nc

This should slowly rock the X-axis by 0.5mm (or 18 degrees on a 1610 screw) - wrap a bit of tape around the x-axis screw with a visible tail and run this g-code through the controller and observe the tape. The G-code has got a feed rate of 10mm/min so my poor maths suggests around 3 seconds to go 0.5mm (18 degrees) and 3 seconds to go back to 0 (0 degrees). It repeats... a few times. No spindle and no z-movement.

This is just to verify that there's no backlash compensation active erroneously or not in the controller. You'll have to eyeball the 18 degrees rotation on the screw/tape.

Remove tape.

test.nc

This one cuts two pocket outlines - with your 12.7mm milling bit, starts at (0,0) and cuts a 3-tooth comb with a positive displacement on X, 50mm between teeth. After the 3rd tooth it reverses and cuts another 2 teeth offset in Y 30mm back the other way also 50mm apart. This to verify again that there's no backlash effects or compensation in operation.

Sorry, that's all I can think of at the moment.

[Boyan Silyavski]

The easier way to find the edge in the settings is to profile say a 50mm circle with each pass say 0.2mm deeper, so soon its starts to get clear what's happening

50mm circle inside a square is the method i use to test for eventual axis or electronic problems

[Desertboy]

I had a blonde moment today, I dug out my old pc which has linuxcnc on it and brought it home to try with the machine I was just going to wire the X,Y,& Z see if the sizes are still out and if so are they out the same amount.

When I got home to set it up I forgot a VGA monitor lol, no HDMI out on this machine.

I need to go work again tomorrow so will have to wait another day.

At the moment I've set the motors to ~3amps on the stepper drivers by jumpers they should be ~ 4amps and they don't get warm even after hours of machining but I will connect them to the PC so I can autotune everything.