Boxford 165 HMC

[uli12us]

Yes, you enter a little bit less then in reality, move so much that you are free, after that you turn back to the nominal amount. So you have always pressure against the ratchet. I don't know if 1degree more is enough, you should test some different parametres, until it runs correct.

Or you can make a new roundaxe without a ratchet and add a small hydraulik diskbrake from a Bicycle. So you can move in every desired angle.
But because of backlash unfortunately only in one direction

[Neale]

Can you fake it by resetting the A machine coordinate to the correct value after each move? Not exactly an elegant solution...

[chris w]

Hello Neale I think that is my answer or solution for the short to medium term as I tried all the positions on the ratchet locking and it varies about .3 degrees so that stops me from allowing for a fixed error,
is there a way to reset that coordinate within the g code program?
i.e.
G0G90A-90.
(reset DRO)
machining
A-90.
(reset DRO)
machining

that will essentially be indexing incrementally but as long as I remember that it will be fine,
chris w.

[Neale]

Chris, please bear in mind that I have not tried this, but I believe that the sequence you need is, basically:

G91 (set relative mode)
G0 A95 (turn axis but deliberately overshoot)
G0 A-10 (turn back to lock position)
G90 (switch back to absolute)
G92 Axx (where xx is the value you want to appear in the DRO display at this point)

Alternatively, if you are resetting the DRO to the correct position each time, you can probably skip the switching relative/absolute bit. Turn to the required angle plus a bit of overshoot, turn back by enough to make sure that the axis is back on its ratchet stop, then use G92 Axx to reset the DRO to the correct value. Absolute moves should then work OK. Good luck if you want to build this into your post-processor!

[chris w]

Yes thanks for that it's been a long time since I used a G92 but I understand it,
chris,