Boxford 165 HMC

[uli12us]

First I want to make snails for transporting of plastikbottles on the Machine. All other can wait until this job runs good.

At the moment I must first to get Linuxcnc running with the mesa7i76E ethernet BOB or better motion controller.
And change the integrated working but softwareless controller
to the mesa.

After that, I want to make the mechanical parts for the X-A
Bridge. Thats relatively easy, because I "only" need a part
like the X-slider, 2 blocks for adaptation from my
Guidance to the tailstocks with a toothed belt drive
and a ballscrew on the side.

All the other parts are not so important and I can make it whenever I like it.

[chris w]

Hello I have got the movements smooth and the correct programmed amount in each axis so now I want to understand how I can program the a axis (rotary) it has a ratchet wheel under the table and it locks every 45 degs but to lock it it needs to move a couple of degrees in the opposite direction.
so if I program A180. The move is good but it doesn't lock so I move -A180. Then A2. And it locks but the DRO on Mach displays A178. Which is no good as it affects the next move, how do I get round this please?
chris w.

[uli12us]

Thats the problem with steppers, they have no feedback for direct reading of the position. Eventually you can enter a little false value into the parametres, so you turn maybe 180° with an amount of 185° and 5° back.
In reality it moves only 184° and back to 180° until the motor stalls.

[chris w]

Do you mean alter the movement amount on the axis in motor tuning to trick it?
to let you know how I start up, I move the axis to lock it in the nearest square face of the table in relation to the spindle then reverse it a bit so it's locked then zero the DRO, so now I mdi g0g90a-91. Then table move and next line is a-90. Which leaves readout in right position but not quite locked the table so I need to move to a-89. And it locks and ok but the readout displays 89.62 or another number which makes a program impossible as I don't know how much the next move needs to compensate for the clamp amount,
should I consider changing the axis motor for a servo but it still needs to clamp before machining and I don't want to be involved with a compressor for a brake........ I dunno,

[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.