Hello,

I am assembling a CNC mill based on a 1980s vintage Taiwanese built Husky knee mill. This Husky seems to be the prototype for mills now sold that bridge the gap between drill mills/platform mills and small Bridgeport sized machines, except that its castings are noticeably heavier and bigger than most of the current crop of imports (Grizzly G0678 is very similar).

I plan to use the quill for my controlled Z axis, but it has only 3.5" of movement. I have numerous projects planned that require more than that.

I have a Galil DMC-1750 controller, so I can add a servo to the mills knee and control that as well. I'm hoping there is a way to combine the motions of the quill and knee into one Z-axis command. This would be very desirable to me as my CAM software (Alibre/VisualCAM bundle) is limited to 3 axis (add one more for another $1000.00, ouch).

I'm knowledgeable about electronics, mechanics and programming, but CNC is all new to me and I have just now reached the conclusion that Mach3 is the only sensible control software for my planned setup.

I've about assembled all of the needed components and have begun the arduous task of constructing the various hardware components required to mount the drive motors and their associated trains. I'll be running Baldor 2250 motors through gear reduction boxes for X, Y, and quill Z and have a Kollmorgen U12M4H for the knee Z.

I've acquired five Copley drives, the Galil interface box, cable, connectors, etc and have the needed materials to build up a 40 Volt/40 Amp (continuous) power supply.

I kinda know what I am doing, but am having lots of "learning experiences" as I go, so any hints, suggestions, pointers, etcetera that might save me some agony will be welcomed.

As stated above, I really would like to combine the knee and quill drives into a single Z axis software command.

Thanks

From the GCode point of view, this is not a problem.

Manually edit each file, adding a 2nd Z movement at the beginning of the file.

For example, G1 A4.000 F50 might be used to send your 4th axis (second Z) to 4". This assumes your 4th axis is labeled "A" in Mach, and perhaps D in the galil card.  Adding this to the beginning of each file you make would only take a minute, and could be particular to that specific setup.

As for the galil side, some help should be along shortly!

Rob

If your CAM is only producing 3 axes, then you are going to have a problem.  There is nothing in Mach that can take one Z movement and split it into two separate axis movements.  As far as the Galil is concerned, it is going to do what Mach tells it to do.  So no help there.

As Rob suggested, you can do this manually by editing your Gcode.  But there is nothing automatic going to happen for you if you can't do this from you CAM software.

Steve

Steve,

Is it possible to assign his second Z axis to "A" in mach, and set that as a linear?
I did not think Mach really cared which axis is assigned to which.  I think his answer is yes, Mach can do it.  So long as he hand-jams in his own code for the second Z.

Rob

Rob,

Yes, he can assign his second Z axis to A in Mach.  But he wants to have his CAM software output XYZ moves and Mach to take the Z moves and split them up into A (knee: Z moves > 3.5" rough position) and Z (quill: Z move < 3.5" fine position) on the fly.  Unfortunately, that is not possible.

Steve

Thanks for the responses, even though it's not what I wanted to hear....

So, to reiterate what I've read here:
The required approach will be to edit the Post file and alter the Z-axis motion commands so that they are split into two, one for the quill and one for the knee.

(Pause for deep thinking, for a moment)

It seems to me that this would actually be a pretty straight forward thing to do, as the two "new" commands would be identical to the original, except that one would address the knee axis and both would have altered values which should follow a prescribed formula. I could probably  dust off my long latent Pascal programming skills and write a small command line utility the would "Post" the Post to accomplish that task.

It certainly seems like something that is sufficiently doable  to warrant the installation of the hardware to drive the knee, especially as I already have the controller capacity, a drive and a motor. As I wrote previously, this is a project in process, so I won't be writing such a utility anytime soon, since I'm still in the hardware fabrication stage.

On the other hand, if anyone comes up with a slicker way to do this, by all means, please suggest it!

Yes, a post processor for the post processor.    But...  in order to do that, you will have to set the top of the part (Z = 0) with your quill in the fully retracted position.  Otherwise, how will your knee movement computations know that there is less than 3.5" of travel available on the quill.  And then you might want to fudge a bit, say .200", for a rapid plane.

Steve

Yes, some sort of initial reference location will be essential. I may start with the knee at the bottom and the quill fully retracted, therefore initializing at maximum Z. I'm certainly flexible, at this point.

One thing that I'm curious about is what sort of numerical  scale I will find that specifies the Z position, with what resolution? I've seen some systems that claim a numerical resolution of +- 2 billion, which I take to be a signed 32 bit (+- 31 bits) value. Is this standard, and/or what Mach3 expects?

If that be the case, then my initial thought would be to use an unsigned 32 bit " zero" value for Zmax, which would be Home. For arguments sake, lets say that value will be 21". 1/6th of that, or 3.5", will be quill travel. If I use a bit mask  to "and off" the top (2?) (most significant) bits, the resultant value, which may require scaling, will be the quill position. Similarly masking the (30?) least significant bits, again perhaps scaled, should provide the knee position.

This is all tenuous for the moment. Comments and suggestions welcome.

I am not sure how Mach handles the Galil commands, but  in the case of the Galil axis gearing command, this would normally be done with the Z being the master and the A tied to it as slave, the gearing ratio of which could be changed on the fly.
There would be only one Z axis command.
I don't know if this would achieve what you are trying to do?
Nosmo.

Yo NosmoKing,

You may have hit on the ideal solution. After seeing your post, I looked up the Galil command GA and its related commands GM, GD, GR, etc. This family of commands would seem to be ideal for basing the combining of knee and quill movement into one Z motion command. However, from what I can tell, this feature would best be implemented in the Mach Galil Plugin. Unfortunately, that's a bit beyond me, at this point. If those wonderful, kind, generous, community spirited (OK, I think I've piled it deep enough.) fellows who created the Plugin were to implement my request, I would be only too happy to test it, once I actually have a machine up and running, that is....