Messages

1451

General Mach Discussion / Re: Bugs in Mach 3.42.015

« on: November 15, 2008, 10:10:07 AM »

Simpson,

    Having the home switches in the middle of travel is quite common - you can put them anywhere you like.  In fact, I'm adding optical limit switches to my machine, and may decide to put home in the middle of the table, for the reason you suggest (although Z pretty much HAS to have home in the full up position for, I think, obvious reasons....).  It was the idea of having multiple home switches that seemed a little silly to me, and suggested that the OP didn't understand the purpose of the home switches, nor the function of work offsets.  When you have multiple sets of home switches, they're really no long home switches.  And even on a large machine, I can't imagine the time saved to be worth the problems all the added switches and wiring will create.

Regards,
Ray L.

1452

General Mach Discussion / Re: Accuracy or repeatability of homeing switches, something to worry about?

« on: November 14, 2008, 07:12:55 PM »

They are nice switches Ray but just be carefull with the wires, they are easy to pull off. I put a cable tie (zip tie to you guys I think) round the wire inside so that there was slack inside even when the cable was taught.

Hood

Hood,

    Will do.  Thanks!

Regards,
Ray L.

1453

General Mach Discussion / Re: Accuracy or repeatability of homeing switches, something to worry about?

« on: November 14, 2008, 06:51:21 PM »

I've managed to score several Industrial Hobbies optical limit switches at a great price.  I can copy them for the rest I'll need.

Regards,
Ray L.

1454

General Mach Discussion / Re: Bugs in Mach 3.42.015

« on: November 14, 2008, 10:58:46 AM »

There is no contradiction.  AFAIK, the *only* way to zero machine coordinates is through a homing operation, which means switches that tell Mach where "home" is.  Your question was "why not have multiple sets of home switches", and I indicated that you could, but it would be silly.  The first statement still stands, AFAIK, and I think that has been confirmed by others on here already.

Regards,
Ray L.

1455

General Mach Discussion / Re: Can someone explain the current draw of these stepper motors, please.

« on: November 14, 2008, 10:16:27 AM »

Servos will not magically turn a bad machine into a good machine.  You need to lap the ways, and probably make new gibs, and get it moving smoothly over the entire travel.  If you're losing steps, it's not a function of stepper vs servo, but rather that you're expecting more from the motors than they can deliver.  A servo, under the same conditions, will do the same thing.  Fix the machine, and the motors will be fine.

Regards,
RayL.

1456

General Mach Discussion / Optical Limit Switches

« on: November 13, 2008, 11:25:59 PM »

Does anyone here have a design for good, coolant-proof optical limit switches?  I hate to re-invent the wheel....

Regards,
Ray L.

1457

General Mach Discussion / Re: Pulley Settings

« on: November 13, 2008, 10:19:14 AM »

So what exactly does Mach do when it determines you're on the wrong pulley?  And how do I tell what pulley I've changed to?

I've made a custom post for my CAM program (SheetCAM) that takes to tool RPM specified for each operation, and determines what the correct pulley and VFD frequency is, inserts an M00 prompting me to move the belt it necessary, and feed the VFD frequency to the S commands in the G-code (I've scaled the spindle speed response so this works correctly).  It also minimizes pulley changes, by retaining the previous setting if possible.

I"m trying to figure out if there's a better way of doing this.

Regards,
Ray L.

1458

General Mach Discussion / Re: Spindle Speed Troubles

« on: November 12, 2008, 11:58:22 PM »

I've mentioned it to him, but not much he can do until I have more information about the nature of the failure. 

Regards,
Ray L.

1459

General Mach Discussion / Re: manual feedrate override pot

« on: November 12, 2008, 09:31:48 PM »

Cutmore,
 I actually said I think
 The way you said is what I ws thinking, set up the A as an input or oem trigger and the B up as another. You could then make a Brain to look at these inputs and do a Up or Down button press. Whether it will work I dont know as I have never tried, possibly the pulse from the encoder will be too short to be seen properly.

Hood

The service rate on brains is rather slow (4-10 times per second, IIRC), so I think this would be very unreliable, unless you turned it very slowly....  And with quadrature, if you miss a transition, the next one can be interpreted as a move in the opposite direction.

Regards,
Ray L.

1460

General Mach Discussion / Pulley Settings

« on: November 12, 2008, 09:12:45 PM »

What are the pulley settings for, and how are they used?  Do they do more than scale the RPM DRO?  How do you tell Mach which pulley is engaged?

Regards,
Ray L.