To DRO or not to DRO is the question.

[Cartierusm]

As in my other posts I'm doing a CNC conversion of my BP clone. The problem is I didn't realize it was going to cost so little that when I was taking it apart to clean and fix all the broken lube lines I decided to do the conversion. I was fixing everything because I had just ordered a new DRO because the last one went tits up.

So the question is do I install the new DRO and use it make sure the cnc conversion is working correctly and/or use the scales as feedback in Mach 3 (not sure if it can do that as I'm using steppers) and/or install the DRO with the intent in the furtue to hook a CNCBrain if I ever feel inclined, right now I have no need for a CNCBrain?

Or do I sell it as new on Ebay and use the money toward the conversion?

[HimyKabibble]

Originally Posted by Cartierusm As in my other posts I'm doing a CNC conversion of my BP clone. The problem is I didn't realize it was going to cost so little that when I was taking it apart to clean and fix all the broken lube lines I decided to do the conversion. I was fixing everything because I had just ordered a new DRO because the last one went tits up. So the question is do I install the new DRO and use it make sure the cnc conversion is working correctly and/or use the scales as feedback in Mach 3 (not sure if it can do that as I'm using steppers) and/or install the DRO with the intent in the furtue to hook a CNCBrain if I ever feel inclined, right now I have no need for a CNCBrain? Or do I sell it as new on Ebay and use the money toward the conversion?

I would sell it. There's no way Mach3 will use it for anything more than display purposes - Mach3 does NOT do closed-loop control. And if you can't believe the machine is where you commanded it to be, then you're either under-designed or over-driven it.

Regards,
Ray L.

[BobWarfield]

Install it to check the proper operation of the machine, map the ballscrews, and make sure you're getting the level of accuracy you'd like. Then either keep it for similar future work or sell it on eBay.

Best,

BW

[LMSC]

Originally Posted by Cartierusm As in my other posts I'm doing a CNC conversion of my BP clone. The problem is I didn't realize it was going to cost so little that when I was taking it apart to clean and fix all the broken lube lines I decided to do the conversion. I was fixing everything because I had just ordered a new DRO because the last one went tits up. So the question is do I install the new DRO and use it make sure the cnc conversion is working correctly and/or use the scales as feedback in Mach 3 (not sure if it can do that as I'm using steppers) and/or install the DRO with the intent in the furtue to hook a CNCBrain if I ever feel inclined, right now I have no need for a CNCBrain? Or do I sell it as new on Ebay and use the money toward the conversion?

You should keep it, install it and use it. You can use it as a standard dro systems and use it as feedback for a future cnc control. It is not a problem to share the power and the signals. I have installed at least 10 systems this way. I make a small box so I can run the signals from the scales to the display and the cnc control.

Regards,
Tim
LMSC

[Cartierusm]

Thanks for the help.

Bob, I remember reading about mapping ballscrews years ago when I built my first CNC, how is this done?

[HimyKabibble]

Originally Posted by Cartierusm Thanks for the help. Bob, I remember reading about mapping ballscrews years ago when I built my first CNC, how is this done?

Of course, mapping your screws is probably largely pointless unless you have a temperature-controlled shop....

Regards,
Ray L.

[Cartierusm]

God controls it, does that count?

Yeah but if the screw are .003 accurate wouldn't mapping them at 70F at least give me an idea if they are off a little?

[BobWarfield]

Originally Posted by HimyKabibble Of course, mapping your screws is probably largely pointless unless you have a temperature-controlled shop.... Regards, Ray L.

Of course that's not really true for many of the lower end ballscrews where the error rates can be several thousandths over a foot.

I'm surprised at you Ray, you silly goose! After chiding me for essentially mapping mine over a short distance because you thought the errors could be much greater over a longer distance you're now going to swing way over to the other side and insist this only matters to a temperature controlled shop?

I certainly found enough error over the 6" I measured that it was a valuable exercise, though I accounted for it in the steps per inch setting rather than in the leadscrew map.

To answer the question of how, you use the DRO to compile the actual position at various points as you jog over the full distance of travel. Take a measurement at 1" intervals or whatever. Record two columns in a spreadsheet. One column is what the Mach3 DRO says, the other is what your external DRO says.

There is a screen in Mach3 where you then enter these values. Mach3 will interpolate in between to eliminate the leadscrew errors. Art has said it works pretty well.

I got a screamin deal on a new Fagor DRO that I plan to use for exactly this purpose.

Cheers,

BW

[Cartierusm]

Fagor? Wasn't that the assistant in Young Frankenstein? LOL

I'll try that, Art really has made a good program, even though he doesn't own it anymore he still answers pretty quickly via email.

Bob, here's another thing, I use my current cnc for a cnc router, I'm sure I've read it somewhere, but Can I load a specific file for Mach 3? What I mean is I have quick disconnect for all the wiring going to the machine and I'm going to move the computer back and forth to each machine as I need to save money as I have high end drives and electronics. I only use one machine at a time anyway. So how do I load Mach with machine specific settings including the Motor steps and such? Thanks.

[jalessi]

Cartierusm,

Use the Mach3 Loader, Create a new profile for each machine.

Then from the Mach3 Loader select the machine profile you would like to control.

You can even create a shortcut to make it simple to access from the desktop.


Jeff...

[Cartierusm]

Thanks.

[HimyKabibble]

Originally Posted by BobWarfield Of course that's not really true for many of the lower end ballscrews where the error rates can be several thousandths over a foot. I'm surprised at you Ray, you silly goose! After chiding me for essentially mapping mine over a short distance because you thought the errors could be much greater over a longer distance you're now going to swing way over to the other side and insist this only matters to a temperature controlled shop? I certainly found enough error over the 6" I measured that it was a valuable exercise, though I accounted for it in the steps per inch setting rather than in the leadscrew map. To answer the question of how, you use the DRO to compile the actual position at various points as you jog over the full distance of travel. Take a measurement at 1" intervals or whatever. Record two columns in a spreadsheet. One column is what the Mach3 DRO says, the other is what your external DRO says. There is a screen in Mach3 where you then enter these values. Mach3 will interpolate in between to eliminate the leadscrew errors. Art has said it works pretty well. I got a screamin deal on a new Fagor DRO that I plan to use for exactly this purpose. Cheers, BW

Aw, come on, Bob! It's fun! Actually, I never really looked in any detail at the magnitude of thermal expansion on these things. Unless I've slipped a digit somewhere, it's a lot less than I had assumed. The coefficient for steel as roughly 12 x 10-6, which, over the working length of a Bridgeport table (about 34") amounts to less than 0.0004". Not bad. Now, the amusing thing is, the glass scales will themselves experience about 2/3 of that. So, I think we need to get some diamond scales.... :-)
Are your new scales actually glass? Or Mylar? I would expect Mylar scales to vary pretty widely.
I would be very curious to see what the variance is over the length of a long screw, to finish off the discussion last week re: screw accuracy, and lead consistency.

Regards,
Ray L.