Messages

391

General Mach Discussion / Re: Accuracy of Homing Devices? Pro's and Con's of Different Sensors

« on: October 15, 2012, 11:01:47 PM »

Thanks very much for the input gents.

I'm actually working with a lathe instead of a mill and was hoping to find a way to consistently & very accurately set at least the X-axis zero point so I wouldn't have to use standard methods to indicate to the work.  A known refererence to the spindle centerline would be useful methinks.

What I was thinking was to have a regular mechanical switch to identify the initial rough home point and then have a slotted disc/optical sensor on the ballscrew.  Is it possible to configure Mach to recognize the rough point, slow way down then count a couple turns of the disc and stop/zero at the edge of the slot?  Seems to me that would produce a consistent zero point, no?

392

General Mach Discussion / Re: Accuracy of Homing Devices? Pro's and Con's of Different Sensors

« on: October 15, 2012, 06:54:33 PM »

No matter what type of sensor or switch you use it will not be super accurate all by itself. For really accurate homing it is best to use a combination of a home sensor/switch and an index pulse on the axis motor itself. The home sensor/switch and the index pulse are seen at the same time the controller considers this 'home'. Since the index pulse is based on the angle of the axis motor itself it is very accurate.

I recently stumbled across this powerful statement and was wondering how one accomplishes "an index pulse on the axis motor itself" and if it's possible on a regular stepper motor without a shaft encoder.  I'm intrigued by this concept and would like to learn more.

Anyone have further info on the matter or links?

Thanks!

393

Show"N"Tell ( Your Machines) / Re: I wanted to show my homemade CNC.

« on: October 14, 2012, 09:19:23 AM »

Great job!  I enjoy making things frugally too; it's very satisfying as well as keeping peace with 'er indoors!

One suggestion though: get some nice machine grey paint on it.  Not only will it look better but it'll reduce the wood's tendency to expand & contract with humidity changes.

394

Show"N"Tell ( Your Machines) / Re: A few of my projects..

« on: October 10, 2012, 01:40:49 PM »

The next "Feature" will be a 2 axis (linear and rotary), live tooling attachment for the cross slide, but only if I get bored and actually finish designing it.

Funny, I'm working on a live spindle for my ORAC as we speak.  Got most of the parts already but am waiting for couple more ebay items to arrive.  It's gonna be pretty small; an ER16/10mm straight shank collet chuck as the spindle, couple of small sealed A/C bearings, belt drive 24VDC Pittman motor, 36V KBIC-120 DC speed control, 5/16" ballscrew and a belt drive NEMA23 stepper motor.

It'll be mounted on an old Craftsman 6" lathe compound mounted vertically to an extended tooling plate on the carriage.  I have a use for it making a part that requires a milling cut across a turned part, change to a drill, dropping down a bit and drilling a .090" hole on center.  It'll also have a crude indexing plate/manual lock on the spindle to lock it down while those ops are being performed.  That's the way I see it now anyway.  "Think-building" is always so easy!:)

395

Show"N"Tell ( Your Machines) / Re: A few of my projects..

« on: October 09, 2012, 09:14:36 AM »

Interesting pictures there S/S.  Like Ricky Ricardo once said: "Lucy, joo got some splainin' to doo."

Please tell us what all you got goin' on there.  A picture's worth a thousand words and all but some descriptive words here & there would help (me at least).  'Specially the lathe...I'm in a 'tinker with a CNC lathe' mode lately.

396

General Mach Discussion / 3rd axis on a lathe?

« on: October 06, 2012, 09:43:35 AM »

I'm accumulating the nec. bits & pieces to add a small powered aux. spindle on my ORAC.  It'll be a while before it's done but was curious how to get the extra DRO window added to my screen.  Are there any screens already out there with an extra axis?  Will the tool path show up in the preview screen?

I figure if I start now, maybe I'll have a clue how to do it when I actually need it 2 or 3 mos. down the road.  I'm slow.

397

General Mach Discussion / Re: Spindle Control Seig SX2 Mini-Mill w/Brushless Motor

« on: September 28, 2012, 08:11:34 AM »

Hey Kyle....stumbled across this last night.  Check out post #129.  It has a schematic and detailed instructions on how to build your own.  I can think of a couple manufacturers that should do as good a job of documentation as this fellow does for free!

http://www.cnczone.com/forums/benchtop_machines/117282-lms_hitorque_mini-mill_cnc_conversion-11.html

398

General Mach Discussion / Re: Spindle Control Seig SX2 Mini-Mill w/Brushless Motor

« on: September 27, 2012, 06:59:32 PM »

Looks like you'd have to get one of these: http://www.littlemachineshop.com/products/product_view.php?ProductID=4213&category=1687114045 or one like it from another source maybe?

399

General Mach Discussion / Re: Variable speed drive for mill spindle mach3 control

« on: September 27, 2012, 04:06:08 PM »

I just recently got one from Peter Homann so I can control an analogue servo for my spindle, it was a breeze to set up and is very linear in its output, definitely a quality product.

...and doesn't have isolation issues either if memory serves.

400

General Mach Discussion / Re: Variable speed drive for mill spindle mach3 control

« on: September 27, 2012, 11:56:13 AM »

Are you planning to use a VFD for an AC motor or a DC motor with a speed controller (KB, Minarik, etc.)? 

If it's the latter, I recently installed a KBIC-120 DC speed contol and CNC4PC C11 multifunction B.O.B. with 0-10V analog output and had lots of problems with isolation between them.  Had to use a KBSI-240D Signal Isolator to get it to work.  Works great now.  Mach controls the rpm very close across the range and is dead-solid..