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View Full Version : Electronic Lead Screw - anyone ever make one?



rantbot
01-07-2007, 05:13 PM
http://www.homemetalshopclub.org/projects/electronic_lead_screw/els.html

I don't think Part 2 was ever posted. It's a position controller using a phase locked loop to generate a motor signal for the leadscrew. There was some discussion involving it on this board but that was about three years ago.

My concern is the steady-state position error which is inherent in the control system as sketched out on the page above. If anyone has made such a device and if it works as it should, then my concerns might be exaggerated.

nheng
01-07-2007, 05:23 PM
That thread was interesting to me and lead to this one on this forum:

http://bbs.homeshopmachinist.net/showthread.php?t=3949&highlight=kermit%27s

The Frog CNC controller is now discontinued but the same functions could be re-created with far greater capabilities using something like Mach3 turning software.

The threads I posted in that link were cut on an Emco Maximat gearhead lathe. Due to the gear reduction AND a delay which the Frog takes before each pass as it syncs up, the threads are pretty good ... considering that only a single point sensor is used. That factor (impact of stable rotational speed) is also discussed in the thread.

I think one of the higher end Prazi lathes has an electronic QC box.

Den

John Stevenson
01-07-2007, 05:48 PM
There is a group on Yahoo doing just this.
Do a search for Electronic leadscrew or ELS, it's been going a while and in it's infancy there were two schools of thought, one was a satnd alone jobbie like the Frog and the other school was suggesting to use one axis of a controller program such as TurboCNc or Mach2 as it was then.

Over time the stand alone guys moved the concept on and they now have a working system which now it's gone full circle has become a one CNC axis. :o

The chief contender and architect John Dampier <sp> has now joined the mach3 group and is asking questions there.

.

lazlo
01-07-2007, 06:47 PM
There is a group on Yahoo doing just this. Do a search for Electronic leadscrew or ELS,
The chief contender and architect John Dampier <sp> has now joined the mach3 group and is asking questions there.

That would be John Dammeyer. The group is here:

http://tech.groups.yahoo.com/group/E-LeadScrew/

He's made remarkable progress in 6 months or so. He's built a standalone feed-forward stepper-driven leadscrew. It's basically a programmable divider circuit a lot like John's Eee-lec-tronik hobber, or "The Frog" electronic divider. He's using a PIC to do the step dividing and a basic LCD display. The grid of pushbuttons set the various "gear" dividers, and the jog wheel on the right scrolls through the menus:

http://www.pacificsun.ca/~john/ELS/ELS_Nest.jpg

Here's a picture of some wacky threads he's made, mixing metric and imperial on the same workpiece:

www.pacificsun.ca/~john/ELS/thread_5-16.jpg
www.pacificsun.ca/~john/ELS/METRIC1.JPG

He's also published the initial prototype in the November 2006 Circuit Cellar Magazine.

Robert

Dawai
01-07-2007, 10:47 PM
Fenner Mtrims.. digital follower.. been out about twenty five or more years.

On paper machines, one side is ran by a ac motor, other side tracks and corrects with a fenner control. WHY you might ask? for bow and skew correction. You know how brittle paper is to rip in two?

Yeah, reinvent the wheel.

Newer Allen bradley 1336 inverters have the capability to "step" like a actual stepper motor with Dc injection.

All the single axis controls, when you get it all said and done you could have had a real cnc for near the cost.

We did a similar system using Allen bradley 5/04 plcs.. my partner then, he didn't want to tune in a pid loop so he did the old "add one per program loop" till over shoot then subtract one.. The system had several process applications and the need was to put the current dye roll in "lead" format and all the other drives track it's position. I tried to tell him his control scheme was all wrong.. one day the seam parted , the carpet came out the back of the machine wide open.

The smallish plc I am using on my cnc tube bender, a unitronics M91-R1, has a lcd display,keypad, 3 high speed quadrature encoder inputs, four other inputs, six relay outputs and 232 port and cable included in the $500 price. Mucho cheaper than most DRO's and it "CONTROLS"...

I got this rig downloading from my laptop now, it can download 30 xyz bend tables direct from my design software.. it controls all three axis on the ten foot gantry rig, and yes, the X follows the Z bender shoe.

Positioning, think old, use old. Technology has gotten cheaper.
http://www.unitronics.com/m90.htm
http://www.unitronics.com/images/all_in_one.gif
I've actually gotten quite adept at programming this lil rascal.. using the dll to read and write to it's registers. One drawback? it does not do floating point math.

Ohh, I think it's isralie... it has some hebrew here and there, not that matters to me.. nice lil compact simple to program unit.