Messages

381

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

« on: October 18, 2012, 03:56:00 PM »

Hi John, nice to see a fellow ORAC user here; I may have to pick your brain later!;D

Yep, I'm familiar with the switch actuator rod you're referring to.  Mine didn't come with one and I figured if I had to make something I might as well use a manual switch on that rod and add the indexing disc/opto sensor to the stepper to get even more accuracy.  I have double shaft motors so it shouldn't be too hard to do.

382

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

« on: October 18, 2012, 01:05:40 PM »

Ahh, OK thanks.  I figured I'd have to play around with it to get it to work.  Hopefully the sensor electronics don't do anything weird on power up but come to think about I could leave it powered up and just switch the signal?

Being a retro'd ORAC lathe it has little X-axis travel and with a very slow homing feed rate it won't take long at all.

383

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

« on: October 18, 2012, 11:36:19 AM »

If I was to install one of these http://www.ebay.com/itm/110936667967?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649 and a disc with one hole in it on the end of my double shaft stepper with a mechanical switch on the axis slide adjusted to switch "on" the ground to the opto device close to the home position, I would have a very accurate and repeatable home, yes?

This assumes that the opto is set up as a normal home switch input in Mach and the mechanical switch does nothing but switch on & off the ground (or power?) to the opto.  If this has been discussed before and I missed it I apologize.  Seems like it ought'a work a treat??

384

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

« on: October 17, 2012, 03:15:21 PM »

Thanks mc, I wish I could have had you looking over my shoulder when I was having C11/KB speed control isolation/hookup issues.  I think the C11's a good value but some sections of the manual drive me nuts.

Thanks Dan your opto switch unit really looks great!  What would a couple cost including shipping from Oz?  Might be more than my tightwad budget can afford but shoot me a PM when you get a minute.

385

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

« on: October 17, 2012, 01:07:41 PM »

It's connected through a BOB that has pull down resistors, so all I needed was a PNP version (you'd need a NPN version if you have a pull-up resistor).

Oh yeah, to me that's definitely electronic wizardry.

Now you're gonna make me try to decipher my C11 manual again.  I went to the Jethro Bodine School of Cipherin' and Goesintas and have a long way to go to understand what you said.  I went with a C3 for my spindle index sensor (which works great) but definitely want to avoid buying 2 more of them if I can do it without frying something.

386

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

« on: October 16, 2012, 07:14:09 PM »

Thanks mc, what kind of electronic wizardry goes between the sensor and your B.O.B.?

387

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

« on: October 16, 2012, 10:56:27 AM »

Ahh, I see (said the blind man)  Thanks, that looks very doable!

388

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

« on: October 16, 2012, 10:29:42 AM »

Why not just make up some optos in a sealed box, you will have very accurate homing and wont have to mess about fitting pseudo encoders.
Hood

I read your description of that earlier in the thread but I must be even more dense than usual today.  (Too much blood in my coffeestream?)  Got any dusty ol' .jpgs lying around somewhere to help edumacate me?

389

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

« on: October 16, 2012, 10:04:00 AM »

Thank's Russ, sounds good!  Should be easy enough even for me.  I'll be experimenting with that down the road a bit.

390

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

« on: October 16, 2012, 08:56:34 AM »

The machine ran 500+ parts per day for months and was shut down every night.
It was imperative that the operator fired it up, homed it and went right on making parts.

Exactly.  I don't run near that many parts and the operator is always me but having the machine start from the same point is important to me as well.

My other machine, crude as it is, has old style stepper motors with very strong cogging (proper term?) without power.  I guess it's dumb luck but the machine has no motor movement whatsoever when powered down or turned on.  I did a run of 1100 parts over a period of 4 months and the only time I had to reset the zero point is when I screwed up & crashed it.  All I had to do was shut it down properly, close the lid to keep out pesky cats and I knew it'd be right where I left it the next day.

The new machine's more modern steppers turn easily when no power is applied and jump a bit when powered on, hence my desire to have an easy, precise method of zeroing it.  They are double shaft motors so I guess I could rig a mechanical lock on the unused end to lock down before turning the machine off for the day.

I was hoping you experts would say "Oh yeah, piece o' cake, put a sensor & slotted disc on the stepper, $2 Radio Shack switch on the carriage, write a simple macro in Mach and Robert's yer Father's brother."