PCNC1100 Belt Position Sensor?

[btu44]

Hello,

I have finished installing a dual parallel port PCI card in my controller.
I'm going to use it mostly for Run, Pause, Stop buttons and a spindle tachometer.
I have a few inputs left, so I was thinking about a spindle belt position sensor.
Then maybe a macro in Mach3 could automatically change the pulley from high to low or visa a versa after a belt change.

I've been thinking of this a while but can't think of a good belt position detection method.

Any ideas ???

Thanks,
Barry

[mrquacker]

A laser tachometer works by bouncing a beam off something reflective.

On that note, a positional sensor could be made that uses similar laser tech. By making the reflective surface coded, you can read its position; like Morse code. So having two strips of reflector real close together, and then a measured distance, followed by two more strips. When the laser sees that, it can tell where the belt is. You should be able to get 3-4 positions on a belt that way.

Like: belt --- reflector [

---[-[----[-[----[----[----[-[-[---[-[-[--

[btu44]

Thats an interesting idea. But I wonder if Mach3 macro could be written to decipher a code.

This is the sensor I was going to use for the spindle tach.

http://www.optekinc.com/datasheets/O...16-717-718.PDF

Maybe I could use another one to read a white painted belt. Then position it so it only see's the belt in the low speed position. That way a get a simple high/low logic signal the Mach3 should be able to handle.

This should work...Thanks

[Zetopan]

Rather than using reflective sensors you should be using transmissive sensors.
Position two transmitters inside or outside the belt loops and the receivers in
the opposite locations (outside or inside respectively) and you can distinguish
between no belts, one belt in either position or two belts. For simplicity you
could simple use a single transmitter and receiver to detect the belt position
on one pair of pulleys.

[philbur]

OK, I'll ask the question many are possibly thinking.

Why?

Phil

Then maybe a macro in Mach3 could automatically change the pulley from high to low or visa a versa after a belt change.

[Steve Seebold]

WHOA!!! You guys are way beyond me. Besides, I like the way my machine works, JUST fine.

[doorknob]

What about doing something simple, such as using two microswitches, one above the other, each with a roller arm/lever that either senses the presence of the belt or not... It would require some care when repositioning the belt, however, and you would want to make sure that the belt drive would not have any vibration modes at any speed that might lead to unwanted on-off switching.

[btu44]

I appriciate the suggestions. The biggest problem is avalible space with the power draw bar. Belt changes are slow enough as it is. Having a couple of senors or limit switches would complicate belt chages even further. I don't want the 'fix' to be worse than the problem.

As for the why? On rare occasions I'll have a belt change in mid program...usally a large drill bit op. And a few times I have forgot to change Mach3 to the new pulley. This sometimes can really jack things up. So if I could make the pulley change automatic in Mach3, it would be one less way to scap a part.

But the way it looking, belt detection would cause more problems than it fixes. Not to mention a 'mid cut glitch' that toggles the pulley in Mach3. I think this is another of my great ideas that wasn't.

Thanks for the ideas anyways,
Barry

[MichaelHenry]

OK, I'll ask the question many are possibly thinking.

Why?

Phil

I can give you one reason.

We have frequent power outages here, and every time we do, Mach has to be re-booted and defaults to the low-speed pulley setting whereas I almost always use it on the high speed setting. If I forget to change the pulley position DRO in Mach after the system has been restarted, the first program run will almost always be running the spindle at the wrong speed. Sometimes I don't catch that until the cutter breaks and at times like those it would be nice to a belt sensor that would automatically switch the pulley position DRO to the correct setting.

Mike

[Zetopan]

What about doing something simple, such as using two microswitches,
one above the other, each with a roller arm/lever that either senses
the presence of the belt or not...

That would be a bad idea. The rollers on microswitches are designed for some
occasional slow rotation, not for high speed continuous rotation. The bearing
would fairly quickly heat up and potentially seize or otherwise self destruct.
And there is also the issue of belt whip, which happens at the higher RPMs.

The power outage problem, where Mach3 defaults to the lowest pulley speed
setting, could be handled in the following way; this also does not require any
belt position sensing. Install a convenient and labelled switch in the mill head
that indicates belt up or belt down (the two pulley positions). Whenever you
change the belt position set the switch to the matching position. A spare pin
on a second parallel port could interrogate the switch and update the Mach3
pulley speed setting display. Since I have added a second parallel port to my
Tormach for my not yet completed 5th axis, as well as zeroing both the 4th
and 5th axis rotary tables, I might do this pulley setting switch mod as well.

Note that you could place this switch on the electrical cabinet front panel but
actually having it "hidden" within the mill head would help to serve as a more
automatic reminder to change it when you are changing the belt speeds. This
switch could be placed in any obvious location where it will be noticed when
changing the belt pulley setting.

[doorknob]

That would be a bad idea. The rollers on microswitches are designed for some
occasional slow rotation, not for high speed continuous rotation. The bearing
would fairly quickly heat up and potentially seize or otherwise self destruct.
And there is also the issue of belt whip, which happens at the higher RPMs.

I have seen such switches used on conveyor belts, and so there must be versions having bearings that are suitable for high-speed, continuous use.

As for belt whip, I agree, which is why I did caution "to make sure that the belt drive would not have any vibration modes at any speed that might lead to unwanted on-off switching".

[nitewatchman]

Perhaps consider a Capacitive Prox Switch. I use them to sense non-metalics.

nitewatchman