Messages

11

General Mach Discussion / Re: Encoders config

« on: October 08, 2012, 12:21:36 PM »

No, this is a completely separate unit coupled to the motor shaft with a plastic coupler to adjust miisalignments.

12

General Mach Discussion / Re: Encoders config

« on: October 08, 2012, 10:27:31 AM »

Not completely sure although in the encoders data sheet ((http://gap-sa.com.ar/pdf/HE.pdf) there's a 'bearing life' parameter, so I guess the do have bearings. 

13

General Mach Discussion / Re: Encoders config

« on: October 07, 2012, 01:08:38 PM »

Right now I'm using the same parallel port (LPT1) to control the 3 axis and also to input 5 of the 6 signals from the 3 encoders.

So in all the tests I've run every signal when in and out through the same port.

Would it make any difference if I use the second LPT port to input the encoder signals?
could this help get both the encoders and the DROs read the same values?

14

General Mach Discussion / Re: Encoders config

« on: October 07, 2012, 10:13:50 AM »

The encoders always show more distance than the DROs, so there are no missing pulses but extra ones.

Some of you may have read my recent post about electric noise affecting my probe. The solution was to a dd a few small capacitors across the inputs.

I'm starting to thing there may be noise here too, although what's strange is that the results are too similar over repetitions. If the problem were noise it should be random.

15

General Mach Discussion / Re: Encoders config

« on: October 06, 2012, 04:10:26 PM »

The signals go to a board that isolates the PC's parallel port

16

General Mach Discussion / Re: Encoders config

« on: October 06, 2012, 02:04:29 PM »

That's right.
I tested it both with MDI movements and manual and in both cases I get the error.
When doing MDI movements, I start with same position indication in DROs and encoders position, after the move both values do not match.

17

General Mach Discussion / Re: Encoders config

« on: October 05, 2012, 06:49:11 PM »

Encoders are 1000ppr.

The error is always close to 1% of table displacement, not a constant value.

18

General Mach Discussion / Re: Encoders config

« on: October 05, 2012, 06:13:11 PM »

I 'm using the default 25 kHz.
I just tried with 35 kHz and 45 kHz with no changes. I still get little over 4mms in a table 400mm movement.

19

General Mach Discussion / Re: Encoders config

« on: October 05, 2012, 04:48:07 PM »

Yes, ballscrews are 5mm pitch.
Automatic movements (with the steppers) seem to be moving the desired distance. At least in this test of 400mm I checked and it's definitely closer to 400 than the 404 the encoders give (measured manually with a tape).

20

General Mach Discussion / Encoders config

« on: October 05, 2012, 04:13:48 PM »

Hi everyone.

I converted a manual mill to CNC and installed ballscrews, steppers and also encoders, so I can keep the 'manual mode' where the encoders tell Mach3 how far I manually move the table.

My encoders have 1000 ppr and the ballscrews have a 5mm pitch, so the counts per unit should be 800. This is my current setup.

Now, after some testing I discovered the following:

I marked the 400mm on the table and double checked this with movements with the steppers.

To make sure I'm not dealing with any noise coming from the steppers or the drivers, I turned them all off and moved the table manually.
I move the table 400mm and the encoder says I moved 404.125mm (not sure if the decimal portion of the 404.125 is ok, but for sure it was a little over 4mm more than expected).
This means I have over 10% of error, way too high.

Why could this be happening?

Thanks in advance to everyone.