PRS Alpha Missing Steps

[richards]

On my old PRT-Alpha, if I remember correctly, the JOG command enabled the stepper driver to change the number of steps per revolution from 10X to 1X (or 1X to 10X). The Alpha drivers could send two different steps per revolution 1X and 10X. I'm wondering if the underlying problem shown by changing the J3 command to a M3 command relates to the 1X vs the 10X step resolution and if that could be solved by changing the jog speeds/ramping?

[chubb]

Hi Mike,

Changing the jog speeds/ramping values was something I wanted to try and see how it pans out.

I haven't yet gotten the chance to test an unamended cutting file with the jog speeds or ramping speeds changed (still catching up on work that was delayed due to this issue). But I should be able to do a quick test tomorrow morning before we start work for the day.

At the moment we are just switching all J3 commands in the cut files with M3, to avoid any problems. Lengthens the time slightly, but losing 1/5th of cutting time becomes somewhat significant over the course of a day...week....month. So really wanna try anything that will get me back to using jog commands.

Will give it a shot and update tomorrow.

Mark

p.s.
Does anyone know of any articles/whitepapers/books that explain the underlying systems in a shopbot? I'm thinking it would be worth a read just to have a better understanding of how it works through and through.

[Brady Watson]

At the moment we are just switching all J3 commands in the cut files with M3, to avoid any problems. Lengthens the time slightly, but losing 1/5th of cutting time becomes somewhat significant over the course of a day...week....month. So really wanna try anything that will get me back to using jog commands.

Why are you doing this? Jog speeds should be fine @ 12IPS XY and 3 IPS Z, since the tool is up in the air moving to a new location to cut. Move Speeds should be pulled down to something more reasonable, as I mentioned before.

-B

[chubb]

Hi Brady,

As mentioned in the previous post, Post #16 on Page 2 . On the advice of Tech Support, we changed changed all the 'J3' commands to 'M3' commands. When we do this the file cuts without any offsets or errors.

Running the machine without this change in the commands results in errors and offsets. Generally, no one is quite sure why it's happening. But there are several plausible ideas floating around that I'm trying to work through.

Also, we already tried lowering the move speeds right down to 3IPS and it made no change whatsoever (Post #11). We still got E's and offsets.

The only values we haven't tried changing and seeing if they have any effect are the jog speeds and the ramping values. So it's worth a shot.

Until we can figure out what the gremlin is, just so that we can keep cutting without worrying about offsets, we are still making the J3->M3 changes to all cut files. It may take longer, but it's better than wasting material and even more time.


Mark

[ken_rychlik]

The Machine must have gotten out of square/adjustment/V rollers, motor distance to the rack, ect.... When I had my prs, keeping it tuned up and smooth running always needed attention. With the power off and the wires to the motors unplugged I would move each axis all the way over it's travel by hand. This showed me where adjustments were needed. Once I had everything moving smooth by hand, then I would plug the motors back in and the missing steps were gone.

The move speeds can overcome the troubles of things being out of adjustment, but at jog speeds they could not keep up. Changing the jog speeds will help, but fixing the issue would be better.

[Brady Watson]

Hmm...wondering if your step multiplier values under VU are correct & in turn, the switches on your drivers are in the correct positions.

-B

[gerryv]

I notice that you said you were running in metric. I think I recall a very recent discussion that Ted was involved in that indicated an issue with metric.

[chubb]

The Machine must have gotten out of square/adjustment/V rollers, motor distance to the rack, ect.... When I had my prs, keeping it tuned up and smooth running always needed attention. With the power off and the wires to the motors unplugged I would move each axis all the way over it's travel by hand. This showed me where adjustments were needed. Once I had everything moving smooth by hand, then I would plug the motors back in and the missing steps were gone.

The move speeds can overcome the troubles of things being out of adjustment, but at jog speeds they could not keep up. Changing the jog speeds will help, but fixing the issue would be better.

Hi Kenneth,

Haven't given the machine a detailed look over in that respect. Just did a quick check by eye and all seems to be well. But will try that out and see how it goes.

Thanks for the idea. Hoping anything will work at this point. Still getting the offset uptil now if I don't chane the 'J3' command.

Hmm...wondering if your step multiplier values under VU are correct & in turn, the switches on your drivers are in the correct positions.

-B

Hi Brady,

Just recently checked the VU's and they were all spot on. Driver switch positions are also correct.

I notice that you said you were running in metric. I think I recall a very recent discussion that Ted was involved in that indicated an issue with metric.

Hi Gerald,

Yup, that seemed to be the indication as well when I spoke to tech. That it might be an issue with the Actual "J3" command and how it's handled by metric machines when there are so many (especially one after the other). Had a file this week that was giving me the offset error when I didn't change the "J3" command. So ramped down the jog speed to match move speed and still got the error, so then switched out all the "J3" commands with "M3" (still at the same lowered speed) and didn't get any offset errors.

There's still no solution to this issue. Tough to predict when it will happen, so still doing the command switch-out for all jobs.

Dunno if tech is still trying to figure out what the problem may be, but haven't heard anything from their end on any ideas for a permanent solution. Might just have to wait for the next SB controller release and see if it solves the problem. Still trying to do tests to resolve it whenever I get the time, but it's a slow process and I'm running out of ideas.

If there's any progress, I'll keep the thread updated. Thanks for all the input guys. Still working on it and testing things out.

Mark

[ken_rychlik]

In the mean time it will be MUCH easier to change your post processor to have it put move commands instead of changing them one at a time.

[scottp55]

Mark, Almost posted yesterday, But don't know PRS Alplphas from shinola. Showing my ignorance but noticed 3.8.12 addressed some metric issues. Would any help?