Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: DMBGO on October 19, 2010, 07:46:57 PM
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Hi again,
I was just wondering how Step / Velocity jog mode is designed to behave. I have one of Peter Homann's excellent MP-03 pendants. When I select step / velocity mode I seem to get straight velocity mode.
I have spent a lot of time calibrating the mpg, and have experimented with doubling and halving mpg values to see what happens. I can easily alter the way velocity mode behaves by doing this, but step / velocity just follows whatever behaviour I get from velocity mode.
While I haven't read this anywhere, my concept of step / velocity is that when you turn the mpg under a predefined rpm the axis would behave as if it was in multi step mode, and as you break the predefined velocity rpm threshold it would switch to velocity mode.
This seems to me to be a very useful (imaginary?) l mode, if indeed this is the way it's meant to work, since it would allow both coarse and fine manual axis adjustment, without having to change jog modes.
I have done a bit of searching and have read through the thread below, but step / velocity isn't mentioned
http://www.machsupport.com/forum/index.php/topic,13531.0.html#lastPost
Cheers
Dave
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What you describe is exactly the way it does work.
Regards,
Ray L.
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That is the way it is meant to work but as far as I know it never has worked correctly although I have not tried it for probably 6 years.
Hood
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Thanks Ray and Hood,
Ray when you say that is the way it does work, is it working that way for you?
If it is just one of those things that should work but doesn't I'll drop it, but if you have it working, I'd really like to know what might be wrong.
Cheers
Dave
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I am 99.99% certain it doesnt work. I can remember when Art was trying to add it in and during all the testing it was never great and I am almost certain it was removed.
I have just tried to get it working on my mill and it just stays in Velocity mode where as years ago it would change from Step to Velocity, just not very well, so looks like it was taken out but just the screens not changed.
Then again I use the SmoothStepper so that may also have a bearing on things.
Hood
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Thanks Hood, I'll give it a try with an mpg on the PP, since I'm using a SS as well.
If that doesn't work I'll move on. I will let you know the result on this thread. If anyone reads this and has it working with a current version of mach3 please let us know, although I'm pretty sure now that it doesn't work, since if Mach can detect the velocity of the MPG, then it should just be working ;)
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allow both coarse and fine manual axis adjustment
I just use my MPG's for positioning mostly, sometimes for machining small things. They are not calibrated and 1 turn of the knob
gives about .010" so i can easily adjust position to .0001" when turning it slowly yet on fast turning you can move the axis
rapidly for rough. Two different MPG's are used as one has a higher encoding than the other so the in the case of the lathe the lower
resolution one is used on the Z axis. Velocity mode is checked. The Xbox 360 is really great for moving around with a lot of flexibilty,
such as a crawl to full rapid,but only use it when tracing out a contour in Copycat.
A little off thread, but FWIW,
RICH
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Hi Rich, sounds like you've got a good system that works. I've only just got my lathe cncing, so I have been experimenting to find the best way of positioning etc. Part of the process is finding out what does and doesn't work, so I appreciate your comments
thanks
Dave
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Dave,
To each their owne i guess. I had considered mounting the mpgs on the carriage like a mannual lathe which would give a natural feel in their use
but i didn't. As far as the lathe goes, use the standard screen to get familar, then use Phil's screen set, and you'll appreciate the difference.
Now way off thread .............got to go...... ;)
RICH
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Dave
I use the MPG on both Mills and Lathe and really only for positioning. I use Velocity mode and multi step mode and find it works well. I have a button on my panel which changes between MultiStep and Velocity mode on the lathe and on one of the mills I have a rotary switch which has 4 positions, one is Velocity, Two is MultiStep at 0.01mm MultiThree is Step at 0.1mm and Four is MultiStep at 1mm. I find the rotary switch the best method and I will eventually do that on the lathe as well.
Hood
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Rich we are OT, but such is life, I had the same idea re 2 mpgs on the lathe, but they are still in their boxes and probably will stay ther for the time being.
Hood, I'm using Scott's plugin with Peter's pendant, but to switch between multi step and velocity, I have to do multiple button presses, a switch sounds easier. I' m sure Scott in his normal helpful manner will change his plugin to remove multi step from the button push cycle if I ask him :) my lathe is quite a distance from the pc screen, so at the moment, i have trouble seeing what mode I'm in. This will change! I was trying to be nice to the SS, which is very scared of my VFD.
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I am not sure how the plugin actually works but I think I remember Peter saying that the MPG with Modbus via Plugin is not as good as Modbus via the old serial interface.
My MPG is not via Modbus at all so cant say one way or the other for sure.
Hood
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Just went to the Yahoo to search to make sure and it just so happens Peter is discussing this at this very moment, heres what he is saying
"Hi Andy,
Wether the MPG is coming from a ModIO or MP-01 pendant, the Modbus data
entering Mach3 is identical.
The only difference I can see is that using the legacy Modbus serial
interface produces smooth movement, whereas using the new Plugin support
Serial interface does not.
In the early days, Art and I had a lot of correspondence to get the MPG
smooth in the Legacy serial Modbus interface.
I have asked Brian a couple of times to look at the MPG issue that Mach3
now has. I even sent him a ModIO to test with.
As I understand it, Brian is too busy with other issues, so fixing the MPG
issues is lower on the list.
If there was anything that I could do from my end, I would. If Brian needs
anything from me, I'm happy to provide it.
It's a bit of a shame that Modbus does not bet a higher priority,
considering it is probably the most widely used communications protocol in
industrial control."
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I wonder if it's my inexperience with mach3 that makes me put such emphasis on this?
I would have thought that this would have been discussed and resolved ages ago if it was a real issue. I suspect that once I've spent a bit more time on Mach I will realize that it's not particularly important.
Having said that, when showing off one's new cnc machine to the uneducated, it is nice if it moves in a smooth and controlled manner :)
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Thanks Ray and Hood,
Ray when you say that is the way it does work, is it working that way for you?
If it is just one of those things that should work but doesn't I'll drop it, but if you have it working, I'd really like to know what might be wrong.
Cheers
Dave
Yes, that is how it works for me, with a VistaCNC pendant. Should work that way with any MPG.
Regards,
Ray L.
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I am not sure how the plugin actually works but I think I remember Peter saying that the MPG with Modbus via Plugin is not as good as Modbus via the old serial interface.
My MPG is not via Modbus at all so cant say one way or the other for sure.
Hood
Hood,
I run my VistaCNC through a ModIO, and it works fine....
Regards,
Ray L.
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Ray
Certainly doesnt work via SS that way, also cant remember it working that way via the PP or maybe I am just remembering that it didnt work very well. It works well in Velocity mode and also in Step or multistep mode but Step/Velocity mode doesnt, I hav to physically change between Velocity and Multistep via switch or screen.
Dave
Have just taken a vid of the mill moving via MPG and am uploading to you tube as I type. I have a cold so you will maybe not be able to make out what I am saying very well but at least you should see the motion.
Will post a link when its done.
Hood
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Ok heres the link.
http://www.youtube.com/watch?v=RVAPVM3s0jg
Hood
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Hi Hood, your video seems to be gone from you-tube (video removed by user). I will try one of my spare encoders on the parallel port today and report back. I am starting to wonder if it is a configuration issue somewhere if it works for Ray.
Time will tell.
Cheers
Dave
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Yes I removed the video as I presumed you had watched it :(
What it showed was the motion was smooth and controllable in Velocity mode, the biggest issue being the detents in the MPG making it hard to keep a very consistent slow speed if you were wanting to use it for actual machining on a regular basis. Taking the detents out and replacing with a small amount of constant friction would solve that. I dont need to do that personally as I only use for positioning and edge finding and find MDI much quicker and better for quick machining if needed.
Hood
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Hi Hood,
That was good timing, I just connected a spare mpg to the PP, just about to try it. back in a few mins
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Right, I've tried it with an MPG connected directly to the PP without the smooth-stepper enabled and things are just the same, so it doesn't look like the smooth-stepper is affecting the results.
I even recalibrated the MPG and set the max speed and step / velocity change over to 1000 detents / sec, to ensure that it would be stepping if it was going to, and it didn't, it just ran in velocity mode.
It was quite smooth, probably a fair bit smoother than the serial mpg, but that's probably to be expected.
Not sure where to go from here, perhaps into the house for a cuppa? :)
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BTW Hood, if you want to put your video back, I can watch it this evening, but don't go to any trouble.
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Sorry not been at the workshop today, that is where the vid is. If I remember tomorrow I will repost it.
If possible it might be better to connect your MPG via Port3 of the SmoothStepper.
Hood
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Afraid I had deleted the vid from the computer here at the workshop so made another one and uploaded it. Let me know when you have seen it and I will delete.
http://www.youtube.com/watch?v=5gIKfSsgFE4
Hood
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Thanks Hood,
Your axis are definitely a fair bit smoother than mine. I think I'll try your suggestion and hook the mpg up to port 3 on the SS. I appreciate you going to the trouble.
I am still mulling over the step jog thing, I would have dropped it if Ray hadn't said he had it working.
Ray, if you read this, what version of Mach are you running?
Cheers
Dave
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I have servos on my machines with fast acceleration and that actually makes it slightly less smooth when at slow speed in Vel mode. The Bridgeport has steppers and accel is a lot slower but the MPG is smoother at slow revs, then again if it was to be used for manual machining I would remove the detent from the MPG as that would help keep a more consistent slow turning speed.
Hood
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Thanks Hood,
Your axis are definitely a fair bit smoother than mine. I think I'll try your suggestion and hook the mpg up to port 3 on the SS. I appreciate you going to the trouble.
I am still mulling over the step jog thing, I would have dropped it if Ray hadn't said he had it working.
Ray, if you read this, what version of Mach are you running?
Cheers
Dave
Dave,
I'm using 3.042.020, with a SmoothStepper.
Regards,
Ray L.