Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: ffulmer on December 21, 2007, 10:10:26 PM

Title: Losing zero by alot and can't cut a circle
Post by: ffulmer on December 21, 2007, 10:10:26 PM
I have a Dyna 2800 with steppers and I have two problems. First I have spent all day playing with the motor tuning trying to get it to cut a circle with out jumping around when it rounds on either end of the X movement. At a point on either side of the maximum X travel the motors growl and vibrate. I have read every post and made every adjustment I can think of. Do I need to replace the stepper boards and/or the motors???

The second problem started today; it now loses it "0" setting. If I try to cut a circle it will first run off and start cutting it off to the side and I mean almost an inch off of center. I also noticed when I zero the X setting it always has a - (negative) in front of it and not a + like the others.

I have burned out with this, anyone have any ideas? Help!!!!
Title: Re: Losing zero by alot and can't cut a circle
Post by: dfurlano on December 22, 2007, 11:58:01 AM
I would check with an indicator if the is any side to side movement in your table. I say this because it sounds like something is binding.  Put an indicator on the end of the X axis and hang it off the head or table, something not connected to the table.  And with your hand see if you can move the X axis table front to back.  If so you need to adjust the gibs.

Just a guess.
Title: Re: Losing zero by alot and can't cut a circle
Post by: ffulmer on December 22, 2007, 03:35:47 PM
dfurlano

Thanks for the reply and I will  re-check for physical binding, but I can grab the stepper motor shaft between my thumb and forfinger and turn it with no problem. The screws look like new and are protected by bellows,the gibs are set about perfect and this machine has an automatic oiler which keeps everything smooth.

When I went to the motor tuning and changed the pulse to 8 as they recommend 1-5 it did seem to get a little better. Can someone explain the function of the pulse setting. Does it have to do with the computer, the motors or the driver boards?
Title: Re: Losing zero by alot and can't cut a circle
Post by: Chip on December 22, 2007, 06:42:17 PM
Hi, Ffulmer

It give your stepper control more time to see the Pulses from Mach3.

Thanks, Chip
Title: Re: Losing zero by alot and can't cut a circle
Post by: Chip on December 22, 2007, 10:14:10 PM
Hi, Fred

Have you tried a smaller circle, Maybe your actually hitting the X max/end's.

Call me or email your phone #.

Thanks, Chip
Title: Re: Losing zero by alot and can't cut a circle
Post by: Whacko on December 23, 2007, 04:20:11 PM
Depending on the lenght of your cables and the drivers for your motors, there is a good chance that your problem stems from the drivers. Stepper motors have resonance at certain phase angles. Advanced stepper drivers use algorithms to dampen this resonance. Any play in the drive mechanism will result in a loud chatter of the motors. The cable length is also a factor as is the conducter size. The fact that the chatter is at vector changes indicates free movement in the drive mechanism. In some cases it would require the change of your drivers. Also the fact that the chatter is less with increase of microstep ratio points to the resonance as the most probable cause.

Whacko
Title: Re: Losing zero by alot and can't cut a circle
Post by: ffulmer on December 23, 2007, 06:13:07 PM
Hello again Whacko

This appears to be the best answer so far. I do appreciate all the help I have gotten from everyone. But if their is any play in the table or ball screws on this machine I can't find it, at least not what I can see on a dial indicator. I can move the tables by just my thumb and forfinger grabbing the motor shaft. With the exception of the motor clogging they move smooth and free. The motors appear to be very high end 1.8 degree, 8 wire Escap (Swiss made) disk which I believe use rare earth magnets. But the driver boards are the old original ones and I too think this is the root problem.

The wire on this machine is all shielded cable, I'm not sure of the length, I will say it's not much over 4 feet. I am going to order new driver boards and pick up a faster computer. Thank you.

Fred

Title: Re: Losing zero by alot and can't cut a circle
Post by: Whacko on December 24, 2007, 01:33:09 AM
You should try a driver board with a higher step resolution. I will pm you with some info

Whacko
Title: Re: Losing zero by alot and can't cut a circle
Post by: Whacko on December 24, 2007, 04:17:25 AM
Fred, I sent you a pm

Whacko
Title: Re: Losing zero by alot and can't cut a circle
Post by: Apen-nootjes on December 31, 2007, 08:58:35 AM
Hi,
If it is any reassurance, I can tell you that I am experiencing the same problem as you do. Only not with cutting a circle but by doing an angled movement (the worst with a movement to the up and left). Halfway through the machine stops dead in its track and makes a lot of noise, after that it continues its program but Mach3 thinks it is way ahead so the whole thing is ruined. This behavior happens when moving in G0, in G1 movement this hasn’t occurred as far as I know. A solution or help to get to the solution will be appreciated by more persons than just the topic starter so if you guys know anything, please put it here :)
Thanks in advance and excuses for the bad English (I’m Dutch :P )
Title: Re: Losing zero by alot and can't cut a circle
Post by: Hood on December 31, 2007, 09:15:05 AM
Hi,
If it is any reassurance, I can tell you that I am experiencing the same problem as you do. Only not with cutting a circle but by doing an angled movement (the worst with a movement to the up and left). Halfway through the machine stops dead in its track and makes a lot of noise, after that it continues its program but Mach3 thinks it is way ahead so the whole thing is ruined. This behavior happens when moving in G0, in G1 movement this hasn’t occurred as far as I know. A solution or help to get to the solution will be appreciated by more persons than just the topic starter so if you guys know anything, please put it here :)
Thanks in advance and excuses for the bad English (I’m Dutch :P )


 This is a classic symptom of your motors not being tuned properly, you either have the velocity set too high or the acceleration too high. If it happens near the start of th G0 move then likely turning your acceleration down slightly would cure it. If it happens a bit later into the move then it could be the velocity thats too high.

The noise you are hearing is your motor losing steps.

Hood
Title: Re: Losing zero by alot and can't cut a circle
Post by: ffulmer on December 31, 2007, 03:45:25 PM
Hello
Please excuses my bad English I'm American and to me English is still a difficult language.

Sounds like you are also losing steps, what type of machine do you have? What are the motors? A person on this forum that goes by the handle of Whacko is very knowledgeable of this and he can give you the run down on what to check as far as your power supply, motors and etc. You could also try going into Mach3 motor tuning and increase the step and direction pulse to 8 and that will give your stepper boards more time.

But I felt that my drivers are too old (1989 to 1990's) and not able to do the microstepping I need along with my motors are Disk type made by Portescap (Swiss made). So in the end I bought faster computer a Compaq Pentium 4 with 2GHZ speed, three new Gecko G203V controller boards and three PacSci NEMA - 665 in/oz. stepper motors with encoders.

Let me know if the step and direction change make an improvement and we can go from there.

Fred
Title: Re: Losing zero by alot and can't cut a circle
Post by: Apen-nootjes on December 31, 2007, 04:27:28 PM
Hello
Please excuses my bad English I'm American and to me English is still a difficult language.

Sounds like you are also losing steps, what type of machine do you have? What are the motors? A person on this forum that goes by the handle of Whacko is very knowledgeable of this and he can give you the run down on what to check as far as your power supply, motors and etc. You could also try going into Mach3 motor tuning and increase the step and direction pulse to 8 and that will give your stepper boards more time.

But I felt that my drivers are too old (1989 to 1990's) and not able to do the microstepping I need along with my motors are Disk type made by Portescap (Swiss made). So in the end I bought faster computer a Compaq Pentium 4 with 2GHZ speed, three new Gecko G203V controller boards and three PacSci NEMA - 665 in/oz. stepper motors with encoders.

Let me know if the step and direction change make an improvement and we can go from there.

Fred

Fred, thank you very much for your reply. I will try to change the step and direction this week and let you know the results.
Title: Re: Losing zero by alot and can't cut a circle
Post by: Apen-nootjes on January 05, 2008, 06:23:38 AM
Hello,

I have tried the solutions provided by Hood and ffulmer. I started off with the changing the step and direction pulse to 8, but this made the mill behave even worse, so changed that back to 6. After that i lowered the Velocity and Acceleration and hey presto! The movements are better! Changed it another bit and it seems to work fine now! So thank you guys so much!

Vincent
Title: Re: Losing zero by alot and can't cut a circle
Post by: Hood on January 05, 2008, 08:26:13 PM
Glad you are sorted

Hood