G203v, Plain BOB, Losing Steps

[pzzamakr1980]

Hello, I am having a huge problem with lost steps. I am running 3 gecko 203v's, with a plain BOB, a 860w 72v 12a power supply, 2 nema 23 276oz steppers, a nema 34 640oz stepper, all powering a CNC fusion ballscrew kit on an X3. I have the steps set at 10,000, acceleration set at 1, and rapids set at 60 for x and y, 40 for z. I am using the backlash compensation with movement rate set at 40% with shuttle acceleration set to 0.1. The system is capable of rapids being set much higher, but I turned them down when i started having these problems. I am also noticing that the x and y motor seem to make a beeping noise as they travel along, with the null noise as well. I dont ever remember them making a beeping noise before.

I know that you are not supposed to use a straight BOB with other gecko's, but I understood that it was okay to use with the 203s. Is this the case or no. Also, somebody mentioned in another post that you can adjust the pulse settings to get longer pulses which may help.

Thank you.

[tauntdesigns]

My ballscrews from the deluxe kit are 5mm per turn. If you have 5mm per turn ballscrews you need to set your steps to 10160.

1 inch = 25.4mm
10,000 steps = 5 turns and 5 turns times 5mm = 25mm
160 steps = .4mm
10,000 steps plus 160 steps = 25.4mm which = 1 inch

[pzzamakr1980]

That is true taunt, and I suppose I should have put that yes, it is set at 10160. not 10. But that would not cause the very obvious differences between each pocket that i am seeing. I will try to upload a picture to give an example. The first picture shows what its supposed to look like. The pocket is centered with the hole. The others show how it gets worse and worse.

One other thing, the computer is not the problem, cpu usage is barely 2% at any given time during a run.

[tauntdesigns]

Kool,

I saw in your post, 10,000, so the first thing that came to mind was 10160.

Are you taking it all in one bite (pass) or multiple cuts. if multiple cuts they look pretty uniform.... missing the same steps.

If your taking it all in one pass, try one hole/pocket just .050" deep and see if it's still missing steps... just to rule out the possibility of bogging down the motor or a coupler slipping on a shaft.

Jack

[pzzamakr1980]

Well, it will drill all of the holes perfectly. Then the first pocket comes out okay. In fact, it came out perfectly, exactly the size I needed. Then the next one started off center, and it got worse with each consecutive hole. I just realized I am experiencing the same problem with the z axis. Its drilling shallower and shallower with each pocket as well.

Also, how much difference would 160 make over 3 inches as an example.

Each pocket is .3 deep, .315 diameter. I am using .1DOC with 50% stepover with a 1/4in cutter. It takes 3 passes to get to depth using a spiral cutting method. If i was having problems with incorrect steps per inch, it would also show on the first hole correct.

[tauntdesigns]

All the holes come out perfectly,... they're evenly spaced or they're exactly the programmed distance apart?.... if the steps are off then the holes would not be the correct distance apart, but they could be equally spaced. Also, if the steps were off you wouldn't get the correct size on your diameter. (although on a .315 dia. you'd only see .003-.005 difference)

160 steps = .4mm and about .016" of a inch So, 3 inches would be .047" of a inch.

The chance that all three axis couplers are slipping is very slim to none.

Are you writing the program code or is a CAM doing it. If a CAM is using incremental movement programming the difference in steps would accumulate on each move.

I'm just thinking out loud trying to eliminate possible causes,
Jack

[pzzamakr1980]

The holes that are coming out right are drilled holes. They are the correct distance apart. I start to have problems when I do pocketing or contouring. The first pocket is usually good, its the ones that follow that aren't. The couplings arent slipping, because I cant hold the table back when its moving, if I jog it back and forth for instance. Mastercam is what I am using, and I didnt have problems with it before. This problem has just started cropping up within the past two months.

[tauntdesigns]

It's strange that point to point seems to be OK, but under milling it loses it's mind!

Sorry I couldn't help,
Jack

[DR-Motion]

Hi Pzzamakr,

I have had exactly the same symptoms where the drilled holes where bang on but the interpolated holes were off position. I finally traced it down to the step pulse setting.
I was using G201's which require an active low for the step pulse... with your G203V's you need an active high pulse. In Mach3 I believe that means unchecking the active low enabled.

Let us know if that fixes you up

regards Gary

[DR-Motion]

Upon further consideration, regarding the noise, you may be correct in thinking it's related to the length of the step pulse. That can be adjusted in the Mach motor tuning screen.

A client of mine had a problem with his setup and Mariss from GeckoDrive told me to set the pulse width for the G203V's to 3uS (the 'u' is impersonating a greek 'mu'... as in 3 microseconds).

HTH

[Mariss Freimanis]

In Mach3, ports and pins: Make 'step pulse' 'active high'.
Under motor tuning: Make 'step pulse width' '2uS'.

Mariss

[pzzamakr1980]

Ok thx, I wont be able to do this because the x axis motor just died. It got really hot, and when it tried to push the axis, the shaft stopped turning after it stalled for about 3 seconds. I ordered two new steppers for the x and y axis. Two keling 425s. I believe I already had the step pulse set to high, I'm not near the comp right now, but I will set the pulse width when I get the motors back up.

I also just thought of something, in that I might not have switched the resistors when I had switched the x and z around. Would this have been a factor? It could right? I need to purchase two new resistors for the new motors anyways, so I will purchase one for the z just in case. I should get everything back up by next weekend so I will post results.

Thank you very much for everybody's help and suggestions. It is much appreciated.