loosing steps at slowr speeds?

[bearwen]

Well,
I just bought and installed Mach 3 I have my motors tuned and I dont loose steps at 70 inmin X and Y. I was doing a trial run of some Joe 2006 parts (no wood being cut router just cutting air)and well at 55 inmin feedrate I am consistently off by .042" on the X axis( by this I mean when the part is done cutting and the machine comes back to my start 0,0,0 the X axis has gained .042" so to be at 0 on the Xaxis I am reading in the DRO -.042" the Y and Z are fine ther .002" or less) when I tried slowing it down to 22 in min I was .362" off? I am curently running Mach 3 version 2.42 on a 400Mhz pc that is striped down and had the optimization done to it it has 256 meg ram and XpPro there is nothing on the pc but windows and Mach 3 the control cards are Pminmo 3977 boards @30vdc ( Gecko203's are in the mail )I have 269ozin steppers I am running in 1/8 step and I have a 1/2 10 acme screw the machine is a JGRO that was built with basic power tools. Mach 3 is setup at 25khz speed is set at 65inmin velocity and accel is 3.5 step pulse and dir pulse is set to 0 default the thing seems to jog great no lost steps at least not measurablly large enough to be concerned. I am confused I thought slow down get more accurate and not drive cnc so hard this has me confused!

Thanks all
Bearwen

[pminmo]

Did you read the note on minimum pulse width here: http://pminmo.com/ss3977/ss3977.pdf I suspect you are missing mach step pulses. Which version of copper did you etch? Depending on version, there are three 10K resistors in series with pin 1, pin 3, pin 5 of the 10 pin connector with a 470pf cap to gnd. You can drop the pulse width minimum by lowering the value of those 10K resistors or 470pf resistors. At 10K and 470pf, depending on the PC and component tolerances, you are at the edge of passing 3.5us pulses.

[bearwen]

Phil,
I did notice that but I am not sure as to what that is telling me where do I put this setting and also what does it mean by steppers torque drop off above 8Khz in 1/8 step that is not the 25Khz setup in Mach3 is it please explain these as to what they mean to me and the stepper motors etc. Oh hey the minumum step pulse width is that the step pulse setting in mach3 under motor tuning screen next to the G force box in Mach 3 this box says step pulse 1-5 us (micro sec) and direction pulse is next to it and says 1-5 should these be changed and what do they mean? Not sure what version copper I am at work but I will check when I get home and let you know what size caps and resistors.

Thanks

[pminmo]

Motor tuning. picture attached. If you have some 2.2k or 3.3k resistors replace those three 10K's. If I know which version I can tell you R numbers. You won't get as much pull out torque, or holding torque in 1/8th step. 1/4 step is better, 1/2 probably the strongest for the 3977. Full step is so resonance prone unless you want to move slow....

[ger21]

The minimum recommended PC is at least 1 Ghz, so you need a 2-1/2 times faster PC. Run the driver test (drivertest.exe) and post a screen shot of it.

[bearwen]

Phil,
In the pdf you posted it says 10 micro sec but in the Mach screen it says 1-5 micro sec under step pulse so in mach I can only get 1-5 micro sec per step? so I will have to change resistors? I wish someone could explain all of this as to what the timing is and what not and how they all interact with each other the Frequency and step pulse on card and step pulse from mach etc where and how to figure the timming such as the step pulse micro sec (I am really worried that since I dont know how all this stuff interacts and what it means that when I change to geckos or large power supply or different motors or screws etc that i am not going to be able to set it up again with out lots of forum questions and well I would like to know how to figure this stuff out so i can try and then ask questions).

Ger 21,
As soon as I get home Ill run it but that computer is not connected to the internet and it doesnt have a burner (I have not bought a router yet to network it to the house either) I will run it and tell you what it looks like. Oh where is that file I assume in the Mach folder somewhere correct?

Thanks for the help

[neilw20]

I only miss steps on rapid feed (G0), so until I upgrade my 600mHz HP with the Mach3 driving an X3 sieg, I will use F800 or F1000 with G1.
Don't select a value higher than 50% of what works, because if you over-ride the feed at 200% you will still break the bank.
More haste, less speed.

[pminmo]

Originally Posted by bearwen Phil, In the pdf you posted it says 10 micro sec but in the Mach screen it says 1-5 micro sec under step pulse so in mach I can only get 1-5 micro sec per step? so I will have to change resistors? I wish someone could explain all of this as to what the timing is and what not and how they all interact with each other the Frequency and step pulse on card and step pulse from mach etc where and how to figure the timming such as the step pulse micro sec (I am really worried that since I dont know how all this stuff interacts and what it means that when I change to geckos or large power supply or different motors or screws etc that i am not going to be able to set it up again with out lots of forum questions and well I would like to know how to figure this stuff out so i can try and then ask questions). Thanks for the help

When I did the original 3977 (website) I wasn't using Mach3. I can't remember all the history, but sometime in the future I became aware of Mach3 as a user was having problems and I became aware the MACH3 pulse width maximum was right on the designed filter edge. It's not a dead certain problem, it depends on the PC and the component tolerances. Even at worst case it's just marginal, kind of like your experiencing. In the boards I sell, I revised the filter components to be compatable with MACH3. Now, the bad on my part is I thought I had revised the free version on the website with a note on the filter, looks like I didn't. If it is in fact the problem and it really sounds like it, you should have not had this issue if I had done what I should have, or thought I had. As for the G203s, you will change things. Your will retune your motors, pulse timing shouldn't be an issue. As for changes to your setup, if you have questions, feel free to ask me or email me. It's not an issue.

[bearwen]

phil,
could you explain the pulse timing and what it means such as mach 3 I can set pulse step from 1-5 micro sec so how do I know what to use and how do I figure out the pulse step on the card you said to change the 10K resistors but how do I know what to use (other than you gave me the numbers) but if I wanted to calculate this myself how do I do it and what am I wanting to get? What does mach3 put out and when I change the step pulse in mach3 what is coming out then? Phil I just checked my printout and I noticed that I have writen in to change the 470pf caps to 220pf I checked my caps and they are 220pf so now what?

Bearwen

[pminmo]

Originally Posted by bearwen phil, could you explain the pulse timing and what it means such as mach 3 I can set pulse step from 1-5 micro sec so how do I know what to use and how do I figure out the pulse step on the card you said to change the 10K resistors but how do I know what to use (other than you gave me the numbers) but if I wanted to calculate this myself how do I do it and what am I wanting to get? What does mach3 put out and when I change the step pulse in mach3 what is coming out then? Phil I just checked my printout and I noticed that I have writen in to change the 470pf caps to 220pf I checked my caps and they are 220pf so now what? Bearwen

You shouldn't have to worry about the pulse timing, other than what the driver you are using says it needs. The G203V will respond to the minimum MACH3 can put out.

As for the filter on the 3977 board, if you put in 220pf instead of 470pf I don't think the issue is pulse width. Lowering the filter caps is the same as lowering the resistors. Put in 4 or 5us for step and direction pulse width in the motor tuning for the axis that you have an issue with. If that doesn't change your result, then you maybe faced with too slow of computer for MACH3 as ger21 suggested. You can also try loading a free dos based controller like CNCpro or TurboCNC and see if you get the same result.

Did you etch a new X board like you talked about?

[bearwen]

Phil,
No I did not etch a new board My wifes uncle saw my machine and what I have done and he asked me to figure up what it would cost so I figured it for geckos and when I went to gecko to price there boards I saw they were on sale so I bought 2 one for X and one for Y and I plan to use your 3977 to run the Z for now so I have 2 spares hahaha. Thanks for the help so 5 us thats as close as I can get to the 10 your card needs and you said that the geckos can run at the lowest ie 0 or 1 micro sec correct? I still dont understand why I am gainning steps and only on the X the Y is fine and the Z has always been fine by gainning steps what is happening is when the machine comes back to 0,0,0 after cutting the part the X says 0 but I have to manually back it up (move negativve direction) to get it back to the actual 0 spot that I have marked and its always -.0422 to -.462 on the dro when I hit the actual 0 spot the Z and Y come back to 0,0,0 within .002 or less every time?

Hey thanks again and I have a possible PC replacement comming ( friend is buying new PC so hope he gets it soon)

[ger21]

Are you sure the X isn't binding anywhere?