I have a smoothstepper on a large mill with stepper drives and what ever code that is being run through the smoothstepper it will not make the whole stepping distance ie: if the code is X-1.250, Y1.250, Z-.750 the actual distance the smoothstepper will make is X-1.2499, Y1.2502, Z-.7499. Can anyone explain why this happens and what the fix is? If I run the machine thru a parallel port this does not happen. The drives are being run in step and direction mode. I have used a dial gauge on the axis and it confirms the over travel and under travel with the smoothstepper.

cv580

What are your steps per unit?

Hood

Steps per unit are 10,000 (ball screw makes 5 turns to 1 inch of travel), I have tried different step per unit settings but then distance travelled becomes incorrect in a big way. The undertravel or overtravel remains constant until the axis passes thru 0.000 and then the change of plus or minus a step will happen.

cv580

I cant remember exactly what it is but Greg did explain it to me a few years back, its something to do with the way things are calculated but it doesnt accumulate. In fact I cant even remember if its just a display thing or actually a real value but either way 0.0001 is an insignificant value. I agree  it is f a visual nuisance but you soon forget about it when you realise how small it is


Hood

It is actually .0002" as it will go plus or minus .0001" and it can be more than a nuisance especially when you look at the DROs while running code and see a bunch of 9's because it has rolled back .0001", also I have been doing some very small engraving of serial numbers and losing a .0001 step makes for some difficulties also so it does depend on what you are doing will make it a small or big issue.
Does Warp9 still support the smoothstepper as I have tried to send them e-mails about this problem but never receive a reply?

cv580

Hey cv580
I have the exact same problem with my smoothstepper, I have been told that it is no big deal as it is such a small step and there is more back lash in the axis than what travel the smoothstepper cannot make but I disagree with that thought as we are now working with electronics that can be super super accurate, basically I see what the smoothstepper doing here is a form of electronic backlash. I have talked to other people that are having this issue with the smoothstepper and it is only happening in the step and direction mode, I know one shop that have this issue and they were talking to Warp9 about this and the explanation came back something along the line about it being a problem with the algorithm not being right for the step and direction mode and using a hysteresis for the step and direction mode which is not used for the quadrature mode, from this I gather the smoothstepper is not really designed for step and direction mode. I do hear a lot of comments of it is just a small step and not to be concerned about it, which I do not agree with because here is a product with great potential but it is put on the market as is with no feedback from the machining community then it will remain a half built product that is not right, I do not know of another motion controller on the market today with this sort of lead and lag. I gather that the designer of the smoothstepper is not a machinist and if everyone in the machining world comes across with the attitude of plus or minus .0001" is not a big deal then nothing will be done by Warp9 and you will be stuck with a motion controller that has lead and lag. He has to know what is not working properly, so yeah + or - .0001" steps is a concern for some of us chipmakers. As for support for the smoothstepper from Warp9 I am not sure what their take is on this issue, I understand they are a moderater on this forum maybe they could let us know what their thoughts are! 

millmaster

Your steps per unit are 10000, so if all was perfect ( which it is never true ) the very best you can hope for in
position is 0.0001" plus or minus. To do better than the 0.0001" the mechanical axis needs a required steps per unit
at 20000. 

It's an emotional issue to see say 1.9999 instead of 2.0000.
I never had a display problem with any of the machines, SS or PP,  if the steps per unit was reasonable above 10000.

Do small engraving and say it makes a difference on small engraving of letters.......how small and how deep and what is your runout at the tip of the point. Best i could ever do is 0.0005" tip radius which won't even last in scribing butter.  And you will not scribe a single point / line width of 0.001" since there will be spindle runout and ovality of the point. Sorry, just don't buy a practical impact on lettering because of the .0001" . FWIW my engraving
machine requires  253000 steps per unit , slow,  but accurate as can be in positioning. Small quality letters or numbers .010" high are a real challenge, almost not practical.

RICH

   

 

can I ask the specs of your machine please?

Hood

Hey Rich
I think we are looking at a electronic issue here, you are thinking of a mechanical issue with the machine. What mode are you running your machines in? Step and direction or quadrature? The mode will make a difference in what the display shows.

millmaster

millmaster
 what machine do you use the SS on?

Hood