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Author Topic: Smoothstepper step problem  (Read 19109 times)

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Offline Hood

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Re: Smoothstepper step problem
« Reply #20 on: January 16, 2010, 05:02:22 PM »
millmaster, read my second post in this thread I said it was something about the way it was calculated by the SS, so dont know why you say
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Finally someone admits that there is a problem with the smoothstepper
Now to answer your next question
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Why would any problem with the smoothstepper be low on Greg's list??
The reason it will be low on the list is because there are other things much more important to users that are needed to be worked on first. Are you seriously telling me that you can measure this +- 0.0001" out of dimension on anything you have machined ?

Hood
« Last Edit: January 16, 2010, 05:06:20 PM by Hood »
Re: Smoothstepper step problem
« Reply #21 on: January 17, 2010, 12:50:39 AM »
Nope never made mention of measuring machined parts for the +/- .0001". My beef is at the control level .. the smoothstepper as it cannot manipulate the g-code correctly, but I see everyone is looking at the machine first and quoting specs, tolerances and steps and how one cannot measure .0001" (there are several measuring tools on the market that will measure .0001", some real low budget import ones also), and if you read Jeff's post he states this issue has nothing to due with the actual smoothstepper, the opposite of what Hood states, so yeah it is somewhat confusing with the info you folks are posting in regards to wether the smoothstepper has an issue or not. Like I say I have not seen another control that connot count and display steps properly to the code that is being run. So now I am curious what other things more important to users that are needed to be worked on first that puts this low on the list?

millmaster

Offline RICH

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Re: Smoothstepper step problem
« Reply #22 on: January 17, 2010, 09:27:28 AM »
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So now I am curious what other things more important to users that are needed to be worked on first that puts this low on the list?
The evolution of Mach to rev4 and all that is required to get it done while also maintaining functionality and usability along with step change improvements to Mach3. The order of effort can only be determined by those actualy doing the work  and in that light i am sure the demands on those folks are great.There are more important things that need to be addressed than what has been discussed in this thread for sure.

So i will bluntly say that surely a concern will not go un-noted but will be addressed when appropriate
and not necessarily in the order we as users would like it. Such is life!

As I replied before, those who are dealing directly with the hardware and software would be the definitive source.
Thus we have tried to provide insight relative to your basic question as we relate to it.

RICH

Offline Hood

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Re: Smoothstepper step problem
« Reply #23 on: January 17, 2010, 09:50:12 AM »
Ok so what it all boils down to is the display sometimes shows this 0.0001 out. That 0.0001 seems to be the same numerical  value whether in metric or imperial mode which would suggest that it is just a reporting issue to the DRO. Even if it was a real error none of us here or most in general  industry for that matter,  have machines capable of position to that accuracy and even if we did we would need temp controlled environments and a means to measure to that accuracy.
 If you read Jeffs post again I think you will see he said it was a DRO rounding issue and not a SS hardware issue, in other words it is a software issue and the software being the SS software as it  is telling Mach what to put in the DROs.

These measuring tools that can measure to 0.0001" that are cheap I dont know of, I have bore mics that have graduations to 0.001mm but their accuracy is only +- 2um, if you need to measure closer than that you will need something that has a resoltuion of 0.0001mm and then you will need to make sure all measurements are taken in a controlled environment.

So what does this all boil down to, we all seem to be agreed that it is unlikely that it is an actual positional problem and if it is it doesnt matter as we cant work to that resolution accurately anyway. You seemed to be disagreeing in your first post you said
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so yeah + or - .0001" steps is a concern for some of us chipmakers
but I will now assume in that you are agreeing with the above and it is only a visual annoyance rather than any physical problem which would affect our work.

So what are the other things you ask, well for many backlash comp is wanted and Greg has been working hard to get that implemented, to me it is not important but to many it is and I think it is top of the list.
 THC is another, again many people waiting for this and I believe that too is near the top of the list.
For me personally the spindle control is not perfect when using a servo, it works but there are niggles. As most people dont have servo spindle I will assume this is lower on the list.
 Swap axis is again wanted by some, me included but again probably of no concern to the majority of users so again presume it will be further down the list.
Greg has many things on the list but has to prioritise these things in order of what he and users think is most important and at the moment I think the backlash guys have the loudest voice and have been waiting the longest so I will presume that is top of the list, and it is probably the hardest and most complicated thing that will have to be done so I dont envy his task.

Hood
« Last Edit: January 17, 2010, 09:52:37 AM by Hood »

Offline Jeff_Birt

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Re: Smoothstepper step problem
« Reply #24 on: January 17, 2010, 09:56:53 AM »
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My beef is at the control level .. the smoothstepper as it cannot manipulate the g-code correctly

The SmoothStepper or any other motion control device that works with Mach DOES NOT interpret or manipulate the G-code, Mach ALWAYS does that. Mach's planner interprets the G-Code and breaks every movement down into the itty-bitty movements that needs to take place between each clock cycle; by clock cycle I am referring to the 'kernel' rate on the parallel port drive and the 'Controller Frequency' and 'Max Step Frequency' in the SmoothStepper configuration. In the SmoothStepper you can think of the 'Max Step Frequency' as sort of a kernel frequency that you can assign per axis. Just like with the parallel port driver, the steps/unit and max velocity determine the frequency needed.

In either case lets say you are starting from 0,0,0 and have a 'G0 X0.1234'; Mach will break that distance down into the small bits that need to be moved to each clock cycle (accounting for acceleration, deceleration and velocity, steps/unit). If your using the LPT driver then this clock is the kernel frequency, for the SmoothStepper is a combination of the 'Controller Frequency' and 'Max Step Frequency' as mentioned above. In some case breaking down a movement into all of these little steps leads to very minute rounding errors in the axis DRO. Since Mach runs a sort of cumulative axis DRO this is not an actual error as if it could not break a move down into an even number for display purposes the next move will be calculated properly, so any single step will be taken up on the next move. A crude analogy would be typing '1/3' into a calculator. You'll get 0.33333333...which we would just say is '0.3333' but if you type '2/3' you will get '0.666666666...' which we would say is '0.6667'.

If on the SmoothStepper has its 'Max Step Frequency' set to high for an axis it will limit the output resolution for that axis. You can get an idea of what this frequency should be set to by knowing your steps/unit and max velocity.

Steps/Unit * Units/Min = Steps/Min, Steps/Min / 60 = Steps/Second

This Steps/Second is the needed step frequency for that Axis, you should set the SmoothStepper 'Max Step Fequency' to the lowest value that is equal to or greater than your Steps/Second. Once you get all your axis' 'Max Step Frequency' set, adjust the 'Controller Frequency' to the lowest value that proved Smooth movement, the note of the SmoothStepper configuration page says higher settings will limit resolution.

So no, there is not a 'problem' with the SmoothStepper. Your worried about a non cumulative rounding error (i.e. display issue) that is in the ones column of your steps/unit (i.e. in the noise anyhow). It's possible that by properly adjusting the SmoothStepper it will go away, but as has been mentioned numerous times your getting all worked up over a display issue, not a positional issue.
Happy machining , Jeff Birt
 

Offline cv580

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Re: Smoothstepper step problem
« Reply #25 on: January 17, 2010, 12:50:09 PM »
Millmaster I think you are wasting your breath trying to get your point across to the virtual/armchair machinists here, I am sure they have more important things to do instead of making the smoothstepper work properly, like get the calculator out figure out the max amount of steps per unit so they can engrave their butter, collect some machine brochure data to post some useless gibble to make themselves feel like an expert, and search for a measuring device that can measure a ten thou. yep impressive! Meanwhile the high school project like smoothstepper is still a huge sponge for EMF with no built in filtering and was designed for servo operation (stepper was a afterthought) being produced in mom and dads basement, again I have sent a e-mail to Warp9 and no reply, they do NOT even have phone number on their site .... bottom line NO SUPPORT 

Offline RICH

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Re: Smoothstepper step problem
« Reply #26 on: January 17, 2010, 12:54:04 PM »
cv580,
Don't test your luck, I am being tolerant.
 
RICH
« Last Edit: January 17, 2010, 12:58:11 PM by RICH »

Offline Hood

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Re: Smoothstepper step problem
« Reply #27 on: January 17, 2010, 01:02:56 PM »
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Millmaster I think you are wasting your breath trying to get your point across to the virtual/armchair machinists here

Now that is funny, especially coming from a guy that wont tell us what machine he is using other than to say its a large mill with steppers and then goes on to say that when engraving with this machine the +- 0.0001" error is a problem because he is doing such small work. Ever think about things a bit deeper, like to get your resolution of steps/per unit to the 10,000 you have you are using microstepping, how accurate do you think that is?

For your information for the last 15 yrs I have made my living using machines, I am not a trained machinist  but unlike you I live in the real world.

Hood

Offline Jeff_Birt

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Re: Smoothstepper step problem
« Reply #28 on: January 17, 2010, 03:56:12 PM »
Funny how you can't be factual about how things actually work without hurting somebody's feelings.
Happy machining , Jeff Birt
 

Offline RICH

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Re: Smoothstepper step problem
« Reply #29 on: January 17, 2010, 04:21:31 PM »
CV580,
As i rocked in the arm chair and calculated if the additional mechanical axis reduction would provide for an
appropriate resolution, I cut the following letters in butter, so to speak. Sorry I didn't make note if the DRO
 was within 0.0001" since that would be 1/20 th of the 0.002" hair shown in the picture MY TEXT IN  BUTTER .
But in the 30x or so magnification it was not to be found. I originally tried cutting on my mill, but all the letters
 just came out as a blob, comparatively speaking, because of how good the mill is as a system. Don't know how
 i can get the periods after the letters to show as cut circles ( the period is a circular cut with a diameter of .001").  

Do you think that a change in DRO will get me to the tolerance that i am looking for to those cuts?

RICH