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Messages - wrench

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What product has the largest number of I/O out there?  I've been looking around and there are quite a few breakout boards, ModBus boards, etc, that have 5 to 8 I/O, but I'm guessing there is something that has substantially more than that.  Does anyone have candidates?

Thanks,
Alan

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General Mach Discussion / Re: Deckel Mach Retrofit
« on: August 15, 2007, 05:52:46 PM »
Hi Jeff,
You hit the head of the nail in your response.... OK, that is what I was looking for.

Thanks for confirming my thoughts.
--Alan

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General Mach Discussion / Re: Deckel Mach Retrofit
« on: August 15, 2007, 03:19:05 PM »
Hi Jeff,
I had just added some more information to my post and when I refreshed I saw yours.  It seems like my assumptions are correct.  This really gets down to a tuing thing.  The assumption is made that, due to tuning, when Mach3 terminates sending pulses, the servo motor can stop rotation (and be within the tolerance of the following error).  If additional rotation is required, then I believe my original concern is still valid.  If Mach starts pulsing the second axis, then the result will be a kind of chamfer, not a theoretically sharp point.

Alan

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General Mach Discussion / Re: Deckel Mach Retrofit
« on: August 15, 2007, 10:53:16 AM »
I have a question that keeps nagging me regarding the open loop concept.  The control outputs steps to a Pixie (for instance) that then transforms this to analog for a pseudo-closed loop.  That is great for monitoring errors, but the part I do not get is how chaining is done reliably, aka look-ahead. 

As an example take an external right angle... Unless you are at the terminus of the first line, you don't want to start the second.  If you did, you'd end up with a fillet, which obviously is not good.  By the same token, if the control assumes it takes 1 minute to go to the terminus of line 1 and it only takes 45 seconds, then there is a 15 second dwell time; needless to say, that is not good either. 

The real pickle is that the time for the cut of the line can vary a bit as a result of loading, so I am at a loss to figure out how any open loop system can reliably make something as simple as a right angle *without* dwell marks resulting from an artificially long delay between successive commands.  If someone can explain that to me, I think it will go a long way to making me feel more comfortable wiith the whole approach taken with Mach.  I must be missing some fundamental, and simple, piece of the puzzle.

[on edit] In thinking about this more, I am coming to the belief that this is all about tuning... Obviously there is an acceleration and deceleration programmed into the control.  I am assuming that the control assumes the servo is "caught up" when the control ceases to output additonal pulses.  This makes sense, I suppose, if the tuning is such that the servo isn't trying to catch up.  So.... Is that the piece of the puzzle I was missing?

Alan

P.S.  Lines went away magically.... Ahhhh   :)

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General Mach Discussion / Re: Deckel Mach Retrofit
« on: August 14, 2007, 11:22:18 AM »
I must have missed your post, Hood, on the underlining thing.... Sorry.  I'll go back and look later in the day.

You all have very compelling arguments.  I don't know that I will ever be comfortable with Windows running a substantial machine, but I do see that Mach has some big advantages too.  As the hardware variation is getting smaller all the time, my inclination is to do a two pronged approach... Develop a Mach solution first.  Even if this works great, I will probably look at an EMC afterwards (but hey, this is a hobby, so that could be a long ways away!).  If I do the software correctly, it should be fairly transportable.

There are several reasons why I am taking this position.  First, my previously mentioned concerns of Windows.  Second, I program professionally and have always felt a bit of a "hole" in my Linux... An EMC integration will help force a filling of that hole.  Kind of killing 2 birds, type of thing.

Next stop is to download the demo of Mach again, and do more research on the app, itegration to it, emulator functionality, etc, etc.

I would like to express my sincere thanks to you all...  It is a pleasure talking with you.  I love learning and am willing to acknowledge that there is a great deal I do not know.  Your patience and comments are veyr much appreciated.

Regards,
Alan

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General Mach Discussion / Re: Deckel Mach Retrofit
« on: August 14, 2007, 03:00:18 AM »
Hood,
Not at all... I think you misunderstood my meaning... Digital interfaces for servos are not unusual, although I do not profess to be an expert in that area (my CNC machines are either pure stepper or 1 to +/-10VDC servo amp based.  I do know that there are digital servo systems out there...  They have historically just outside my price range and/or need.

The comment I was making was that digital amps for servos need not be limited to step/direction.

Alan

P.S.  Am I the only one that has underlining of all the poster's thread text in this forum?  It is *really* annoying!  Argh!  I've got to see if there is a setting on my profile.  Separating the lines is tough on my computer.

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General Mach Discussion / Re: Deckel Mach Retrofit
« on: August 14, 2007, 12:05:28 AM »
Found the Roger board and I'm happy with that.... I do have a concern about the fact that it is a parallel device though.  To devote one of the two printer ports (hmmm, can't remember the I/O map on the PC... is it 2 ports or 4...) to the Rogers seems risky. 

What type of implicit support is there in Mach for eithernet or USB based devices?  Do you need to write all of that yourself?

I am liking what I am seeing but I am still very uncomfortable with the Windows platform...  I would love some compelling arguments for why I should *not* be worried about it.

Alan

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General Mach Discussion / Re: Deckel Mach Retrofit
« on: August 13, 2007, 11:48:22 PM »
<chuckle>  Sean has taken a picture of my machine.... He has been storing it a year and I'm getting a good laugh because he now voluteering it as a guniea pig <LOL>.  I say this, of course, with a good dose of humor because it doesn't bother me in the least (and I suppose there is tacit approval anyhow).

Alan

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General Mach Discussion / Re: Deckel Mach Retrofit
« on: August 13, 2007, 11:45:38 PM »
Is there a way to get rid of the annoying underlining of posts?  Every word you folks have written in your threads is underlined for some reason???  Wierd.

OK, Brian, I have a quick question for you.  Can you point me to this board by Ron Rogers.  I'd like to read more about this and to better understand how this integrates in with the control.  Specifically, you mentioned that a plugin you wrote for the card provides positional information back to the control.  What is the control doing with this.  My understanding is that because Mach is open-loop, it has no capacity to use this type of information.

The next question I have is related to your comment about how Fanuc and other machines work.  I am baffled because you have stated that they work in an identical fashion as the open-loop Mach.  But those systems do not have pixie interfaces in them.  The encoder feedback is fed directly into the control and the PID is performed within the control.  If your contention is that the internals of the control are doing the same thing as the Pixie, then I would agree with that.  One way or the other a PID has to be performed on a servo based system.  So long as the following error can be accurately monitored and error trapped, I personally don't care too much about where this is performed.  Of course, having it inside the control does give one a bit more flexibility in configuration. 

Finally, I am confused about the comment regarding the digital drives.  I have heard a myriad of different comments regarding this.  Some state that steppers are coming back into vogue.  Others claim that the manner in which the control indicates the desired position is changing, specifically to a digital format.  I guess that I really don't care one way or the other. I would agree that the digital invocation of position is probably becoming much more popular, but servos still seem to rule the roost over steppers... I'm curious about your thoughts on that though.

I'd love to hear your comments on these... I am one of the (more vocal) members in the thread that Sean was describing before.  For the record, I think Mach is a great product.  I am less thrilled about making anything on a Windoze platform though.  I just don't trust that.  For that reason, I am actually more of an advocate for doing this project in EMC than Mach.  However, I have also readily acknowledged that doing the project in Mach would be faster and hence that is attractive.  In the long run, however, I think I would ultimately move it to EMC for the previously described reasons.  The (ultimate) donation to Mach would be easily given as I think the application should be supported. :)

I guess that is about it.... If you can provide links to any useful tools/accessories/interface boards/etc, that would be great....

Oh, one last thing.... I spend my days in VS2005... I am assuming that this is OK too?  Sometimes the upgrade path between 2003 and 2005 is a little "murky", so I thought I should ask.... 

Alan

P.S.  Just for kicks, I am currently looking into Mono to see if I could use .Net for EMC.... That should be "interesting"  :)

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