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Messages - simpson36

1061
General Mach Discussion / Re: db25 parallel v. serial pinout voltage
« on: July 19, 2009, 06:52:50 AM »
I *think* you can use a 1k resistor in the 12V to knock it down to 5V

BUT, please confirm that with the electron guys before you act on it. I am unqualified in the area of electronics.

1062
Feature Requests / Re: Full featured Serial Communications
« on: July 16, 2009, 05:56:16 AM »
I wasn't thinking so much of Mach being fully inegrated with the loop as I was having some ability to get info from the drives and make decisions based on that info. And also to set certain of the drives parameters from within a program to tailor the performance for the particular task. This really is just an expansion of the tailoring already done in terms of spindle speed, feedrate, depth of cut, etc. Simple examples might be:

1) rather than have the servo drive just stop the parade, it could signal a problem and a macro or brain could query the drive as to what the problem was. If, for example the encoder has failed completely then  of course stop the parade, but if the following error has exceeded a certain amount, but has now recovered, then do nothing, but the operator would have some insight into what part if the program was causing the fault and could go back and modify that portion rather than slow the entire production down to avoid a single problem spot.

2) if the following errors are consitently over a precsribed amount, reduce the feedrate.

3) set the faulting and folowing error at the beginning of each program. For close tolerance finishing work, the following error could be set small and for roughing it coudl be set high.

4) I would prefer to see a flashing red light on the screen if I am observing the machine. This would be a great diagnostic and  tuning tool. If the machine is unattended, then the same fault should stop the program. I think this would be a useful function to add.
 
For my current effort, this whole topic has become moot since none of the drives I have tested so far are going to be useable for such a process.


1063
I knew they were a Chinese company. Sneaking the word 'American' into a company name set up to operate in the US is nothing new. That just shows that the marketing people understand the American mind set.  I was just making the point that the ISO designation is meaningful, no matter what country the factory is located in.  The Chinese companies had a leg up on their world wide competition because there was so much government subsidizing of their 'development', but as far as I know, even the government can't buy an ISO certification, so hopefully it will remain a standard by which manufacturers can be compared. 

*soapbox off*

What appealed to my Geek side was that I could tell right away just by the way the Leadshine literature reads that AMT is populated with 'pocket protector' types . .  gives me a warm fuzzy . . . :D

How did you come to select Leadshine stepper drives? I'd be interested to know your take on the dmm-tech products?



1064
I really do appreciate your effort, but you're over my head. I'm going to need to do a lot of homework on this topic obviously.

If I want to dabble in the AC servo game, I should start with a NEW drive and motor from the same company.

Check this out!  Already set up to work with MACH3!  Do you have any opinion on this?

http://www.dmm-tech.com/Pricing.html

1065
Hood,

The factory is ISO 900x in contrast to some of this stuff that seems to be made with a soldering iron at the Kitchen table . . . not saying there is anything wrong with that, but ISO certs are not handed out like candy and I woud not be surprised if China now has more of them than any other country. You know where the money is coming from for the stimulus, yes?

NosmoKing,

I only wish I had a clue what you just said . .  :-[

EDIT: Seems you know your way around the AC servo areana. Any chance you might cruise ebay and pick out a couple of (hopefully sub $100) motors that would be compatable with the Leadshine AC drive?

1066

Below is my solution to the resistor heat issue, FWIW. The fan at the bottom blows into the box and cools the Rutex drive inside and the air exits the top and flows past the resistor, which is bolted to the box along its rear edge. It stays cool enough to touch most of the time.

Final score on the servo drive. With the Gecko I could get a .015 cut at about 700 RPM max spindle speed. With the Rutex drive, I am getting an .080 cut at 1,100 RPM max spindle speed. There seems to be power available to exceed this, but the maching rigidity is now the limiting factor. Needless to say, I am well pleased with that result  ;D

I am sort of a servo junky now and I'm waiting on yet another servo drive, this time a Leadshine 810, to put the small NEMA 23 servo (from iteration 3 or 4 of the 4th axis project) on my X axis.  Now I have discovered a small very reasonably priced ($180) AC servo drive made by the same outfit . .  so probably I'll be playing with that sooner or later . . . my wife just got a new dining set, so I may be able to spend a little more on my toys . .   :-X

Review and comparison of the servo drives I have played with so far is here if anyone is interested: http://www.thecubestudio.com/ServoDriveReview.htm


1067
Just an FYI . . 

I am awaiting a new servo drive from a company called American Motion Technology. That same company makes a very reasoanbly priceS ($180)  AC servo DRIVE as well as matched small AC servo motors. I have not found pricing on the motors, but they seem to be new and have not made it into the product lineup for the US.

Might be worth a look see.

http://www.americanmotiontech.com/Products/

1068
General Mach Discussion / Re: Total NOOB Quick start guide. ?
« on: July 14, 2009, 09:27:28 AM »
I think it would be nice if someone compiled all of the available Mach documentation into one place or one set of links. Information, especially on VB script seems scattered all over so how can one know when and if they have stumbled over all of it?

Many forums have an FAQ sticky  . . . it is always a good idea . . but nu-bees seldom use it . . .  as has been said it is what it is . . .

Personally, I know as a nu-bee, I would have benefited greatly from some published reviews of the bewildering array of products out there. After someone goes thru the pain of getting something sorted out, it really IS a shame that the knowledge get so quickly buried on page two. For example I posted my results with a specific parallel port card. Wouldn't it be better for a nu-bee to read that and get a card that is known to work rather than have everyone guessing how to fix the card he did buy? For my part, I am just finishing going thru several differnet servo drives and to keep the info available to nu-bees (old or new), I put the experiences down in a review/comparison, but there seems no obvious collection point for such things. If there were, I would post it there and also be more inclined to write more reviews as I'm sure others would as well.

It is here if anyone is interested:  
http://www.thecubestudio.com/ServoDriveReview.htm

1069

It is really only useful to speak in terms of power. Torque is a static measure, and has no meaning by itself. For example torque being zero at max speed is not meaningful because that is no load speed and the motor is not doing any work. As soon as you place a load on the motor, it slows but begins to produce a measurable torque. The more load is placed on it, the more static torque it produces,  hence the torque curve you referenced.

Some confusion results when torque is discussed as if it is power. Seems I have contributed to that in this instance. Power is what moves things and power is work done over time. In the case of motors, power is torque x RPM so the faster the motor rotates the more power it is generating until the point where the torque is dropping faster then the speed is increasing.

In the case of steppers, the torque falls off very quickly per speed increase and therefor they are actually making significantly less power the faster they go. Servos on the other hand, continue to make relatively contant power over their RPM range. From the actual power curves I have looked at for servo motors specifically (as opposed to a regular DC motor as for a treadmill, etc) the motors are not linear in response. That supposedly is the difference in a servo motor and hence the high cost comparatively speaking.  The skewed rotor designs have something to do with that, but that level of tech is over my head.

I don't know how or why AC motors are different performance wise, but I have read in enough places (including manuf who make both types) where the AC motor's superior holding power are cited as as justification for the higher cost, that I believe their must be some credibility to that claim.



1070

DC motors are the contrary to VFD - they have max torque at zero speed and it drops liniary as you increase the speed. At max speed the torque is zero.

Daniel
 

True only for DC steper motors.


I have read that AC servos have superior holding power  . .  an important consideration for my 4th axis application.

A huge disadvantage of an AC servo is that my wife will kill me if I spend any more money on this CNC project . . . LOL!!