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Author Topic: What size motors?  (Read 15053 times)

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Re: What size motors?
« Reply #10 on: April 18, 2009, 05:34:28 PM »
Hey Bill,
   Not ruffled here.... just embarking on a similar build/retro and am a glutton for info, hence the question, NOT contradiction. I am planning on AC servos 1:1 belted.
Never saw a BP type direct coupled but see it's common on dinky mills. Seems it would be awkward.
Wasn't aware of the constant tuning either....thought that was a one time deal.  Bummer.
Thanks for your pennies,
RC

 

Offline Hood

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Re: What size motors?
« Reply #11 on: April 18, 2009, 05:38:30 PM »
RC tuning is a one time thing, well if you get it right anyway ;D
Hood

Offline budman68

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Re: What size motors?
« Reply #12 on: April 18, 2009, 05:49:13 PM »
Quote
I'm generalizing by passing on my experiences with this. Didn't intend to ruffle any feathers. That seems easily done here....I guess I should just keep my experiences to myself, meaning that I'm not welcomed here?

Fine

Bill C.

Bill, don't ever feel that way, we're people and the internet is not the best way to get our points across sometimes. I can piss people off all day and I never meant a bit of it the way that it was taken. It's the loss of "inflection" that screws it up for us. It's too bad we can't all be in the same room at times, but of course, we may end up beating the crap out of each other too,  who knows,  :D

No worries here -  8)

Dave
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Just because I'm a Global Moderator, don't assume that I know anything !

Dave->    ;)

BClemens

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Re: What size motors?
« Reply #13 on: April 18, 2009, 06:45:49 PM »
Ha ha, good term: "inflection"...

 So the next milling machine that I convert will have steam engines on it, but was wondering which to use - turbine or reciprocating? Doesn't really matter because I could snap a 4 inch end mill at will! And rapid travel....? I could over in to next week in a wink.   ;)

A commercially available NC mill is using direct drive series 34 stepper motors and they give reasons why. http://www.cncmasters.com/CNCMasters_Supra_ProductGuide.pdf

We are seriously looking at purchasing one of these...

 Thanks once again,
Bill C.
Re: What size motors?
« Reply #14 on: April 18, 2009, 07:06:54 PM »
Dresda,
   Here is some info that may interest you.

http://geckodrive.com/support.aspx?q=10002

They have Coal fired, Wood fired and Nuclear. he he he

Bill,
   That's a neat looking little mill, first one I saw like that.
 Might consider that on mine.....thanks. Would be nice to eliminate the belt and pulleys, especially if it's 1:1 anyway.
RC
Re: What size motors?
« Reply #15 on: April 18, 2009, 08:29:26 PM »
Ha ha, good term: "inflection"...

 So the next milling machine that I convert will have steam engines on it, but was wondering which to use - turbine or reciprocating? Doesn't really matter because I could snap a 4 inch end mill at will! And rapid travel....? I could over in to next week in a wink.   ;)

A commercially available NC mill is using direct drive series 34 stepper motors and they give reasons why. http://www.cncmasters.com/CNCMasters_Supra_ProductGuide.pdf

We are seriously looking at purchasing one of these...

 Thanks once again,
Bill C.

Probably a nice machine, but 50 IPM is a *painfully* slow max speed for a machine that size.  That's almost as full minute to go end-to-end on the X axis, and almost 20 seconds on Y.  The basic machine is identical to mine - same castings, same paint even.  It is a very good basic machine.

Regards,
Ray L.
Regards,
Ray L.

Offline dresda

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Re: What size motors?
« Reply #16 on: April 18, 2009, 09:08:23 PM »
Hood,
 I will have to learn VB for multi axis and tool changers etc.
ray.

Offline Hood

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Re: What size motors?
« Reply #17 on: April 19, 2009, 05:04:38 AM »
dresda
 I dont really know VB but managed to write macros for the toolchanger, m3,m4,m5,spindle speed etc on my lathe, its not that hard but if you need help there are lots here that are good with VB so I am sure you will get all the help you need.
 I also used a PLC for the tooldhange on my lathe, depending on how yours operates it may be something you will need although possibly the DSPMC will provide enough I/O for you (dont know much about it)

Hood

Offline simpson36

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Re: What size motors?
« Reply #18 on: April 19, 2009, 05:37:15 AM »
What's better Ford or Chevy? That is an emotional or personal opinion type of debate and is therefor unresolvable. The debate betwen steppers vs servos will also be unresolvable so long as it is argued by fanboys instead of facts.

I have lost count of how many of these debates I have read and probably less than 10% of them have any facts whatsoever.

Servos are more expensive than steppers in the same way as a Corvette is more expensive that Ford Escort. It is frankly rediculous to compare those two cars based on price alone and make a blanket statement the they are both 'cars' and therefore the  Escort is 'just as good'

If your objective is to take your kid to school over surface streets at 35mph max, THEN there may be a valid argument there. If your objective is to autocross without building a race car from the ground up, then it matters zero how little the Escort costs because it is simply incapable of doing the job.

If one prices out, using CURRENT pricing, servo motors and the required encoder and driver and a stepper and required driver in cases where anything resembling  equivalent performce is a criteria, then steppers and DC servos are very comperable in price.

Exactly how does one go about comparing steppers and servos? I have seen people compare the torque, but that is a completely invalid comparison because the motors are rated differently and have vastly different charactaristics. Torque is a STATIC measure. That's not an opinion, that is a fact. Moving objects requires POWER. That is also a fact. POWER is about doing work over TIME, also fact. Torque  is ONE number in the equation. I did a comparison of stepper vs servo of similar 'rated' torque and posted it in this forum. I also posted the formulas used so anyone was free to discredit them. Nobody did.  The servo was many, many times more powerfull.

A Corvette motor has 500hp and a semi diesel has only 300, therefor a Corvette engine will perform better in a semi truck than a diesel. That is simply an uneducated statement and is the type of logic that often defends stepper motors.

I have to agree with whoever said that the stepper powered full size mill that was used as an example is pitifully slow. I would add that is is also pitifully weak.

Servo motors top out early in the power game and above that there is only a choice between DC servos and AC servos. A Ford Escort gets much better mileage than a semi, so putting a Ford escort engine into the semi would result in much better mileage for the semi. This is also the type of logic that defends steppers on big machines.

It is really like comparing a pickup truck and an earth mover and saying the pickup is 'just as good' because it also can move dirt from point A to point B and it is cheaper.

Flame suit *on*  >:D
« Last Edit: April 19, 2009, 05:54:25 AM by simpson36 »

BClemens

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Re: What size motors?
« Reply #19 on: April 19, 2009, 06:37:13 AM »
All well and good, but the USE of these two motors is what is specifically asked by the OP. While a servo motor is quietly absorbing 'inrush' current to begin to move - the stepper motor has already moved - more poles more power - simple. Once the servo motor takes enough current to overcome the load - then hands down the servo motor takes off and wins the challenge and can continue to climb in speed with the same 'power' that it required at the start then actually become more efficient. The stepper cannot keep up and becomes less efficient at speed. Most people know that already.

But, for slow, precise, powerful movement of a device that must be moved by controlled and accountable movements. The stepper wins. And I did say slow as well.

I'll take steam power. I also don't believe the OP was interested in all this super factual information - he was merely asking for opinions. If you like to poo poo others' opinions and experience, then you may require your flame suit but not for my account. Using the Ford Escort and Corvette as a parallel here is totally invalid and is a basic over simplification - although I always buy USA made products when available.

I read where you come off, as a rolling boulder of knowledge.

Bill C.