Thanks Gerald.
What do you think about my motor selection ?
Any suggestion & comments ??

It makes much more sense to use the same motor for everything. For example, next year you have one motor that becomes suspicious . . . . what will you use to exchange it with so that you can diagnose the problem?

Yes, you can have too much torque for an indexer.....you can have too much torque for anything......

When you have a 30:1 ratio for 16" diam work, you have no need for a bigger motor than the "linear" axis direct drive motors.

Gerald, Aside of « suspicious » motor malfunction, what would you say that makes selecting all the same motor in a set up a more sensible choice??
In my purchase forecast, I figured it be wise to buy an extra MotionKing motor at the same time since it’s only an extra +/- 40euros and the bulk of the total cost is more in the courier charges ( +/- 250 to 300 euros per order!).

Maybe I’m having one of those translating moments or I’m just not understanding but what do you mean by “ When you have a 30:1 ratio for 16" diam work, you have no need for a bigger motor than the "linear" axis direct drive motors “ it's been keeping my mind busy this last couple days !!!

Would you consider the 34HS 2802 (a 680N.cm motor) with a 30:1 trans to big for an indexer with the ambition to turn / index small light pieces up to hallow but still heavy wood stock of +/- 40cm x 230cm ( 16” x 90”) ??
If so, what should I look at ?
Thanks for your attention to my quest in understanding more on motors and proper motor selection :o
Robert ;)

Take your x-axis; there your direct-drive MotionKing will have a 20 tooth pinion. One turn of the motor will move the cutter 3.14" The motor torque will give you enough force to move the cutter, or, to hold the x-position while the y-axis is doing a move.

Now, convert to the rotary "indexer" equivalent, by wrapping your table around a cylinder. Let's take an x-axis of 96", that means a table and rack length of 96". If that is wrapped around a cylinder, the table diameter is 30" and the rack becomes a 30" diameter gear with 600 teeth. This gives you an "indexer" of 30:1 ratio, capable of handling 30" diameter work at the same cutting speeds, cutting forces, holding forces. That is why I say that 30:1 ratio will hold/cut 16" diameter work, without needing a bigger motor that you use to drive the x-axis, or y-axis.

Why not get very complicated?; the x-axis can have smaller motors than the y-axis, because there are two motors on the x sharing the load. The z can also be smaller than the y. Or, maybe you can make the x and z the same size and get a big y? You can make yourself mad asking all the questions all the time.

Would a motor be too big? Well, there is a whole thread about that. Would a certain MotionKing be too big? I have no idea - I have never seen any MotionKing motor.

Robert,

Gerald has given some good advice. I had to read the indexer part several times before I "got" it, but his reasoning makes perfect sense.

Like him, I have never used a MotionKing motor, so I would only be guessing if I suggested any of their motors. The specifications look good, but over the years, I've bought a lot of motors from a lot of companies that didn't work as advertised. When I found Oriental Motor, I stopped testing other brands of motors. The Oriental Motor did everything that it was supposed to do and did it day after day after day.

If I were going to specify motors for your machine, I would use the Oritiental Motor PK296A2A-SG7.2 motors for the X, Y and Z axes. That particular motor seems to be working well for those who have already built their machines. For the indexer, I would have to do the math to see which gear ratio would work best. A 16" diameter is about 50", so 50 inches / 2000 steps = 0.025" per step. If you wanted a resolution of 0.001" per step, you would divide 0.025" by 0.001", which would give you a 25:1 gear ratio, so your specification about using a 30:1 gear ratio seems to be valid.

Because the Oriental Motor PK296A2A-SGxx motors are relatively inexpensive, I would use them until I needed something else. Granted, their gear boxes have a little backlash and granted that their gearboxes cannot handle all the torque that the geared motor can produce. However, the gearboxes seem to be more than adequate for the speeds and feeds required.

I would use a 25VDC to 35VDC power supply (I've used both with excellent results).

EDITED: I would wire the motors half-coil for use with a power supply in the 25-35VDC range. If you wire the motors full-coil (bipolar series), you'll need a power supply closer to 70VDC.

One note about building belt-driven transmissions: Although a single-stage transmission is easy enough to build and fairly inexpensive, just bolting a geared motor onto the motor-mount is sooo much easier. I've built several versions of 3:1 belted transmissions for my shopbot; however, I've replaced those motors and transmissions with the 7.2:1 geared motors that Shopbot offered. As far as I can see, the 3:1 and the 7.2:1 produce cuts of equal quality. Both the 3:1 and the 7.2:1 produced cuts that are far superior to the non-geared 1:1 motors that came with my machine. The 1:1 produced significant "chatter". The geared motors still show some "chatter", but nothing that can't be sanded out with a few strokes of 100 grit sandpaper.

Gerald, Allow me to say this old proverb / joke : “Ahhhh, now I can see much better, says the blind man ”.
Thanks for this “rotary indexer equivalent” info, much appreciated :)

I have this Excel sheet (witch I can’t really remember where I got it, excuse my lack of knowing the original writer! ) about proper motor holding torque size calculation ( see the attachment), but not certain what are the weight of the individuals axis of the MM for using it ??
Well on the other hand, fine about having this excel figuring out the proper motor torque size, but what’s the real draw back of getting a motor a little bigger than prescribe by this sheet ?

What I mean by little bigger, say going 20 – 25% stronger holding torque then what it calculates with out exceeding this 1000oz-in barrier !? ( again, today my brain is getting buzzed with me getting in this motor thing, so sorry if I can’t really remember where & why I read this but I think it was a quote from Mike Richard and/or Marris recommending no one should exceed this 1000ioz-in ???).

Making yourself mad you say… My family is seriously considering calling the guys who gladly come and pull people out of their home with a “white vest” :eek:
All this because I keep on saying I’m having a blast with all this !!
Improving my knowledge has never been so fun & rewarding….
Thanks MechMaters, thank you so much Gerald ;)
( for the attachement change the extention from .txt ->to -> .xls )

Do you think that the 1000 oz-in is suddenly bad, while the 999 oz-in is still good? What is the shape of the good/bad graph before we get to 1000 oz-in?

The "ideal" motor, when used with a gearbox or belt-transmission would probably be the PK296-03AA (which is probably the motor used in the PK296A2A-SGxx geared motor - when you compare the specifications).

With a 30-tooth pinion gear (inch measurements), you get a pitch diameter of 1.5-inches, or 4.71 linear inches of motion per pinion gear rotation. That means that with a 7.2:1 gear drive, the stepper motor is going to be spinning between about 200RPM and 650RPM when the feed rate is between 2-ips and 7-ips - which is where I personally cut almost 100% of my work. Those speeds fall on a very strong portion of the trorque curve, and with the 7.2:1 gearbox, the gearbox is the limiting factor for torque, not the motor.

At 7-ips and a 7.2:1 gearbox, that motor requires about 21,000 steps per second, meaning that even a modest computer can drive Mach3 at those speeds.

Power requirements are fairly modest. Voltage requirements are modest. Heat generation is modest. Power is sufficient. What more could you ask from a "universal" motor?

Hi Mike, Thanks for your input and these math. :):)

It’s no secret that I’m seduced by the approach of making my own belt-drive transmission for quite a wile and that make me look at other option / alternatives than those PK geared motor set-up.
I’ve drawn a trany with a 4:1 ratio for the X, Y & Z and another with 30:1 for the indexer.
Beauty of those as you know is I can eventually change their ration as I please / need or testing , with-in a reasonable range !

Reasons why I’m looking / thinking at the MotionKing motors is to add info on this brand for others & future MechMate builds, and also they seem to have a wider range. Although, I’m totally lost in this range selection thing, once I understand this better and make more sense I too will share & help… hopefully ?
Don’t read me wrong, I have nothing against Oriental Motors, their track record is not to question. But knowing about other brands may help !!
Never read anything wrong about MotionKing… YET!
If at the end of the “funnel” there is only Oriental Motor to be, than that’s that !

Gerald, I’m sorry if I got there (1000 oz-in) but I don’t have the know-how, knowledge or pretension of knowing how to determine what oz-in torque is crucial or bad, it’s only a “figured value” I remember reading somewhere and I can’t remember where, but if my memory isn’t playing to much with me, it was a good credible source !!

What are the weight of individual axis on a spec regular MechMate, so I can juggle and learn with this Excel sheet ??
Also, what are the drawbacks (if any) for selecting a motor with a little more holding torque, say +/- 20-30% than prescribe ?
In a typical MechMate set-up / case, why 450 N.cm is OK and why not 580N.cm ?
I read you clear when you say “you can have too much torque for anything......”, but timid to ask… why :o :confused:
Don’t get me wrong, I’m not suffering of the Tim Allen syndrome “ BIGGER IS BETTER” au contraire, I too am a preacher of selecting the proper part needed”. It’s just that I’m questioning it to improve & understand more on this.

Say a motor manufacturer offers virus motor specs for the same given motor torque ( In this case see MotionKing 450 N.cm series, there are three different ones)
How and what would make one select a specific type vs the other ones offerd ?
Question is in relevance on a MechMate set up / application, OBVIOUSLY :D

The way I see it is it’s always seem more fun & rewarding making a “more” calculated compromise, if I’m allowed to say compromise, when selecting a motor set for a CNC that will perform various but similar task : eek:

Again, many thanks for your patience and sharing some info.
It’s not because I’m French, it’s only because I need more info before I “gabish” :)
Amicalement, Robert ;)

Robert, you have tried to get me to answer these questions many times, and you should have figured out by now that I am not going to answer them. I do not have the experience to give a correct answer. Maybe you should try another forum?

Sorry if I’ve worked on your patience Gerald, didn’t realize I’ve gone that far. Got blinded in this questioning after spending soooo many hrs this past week-end reading & searching for motor answers, Thanks ;)

When three motors have the same torque figures but different inductance figures, use the inductance data to compare the motors. The higher the inductance, the shorter the torque curve. In other words, if the application called for high torque at slow speeds, you would choose a motor that had higher inductance. On the other hand, if you needed the highest possible torque at faster speeds, you would choose a motor that had lower inductance.

Of course, you would have to do some testing. You would have to build several power supplies, or use an expensive Variac to alter the voltage.

Most companies spend a lot of time and development money testing various components in their search for the 'right' parts. Since it can easily cost thousands of dollars to thoroughly test electronics for a CNC router, I would strongly suggest that, if at all possible, buy the Oriental Motor stepper motors that everyone else is using. The cost of testing other motors will be much higher than paying for the Oriental Motor steppers.

Mike, I’m Very grateful of your time in helping clarify this.
Amicalement, Robert ;)

Has anyone installed these M.K. motors on any router yet? I can't see that anyone is talking about them anymore. Was this a good idea that just didn't work?

Dave

Kobus used the motion king motors. Here is the post where he tells you which model number. Check out his build logs. :)

http://www.mechmate.com/forums/showt...9&postcount=70

Hi Dave,

I haven’t tested or installed nine as of yet, my work & other priorities has thrown some ice on my indented schedule.
One thing I can testified is they have an excellent service & shipment was within the promised window ( less than 3wks from payment ). When kitchen table will be completed & running, I will report on those.
Amicalement, Robert ;)

I am still happy with mine...no problem to report.

Robert,
Did you go with the same model as Kobus?

I decided to go with the 34H9802 !
Robert ;)

Robert

Are you going to go direct drive, or some kind of reduction?

Dave

Dave, for starters I’ll be direct drive to iron out the first steps of the machine. Then, I’m planning to make my own 4:1 belt reduction drive ;)

Well three of us are about to bite the bullet and start building. They will be triplets. Startup should be sometime in February, since we're building them side by side the only difference in start up will be because of fine tuning. I'm going to go direct drive, Dennis is going 3:1 belt and Scott hasn't decided yet. this is going to be fum.

Dave

I wanted to share a PM to me from Heath
Heath, since it is policy on this forum I will not disclose here what I paid unless Gerald allow it !
On the other hand, it is no big secret, just plainly email to MotionKing direct and you’ll receive promptly an answer to your question w/ quote.
I ordered directly from MotionKing.
One thing I know I can tell, TNT charged 248Euros + 25$can brakeage fee.
Again, I’m very pleased with their boxing, service & delivery promises.
Hope this help.
Amicalement, Robert ;)

Robert,
Yes I know you can order directly from Motion King, but I was hoping that there was a North American distributor that handled their products. Dankie for the reply. :)

Darn, shipping cost they charge from China to India is cheaper than what they quote me for China-Malaysia..... like they charge me 50% more. We also have TNT here.

This was my quote in April 2008...

Thanks for your inquiry for our stepper motors.
As per your request, the costs are as below:
34HS9801, EUR48.00/pcs, 4pcs ------------- EUR192.00
TNT Express Charge ------------------------------ EUR304.00
SUM ----------------------------------------------------- EUR496.00

Be glad you do not live in South Africa :(

Last august MotionKing charged me Eur250.00 for TNT Express from China to Canada.
But also, TNT charge me a extra 35$can to handle the paperwork & brokerage !!

Hello Nikonauts,
You may be interested to know that Oriental motors in Singapore will charge you SG$288 each for PK296A2 SG7.2 just across the bridge from Johor. This is a metric version of the motor sold in the USA PK296A2A -SG7.2. (The only difference is the the metric option has a shaft with a keyway and the dimensions are in mm). I suggest you give them a buzz on 1800 80 6161. That is a toll free Malaysian number. It may be better than chasing suppliers who are very far.

Regards,

That is a very good bit of info Jama, thanks! Hmm . . under US$200 for a nicely geared motor . . . .