Selecting motors for the MechMate - some history - Page 2

#31 Mon 12 February 2007, 20:17

Not quite right. The 25X is the absolute limit - it can be less. In this case the Gecko is limited at 80V, and this becomes your design voltage. The motor draws 1.5 Amp max. So the 75-80Volt / 300VA power supply illustrated there will do just fine.

#32 Tue 13 February 2007, 15:49

Thanks Gerald, I placed my order today.

I might remind everyone that the free UPS shipping ends March 31st 2007 at Orientalmotor, so you may want to pull the trigger now.

#33 Sat 03 March 2007, 19:00

http://www.xylotex.com/4AxSysKit-425.htm
can you use this system for the mechmate?
why, why not

#34 Sat 03 March 2007, 20:37

Sorry, too small and underpowered.

#35 Mon 05 March 2007, 10:31

Hi Gerald,

In a post on Fri. Feb 2 at 6:30 PM you had said the following:

"A commercially acceptable cut quality (smoothed with a few wipes of sandpaper if necessary) could be obtained with direct drive motors from about $50 to $110 each (Chinese)"

My question is which brand motor can be used for $50 to $110 dollars, and would you recomend them?

#36 Mon 05 March 2007, 11:15

Have a look at the posts above that one - I don't think I can say much more than that until I have actually tested the motors myself. (If shipping costs out here were not so darn expensive, I would have tested these economical options long ago) On the other hand, it will help if other guys tell us how the cheaper motors work in their MechMates, but nobody has gone this route yet. Want to be the first guineau pig?

#37 Mon 05 March 2007, 13:12

Sure I'll be the g-pig, recomend some $50 range dollar motors and I'll try them out ASAP.

#38 Mon 05 March 2007, 22:12

Have a look at the MotionKing page.

#39 Tue 06 March 2007, 05:25

Loren,

For a very good motor from an excellent supplier between $69-$89 follow this link. http://www.kelinginc.net/

I have been using this model KL34H280-55-4A on my current cnc machine http://accurate-inspections.com/pr%20cnc%20upgrade/ for about six months with excellent results.

These are not geared so you will have to go the gear box route for better resolution, but even at 1-1 I have done some very nice v-carving with these.

Tom

#40 Thu 08 March 2007, 13:12

I'm curious of the specs on those motors. They are rated 5.5amps at 2.4v which then require a 55-60V powersupply at 23-25x rated voltage but then with four motors in theory you need 22amps from the powersupply thus a 1200VAC powersupply for optimum performance? (but then you need to multiply this with that and so on and so forth and this is worst case, the motor may not be wired as bipolar(series/paralell?) which the rating is for, I'm totally at loss when it comes to figuring out this stuff, etc.) It also seems to have a little lower holding torque than the recommended vextra, but that may not matter.

What I wonder, if you can use a 300VAC powersupply with the vextras and the kelling motors may require four times as much power with possibly lower holding torque, where does all that energy go? Heat?

#41 Thu 08 March 2007, 23:19

Bugmenot, the guys who were recommending the 23-25x are now saying 20x as the max voltage - you can use less.

But, to get to your main point, where does all this power go....? This is a question for which I would really also like an understandable answer. If I had money/time/space I would be buying all these motors and testing them against each other.

One group of guys have the logic that more power is always better. (Tim). That's fine, but then we must have a reliable way of getting rid of the excess heat. A 300VA supply is easy to cool without blowing it full of dusty air. The big power supplies need breathing air and get choked on dust.

#42 Fri 09 March 2007, 15:03

I tend to agree that more power is better than being short of power if optimum performance is needed, obviously considering cost.

Doesn't more current mean more heat, thus the vextras should run cooler? I would really like to know if there is a rule of thumb where more current is better for high speed or vise versa or better for low speed torque, but I guess that is a question for the people at geckodrive.

#43 Fri 09 March 2007, 20:52

Generally, current relates to torque and voltage relates to speed. For a given motor, the more current that it has available (up to the maximum rating for the drive) the more work it can do. And in the same way, the more voltage available to a motor (up to the maximum allowed by either the stepper driver or the maximum recommended by Gecko, i.e. 20X or 25X of the rated voltage), the faster the maximum speed will be.

Recent tests on my test bench have shown that a moderately sized motor (PK296B2A-SG3.6) can be spun faster than a larger motor, so, if gearing is available, the PK296 (300 oz*in) or PK299 (600 oz*in) seem ideal for the job. Even without gearing the PK299 size seems to be a very good match.

#44 Thu 22 March 2007, 12:23

First post edited to prefer the modern square body motors.

#45 Thu 29 March 2007, 05:25

Hi,
New member here trying to gain some knowledge and insight on building a CNC and converting 2 convential machines o CNC. My question is what size motor would you think I would need for a 9" South Bend Lathe and a small Enco knee mill? I'm not well vrsed in electronics so this is pretty much all new to me. Also is there a means of compensating for the backlash in the lead screws without going to ball screws?
Thanks to all you really got an interesting site here and I hope to learn a lot from it.

#46 Thu 29 March 2007, 06:18

Hi Glenn, I'm sorry to tell you that we specifically want to cover only "big" CNC routers on this site.

However, having looked at your profile, I feel jealousy (you have a Multicam) and sympathy (you are a schoolteacher(I think)).....

Non-CNC routers are tools that need 2 hands to push around. Small non-CNC lathes and mills can be operated with one hand. Therefore you are needing smaller motors to replace the humans for small lathes/mills than for routers. (Big lathes and mills are a different story). Where we are using NEMA 34's for routers, you should be okay with NEMA 23.

www.cnczone.com would really be the right place for you to get all your answers. Good luck.

#47 Thu 29 March 2007, 08:33

Hi Gerald,
Sorry to tell ya, you ain't getting rid of me that easy. LOL I have a second Multicam coming in the next school year (yes I am a school teacher and I appreciate your sympathy). In addition to converting the two machined above I intend to build a mechmate for home. I downloaded your plans and haven't had time to fully review them, but what I have seen and read really look great.
My biggest weakness in in the setup and understanding of the motors and the controls, but have been getting a better understanding from sites like yours.
Glenn

#48 Sun 13 May 2007, 08:25

I have been turning over the stepper vs. servo motor option all week. I was wondering if anybody new of a N. American source for servo motors that will work with the gecko 320/340 drives. Most of the Motors i am finding are designed to use their respective manufacturer controllers (I'm finding some that have bus voltages of 325vdc-560vdc!). Any idea would be great. The conclusion is if i can afford a servo setup, that the way i will go, if not, then geared stepper like the $260 ones from oriental. looking to build the controls by june 30, then start in on the steel.

#49 Sun 13 May 2007, 10:04

AHHHHHHHHHHH!!!! whew, i feel better now. All this stepper vs servo stuff is making me go bananas. After i posted the above message, i read the servo vs stepper thread. Ok, I need to know a little more before committing to a motor.

How much hand finishing would be required on a circle cut using a mechmate with properly sized and configured stepper motors?

I am believing that a geared stepper motor can hold the stationary axis stationary. Is this correct?

Ok, originally i was typing the desired accuracies of the machine, then i divided out the fraction and realised that even the most basic control system will be more than accurate enough.

So I guess as long as i'm not gonna hafta spend an hour filing or sanding cut parts, it's steppers and little green lizards for me!

#50 Mon 14 May 2007, 09:32

Hi Frank

I was hoping that somebody else would chime in here since you all must be very tired of hearing my biased opinions.......

To answer the easy question first; We have un-geared steppers on two tables and we don't have problems holding the stationary axis stationary. My impression is that the people who have reported problems in this area are using Oriental Motors Alpha controller's with feedback from the motors, and that these motors "hunt" to hold a fixed position (The I in PID?).

The tricky question, "how much sanding on circles". It won't help you if I honestly replied that we never sand any circles, because we simply don't do any post-cutting finishing service. Our clients do that themselves and we don't compete on their turf. The few times that I have made things for myself, and have wanted to remove the chatter marks that occur on parts of circles only, I reckon that it took about 10 strokes with 80grit paper?? Can anyone else give a better answer to this valid question?

Realising that we have direct drive motors, the general client feedback is that they are happy with MDF and softwood cut for them, but that they want better for acrylic plastic (perspex). If we had gearboxes, we could probably also satisfy the plastics guys.

#51 Mon 14 May 2007, 10:06

Hi,

Here is my 2 cents.
I don't really know how much "mill mark" there will be when cutting circles using ungeared motors since I haven't used them yet so in that respect I can't comment.

How about someone posting some pics with wood and plastic?

I do know this, if was to cut circles say with my bandsaw, I would have a considerable amount of sanding with a power sander then alot of hand sanding. If all I have to do is sand 10 strokes with 80 grit sand paper, I will be most pleased. I have purchased the ungeared motors from Oriental (as recomended) and will using them. I will play around with them when I get them moving. I would think that no hand held or hand propelled power tool would be able to hold any kind of smooth transition through a radius. I don't know if this is a better answer but I will take a router cut over my bandsaw any day much less my jig saw.

#52 Mon 14 May 2007, 10:29

Guys, thanks for the info. I agree with the notion that 10 strokes of sandpaper is nothing, I always dress cuts anyway. And Gerald, your opinions are what got me thinking i could build one of these things. And the guys in this forum reaffirm that. So anyhoo, I guess now I'm on the hunt for some motors. Any thought on the gecko drive? 202 v 203. Can't figure out what the differences are from the blurbs on there site. I'll keep reading and can't wait to start posting pics.

#53 Mon 14 May 2007, 15:54

Hi all, Gerald.,

Can?t seem to find posts on the MechMate speed ( ipm) subject.
I?d like to know more on the possibilities of its cutting & transient speed capabilities of a tipical MechMate set up. Don?t get me wrong here, I?m not hopping to get anything like this ?Tim Allen type? worthless supersonic speed !!
No?no, just curious on what to expect and hopping to find out more & the how on the ipm achievable?
Thanks, Robert

#54 Mon 14 May 2007, 16:51

Robert,
A search of (ips) will find the topics.
Never have been sure which to quote - IPS or IPM

I use 7.2 reduction and a 35 tooth pinion.
It will surface the spoilboard at 400 ipm
At 575 ipm it loses steps.
The Mechmate is able to cut much faster than I am comfortable with.

DocTanner

#55 Mon 14 May 2007, 19:56

Thanks doc,
It?s what I was hopping to get!!

Later, Robert

IN-WondeR · #56 Tue 22 May 2007, 08:21

Is this motor enough to drive the Mechmate... it's rated at 3.33Nm so it should be strong enough, or am I missing something...
http://motioncontrolproducts.co.uk/p...products_id/83

KM

Gerald D · #57 Tue 22 May 2007, 09:12

Kim, the smallest one is 3.33Nm which is a bit light. You should be looking at FL86STH80-4208 at 4.51Nm minimum. They are calling it Nema 23, but the sizes look like the Nema 34?

Frank, if you are still reading this, you may want to look here for pics of various cut qualities with different machines and speeds. We normally get much better than the best of those with the MechMate.

IN-WondeR · #58 Tue 22 May 2007, 10:21

Thx Gerald....

I will go with the 4.51Nm version then, it's only £42 a piece, which is very cheap... Maybe I'll even go with the 6.5Nm version to get bigger torque... And possibly more control of the gantry...

Gerald D · #59 Tue 22 May 2007, 10:37

I don't know what the shipping costs are like, but it might be worthwhile to buy only one of each now and test them. Put the "worst" motor on the z-axis where it doesn't work so hard, and get the better motors for the other axes.

Alan_c · #60 Sun 27 May 2007, 13:09

Doc
Have you any further comment on your setup with the 7.2 geared motors? Is the 1A sufficient or do you see the possibility of needing a 2A motor? What sort of jog speeds, and move speeds while cutting are you achieving?
I am getting close to making a decision on motors and would appreciate your input.