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  #241  
Old Sat 11 September 2010, 10:01
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
The Oriental Motor PK296A2A-SGxx geared motors are rated at 1.5mH when wired half-coil. The PK296-03AA motor and the PK296-F4.5A motor are also rated 1.5mH when wired half-coil. I regularly run the PK296B2A-SG3.6 motors and a PK296-F4.5A motor from a 35VDC power supply with excellent results. If you need more torque, the PK299-F4.5A motor can be used, wired either half-coil or bipolar parallel. It can use a power supply up to 50VDC, but I use it with the same 35VDC power supply that I use with the smaller motors. It still gives excellent results.

As a general rule, voltage affects top speed and current affects torque. 35VDC allows any of the motors that I've listed to run at 1,500 RPM, which is past the "knee portion" of the torque curve. Going faster is possible, but torque falls off rapidly as speed increases.

You COULD design a microprocessor controlled feedback circuit using an encoder on a stepper motor, but for most purposes it is not necessary. As long as you don't drive the motor too hard to the point that you miss steps, you can always count on the fact that it will move exactly as expected. Every time I've started to design an encoder circuit, I've ended up stopping the project because it would take a very sophisticated circuit to "make up" lost steps (ramping would be involved) while accumulating on-going steps. It would be even more difficult to synchronize several axes. It's much easier to NOT drive the motors past their ability to move reliably.
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  #242  
Old Mon 01 November 2010, 10:26
Sacramento
Just call me: Sacra
 
Lisboa
Portugal
Hi
Can anyone inform me if I can I use MotionKing 34HS9801 with Geckdrives 540?
If not which Gekdrive shoul I use with this motor?
Thanks for your help
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  #243  
Old Sun 07 November 2010, 12:38
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
The 34HS9801 motor is rated 4A and 4.1 mH. The 4.1mH means that it can use up to 64VDC.

The Geckodrive G540 is rated at 3.5A and 50VDC. If you underrated the motors to 3.5A and 50VDC, then you could use the G540. You might loose a little torque and a little speed.

The G201x stepper driver or the G203v stepper driver would let you use the motors at their full potential, but the G201x costs about $115 each and the G203v costs about $150 each. With either the G201x or the G203v you would also need a break-out-board. The PMDX-122 costs about $90.

I have used large motors with the G540 by changing the current limiting resistor to permit only 3.5A or less current to flow through the motors. I have also used motors rated for more than 50VDC with a 50VDC power supply. Those motors still performed very well.

In most cases, we will be more than satisfied with a motor that has a maximum speed of 750 to 1,000 RPM (depending on how much the motor is geared down). Those big motors easily ran at 1,000 RPM on the G540's 50VDC maximum. (As a point of comparison, those same motors ran at 2,500 RPM to 3,000 RPM when run at full voltage on a G203v stepper driver. Those high speeds would not be practical on a CNC router.)
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  #244  
Old Mon 08 November 2010, 14:58
giz
Just call me: Tyler
 
Salt Lake City, UT
United States of America
Good to know. I'm looking into using the Deitech equivalent of the MK 34HS9801 paired with the G540. It seems like a very cost-effective route to take.
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  #245  
Old Mon 08 November 2010, 17:34
KenC
Just call me: Ken
 
Klang
Malaysia
I use matching M860 (~US50) suggested by Deitech, maybe they will recommand a later matching driver model if you ask nicely
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  #246  
Old Sun 14 November 2010, 06:50
J.R. Hatcher
Just call me: J.R. #4
 
Wilmington, North Carolina
United States of America
Send a message via Skype™ to J.R. Hatcher
I have purchased 5 9802 motors from Deitech. I'm satisfied with them except they don't have flats on the shafts ... they have keys. Has anyone removed the keys so flats could be ground? If yes ..... how did you do it?
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  #247  
Old Sun 14 November 2010, 07:24
Kenrbass
Just call me: Ken
 
Richmond Tx
United States of America
JR,

Gears with a keyway can be purchased. I have them on my machine (shopbot) and bought them through them. They were about 15 dollars each. I think the shaft size on my motors is 14mm. I'm sure they could be purchased elsewhere though.

I had a machine with flats for the gears before and I like the keyed version much better. No slippage at all.

Ken
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  #248  
Old Sun 14 November 2010, 09:28
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
I would have much preferred keyways in the motor shafts, the flat spot shafts are way inferior.

If you are set up for cutting the mating keyway in the pinion, with a keyway broach, bushing (& shim), then the process is ridiculously easy.

See http://homemetalshopclub.org/news/10/broaching.pdf

The broach/bushing/shim can be purchased ready-made from a number of suppliers. Example.
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  #249  
Old Sat 12 February 2011, 19:48
KevinP
Just call me: Kevin
 
Wichita (KS)
United States of America
Question about #1 Recommended Motor

Do I understand the specs correctly: The PK296A2A-SG7.2 geared motor is 704 in-oz output at the gearbox output shaft?

If so, the stepper itself appears to supply 98 in-oz plus whatever the gearbox eats up in losses. The output seems really small unless it's a NEMA 23 motor on a NEMA 34 gearbox. That looks possible based on the pictures. The outputs and ratios from the 3.6 to 10 ratio gearbox versions seem to support this. It looks like the 18:1 has been de-rated slightly, or the gearbox has higher losses like it went two-stage.
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  #250  
Old Sun 13 February 2011, 04:18
danilom
Just call me: Danilo #64
 
Novi Sad
Serbia
704 in-oz output is only limitation of the gearbox, motor has more power
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  #251  
Old Sun 13 February 2011, 04:42
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
The gearbox output torque is much higher than 704 in-oz. However, Oriental Motor says to design your application for a max of 704, so that they can carry the warranty. If your application only needs 704 in-oz, you can run at that torque continuously and the warranty will hold and the gears will take a long time to wear out.

On a CNC router, the torque needed to push a cutter is mostly much less than 704 in-oz. However, occasionally we want some reserve torque to kick in and the loading will exceed that 704 for short periods....not enought to strip the gears, but shortening the gear life, yet still giving us years of service.

The 704 was a number picked by Oriental Motor as a "safe" value at which to run the gearbox continuously and keep their warranty claims to a minimum. The 704 number has nothing to do with gearbox efficiency, losses or ratio to motor torque.
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  #252  
Old Thu 17 February 2011, 06:25
Don_Kellogg
Just call me: Don
 
Kalamazoo, MI
United States of America
Has anyone used a closed loop setup like the Shopbots have? I'm getting ready to buy parts and I'm strongly considering the OMs. If I do a closed loop system will I need a special driver and BOB? Or will the Gecko 203v and PMDX-126 work? I've never worked with encoders.
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  #253  
Old Thu 17 February 2011, 08:55
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Don,
The simple answer is yes, servo's have been used - but with not any better success.

(Mike can probably do a better job of explaining this, but here I go)

To understand the motion control aspect of a machine, the resolution is almost always a resultant of the degree of accuracy that can be measured.

The stepper motor accuracy is defined by the resolution of the magnets in the rotor, the electrical pulses (steps) to the magnets and the mechanical drive train to the driven axis. But there is no CHECK and Balance of the step signal sent. It just goes the amount told within the mechanical limits of the motor design.

The servo motor is similar with regards of how it moves, except it has an encoder (or other feedback define - Analog resolver, potentiometer, etc.) to "close the loop" of information to make certain that what the motor was told to do - did in fact happen within the tolerances defined". The benefit of servo's really is seen when you have a motion controlled system that requires more than fractional HP devices to drive the axis. Rarely you will find a stepper in the FT/LB of torque range where servos can reach well into the 100's of FT/LB of torque with accurate resolution.

In CNC world, a servo motor will miss steps the same as a stepper if driven beyond its capacity to do work. Thus, for most applications, the stepper is very high resolution, low cost alternative to perform the same work.

I trust this helps you in your information to decide.

Sean

Note:

Gecko makes a servo driver for this application which requires the encoders for feedback - driver # 320x with quadrature encoder feedback that allows for step/direction input.

Last edited by smreish; Thu 17 February 2011 at 09:00..
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  #254  
Old Fri 18 February 2011, 06:17
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Sean's explanation was excellent. Stepper motors are normally 'open loop' and servo motors are 'closed loop'. Stepper motors remain motionless if the step/pulse source is disconnected but power is fed to the motors. Servo motors run at full speed (usually), if the step/pulse/feedback loop is disconnected and power is fed to the motors. Because of that difference, steppers are 'safer' to use without worry that they'll 'crash' the machine.

I've used the Oriental Motor Alpha motors/drivers, which incorporate closed loop feedback, and I've used Oriental Motor PK299 series motors with gecko stepper drivers, which have no feed back. Used at normal settings, i.e. 1,000 steps per revolution for the Alpha motors and 2,000 steps per revolution for the PK/Gecko motors, the PK/Gecko motors have 2X better resolution (less distance traveled per step). An inexpensive PK299-F4.5A motor has up to 880 oz*in of holding torque and the larger AS911 has 552 oz*in of holding torque (http://powerpulse.net/story.php?storyID=3295), a motor/driver costing about $350 greatly outperforms a motor/driver costs 3X more.

To use an Alpha motor properly, you need to add sophisticated feedback sensing between all the motors, so that all the motors react if one motor slows down. Shopbot does not have that feature.

Encoders, for feedback, could be added to any motor. Motors having the 'double' shaft can have the encoder attached to the back of the motor, but the encoder could be placed anywhere where movement could be detected. Encoders cost between $30 each (at www.digikey.com) to over $100 each (U.S. digital). An auxiliary microprocessor could cost as little as $10 (Atmel AT89C2051 w/oscillator, watchdog timer, etc.) or as much as you care to spend for a ZWorld type controller.

If you drive the motor properly, you won't miss steps, and a standard stepper motor will work perfectly. If you overdrive the motor, any stepper motor will stall and any servo motor will overheat and die.
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  #255  
Old Fri 18 February 2011, 06:31
Don_Kellogg
Just call me: Don
 
Kalamazoo, MI
United States of America
That's what I thought I've not had issues with my steppers on my previous machine. But when I started researching and saw ShopBot talking about closed loop on steppers I was curious.
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  #256  
Old Sun 27 March 2011, 11:09
The_B
Just call me: Steve
 
Bavaria
Germany
Hi,

I'm a member since a long time, but today I got three stepper motors incl. driver-boards (max 36V 3A), and now it's time to start my project.

But I'm wondering what size of MechMate I could realize with these stepper motors:

HY200 2240 0240 AC04
HY = hybrid Motor, with rotor of low lethargy
200 = resolution (200 step / spin)
22 = Nema 2322 => Nema 23
40 = length 4"
0240 = current 2,4A
A = single axis
C = calatog type
04 = number of wires

Torque = 145-148 Ncm
max Voltage: 84V (they will run off a 24V-30V PSU)

Any suggestions?
regards
Steve
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  #257  
Old Sun 27 March 2011, 11:37
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Hello Steve-

145 Ncm = about 205 Oz/in. That's pretty small to drive a MechMate, and the MM design and components generally use NEMA 34 size motors, not NEMA 23 size motors.

MM's usually have motors with Torque in the 640 Oz/in or greater range; sometimes this is accomplished with a gear box or belt drive.

So I would suggest that you not built a MechMate with those motors; if you are interested in small designs, you may want to look elsewhere; if you want a full size MechMate, you'll need larger motors and drivers.
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  #258  
Old Sun 27 March 2011, 11:49
The_B
Just call me: Steve
 
Bavaria
Germany
Hi Brad,
thanks for the reply. In that case I'll use them to convert my lathe and go hunting again for larger motors.


Unfortunately it isn't easy to get the big ones here at a reasonable price... But I keep on searching...
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  #259  
Old Mon 28 March 2011, 03:38
IN-WondeR
Just call me: Kim
 
Randers
Denmark
try www.slidesandballscrews.co.uk I have bought all of my motors and drivers there, at reasonable prices. Around £70 pr. motor @ 4.6Nm or something like 700oz-in
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  #260  
Old Mon 28 March 2011, 03:53
danilom
Just call me: Danilo #64
 
Novi Sad
Serbia
Steve try this guy, I bought all sorts of stuff from him including ER collects and everything was first class http://www.sorotec.de/shop/

p.s.
this motor would satisfy http://www.sorotec.de/shop/product_i...-4-5nm-ds.html

Last edited by danilom; Mon 28 March 2011 at 03:55..
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  #261  
Old Sat 17 March 2012, 18:22
Guillermo
Just call me: Guillermo
 
Puerto Ordaz
Venezuela
Hi all. For my waterjet project y have one concern about motors warming.

Lets make some math.
The waterjet cutting speed ranges between 2 and 22 in/min.
Pinions (in my case pulleys) runs 2.953 in/rev
So in the cutting speed , the pinion will run in the ( 2/ 2.953)= 0.67 and (22/2.952)= 7.45 r/min range.
Lets see the r /min in motor options. (PK296 A2A XX)
Min rev /min max rev/min
1 : 1 0.67 7.45
7.2 : 1 4.82 53.64
18 : 1 12.12 134.10
36 : 1 24.12 286.20

Lets compare with the MM first choise.
7.2 :1 30 tooth pinion it runs 4.71 in/rev

Lets take a cutting speed of 180 in/min
180/ 4.71 = 38.21 r/min in pinion and
38.21 x 7.2= 275 r/min in motor

This numbers shows me that a router low speed is faster than a waterjet high speed.

¿ Would it be for my case the 36: 1 wired bipolar serie and lowering the volts a good option?

Data. Waterjets don’t generates lateral forces in the cutter head and the complete gantry weighs about 50 lbs.
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  #262  
Old Sat 17 March 2012, 18:57
Guillermo
Just call me: Guillermo
 
Puerto Ordaz
Venezuela
Have some one running a test with the PK296AB2A-SGxx near 120 rev/min in motor
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  #263  
Old Sun 18 March 2012, 09:51
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
With your pinion gear moving 2.953" per revolution and a 7.2:1 gearbox, an axis would move 0.00020507" per step (assuming you use a Geckodrive stepper driver). That's 4876.3969 pulses per inch or travel.

2" per minute is 0.0333" per second, and 0.0333 / 0.00020507 = 162 steps per second.

22" per minute is 0.0333" per second, and 0.0333 / 0.00020507 = 1,788 steps per second.

Because stepper motors "step" every time they receive a pulse, the PK296A2A-SG7.2 motors would work. Some motors have a harmonic "problem" at low speeds (growling and rougher than normal operation). You can try wiring the motors bipolar series to reduce the amount of harmonic vibration. The G203v has a trim pot that you can adjust to reduce harmonic vibration.

I ran a PK296B2A-SG3.6 motor on my test bench and compensated for the difference in motor speeds between a 3.6:1 gearbox and a 7.2:1 gearbox. Without a load, the gearbox noise was more than I expected, even when I adjusted the trimpot to its limit, but when I put a load on the gearbox, it sounded about normal. I ran a PK299-F4.5A motor on another axis for comparison. The PK299 motor was smooth and quiet at all speeds. I simulated speeds for the 3.6:1 gearbox, a 7.2:1 gearbox and the 36:1 gearbox. The faster the motor ran (the higher the gearbox ratio), the smoother it ran. So, in theory, a 36:1 gearbox would be better, at those slow speeds; however, a 36:1 gearbox would have more backlash than a 3.6:1 gearbox. One of the problems that all geared motors have is backlash. In the SG series, the higher the gear ratio is, the greater the possible backlash.

Last edited by Richards; Sun 18 March 2012 at 09:54..
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  #264  
Old Sun 18 March 2012, 13:09
Guillermo
Just call me: Guillermo
 
Puerto Ordaz
Venezuela
Hi Mike. Let me put you in context. The idea of building the waterjet is for going in to the decorative , corporative letters and granite business. (not for cutting aerospace or mechanical parts). So it will be satisfactory if i get 0.5 mm (0.02 in) of accuracy in my cuts.
Because of that , ¿ do you think that I must go with the 36 : 1 (and G203v), live with the backlash but have a smooth run and less motor warming risk.
Thanks Mike
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  #265  
Old Sun 18 March 2012, 15:45
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Guillermo,

At those low speeds, you can use a lower voltage. Depending on the Stepper Driver that you use, you could use a 15VDC or a 24VDC power supply. That will eliminate most of the heating. A 36:1 motor/gearbox spins 5X faster than a 7.2:1 motor/gearbox, so the 36:1 will normally generate more heat than the 7.2:1.

I don't think that you would have to worry about heat with either motor. Because I have never used a 36:1 motor and because I don't know how the gearbox is built, I don't know whether you will have a lot of gear noise and backlash.

You might try a single 36:1 motor to see how it fits your application before buying four of them.

An alternative would be to build a 3.6:1 or 4:1 belt-drive. I know that the PK296-F4.5 or the PK299-F4.5 motors would work and the limited tests that I have done with the Keiling motors make me think that they would also work.
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  #266  
Old Sun 18 March 2012, 18:05
Guillermo
Just call me: Guillermo
 
Puerto Ordaz
Venezuela
Mike

Them the options are.

36:1 Works but not proved in the forum and can produce heat in the gear box and exes of backlash

7.2:1 Works and proved in the forum.

PK296-F4.5 or PK299-F4.5 Works and proved but needs a belt-drive.

If were you the one building he machine ¿What would be your choice? (and why?)

Thanks Mike
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  #267  
Old Sun 18 March 2012, 21:45
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Guillermo,

I would add a belt-drive to a non-geared motor because I had excellent success with that combination on my Shopbot. I tried non-geared motors, then I added belt-drives to the motors, and finally I purchased their 7.2:1 geared motors. The geared motors offered no increase in resolution, but they cost a small fortune.

Stepper motors can be driven very slowly without problems. Belt drives are quiet and efficient. Put the two together and you have a great combination.

Because your need for torque is low, a 300 to 450 oz*in motor, similar to the PK296-F4.5, would be ideal, when attached to a belt drive. I would choose an eight lead motor so that I could wire it either half-coil or parallel.
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  #268  
Old Mon 19 March 2012, 20:12
Guillermo
Just call me: Guillermo
 
Puerto Ordaz
Venezuela
Hi Mike

What do you think about the configuration in this drawing.

It could only use one PK296-F4.5 in X axis (440 oz x 9 =3960) and

one in the Y axis (440 oz x 3 = 1320).

My Z axis is manual

An only two G203v.

Thanks Mike
Attached Images
File Type: jpg Selecting motors jpg.JPG (20.3 KB, 603 views)
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  #269  
Old Tue 20 March 2012, 06:07
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Guillermo,

Unfortunately, I'm not a mechanical engineer, but I see no reason that your design would not work, if you used idler pulleys on the backside of the belts and if you used a tensioning system to keep the belts taut.

I would also think that you will need some substantial bracing on the Y-axis to keep things from twisting, even though the load may be much lighter than on a traditional CNC machine.

When you deviate from the standard design, you become the engineer and your machine becomes a test bed for your own ideas. The only way that you will know if a design works is to build it and then improve upon it until it does what you want it to. I built four different sets of belt-drive transmissions before I found one that had all the features that I really wanted. Each design worked, but after using the machine for a while, I found ways to improve the design. You will probably find the same thing.

The one thing that people have learned on this forum is that building a "standard" machine means that others have already found the little things that needed to be changed. The MechMate design is mature and enough people have built machines to prove that the design is reliable. Personally, I would stick to the MechMate design unless you are willing to spend significant time and (probably) significant money experimenting.
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  #270  
Old Tue 20 March 2012, 16:24
Guillermo
Just call me: Guillermo
 
Puerto Ordaz
Venezuela
Hi Mike.

The drawing was just the simplest way I found to show the idea.

I know that the real gantry have to be more sophisticated, excuse me

if I did not explain well but the point is.

Assuming that the gantry works mechanically perfect.
Assuming that the whole gantry weighs 60 lbs
Assuming that you are the one building machine.
Assuming that the money comes from your wallet.

¿ What motor ( PK296-F4.5 , the PK299-F4.5 or other) and what belt drive

(3:1, 6:1, 9:1 or other) would be your option for X axis and Y axis.

Thanks Mike.
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