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  #31  
Old Mon 20 August 2007, 16:24
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Gerald,

Thanks for the info about the higher Mach 3 speeds. I haven't downloaded anything from Art since the stable G100 plugin became available. (I receive dozens of Mach forum messages every night, but usually I just quickly scan the headers to see if there's anything I need - somehow I totally missed the higher speed pulse rate.) At any rate, I've just downloaded the latest software and will soon be testing it at my test bench.
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  #32  
Old Tue 21 August 2007, 05:25
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Mach 3, at 100kHz, is wonderful! For the first time, I can make the motors on the PMDX/Gecko G202 test bench act as though they were the motors on the G100/G203 test bench.

At 100kHz, gear ratios higher than 7.2:1 could be used, but, in my opinion, either the 3.6:1 or the 7.2:1 would still be my preference.

Edited: We need to remember that, even though Mach 3 at 100kHz can spin the motors much faster, the torque requirements on a motor will probably dictate that the motor be used at moderate speeds, the speed range where a stepper motor has the most torque. What I am thinking about, however, is that higher ratio geared motors could be used if good quality gear boxes were used (expensive, more than $800 per gear box) or that brushed servos could be used (also expensive because the ones I've tested are useless without a high ratio gear box). The advantage to using servo motors is that the torque curve seems to be constant throughout the motor's speed range, but the available torque is only a fraction of that available from a smaller and lighter stepper motor. For instance, I have a 34-size brushed servo (ID33004) that is long and heavy and has only 170 oz*in of torque at 70V. However, at 70V, that motor can run all day long at 2,200 RPM. So, with a 7.2:1 or 10:1 gear box to multiply the torque and to divide the speed, that particular motor might be useful on a CNC router. The problem of course is that even though the motor and Gecko G320 servo driver costs almost the same as a Gecko G20x stepper driver and a 600 oz*in stepper motor, the servo requires a gearbox - meaning that a MechMate with servos would probably cost at least $4,000 more than a MechMate with steppers.
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  #33  
Old Wed 05 September 2007, 10:40
javeria
Just call me: Irfan #33
 
Bangalore
India
Hi All,

How about http://www.linengineering.com/site/products/8718.html , i have a quote from them for model 8718S-05P around 250 USD each. Do you all think vexta is better, i think i should find a dealer for vexta here in bangalore

rgd
IRfan
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  #34  
Old Wed 05 September 2007, 23:01
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Suggest you first find the Vexta price before you decide which company is the better supplier. On paper, the motors are very similar.
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  #35  
Old Thu 06 September 2007, 04:33
javeria
Just call me: Irfan #33
 
Bangalore
India
Quote:
Originally Posted by Gerald D View Post
Suggest you first find the Vexta price before you decide which company is the better supplier. On paper, the motors are very similar.
I got the quotes from Vexta distributers its almost 300USD for the ungeared and around 365USD for the geared (3.2) without taxes.

ho ho.............
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  #36  
Old Thu 06 September 2007, 09:14
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Have you considered importing from Motionking, China? They might even tell you they have a stockist/agent in India.
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  #37  
Old Wed 31 October 2007, 14:50
joepardy
Just call me: Joe
 
Lebanon, OH
United States of America
5 axis design & power supply questions

Gerald,

I think that I have read through every post on motors, gearboxes, controllers, and drivers in this forum over the last few days - and though it may not be conflicting - it can get confusing .

I am looking at building a MechMate with a BC head. Ultimately I would like to build a 4x8 machine with a 24" Z axis. I have designed and am about to begin building the BC head. I have selected the following hardware/Software so far:

(1) Gecko GRex-100 Controller (6 axis)
(6) Gecko G203V Drivers
(4) PK296A2A-SG (3.6 or 7.2) Series Oriental Motors (X,X,Y,Z Axis)
(2) PK264A2A-SG (7.2 to 36) Series Oriental Motors (B,C Axis)
Mach 3 Software with G100 Firmware Upgrade

I beleive that this configuration will "work", but I would like to have your input.

Also, with this configuration, can you recommend a "pre-built" power supply? At a minimum, I would like it to be able to handle the power requirements of the controller, drivers, and stepper motors.

I do plan on adding some other "bells and whistles" in the future (vacuum table, motor on/off, etc.) so a little extra would power for the control relays wouldn't hurt.

I am much more "mechanically" inclined than I am "electrically" proficient - hence the hesitation to build my own power supply.

Again, your wisdom & knowledge would be greatly appreciated.
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  #38  
Old Wed 31 October 2007, 17:34
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Joe,
I know that you addressed your post to Gerald, but, if you don't mind, I'll give you my input (and it certainly won't hurt my feelings if Gerald advises something different).

First off, you've made an excellent choice of motors, Gecko stepper drivers and pulse generator. I have almost the identical parts on hand on my test bench and have had absolutely no problems with any of the parts.

To determine which power supply will work best, you must decide whether you want to wire the motors Bipolar Series or half-coil. I strongly suggest that you choose half-coil to get much better response at higher speeds, but you will lose about 30% of the low-speed torque if you choose half-coil. Assuming that you decide to use half-coil wiring, the PK264A2A-SGxx motor will determine the maximum voltage. That motor is rated at 1.4mH (half-coil), so 1000 * SQRT(0.0014) = 37VDC MAXIMUM. I've had excellent results with a 27VDC power supply with the PK295B2A-SG3.6 motor (which is just the PK296A2A-SG3.6 motor with dual shaft). Current requirements would be ((4 X 3A) + (2 X 2A)) * 0.66 = about 11A MINIMUM. And 11A X 30VDC = about 350VA. I would select a 500VA power supply to give some margin.

If you decide to wire the motors Bilevel Series, then the forumula for the PK264A2A-SGxx motor is: 1000 * SQRT(0.0056) = 75VDC MAXIMUM. Personal experience dictates that a power supply voltage of 50V to 70V will work fine, with my personal preference being a power supply that is closer to 50V than to 70V. Current requirements would be ((4 X 2.1A) + (2 X 1.4A)) * 0.66 = about 7.5A MINIMUM. And 7.5A X 60VDC = about 500VA. I would select an 700VA or 800VA power supply to give some margin.

AnTek has a PS-5N30 power supply (30V @ 500W) for $100. They also have the PS-8N54 (54V @ 800W) for $120, which is only $10 more than the PS-6N54 (54V @ 600W).

The G100 comes with its own wall-wart power plug to generate the necessary voltage, so you won't need any other voltages unless you add other unspecified parts and pieces.
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  #39  
Old Thu 01 November 2007, 00:44
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Mike is the right guy to speak to regarding the electrics.
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  #40  
Old Mon 10 December 2007, 20:49
larry1larry
Just call me: larry
 
toronto
Canada
Hi Guys,
This is my first post after reading everything on the forum about stepper motors.
My brain is fried for the moment,so I will make some unqualified statements.
If confused,should I just use a 4 wire motor?
Different wireing schemes result in half voltages or current or whatever.Perhaps the variable is how big a power supply you build.
I read many times in posts of the power supply pushing current to the motors. I thought power supplies provided current to the motors and the motors drew current from the supply,with the gecko's limiting the current.
The geared oriental motors have less torque than the un geared motor?
For the moment my brain is wired bi-polar series,100volts/20amps/80c.
After cooldown things may be clear.
BTW great forum,Thanks
Larry
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  #41  
Old Tue 11 December 2007, 03:47
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Larry,
Keep reading, just keep reading.
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  #42  
Old Tue 11 December 2007, 04:25
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Mike....funny how you mention reading...just keep reading. I was soldering the harness connections on my motor's last night while the kids were busy watching Nemo....just keep swimming...
The kitchen table project has so many parallels

- Almost ready to put power to the box for a test run. Waiting for paint to dry so I can reassemble the cabinet.

Sean
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  #43  
Old Tue 11 December 2007, 13:47
larry1larry
Just call me: larry
 
toronto
Canada
Information overload.
Sorry my brain is still overloaded but I will try to make some assumptions.
From what I have read here,.66 is OK as all 4 steppers are never fully on at one time.the others act as a current dump.
I like the low current and sealed cabinet.For higher current you could cut a hole in the box and mount the Gecko's to an external heat sink.
Larry
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  #44  
Old Tue 11 December 2007, 16:12
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Larry,

Although 66% is generally accepted as enough current, I always go 100%. Power supplies are cheap compared to the material that might be wasted if the motors can't do their job.

As far as heat goes, the G203v doesn't generate much heat. A slightly oversized power supply doesn't generate much heat. I run G203v all the time on my test bench. They've always stayed at, or very near, room temperature. The various toroidal transformers that I use also stay at or very near room temperature.

As to whether a device 'pulls' current from the power supply or whether the power supply 'pushes' current through a device is kind of a loaded question. Sometimes it's easier if we think of a power supply as a device that can produce pressure (voltage) and volume (current). If you've ever played with water, you know that the higher the pressure, the more volume - in a fixed amount of time. So, a power supply can 'push' electricity out to various devices, as long as the various devices can't allow passage of more current than the power supply is able to produce. That brings us to the device. If we use the water analogy again and think of each device as a certain size of hose, it is easy to visualize what is actually happening. Lets say that device A has a 1/4-inch hose and device B has a 3/4-inch hose. Using that example, it is easy to understand that device B will allow more current to pass at a given pressure than device A allows to pass. The same thing is happening with power supplies and electrical components. The power supply is able to push out electricity at a certain pressure as long as the various devices connected to that power supply allow less current to pass than the power supply is able to supply. So, to bring this long analogy to an end, if a power supply can supply 10A of current and all of the devices connected to that power supply can only allow 8A of current to pass, then the power supply can be considered adequate to handle the job. On the other hand, if the power supply could only handle 6A of current and all of the devices connected to that power supply can allow 8A of current to pass, then the power supply would be considered inadequate to handle the job (just like running too many sprinklers off of one water line causes pressure to fall to the point that the sprinklers can't do their job).
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  #45  
Old Tue 11 December 2007, 21:48
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Mike, an early New Year's resolution of mine is to do some measurements of these lovely vague concepts we spend hours talking about. . . . .

1. Put a logging amp-meter on the output of the power supply driving motors which are doing various types of cutting (3D, cabinet doors, etc.). This will tell us if the 0.66 factor is okay.

2. Take a variable transformer powering a recommended motor via a g202 and g203V and log motor temperature versus voltage. This will tell which voltage is the limit for the motor.

But, if Santa has been kind while I am away on holiday, there will be lovely graphs and test reports waiting in my stocking when I get back.
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  #46  
Old Tue 22 January 2008, 12:33
revved_up
Just call me: Craig
 
Hartland, MI
United States of America
Ok, I am about to commit to the build and start buying hardware etc. I have read this thread 3 or more times and agree with many of the posters before me that this can be quite confusing and thankyou Gerald for updating your postings and keeping everything current. Is it a possibility that someone that has tested different motor control combinations could possibly post a spreadsheet to make it easier to compare and list pros and cons. Maybe if possible leave it open for people to add their specs of what they have working on their machines in the future so everything could be in one consise location. I know this may be asking for alot for somebody to take the time for this as time is my most precious asset but it would help all of us with less experience to make good decisions.
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  #47  
Old Tue 13 May 2008, 03:58
turnerseng
Just call me: andy
 
PMB
South Africa
Who is a good source for servo motors in South Africa? and what would the model number be for the replacement to the Oriental steppers PK296A1A.
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  #48  
Old Tue 13 May 2008, 07:03
Alan_c
Just call me: Alan (#11)
 
Cape Town (Western Cape)
South Africa
Send a message via Skype™ to Alan_c
Try CNC Direct in JHB, their prices are not bad, but nobody on this forum has used their motors. The OM motors are available from Varispeed but their pricing is truly laughable if not downright criminal.
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  #49  
Old Tue 13 May 2008, 16:40
Doug_Ford
Just call me: Doug #3
 
Conway (Arkansas)
United States of America
Andy,

If you are planning on using them on a MM, a servo won't work. It spins too quickly.
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  #50  
Old Tue 13 May 2008, 16:52
Marc Shlaes
Just call me: Marc
 
Cleveland, OH
United States of America
Send a message via Skype™ to Marc Shlaes
Doug,

I am surely no expert, but, it seems that with transmissions such as those that JR and I designed and built, they would work.

Today, JR and I should be posting the DXFs as well as a description of just how the cutting of the 1/2 inch aluminum worked.
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  #51  
Old Tue 13 May 2008, 19:23
Doug_Ford
Just call me: Doug #3
 
Conway (Arkansas)
United States of America
You may be right Marc. I hadn't thought of that. Sure sounds like a lot of work and extra money especially when we're not sure it is needed. My machine has power to spare. If I changed my pinion from a 35 tooth to a 20tooth, I don't think I would ever lose a step and it would still probably go fast enough to scare me.
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  #52  
Old Tue 13 May 2008, 19:41
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
...Doug...it doesn't go that fast with 20Tooth......but it does a fine job.
I seem to cut in the 180-225ipm band comfortably all day long. I do think I am going to "upsize" slightly next month when I move the machine. I need a "little" quicker fast moves between parts. I need to shave about 4 minutes off each cut cycle to get a better part/price yield.
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  #53  
Old Tue 13 May 2008, 21:11
Kevin
Just call me: Kevin
 
Canton, NC (In the Smoky Mountains)
United States of America
I think you will need a lot more than 3:1 reduction for a servo motor to work on a MechMate...

Kevin
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  #54  
Old Tue 13 May 2008, 21:46
Marc Shlaes
Just call me: Marc
 
Cleveland, OH
United States of America
Send a message via Skype™ to Marc Shlaes
Kevin, please elaborate. This is something I wanted to learn about for a while. Maybe it is just curiosity. Maybe it won't go anywhere but I would love to know more about servos.

Thanks in advance.
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  #55  
Old Tue 13 May 2008, 22:43
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
The servo motor that I've had for several years is an ID3004. With the Gecko G320/G340 type servo driver, it spins at about 2,200 RPM and gives about 225 oz*in torque. The motor is about 10-inches long.

As you can see, there are two problems, 2,200 RPM with a 20/20 pinion and rack would mean that the axis would move 2200 / 60 X 3.14 inches per second, or 115.13 inches per second. The second problem is that 225 oz*in is only about 1/3 the torque that I would consider adequate.

Most of my cutting is done at 8-inches per second or slower. My preferred jog speed is 12-inches per second. So, 115/12 = 9.58:1 gearing. With belt-driven transmissions, that means you would need a multi-stage transmission, and that means you're going to have a very bulky transmission. The smallest practical pulley on the 5/8-inch motor shaft is 20-tooth and the largest commonly available pulley on the drive shaft is 72-tooth, which gives 3.6:1 reduction, meaning that you would have to use a two-stage transmission. Remember that a transmission will also multiply the torque, so a 9:1 or 10:1 transmission will give about 2,000 oz*inches of torque.

Servo motors are quieter than stepper motors. They have constant torque. Their resolution depends mostly on the encoder that you use. (I use a 500 line encoder that gives 4 X 500 lines or 2000 "steps" per revolution.) However, if something happens to the encoder, the servo is going to run away. A servo also has jitter at rest. And, the servo that I've listed would require a separate 70VDC power supply per motor.

If 7.2:1 to 10:1 gearboxes were available at a reasonable price, I would switch to servo motors, but when the decent quality gearboxes cost around $1,000 each, using a servo motor with a rack and pinion drive is too expensive for my use.

Every CNC router that I've seen that uses servo motors also uses ball-screws. Ball-screws introduce many more possible problems. Dirt and dust are a big problem. "Whip" can be a problem at CNC router speeds. Cost is much higher than rack and pinion. Maintenance is also an issue.

On the other hand, when compared to servo motors, stepper motors are inexpensive, easy to use, maintenance free, and easy to use with rack and pinion. They can be used direct drive or with gearboxes/transmissions. From what I've seen on the forum, the PK296A2A-SG7.2 motors are an excellent match with the Mechmate.

On my machine (Shopbot), I started with direct drive 600 oz*in motors, then added 3:1 belt-drive transmissions to the X and Y axes, and finally switched to 7.2:1 gearbox motors on the X and Y axes. Using either the 3:1 or the 7.2:1 geared motors gave much smoother edges than the direct drive motors that came with the machine; however, the 7.2:1 motors gave hardly any improvement over the 3:1 motors.
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  #56  
Old Tue 13 May 2008, 23:19
Kobus_Joubert
Just call me: Kobus #6
 
Riversdale Western Cape
South Africa
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Yes PLEASE..more servo info. I can lay my hands on some MOOG G4x3 servo motors. If these servo's can be used on a MM, this will be great.

Thanks Mike, we were typing at the same time.
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  #57  
Old Wed 14 May 2008, 19:28
Doug_Ford
Just call me: Doug #3
 
Conway (Arkansas)
United States of America
Sean,

What are you upgrading? Bigger motors or larger pinions? Or something else?
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  #58  
Old Wed 14 May 2008, 20:02
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Doug,

An associate of mine is building a servo based CNC plasma machine at this time and I am paying close attention to his progress to learn a little. The real reason is I plan on building a plasma table in the very near future. I haven't fully decided if I will convert the Mechmate that I just finished to the plasma since it's a classic version. I would prefer to build another MM with Mamba parts and spindle. Just easier to start from scratch then retrofit the existing machine. The cost is about the same!

With regard to your earlier post

"I am going to "upsize" slightly next month when I move the machine. I need a "little" quicker fast moves between parts. I need to shave about 4 minutes off each cut cycle to get a better part/price yield

I will change the pinion size next month to a slightly larger for quicker jogs and fast moves.

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  #59  
Old Thu 15 May 2008, 09:04
Marc Shlaes
Just call me: Marc
 
Cleveland, OH
United States of America
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Came across this just a few moments ago. Pretty good info on this topic. Check it out.

http://www.cnczone.com/forums/showthread.php?t=52090
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  #60  
Old Thu 15 May 2008, 20:47
Doug_Ford
Just call me: Doug #3
 
Conway (Arkansas)
United States of America
I'd love a CNC plasma cutter too but I don't have the room in my garage for another machine. Good luck with it.
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