[Richards]

The 40% figure does not apply. That would assume that the G540 could handle 4.2A, which it cannot do. To compare apples to apples, you have to compare the 3A from wiring the drive half-coil to the 3.5A maximum allowed by the G540 if you wired the drive parallel. That is 6 / 7, or 85%. So, you would lose 15% of the possible torque.

Keep in mind that these motors will be driving an axis via a screw. That screw represents a gear box. A mechanical gearbox multiplies the torque. So, with the screw multiplier, you'll probably find that the motor, even when wired half-coil, can produce more than enough torque to snap a cutter.

I've found that the most common trade-off when wiring a motor half-coil rather than parallel is a change in acceleration. Instead of setting the acceleration at 0.8 second, I might use 1.0 second, or some other insignificant delay. Giving up 0.2 seconds hasn't caused me any grief. The bills still get paid and the components seem to last forever.

Look at the torque curves for a stepper motor. Even an Oriental Motor PK299-F4.5 wired parallel requires a substantial ramp-up to get to speed. I've wired that motor series, parallel and half-coil. Series was unusable for my application. Parallel worked fine at the cost of excessive heat (when full current was expected). Half-coil was the ideal match. Excellent speed. More than adequate torque. Moderate heat.

I doubt that those that demand ultimate speed 24/7 would be using stepper motors. The servos that I use are much better suited to that kind of heavy lifting.

[Crevice Reamer]

The 282 is not a good match for the G540 for these very reasons. Hence my recommendation of the 270s and 387. The G540 will run THEM Bipolar Parallel at 50 volts and full torque without worry about motor over heating.

CR.

[Richards]

CR,

I can understand your logic in recommending other motors, but I'm confused why you would recommend motors with much higher inductance ratings when it seems that your goal is high performance.

The 270 motor has 3.6mH inductance.

The listing for the 387 motor came up "Not Found", but the closest match was the 382 motor at 5.6mH inductance.

The 282 motor came up 2.2mH inductance.

The high inductance rating of a series connected motor is exactly the reason why I've found their performance unacceptable when compared to the same motor wired half-coil or parallel. Granted, a series wound motor has high low speed torque, but, when compared to a half-coil connected motor, the series connected motor quickly becomes a non-performer as the speed increases.

[Crevice Reamer]

We are both right, of course. We each have our own ways to come at the solution.

Both the 270 and the 387 are 4 wire Bipolar Parallel internally wound motors. They are not perfect--No one has yet found a perfect match for the 3.5A 50V G540--but they are close enough to work well. Here's the 387 spec sheet:

http://kelinginc.net/KL23H284-35-4B.pdf

Yes, they are higher inductance than I would like to see, but they are the best available value/performance at present and run well Bipolar parallel without the half coil wiring and commensurate torque loss.

Now I LIKE your half coil idea for a possible Z motor for the X3. I envision a 5.2A 900 oz N34 8 wire motor that could be detuned half coil to operate within the G540s envelope and deliver about 640 oz.

CR.

[mkenney]

Some one has to ask a stupid question, might as well be me:-) What is the difference between the half-coil and parrel wiring in a practical wiring sense. I have a G540 and the 384 drives. They have 4 wires coming out of them. Do I wire up all four or only two? Sorry, very new to this all and can't wait to get things running. Any input on what wire can be used would also be VERY helpful.

Thanks!

Mark [mkenney]

[LaserImage]

Some one has to ask a stupid question, might as well be me

Sorry, I beat you to it a long time ago...

Do you have a schematic for the steppers? That would be the best place to look. As for wire, you'll hear a lot of people talking about length of wire, current and resistance and to look up the current you need to run, the distance and decide from there. Talk to Mariss at Gecko and he'll tell you to ignore most of that, there isn't any significant loss in the short distance the wires run. He told me I almost couldn't buy wire too small for these applications. I did have 18 awg that I used, but only because I bought it before I talked to him. I would probably run 20 or 22 if I were to do it again, they are both much smaller and more flexible and easier to solder into the cups on the db9 connectors!

Gary

[David Campbell]

Talk to Mariss at Gecko and he'll tell you to ignore most of that, there isn't any significant loss in the short distance the wires run.

Based on AWG & copper the following is the ohms/foot
AWG ohm/foot
4 .000292
6 .000465
8 .000739
10 .00118
12 .00187
14 .00297
16 .00473
18 .00751
20 .0119
22 .0190
24 .0302
26 .0480
28 .0764

So for 3 feet, 28 AWG running at 3 Amps you will loose 1.3V
[3 feet x 3 amps x 0.0764 x 2 wires = 1.3V]

Might get a little warm but probably nothing to worry about (5W over a yard length, hmm...). I believe Mariss has a point here.

David Campbell

[Richards]

Parallel wiring requires eight wires coming from the stepper motor.

If you only have four wires, you will have to use two wires for the 'A' coil and two wires for the 'B' coil. Keling has a wiring diagram for their motors on each specification sheet. Part numbers ending in 4B are for 4-wire motors. Part numbers ending in 8B are for 8-wire motors.

On a 4B motor, wire it this way:

The Black wire connects to the A+ end of the A coil.
The Green wire connects to the A- end of the A coil.
The Red wire connects to the B+ end of the B coil.
The Blue wire connects to the B- end of the B coil.

[Crevice Reamer]

Some one has to ask a stupid question, might as well be me:-) What is the difference between the half-coil and parrel wiring in a practical wiring sense. I have a G540 and the 384 drives. They have 4 wires coming out of them. Do I wire up all four or only two? Sorry, very new to this all and can't wait to get things running. Any input on what wire can be used would also be VERY helpful.

Thanks!

Mark [mkenney]

This is certainly NOT a stupid question. You can only wire a four wire motor one way--connect one driver wire to each motor wire. The motor may be wired internally either Series or Parallel, but you cannot change this.

Six or eight wire motors can be wired half coil. It may be an advantage to wire a six wire motor half-coil, because it will run faster this way than wiring it Bipolar Series. Of course, if your driver is unipolar, then you can ONLY wire a six wire motor as unipolar.

Bipolar Parallel is usually the best way to wire a stepper for our CNC purposes, because this gives the most power at the highest RPMs. Half coil wiring will use less amps than parallel, but deliver about 40% less torque.


You can use THIS wire for motor cables and home/limit switches. Ground the drain wire ONLY at the driver end.

http://cgi.ebay.com/Servo-Motor-Wire...3286.m20.l1116

Parallel wiring requires eight wires coming from the stepper motor.

If you only have four wires, you will have to use two wires for the 'A' coil and two wires for the 'B' coil. Keling has a wiring diagram for their motors on each specification sheet. Part numbers ending in 4B are for 4-wire motors. Part numbers ending in 8B are for 8-wire motors.

On a 4B motor, wire it this way:

The Black wire connects to the A+ end of the A coil.
The Green wire connects to the A- end of the A coil.
The Red wire connects to the B+ end of the B coil.
The Blue wire connects to the B- end of the B coil.

Is he USING a Keling motor?

The B in 4B stands for dual shaft. Single shaft motors end in A.

Four wire motors are Bipolar, have 4 bifilar coils inside and may be wired internally (By the manufacturer) either in Bipolar Series or Bipolar Parallel. Generally, if a four wire stepper motor has inductance comparable to a similar 8 wire parallel wired motor, it is internally wired Parallel.

Motors that are Series wired internally will have 4 times the inductance and about half the current draw in amps of Parallel wired motors. MOST of the Keling 4 wire motors are internally wired Bipolar Parallel. This is actually very convenient and easy to wire.

CR.

[Richards]

Sorry, I'm just getting back from a funeral and my mind is not fixed on electronics.

Yes, the 4B is a dual-ended shaft and the 4A is a single-ended shaft on Keling's specs.

In comparing the KL23H276-30-4A, the KL23H276-30-6A and the KL23H276-8A motors, it appears that the 6A and the 8A are the same motors. The 6A has six leads exiting the motor and the 8A has eight leads exiting the motor. In that case, I could select the 8A so that any of the three wiring options (series, parallel, half-coil) could be selected. The 6A limits the choice to series or half-coil. The inductance spec for the 4A shows 4.7mH compared to 2.2mH/8.8mH for the 6A and 8A motors, so it would be a motor that would have performance characteristics somewhere between the 6A/8A wired series and the 6A/8A wired either half-coil or parallel.

Figuring torque is simple, just use SQRT(2) in your equations. A parallel motor draws the current of a half-coil motor multiplied by the square root of 2. A half-coil motor draws the current of the parallel motor divided by the square root of 2. A parallel motor has the torque of a half-coil motor multiplied by the square root of 2 and a half-coil motor has the torque of a parallel motor divided by the square root of 2.

Since a series connected motor uses the same number of coils as a parallel connected motor, it has the same holding torque as the parallel connected motor; however, because a series connected motor has 4X the inductance of a half-coil/parallel connected motor, it would best be used when low to moderate speeds are required at higher torque.

The obvious thought that most of us have when we look at the three connection methods is "Why not just wire everything parallel and get both high speed and high torque?". The answer to that is that a motor wired parallel (and run as hard as its torque limits allow) is going to run very hot. (If it were a DC circuit and inductance were compared to resistance, it would be easy to see that a parallel connected motor produces 4X the wattage as a series connected motor.)

The nice thing about it is that there are lots and lots of motors available. It's nearly always possible to find one motor that pretty nearly matches your requirements. Although I have never used a Keling motor, they do offer a wide range of motors at very reasonable prices. Others have found the Keling motors to be satisfactory. I use Oriental Motor steppers mostly because I've never - ever - had one of their motors fail in the dozen or so years since I started installing their motors in Kodak S printers. It's probably mostly the old-dog, new-tricks syndrome.

[rexstep]

Hi Guys,

I saw some discussion about which steppers are well suited the G540. We don't have them up on the website yet but we have two new motors wound to 3.5A - one in series, one in parallel - both intended for use with G540/G251. Anyone who wants to see the specs can email me at [email protected]

-Rick L.

[Crevice Reamer]

Hi Guys,

I saw some discussion about which steppers are well suited the G540. We don't have them up on the website yet but we have two new motors wound to 3.5A - one in series, one in parallel - both intended for use with G540/G251. Anyone who wants to see the specs can email me at [email protected]

-Rick L.

Why don't you just post the specs please?

CR.

[albert_chuy]

Hello Mr. CR

Thanks for all this info I’m another one of those new people to the CNC scene I just bought a Sieg x2 and I’m turning my own lead screws the Mechanical part does not seem like a problem to me but all the Electrical is not my thing, but enough of that and straight to the point I really want to fallow all your indications on this thread but I cant get over the fact that the motors you suggest are dual shaft I would prefer to have single shaft
Step motors and there is no single shaft 270 oz motor in the Kelingink web page what other stepper motor with a single ¼ shaft can I use for my x y and z

Best Regards

-JR

[albert_chuy]

Hi SSfab. Welcome to the Zone!

There is a lot of misinformation in this thread. The Keling 387 Oz. motors which you are going to use are rated 4.1 mH inductance. That means they are comfortable with up to 65V and Will NOT overheat at 48 or even 50V.

The formula for power supply Amps is total motor amps times .67. Four times 3.5A = 14A. That times .67 = 9.38A required from the power supply. This would indicate the $129 KL 5010 as the best power supply. However, you don't need such large motors except for the Z Axis.

For maximum efficiency, it's best to use smaller motors on X and Y (and even A, if all you are using for a fourth axis is a rotary table.) and a larger motor for the heavy-head-lifting of the Z axis.

The small X2 table can be driven to much faster rapids with the 270 oz KL23H276-28-4B. This 2.8A 3.6 mH motor is comfortable with up to 60V and will run very fast with 48V.

http://kelinginc.net/KL23H276-28-4B.pdf

Keling "kits" are just suggestions. The kit costs just as much as the individual components bought separately. You can "mix and match." Just be sure to check availability beforehand and specify NO SUBSTITUTIONS.

So I recommend this combination for the X2:

G540, two or three $39 270 oz KL23H276-28-4B motors, one $49 387 oz KL23H284-35-4B for the Z axis, the $60 KL-350-48 48V/7.3A power supply. (2.8 x 3 =8.4A + 3.5 = 11.9A times .67 = 7.9A and you won't ever be running all 4 motors together so this is more than enough.)

The above setup should give you 200-250 IPM rapids and all of the cutting power you will ever need. Of course, you can always run it slower by changing settings in Mach.

You will also need some more stuff:

You can use THIS wire for motor cables and home/limit switches. Ground the drain wire ONLY at the driver end.

Servo in RC Engines, Parts & Accs | eBay

You won't need any db9 motor connectors with the G540, as they come WITH it.

You WILL need either 2.7K or 3.48K 1/4 watt current limiting resistors, one for each motor. You can get them here:

DigiKey Electronics - Electronic Components Distributor

If you don't already HAVE them, these are excellent home switches:

6 in Clothing, Shoes & Accessories | eBay

They are NO, so only for home switches. Limit switches need to be NC. You only need 3 but the whole set of 6 switches costs less than ONE switch would cost at Radio Shack.

These limits from Enco will do fine and only cost $2.34 each. Now you know what a deal the home switches are.

http://www.use-enco.com/CGI/INSRIT?P...PMPXNO=7908441


CR.

Hello Mr. CR

Thanks for all this info I’m another one of those new people to the CNC scene I just bought a Sieg x2 and I’m turning my own lead screws the Mechanical part does not seem like a problem to me but all the Electrical is not my thing, but enough of that and straight to the point I really want to fallow all your indications on this thread but I cant get over the fact that the motors you suggest are dual shaft I would prefer to have single shaft
Step motors and there is no single shaft 270 oz motor in the Kelingink web page what other stepper motor with a single ¼ shaft can I use for my x y and z

Best Regards

-JR

[Crevice Reamer]

Hello JR, and welcome to the Zone!

I'm not sure why you want a single shaft motor, other than they cost a couple of dollars less. The important thing is how they drive your axes.

I must tell you that this old thread is outdated. I now recommend the newer Keling 381 motors for all three axes of x2. This motor did not exist when your quoted post was written, and is a much better motor than the 270. Also a much better motor with G540.

I suppose, if you had to, you could just cut off the offending shaft with a Dremel. That would take away the possibility of adding hand cranks for occasional un-powered positioning though.

Good luck with your conversion. Please start a thread and post pics--ESPECIALLY of your ball screw turning. I am sure we all will be most interested in that.

CR.

[albert_chuy]

Hello JR, and welcome to the Zone!

I'm not sure why you want a single shaft motor, other than they cost a couple of dollars less. The important thing is how they drive your axes.

I must tell you that this old thread is outdated. I now recommend the newer Keling 381 motors for all three axes of x2. This motor did not exist when your quoted post was written, and is a much better motor than the 270. Also a much better motor with G540.

I suppose, if you had to, you could just cut off the offending shaft with a Dremel. That would take away the possibility of adding hand cranks for occasional un-powered positioning though.

Good luck with your conversion. Please start a thread and post pics--ESPECIALLY of your ball screw turning. I am sure we all will be most interested in that.

CR.

Thank CR Ill definitely buy the 381 I wanted the one shafts for safety reasons did not want anything out of the machining table spinning around but it is what it is.

-JR