[SSfab]

Im going to be converting an X2, and was leaning towards the xlotex drives, psu, etc.. But after doing some research, the Gecko G540 is more what i need. My only question is, im not sure what power supply to use. It says the G540 is 18-50VDC and 0-3.5A.

Would the Keling 48V/5A unit work? I think im going to go with the Keling 387 oz/in. stepper motors for X,Y,Z,A (Rotary table).

Any idea what kind of rapid i can get out of this setup?

Any help is appreciated.

[LaserImage]

I have a 24v 7a that I am using with Keling 282oz steppers (KL23H276). I get just over 130ipm with that setup and the steppers stay very cool. I also bought a 48v 7a that I had planned to use but decided not to. It would have given me faster rapids but on an 18"x36" machine it wasn't necessary - plus the steppers would have been twice as hot, pushing 100C according to Mariss. If you need a 48v, let me know - the one I have is brand-new, never been hooked up. I paid $57.95 plus shipping and would be willing to sell it for a reasonable price - better here than putting it on ebay.

Oh, and you mentioned 3.5a - that's per motor, you'll need at least 7a from what I understand. Also, you need to calculate the voltage based on the steppers - I'm sure the 387oz steppers could take 48v, but check just to be sure. I would suggest calling Mariss directly - he is very willing to help and knows what works with what.

Gary

[SSfab]

Are you able to get 130 IPM on each axis? Also if it is per motor, does that mean the power supply is per motor also? Because im no math genuis but 3.5x4 is more then 7A.

Thanks, Scott

[Richards]

The KL23H276 motor is rated 2.2mH, so 32 X SQRT(2.2) = 47.5 V MAXIMUM. It is rated 3.0A unipolar (half-coil). If I used that motor, I would wire it half-coil (Coil A = Blue/Red wires, Coil B = Brown/Black wires).

The drives will run hot with a 47V power supply, but they should work just fine. Four motors could use as much as 12A if you really push the machine hard. A 7A power supply will get you started and then you can replace it will one with less voltage and a lot more current capacity. I like to use a power supply that is sized at about 75% to 85% of the maximum for the motor and 100% of the rated current of the sum of the current required for each motor. De-rating the power supply will keep the temperature at 150F (65C) or less when the room temperature is around 75F (25C).

You could also limit the amount of current that each motor is allowed to draw from the power supply by selecting different current limiting resistors. Instead of using 3K resistors to allow each motor to pull up to 3A, you might use 2K resistors to allow each motor to pull up to 2A, which would be closer to the 7A that your power supply can handle.

[SSfab]

Thanks for the info. I want to do this right the first time. I dont want to buy stuff that i know I'm going to replace in the future.

Basically I'd be better off getting the 24v/8.3A power supply. Which would let the motors and drive run cooler?

Thanks, Scott

[Richards]

Scott,

I would run the motors with a 35VDC power supply that could supply 12A. The power supply should have enough current capacity (AMPS) to allow the motors to draw as much current as they need, up to their limit. With the motors wired half-coil, that limit is 3A per motor.

With my CNC router, (Shopbot PRT-Alpha 60x120), I hardly ever push things hard enough to need all the AMPS that the Oriental Motor Alpha motors can handle, but when I do need to push things hard, the Alpha power supply can handle all the current that the motors require.

Twenty-four volts will work, but you won't get all of the speed or torque that the motors are capable of delivering. Even at 35VDC, you won't get all of the speed or torque, but I'm willing to trade some speed and torque for heat. In an industrial environment, where you need to have the machine cutting at full speed until you wear it out, you would want to use a 47V power supply, but most of us would rather have a machine that lasts for years without much maintenance, and that's why I under-rate the voltage by about 20% to 25% when I design a controller. However, I never under-rate the current capacity of the power supply unless I'm very certain that the motors will only be used in a light application, but then why would anyone waste money buying oversized motors?

By the way, AnTek makes the 4N35 power supply for about $100 that would be ideal for this application if you don't want to build your own. If you do build your own power supply, all you'll need is a 300VA rated 25AC toroidal transformer, a 25A bridge rectifier (not much difference in price between a 10A and a 25A), and some 50V capacitors that add up to about 25,000 to 30,000 uF. That would give you 35VDC with very little AC ripple, even if all the motors were being pushed as hard as possible.

[LaserImage]

Are you able to get 130 IPM on each axis? Also if it is per motor, does that mean the power supply is per motor also? Because im no math genuis but 3.5x4 is more then 7A.

Thanks, Scott

I was told to use 2/3 of the total amps to determine the ps needs. I guess I missed the 4 steppers part... Based on that, I would think that 10.5, or more, would work for you. The reasoning behind 2/3 is that it is very unlikely that you will ever have all of your steppers requiring full amperage at the same time. If you want to be sure, get a 14a ps and be done with it. I would recommend calculating the v for your particular steppers - it makes sense to me that they would handle more voltage than mine, so maybe a 48v would work and still give you the speed and torque. My 7a isn't enough for your situation though.

Gary

[Crevice Reamer]

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.

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

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:

http://www.digikey.com/

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

http://cgi.ebay.com/6-CNC-LIMIT-SWIT...742.m153.l1262

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.

[LaserImage]

They are NO, so only for home switches. Limit switches need to be NC.

Please enlighten me on this statement. Why would NO be "only" for home and NC for limit? I have NC for both and it works fine but if there is a safety reason to change it I will.

Gary

[SSfab]

Exellent info. Much appreciated.

Stupid question, what would the home switch before?

Limit switch is a no brainer.

Any recommendation for an e-stop switch?

I do want to run a coolant pump as well. can the break out board on the G540 do this?

Thanks, Scott

[LaserImage]

Exellent info. Much appreciated.

Stupid question, what would the home switch before?

Limit switch is a no brainer.

Any recommendation for an e-stop switch?

I do want to run a coolant pump as well. can the break out board on the G540 do this?

Thanks, Scott

The home switch is to set 0,0,0. If you use Mach then you click on "ref all home" the active axis will run until it triggers the switch. If you have Mach configured, it will zero the dro. I have mine setup so the limit switches are the home switches.

the G540 can trigger a relay which you can use for your coolant pump, or anything else for that matter - dust collector, etc. The manual shows the parts needed and how to wire it up.

Gary

[Crevice Reamer]

You can get the estop switch from Keling also:

http://kelinginc.net/CNCPackage.html

The home switches allow the machine to start from a known point. Actually, on a stepper system, the home switches are more important than limit switches. (The home switches CAN be used either NO or NC--Mach will work them either way. It's just easier to use NO.)

Limit switches are a carry over from the original CNC servo systems. If a servo reaches a limit and stops--It will destroy itself. When a stepper motors reaches a limit, it will just harmlessly stall.

So, many folks only use home switches on stepper motor setups.

CR.

[Crevice Reamer]

Here's a good discussion of limit/home switches:

http://www.cnczone.com/forums/showthread.php?t=24432

CR.

[LaserImage]

Here's a good discussion of limit/home switches:

http://www.cnczone.com/forums/showthread.php?t=24432

CR.

And this seems to sum up the thread:

Some software packages can use a single switch for both a reference home switch and a limit switch. Mach software is one of these. Check the software that you wish to use to see the support for limits and homing functions. There is not really a standard among hobbiest CNC software packages, so it is your obligation to research all software available for something that will work for you.

One can choose to have a single home switch, two home switches, three, or none at all. Same goes for the limit switches.

Personally, I believe in the "less is more" doctrine. I have three switches, one per axis. They are mounted on the moving part of the axis and an adjustable stop at each end of the axis allow me to stop where I want them to. The switches are all NC wired in series so if a wire breaks it will stop the system, signalling me that something is wrong. I'll post pictures when I get a chance.

Gary

[Richards]

The Keling 282oz steppers (KL23H276), in the 10:14 p.m. post has the following specs:

Item number:
9: NEMA 23 BIPOLAR STEPPER MOTOR 282 oz-in, ¼” Diameter Shaft with flat
KL23H276-30-8B (Dual Shaft) Specification Price: $39 ( in stock)

Unipolar: 2.2mH, 3A
Parallel: 2.2mH, 4.2A
Series: 8.8mH, 2.1A

From the specs, the best configuration for that motor is Unipolar (half-coil).

The formula for finding the MAXIMUM voltage for a Gecko stepper driver is:

32 X SQRT(inductance)

so 32 X SQRT(2.2) = 47.46 VDC

The 8.8mH connection will give poor performance with that stepper driver (refer to the manual which suggests the ideal mH rating of a motor to be used with the G540 drivers.)

Refer also to discussions on the geckodrive forum about de-rating the current to 2/3rds of the listed current. That de-rated figure was given for the OLD STYLE round motors. The more modern SQUARE MOTORS should be rated at 100% of listed current. Granted, not all motors will always be drawing maximum current, but IF they do, you'll need 100% of the listed current to get full performance out of those motors.

The KL23H276-28-4B motor suggested by the post at 10:21 has an inductance rating of 3.2mH, meaning that it is slower than the 8B motor when the 8B motor is wired half-coil.

The 8B motor, when wired half-coil, is rated at 3A, so you will need a 3K resistor for that motor and for that method of connection.


For limit/home switches, I use proximity sensors that are available from many sources. The 12mm N/O NPN switch is the preferred switch WHEN you use the proximity switch properly. Some users daisy chain proximity switches (requiring N/C switches). The proper way to use a proximity switch is to have each switch operate an opto-isolator (to convert the voltage from 24VDC to 5VDC) and then to have the transistor output on each opto-isolator feed its own input on a demultiplexer TTL chip (such as the 74LS08 AND gate chip). The ouputs on the 74LS08 chip are each wired so that ONE and ONLY ONE output from the chip goes LOW when ANY of the proximity sensors is active.

Using mechanical switches will work, but the action of a low cost mechanical switch, when used as a homing device, is not nearly as precise as you would get with a properly interfaced proximity sensor. On my CNC router, when traveling at 4-inches PER SECOND, the repeatability is 0.001-inch with a proximity sensor (as measured with a digital indicator).

So that no one thinks that I'm giving out false and misleading information, I run a test-bench 24/7 in my shop where I design stepper interfaces and control units for CNC machines. I also build simple proximity sensor interfaces (74LS08 type) as well as much more complex micro-controller controlled interfaces. My experience in the process control field started in 1977.

As a matter of practice, when a poster lists a particular motor (Keling 282oz steppers (KL23H276), I check the data sheet for that motor and then recommend the components that would work best for that motor. When there is a choice of wiring methods, I suggest the method that would work best with the desired stepper driver. For THAT motor, the ONLY practical wiring method is half-coil.

[LaserImage]

The Keling 282oz steppers (KL23H276), in the 10:14 p.m. post has the following specs:
Unipolar: 2.2mH, 3A
Parallel: 2.2mH, 4.2A
Series: 8.8mH, 2.1A

From the specs, the best configuration for that motor is Unipolar (half-coil).

But Parallel gives you 40% more torque, according to the spec sheet for that stepper. I know the G540 is 3.5A max, but even at 3.5A it should give you more torque than Unipolar, shouldn't it?

I'm still trying to learn enough to get out of the "knows just enough to be dangerous" mode, can you help?

Gary

[SSfab]

How do you figure out what kind of rapids you can get (IPM) with the given motor,driver,power supply. Etc....

[Richards]

Gary,

Yes, the motor, if wired parallel, would give more torque; however, that torque comes at a high heat price. With four coils drawing current, instead of two coils, you'll get a lot more heat. On some Oriental Motor PK299-F4.5 motors that I recently tested (excellent motors, by the way), when wired parallel, the motors quickly stabilized at 85C. When run half-coil, the motors had a hard time hitting 65C. Granted, when wired parallel, the motors had more torque, (SQRT(2) X half-coil torque = parallel torque) but when wired half-coil, and with a 3.6:1 belt-drive transmission, the half-coil connected motors had much more torque than I could use. It proved to me that I could use the smaller and less expensive PK296-F4.5 motors next time.

[LaserImage]

Gary,

Yes, the motor, if wired parallel, would give more torque; however, that torque comes at a high heat price. With four coils drawing current, instead of two coils, you'll get a lot more heat. On some Oriental Motor PK299-F4.5 motors that I recently tested (excellent motors, by the way), when wired parallel, the motors quickly stabilized at 85C. When run half-coil, the motors had a hard time hitting 65C. Granted, when wired parallel, the motors had more torque, (SQRT(2) X half-coil torque = parallel torque) but when wired half-coil, and with a 3.6:1 belt-drive transmission, the half-coil connected motors had much more torque than I could use. It proved to me that I could use the smaller and less expensive PK296-F4.5 motors next time.

Thanks, that makes perfect sense! And to think I didn't plan on learning anything today...

Gary

[Crevice Reamer]

It's all a trade-off. If you are willing to give up 40% of holding/low speed torque--effectively reducing a 282 oz motor to a 170 oz motor--Just to save a few degrees of motor heating (Steppers are BUILT to run hot) than that is your choice. I choose to run at the best performance voltage/torque for my motor, and let the idle current limiting take care of excess heat.

CR.