Upgrading to Gecko from cnc4pc c11 & xylotex

[Vogavt]

I retro'd an X2 with Ron Steele's cnc kit but I'm not happy with the rapid rates I'm getting from the stock leadscrews on the X & Y axes with newly made acetal nuts.

I've been reading for weeks prior to raising some questions.

I.m currently using the c11 Rev 7.2 that opto-isolates the xylotex 4-axis board. I have the xyoltex 24v board and am using Keling's 425 oz stepper motors.

I get tired of the motors stalling when trying to get rapids higher than 20 or 25 ipm at startup. I can get higher rapids after the screws & lube has warmed up. Sometimes I have gotten up to 50+ ipm but I had no confidence of maintaining that during a run.

What I know is that the G540 can only handle 3amps, my steppers are rated for 2.8 so what would I gain by using a 48v PS that can deliver 12.5 amps?

I haven't pulled the trigger on the purchase because I've also read their are other options out there. From what I've read, it seems like the G540 has been proven easy to hook up (not that others aren't as well).

Do I need to totally remove both the xylotex and the c11? Can I get by using the c11 along with the G540, essentially just replacing the xyoltex with the g540?

Would I be okay just using the 24v PS that I currently have?

Any thoughts/comments would be appreciated as long as they're civil. I'm not here to start a flame war as I seen elsewhere. Opinions are okay, just don't carry it over-the-top please.

[doorknob]

I.m currently using the c11 Rev 7.2 that opto-isolates the xylotex 4-axis board. I have the xyoltex 24v board and am using Keling's 425 oz stepper motors.

I get tired of the motors stalling when trying to get rapids higher than 20 or 25 ipm at startup. I can get higher rapids after the screws & lube has warmed up. Sometimes I have gotten up to 50+ ipm but I had no confidence of maintaining that during a run.

What I know is that the G540 can only handle 3amps, my steppers are rated for 2.8 so what would I gain by using a 48v PS that can deliver 12.5 amps?

The G540 can handle up to 3.5 A, so you should be fine with setting it to deliver 2.8 A. Your motor apparently has 8 wires, and the 2.8 A rating applies when it has been wired with a "bipolar parallel" hookup - are you certain that you have wired it for bipolar parallel and not for bipolar series?

Going from a 24 volt power supply to a 48 volt supply should permit you to increase the motor speed (and have better torque at higher speeds). However there are other factors that can affect the maximum obtainable speed from your motors (such as resonance effects). According to the Keling spec sheet, the motor winding inductance (when wired in the bipolar parallel hookup) is 6.8 mH, which is a relatively high inductance. Using Gecko's formula for choosing the driver voltage to optimize motor speed, it would appear that you would like to use an even higher voltage than 48 volts (perhaps in the neighborhood of 80 volts, which is greater than the G540 is rated to handle). But 24 volts is somewhat low if improved speed is your goal.

I haven't pulled the trigger on the purchase because I've also read their are other options out there. From what I've read, it seems like the G540 has been proven easy to hook up (not that others aren't as well).

Do I need to totally remove both the xylotex and the c11? Can I get by using the c11 along with the G540, essentially just replacing the xyoltex with the g540?

Would I be okay just using the 24v PS that I currently have?

Gecko makes other drives that can handle a higher voltage than the G540.

You will probably not see a big difference in speed if you merely replace the Xylotex with the G540 and continue to use the 24 volt supply, but you should see a speed boost with a G540 run at 48 volts, and a potentially bigger speed boost with a different Gecko drive at a higher voltage.

It may not be a good idea to drive the G540 from the C11. The C11 has optoisolators between the PC's parallel port and its output pins, and the G540 also has an optoisolated interface to the PC. Using two optoisolators inline is probably not good practice - for example, it could slow down or otherwise distort the step pulses, which could possibly result in unreliable operation such as missed steps or other problems.

[danielm]

Hi!!!! same opinion. Once used G540 with 24Volts and no reliable high speed was reach. Lost money changed hardware. If you want high speed you should use ballscrews and servos. I use once steppers for high speed and lost steps when machining hard materials. I have use CNC4PC board, Smooth Steper , DMM-Tech drives, GSK, yaskawa drivers and believe me, servos and much better for high speed. But for no big money, simply change drives and use about 65 volts. Gecko burn like bred when reach 75 volts no matter hw many fans you use

[Vogavt]

I use once steppers for high speed and lost steps when machining hard materials.

Only using for rapids. Tired of moving along at the same feedrate. After all, isn't that what rapids are for? <grin>

But for no big money, simply change drives and use about 65 volts.

So you're saying get the Gecko and opting for a larger power supply should help improve my rapids? That's what I've read as well. I'm not too savvy when it comes to Amps vs Volts. I can read the volts with a multimeter but not sure I have anything that can read Amps reliably.

I don't know if using them all simultaneously requires you to have a power supply that can deliver a cumulative amount of amperage. That's sort of the question here too. Why have a power supply that can deliver 48 volts at 12.5 Amps unless all the amperage is cumulative. Then the next question is, if the G540 can only handle ~3amps, is that per axis?

@doorknob,
Yes definitely Bipolar Parallel.

[doorknob]

The G540 current rating is per winding.

It's OK to have a power supply that is capable of delivering more amps than your motors need (in fact, that is a "conservative" way to design your system).

The amps that your motors will draw will vary, and the only good way that I can think of to easily measure the instantaneous current draw is with an oscilloscope, however you probably do not need to measure the current that is being drawn - the 48 volt power supply current rating that you specified should be more than adequate for a G540 using your motors. Some people use a rule of thumb which is to add up all of the motor current requirements, then use some percentage (say, 60 percent) of that for your power supply max current rating. Gecko has a recommendation - I will look for the reference.

This is from http://www.geckodrive.com/support.html

The easiest factor in choosing a power supply is its current rating, which is based on your motor ratings. A motor control will always draw less than 2/3 of the motor’s rated current when it is parallel (or half-winding) connected and 1/3 of the motor’s rated current when it is series (or full-winding) connected. That is to say, a 6 amp per phase motor will require a 4 amp power supply when wired in parallel and a 2 amp power supply when wired in series. If multiple motors and drives are used, add the current requirements of each to arrive at the total power supply current rating.

[danielm]

Hi!!! stepper always consume amps. so, have to add values of all drives. But! remember: you have motors, so, question is how to have maximum safe power of motors. your Keling's 425 oz stepper comsume 2.8 amps per phase in bipolar parallel and draw 2/3 of if so will be 1.86 amps per phase so 540 can handle it. Votls will be between 16.68 and 83.4 but 540 only supports 50 volts so: if want 540 use a 44 volts and 1000 watts. if want better performance use G201X (dont forget to limit current) and 70 volts and 1500 watts. and USE FANS!!! they will get very hot =). Excellent PS will be found on Antekinc