[COMachineist]

Hi All
Happy Holidays to all.
I am installing a 1200 oz/in stepper and a KL-8070D driver on the Z axis of my G0704. I have a KL 48 vdc 12 amp supply for the KL5056/ 570oz/in X&Y. Do I need to step up to and add the 72vdc supply? Also should I be using a toroidal or switcher supply? The reason is, I'm going to a 3ph 1.50 hp motor and a nonvectored VFD drive which is much heavier than the 600 watt, or tread mill motor belt drive I have now. I also plan to add a Hoss style PDB. I may also add a 20000 rpm 2nd piggyback spindle for 3D engraving at some point.
Thanks for any info.
CH

[dick cnc]

I personally would in fact I think I may go a little large on the amperage and then maybe eventually change the X and Y drivers to something that would take 70 V. On the 1200 ounce inch I would also not go to the Max current for the motor set the driver at a lower current the what is stated for the motor. You motor will run more reliable and cooler. And because of the size of the motor you should have plenty of torque

[COMachineist]

Hi dick cnc
Thanks for the reply. I kind of thought the same thing. I read some place that by using lower voltage and current would cut down on noise. I think I'll get go with an unregulated Toroidal supply which should be good to go at 72vdc and 7.5 amp.
Thanks
CH

[SCzEngrgGroup]

Picking a voltage at random is unlikely to yield best performance. Higher is NOT always better, and can easily result in excessive motor heating. There is no advantage to using a supply that is larger than 70% of the peak rated current for the motors it will be supplying. To correctly determine optimal voltage, you need to know the inductance of the specific motor. The ideal voltage will be 32X the square root of the motor inductance, in mH. If the motor is rated at 6A, then a 5A supply is more than adequate, and a larger supply will gain absolutely nothing. A 1200 oz-in motor is likely to be relatively high inductance which means it will have limited high-speed capability. That may, or may not, matter, depending on the application.

Regards,
Ray L.

[dick cnc]

Hi dick cnc
Thanks for the reply. I kind of thought the same thing. I read some place that by using lower voltage and current would cut down on noise. I think I'll get go with an unregulated Toroidal supply which should be good to go at 72vdc and 7.5 amp.
Thanks
CH

I have been using steppers on various machines for the last 30 years. It seems that the calculations of inductance to get voltage will get you close but I found if I always go high on the voltage. Cut back on the amperage by limiting it on the driver I get much better results. When you get your driver motor and power supply. Test it out yourself you can start off at a fairly high amperage and you'll notice motor heat even when At idle. Cut the motor amperage as much as 50% and do some tests. You will see how much cooler and quieter the motor will run. Don't be afraid to go even lower on the amperage. Use the current limiting dip switches on the driver as if it was part of the tuning. Make sure no power is applied when changing or moving dip switches. The reason I suggested higher amperage was to use the same power supply for the other two motors if in the future you wanted to change out the existing drivers to higher voltage models

[hoss2006]

When you don't give the stepper the amperage it is rated for you decrease the torque output.
Run the 1200 oz/in stepper rated at 6 amps at 50% and you only get 600 oz/in from it.
The stepper voltage calc from gecko is to get the best performance from the motor, any more voltage and it is just wasted as heat.
Your suggestions are bassackwards from what is best.

COM, I imagine you are getting one of the 1200 oz/in steppers from automation tech so they are rated for 6 amps and the recommended voltage would be 78-80 volts depending on which of the 4 they have.
A 72 volt supply will give you good results and the 7.5 amp supply you mentioned will be plenty.
The 570's you have on the x and y are the best for performance and the supply you have for them and the 5056 are the best match.
Trying to put on 70 volt steppers to have them all on the same supply doesn't make much sense either.
Hoss

[COMachineist]

Hi All
The motor is the KL-34H2120-42-8A 8 lead. It will be run Bipolar(parallel) Connection. In this Config the inductance is listed at 6.5 mH nominal. It could be higher or lower than that, but figure for average. I plan to use Auto Idle current. I'm of the mind set "better to have and not need, than to need and not have". The driver is the KL-8070D which spec's at 20vdc min and 80vdc max and is programmable .5-7 Amps. If I use an unregulated supply I can reduce the needed current rating to about 70% of the motor. If I use a switcher then I will need about 1.5X in the Bipolar config to avoid current clamp. I want to have good high speed performance if need for 3D ops.
Yes you are 100% correct Hoss that is exactly the motor and driver I have. By the way that was a typo on the lower voltage and current, I think I meant to say Higher Voltage and lower current. Does anyone see a problem using a toroidal unregulated supply in the same controller cab as the rest of the electronics, if properly shielded and grounded?
dick, that is what I thought also high voltage and low/medium current for 90% of the operations. That would cut down on heat of both the driver and motor and increase longevity I hope. I will order the 72vdc unregulated supply today.
Thank all, and Merry Christmas.
CH

[LongRat]

I'd be interested to see how this pans out. A 1200 oz.in motor for your z axis is very big, is this common on this machine? I run a 450 oz.in stepper on my WMD30 which has a huge head casting compared with the G0704 and I also run a large 1.5 HP 3ph motor on the head. I've never stalled the z once and have never felt lacking in speed or acceleration. Running a 5mm pitch 25mm diameter ballscrew, and a low voltage system in comparison - 39V DC @ 6A. My motors have quite low inductance but I have forgotten the number.

[SCzEngrgGroup]

You'd likely get better overall performance with a smaller motor,with lower inductance. If you really want to optimize performance, you need to measure what the actual torque requirement is, decide what performance you want, calculate the motor requirements, and find a motor with the right combination of torque characteristics and inductance to achieve the goal. With stepper motors, larger is very often NOT better, as most larger motors are designed for high torque at low speed, and torque will fall off much more quickly with RPM than is the case for smaller motors. As an example, the motor you're considering will never reach full current at step rates above about 2K steps/sec., which is only 600 RPM, or 120 IPM assuming a 5-pitch screw.

Personally, I can't imagine a 1200 oz-in motor being desirable, much less optimal, for a G0704. You don't even see motors that large on most Bridgeport conversions.

Regards,
Ray L.

[hoss2006]

Hi All
The motor is the KL-34H2120-42-8A 8 lead. It will be run Bipolar(parallel) Connection. In this Config the inductance is listed at 6.5 mH nominal. It could be higher or lower than that, but figure for average. I plan to use Auto Idle current. I'm of the mind set "better to have and not need, than to need and not have". The driver is the KL-8070D which spec's at 20vdc min and 80vdc max and is programmable .5-7 Amps. If I use an unregulated supply I can reduce the needed current rating to about 70% of the motor. If I use a switcher then I will need about 1.5X in the Bipolar config to avoid current clamp. I want to have good high speed performance if need for 3D ops.
Yes you are 100% correct Hoss that is exactly the motor and driver I have. By the way that was a typo on the lower voltage and current, I think I meant to say Higher Voltage and lower current. Does anyone see a problem using a toroidal unregulated supply in the same controller cab as the rest of the electronics, if properly shielded and grounded?
dick, that is what I thought also high voltage and low/medium current for 90% of the operations. That would cut down on heat of both the driver and motor and increase longevity I hope. I will order the 72vdc unregulated supply today.
Thank all, and Merry Christmas.
CH

A 1200 oz/in is not one of the recommended motors on my electronics page, the largest I have is a 906 oz/in nema 34 which has a recommended voltage of 58 volts.
This works well with the same 48v power supply as the 570's and used with the 5056 driver the reduction in current still gives 742 0z/in, plenty of torque.
Just as an fyi, I still have a 570 stepper on the Z plus the weight of the bigger spindle motor, belt drive, power drawbar, air cylinder and the heavy 5th axis attachment, performance is still quite good.
Make sure switch 4 on the 5056 is off for half idle current and the motors stay cool.
Hoss

[dick cnc]

Hi dick cnc
Thanks for the reply. I kind of thought the same thing. I read some place that by using lower voltage and current would cut down on noise. I think I'll get go with an unregulated Toroidal supply which should be good to go at 72vdc and 7.5 amp.
Thanks
CH

The other people that recently posted are very knowledgeable and experienced. I am just working from experience. It always seemed to me if you went with exactly what was supposed to be for driver and power supply for any torque rated stepper motor. They ran hot noisy and drop torque drastically at higher RPM but if you ran higher voltage larger torque motor and limited the amperage which does reduce torque they ran quiet cool reliably when I say reliably I mean for years in industrial situations plus the torque curve didn't drop off anywhere near like it did with the so-called matched or correct power supply and drivers. Here's a picture of a 4' x 4' router I made where I used to work used it almost every day direct drive .200 lead 960 ounce motors there is only one motor per axis. I used to cut and 90 inches a minute with 160 inch Rapids the Z on this is not what I'm comparing to yours but the gantry itself is quite heavy now granted it's not moving vertically but as far as acceleration and deceleration works quite well I started off with a smaller voltage power supply I would be lucky to get 100 inches per minute rapid then I increased the voltage and lowered the amperage. This is not the only example I have done it many many times with good results I think working with steppers is kind of a black art

[SCzEngrgGroup]

...if you ran higher voltage larger torque motor and limited the amperage which does reduce torque they ran quiet cool reliably when I say reliably I mean for years in industrial situations plus the torque curve didn't drop off anywhere near like it did with the so-called matched or correct power supply and drivers.

That is true only if you've found a way to violate the laws of physics. Torque is directly proportional to current. It is physically impossible to simultaneously reduce current and increase torque. Under any given operating conditions, if you reduce current by 20%, you will also reduce torque by 20%. Reducing supply voltage will also reduce average motor current, due to the motor inductance. The higher the RPM, the greater this effect, so reduced voltage will reduce torque across the board, but particularly ay higher speeds. High inductance motors suffer from poor high-speed performance specifically because the average current falls off due to the long coil charge time caused by the winding inductance.

The reduced noise is a direct result of the reduced torque. The noise comes from the step characteristic of position changes in a stepper motor. Reduce current, and you reduce torque, which reduces the amplitude of the torque pulses, this reducing the vibrations which are the source of the noise. Again, you don't reduce noise, without also reducing torque.

Also, stepper motors are designed to withstand heat. Heat is a fact of life for stepper motors, and as long as temperature is kept within the motors ratings (which typically allow continuous operation at up to 85C case temperature), motor life will not be an issue. Certainly, on a hobby machine, worrying about motor life is a little silly, as it will die of old age LONG before it succumbs to any heat-related failure.

For all practical purposes, you are paying good money for larger, more powerful motors, then crippling them by running the, below their rated voltage and current, which reduces their performance to that of a much smaller motor. It simply makes no sense. You might as well buy an 8-cylinder car, then remove two spark plugs. Buy the right size motors, drive them to spec, and you'll get a better overall result.

Regards,
Ray L.

[dick cnc]

Obviously you're very qualified I'm sure you have a degree all I'm stating is from my experience. I personally don't know the reason why it works could be resonant frequency or the lack of could be feedback voltage don't know I've worked with designed packages from Parker Compu motor and other companies that match drivers motors and supplies. And gone back and increased voltage to cure many different problems. And you're right the laws of physics says you don't get any more than what you put in in fact you get less because of friction

[dick cnc]

[QUOTE=COMachineist;1397488]Hi dick cnc
Thanks for the reply. I kind of thought the same thing. I read some place that by using lower voltage and current would cut down on noise. I think I'll get go with an unregulated Toroidal supply which should be good to go at 72vdc and 7.5 amp.
Thanks
CH[/QUOTE I don't mean to belittle the other people that post by any means they are very intelligent this is America and you are free to make any choice you like for your equipment

[691175002]

I would personally go to a 570 motor with 2:1 reduction, as opposed to putting a monstrous 1200oz/in stepper on the Z axis.

I wouldn't necessarily plan on two spindle motors + PDB on the Z axis, especially not if you have a spacer behind the head. After a point you start running into problems with screw windup and flex in the bearing mounts because it just takes so much force to move the head.

[COMachineist]

Hi All
There is a lot of info here to think about. I already have everything but the supply which is what I asked about to begin with. You see when I ordered my kit from Automation Tech in April of this year they did not have any 906 oz/in motors and would not for several months. So they substituted the 1200 oz/in motor driver for the 906 oz and a 8070D driver so I have been running it with the KL-600-48 supply that came with the kit. When I start to add the PDB and the 3ph motor and the other things as a final setup. I was thinking of using the 72vdc supply, recommended for this motor/driver. I have Bill's fine mill mounts and Preloaded AC bearings. I'm not using any column or head spacers as I don't need them for now any way. When I take my Z06 Vet out for a drive I rarely even drive the speed limit, but when I need the 572 hp it is there and is kinda fun. The thing is I don't need the Z06, but I have it and so I drive it at my leisure. I have the 1200 and 8070D and paid only for the 906oz. So I'm going to add the 72vdc supply and limit the I to 70% of rated motor current. I have not wasted any money at all. I got more than I paid for, which was Hoss's Heavy Duty Digital recommendation. At 6 cents KW hour for my coop power, it want brake the bank on power.
Thanks for all your input and Happy Holidays.
CH

[migrusch]

Just an important note on safety for stepper power supplies.

When dealing with DC power supply, generally we can be quite indifferent to safety, certainly compared to mains AC supply.
The reason is that the lower voltages generally used cannot provide the required current in a human body to have ill effects.
Also, some people seem to think DC is 'intrinsically' safe.

However, in general, the accepted safe upper limit is considered in the 50 to 60VDC range. This is why many laboratory power supplies top out around this number.
After this the supply 'could' provide sufficient current to harm someone.

Some of the high stepper supplies could pose a risk, certainly when we start talking 75V or more.
For this reason, people should treat these supplies in the same way as the AC connected to spindle motors etc.

Remember, It is the current passing through your body that harms. And it is the voltage which creates the current (drives the current through the body's resistance)

[COMachineist]

Thank for the safety reminder. It is wise to always practice safety first, no matter what the voltage or current is.
Thank you
CH

[CNC-Joe]

Ray, et al,

Does anyone have a spreadsheet or something that would have all of the power supply, stepper motor, drive card data in it - to crank the equations and tell us novices things like - what voltage of power supply to use? , what amperate rating? etc ?
Seems like there are equations here and there.. but nothing that is pulled together in one place in an easy to use application or spreadsheet.

[hoss2006]

What's the point, folks like me make pages that give recommendations based on the tried and tested equations from Gecko Drive only to have others with "experience" that just wing it and give their own recommendations.
Hoss