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Logthor wrote:

Is it really that significant? Using a 48V PSU vs a 24V psu. Unrelated, but I feel like you may be sponsored by meanwell.


 

No, I can second most of rodw's numbers. I nearly said the same thing earlier and didn't bother, as your original list looked like a good start.

You will get much better speed from your steppers if you power the drives with 48V

The greatest improvement will be that the fast moves between cuts will be faster.

rodw wrote:

1. Doubling the motor voltage almost quadruples available torque
 

No Rod, not always, ONLY at higher RPM, and "higher RPM" for stepper motor hugely depends on size, inertia, inductance...

rodw wrote:

2. Any power supply for CNC can be overrated by about 40% so for 3 or 4 x 2 amp motors a 5 amp power supply is plenty
 

This is OK, but NOT a rule, and it is not overrated, it is underrated.
The only simple general "rule" would be :more voltage = less current, but that does not explain much
There is to much math involved there, together with the above mentioned inductance, etc

rodw wrote:

3, If a drive does not have a max temperature spec, be guided by the temperature the windings start to melt which is typically around 130 deg C but your motors are silent on that too. 80-100 deg C is fine
 

Or simply, if you put your hand on the motor and your skin does not remain attached to the motor, all is good, despite hurting absolutely unbearably to much.
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rodw wrote:

I can't see where you mentioned how many drives you are using. For CNC all motors are almost never running in unison and requiring full current is rarely needed.
 

Stepper motors will draw the maximum current when not turning at all, but most drives have a setting for it to lower current when idle, usually at half the set current.

rodw wrote:

3 motors at 2 amps = 6 amps. 6/1.4 = 4.3 amp power supply required.As I said a 7 amp power supply is probably cheaper.
 

Don't, this implies it is a rule,it is not.
Stick to underrating 40-50% for 24-48V power supplies, 50-70% for 90-130V, roughly. So the lower the voltage = less underrating.

Noted, I kind of like rodw's idea with the separate power supplies.

Given the number of issues I've seen where people have tried to use 5v plugpacks or phone chargers for mesa cards, the extra $10 is a small price to pay for reliability.

I will probably get that device then.

I can't see where you mentioned how many drives you are using.

I'm using three drives

If you follow my advice and run a higher voltage power supply for motors, you need a seperate 24 volt power supply for field power.

Is it really that significant? Using a 48V PSU vs a 24V psu. Unrelated, but I feel like you may be sponsored by meanwell.

Certainly use separate PSU for motor drives vs other electronics. I had overlooked that detail. Most motor drives produce lots of electrical noise which will tend to interfere with the other electronics.

Yes, if you use a capacitor, connect direct to PSU output. A lot of these capacitors have only the -- terminal marked. Make sure you do not connect it backwards. I did by mistake one day, electrolytic capacitors burst when powered backwards. Connect capacitor+ to PSU+ and capacitor-- to PSU--

With your 20A PSU I would not bother, it already contains enough capacitors. Quality Delta and Mean Well PSUs 7A will certainly work. Cheap off-brand knockoffs 7A might work but be plenty small as they are built so light.

I can't see where you mentioned how many drives you are using. For CNC all motors are almost never running in unison and requiring full current is rarely needed. 3 motors at 2 amps = 6 amps. 6/1.4 = 4.3 amp power supply required.As I said a 7 amp power supply is probably cheaper.

If you follow my advice and run a higher voltage power supply for motors, you need a seperate 24 volt power supply for field power. Whilst you could use a buck power supply for 5 volt logic but the power supply I suggested is only about $20. Given the number of issues I've seen where people have tried to use 5v plugpacks or phone chargers for mesa cards, the extra $10 is a small price to pay for reliability.
 

 

I always run 48 volts and sometimes as high as 90 volts but on a small machine I might consider 36 volts depending on manufacturers recommendations. 24 volts leaves too much available torque on the table.
I would prefer you to use seperate power supplies with the 7i96
Meanwell MDR-10-5 for logic (5v)
Meanwell MDR-60-24 for field power (24v) MDR-40-24 is Ok too.
Meanwell NDR-240-48 (48 volts) for motors but a LRS-350-48 (7 amps) might be cheaper and is a popular choice.

I can spend that much but I feel like I'm already splurging with this card. I also feel that the NDR-240-48 might be tool little current. Just curious but why should I swap to a separate power supply for the 7i96.

I like the idea of using a capacitor. I would just put that capacitor in parallel between the positive and negative terminals and add a bleeder resistor also in parallel also between the two terminals, correct? And this would protect my PSU and stepper drivers?

I think your cheaper ball screws would be OK Look at your motor torque allow for any gearboxes. Convert 1700 kgf to Newtons = 17000 N = approx 17 kN so I doubt your motors will get anywhere near that!

In Europe A Beckhoff EK1100 with EL1008 and EL2008 is supported natively by Linuxcnc for you inputs and outputs. You can also add a encoder input (EL5151 from memory) if you wish.Check eBay too but get a price first.

If you can't add the encoder don't worry about it, just use thread milling to cut any threads you need. Its a lot easier on the machine. Because there are metric coarse and fine threads, you don't need that many thread mills initially. eg 12x1.25, 10x1.25, 8 x 1.25 can all be cut with the one thread mill.

Initially home your machine using Linuxcnc and convert to internal homing down the track as it might not be that easy.

and yes, get CIA402 compatible drives as life will be easier.

So much advice already but a coupe of pointers including from some gecko docs I read years ago.
1. Doubling the motor voltage almost quadruples available torque
2. Any power supply for CNC can be overrated by about 40% so for 3 or 4 x 2 amp motors a 5 amp power supply is plenty
3, If a drive does not have a max temperature spec, be guided by the temperature the windings start to melt which is typically around 130 deg C but your motors are silent on that too. 80-100 deg C is fine

I always run 48 volts and sometimes as high as 90 volts but on a small machine I might consider 36 volts depending on manufacturers recommendations. 24 volts leaves too much available torque on the table.
I would prefer you to use seperate power supplies with the 7i96
Meanwell MDR-10-5 for logic (5v)
Meanwell MDR-60-24 for field power (24v) MDR-40-24 is Ok too.
Meanwell NDR-240-48 (48 volts) for motors but a LRS-350-48 (7 amps) might be cheaper and is a popular choice.
 

TL431 was/is some type of low current voltage regulator of reference or ... been over 30 years, so it can not send anything to big resistors.
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Start over:
-get some cheap drives, the so called "TB6600" that do not use the TB6600 chip are very good as they are the cheapest boxed drives, i have probably over 40 in daily use
-Get a MeanWell or Delta power supply, 24V (no, not 36V nor 48V) and 200W or 8.something amps, it is more than enough for 4 or 5 or 6 drives at full current of 3.5A (they are rated at 4.5 or 5A online), never mind the math for now.
-get a used PC with parallel port, or buy an add on parallel port
-wire the drives to the PC, with no BOB (your choice, i never use them)
-start making chips.
Oh cr@p, i just went back and :
-forget the parallel port
-those drives are fine, i have them for over two years.

Logthor wrote:

Are you sure it is 4 amps per motor?

 

4 amps per motor... I was thinking worst case. In practice you won't hit that.

A TL431 Precision Programmable Reference by itself won't handle the current. It will need some form of power transistor to handle the current. My little home-built cnc mill I had for a while had simply a cheap switching PSU powering 3 stepper drives with no additional protections. If a person had to add something I would connect  a 35V 10,000 uF capacitor to the DC bus. This adds cushion to even out short duration voltage spikes from decelerating motors.

Issue 0 = Siqa transport or something like that on Instagram
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Reply 1 = i have some old industrial ballscrews that you can have for very little money, and you can come see them in person in Peja.
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Reply 2 = yes and no, drives should be CIA 402 compatible to work, but not all implementations work as advertised, and some non CIA 402 work just fine
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Reply 3 = I have plenty of experience with Mesa and i can help you with that, free of charge whenever i have time
-3.1 = Mesa has a dealer in Germany, www.welectron.com
-3.2 = Mesa 7i96S with 7i73 OR 7i84. 7i73 is for panels and low level signals, 7i84 is an IO card with 32 inputs and 16 outputs, all from 8-32 or 36V (i forgot). I used 7i84 on my lathe for panel despite having 2 of 7i73 back then.
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Reply 4 = probably, but modbus is not used for anything real time, as far as i know. The new drives have encoder outputs. usually, that can be used to close the loop in LinuxCNC, but this is something you have to decide later, after figuring out ther balscrew/leadscrew situation, or just get linear scales, in your case a much better solution no matter what drives you use. This will also require a Mesa 7i85 for the encoder inputs.
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Reply 5 = depends if you want to also tap, but i would for sure.

How many stepper drives? If 3, then we're looking at 4 amps per motor * 3 = 12 amps total. Your stepper drives will draw less than that. Now, cheap PSUs tend to be overly optimistic with their current rating. I think your PSUs are easily sized double what these specs require. Which I think is a good plan. Go for it. I would buy that.
 
Are you sure it is 4 amps per motor? I thought that at most it'll draw 2 amps between the two windings (2.8 amps if it is peak). Sounds like a plan regardless. I was thinking I might just use a TL431 on the main bus and have it send all back voltage to a large resistor.

Logthor wrote:

So based upon what I'm using you don't think I need to swap out for a different PSU that has said protections?
 

How many stepper drives? If 3, then we're looking at 4 amps per motor * 3 = 12 amps total. Your stepper drives will draw less than that. Now, cheap PSUs tend to be overly optimistic with their current rating. I think your PSUs are easily sized double what these specs require. Which I think is a good plan. Go for it. I would buy that.

Your twisted pair cable looks great. I was just coming back with a suggestion 18 Gauge 4 Conductor Shielded when I noticed your post.