[ryghar]

Hi,

Iam building a CNC based on openbuilds design. I have 4 wantai 57BYGH633 motors with DQ542MA drivers.
The CNC will have 1000mm x 500mm with two motors on Y. Belt driven and leaded Z.
I have so many questions... Can you help me with some of them?

1- I though that six wire motors has to be connected without the center tap (taped off). But researching i´ve seen that many configurations ar available. Half-coil hookup, full coil, etc.
Wich are the pros and cons? I will use the CNC for milling. Recomendations?
2- Drivers configuration related to current. Do I need to limit the current? Iam totally lost here...
3- Power supply. Switching power supply 24v? The motors say 3A, 15A is enought?
4- Anyone have a wiring diagram of this stuff? I will connect this to mach3
5- The PC needs some special requeriments about clock speed or something like that?

Thanks!!!

[he1957]

Welcome!

What do you want to mill (wood, metal, plastic, stone)?
What sizes are your workpieces?
Hobby or other?

Might be worth searching and reading various build posts on this forum to get some background. You will need to identify what sort of accuracy you want to achieve and decide how much budget you have. Add the cost of tooling to your budget as well. Machines can be built from different materials including various woods, metals (aluminium, steel) and combinations. Materials have their different properties, strengths and weaknesses.

These and other factors might determine if what you have is suitable for your needs.

Determining what is right for you goes back to what you want to do, how much precision, performance and other factors including cost.

When you know what you want to do you will be in a better position to ask for assistance.

[ryghar]

Thanks for your reply.
I allready have a cnc at shop and some basic experience using it. The budget is set, I know what to buy and have the plans to do it.
My concerns are in how to setup the motors and driver as you can see.
I will cut wood and maybe not fe metals. I plan to set accuracy to 0.05mm, velocity is more important than accuracy for my. Mill woods at 0.05mm its ok. I cant measure smaller distances anyway xD
So, 1/4 microstep with GT3 and 20 teeth pulley will be the mechanical setup to run at 5000mm/min.
But half coil, full coil? current limit? All the questions in the first post are not aswered with plans or budget. If someone with experience can guide me with the specific components that I arready have, i really apreciate. Im learning a lot in the way but i dont want to broke something or end with a low performance machine for some error.
My english is limited and general information in some cases id difficult to apply to specific needs.

Thnks!!

[ryghar]

Sorry, one more questiona. The motor works and 3v. Do I need to setup something to this?
The motor is 3A. That is RMS or Peak?

Thanks for your patience

[joeavaerage]

Hi,
1) with six wire motors you can wire them in a number of combinations. The most usual is 'parallel bipolar' as that results in the higest
torque, but also requires the greatest current. Trust me, you will want the greatest torque and the highest speed those motors can produce.

2)Most drivers allow you to adjust the maximum output current. You risk overheating your motors badly if you exceed their rated current. Conversly
they will run cooler with less current at somewhat less torque. In the first instance set your drivers to the rated current of the motor.

3)You want the highest voltage the drivers can withstand. High voltage allows the steppers to run fast without losing steps.
Switch mode supplies have become the norm because they are cheaper in high power situations. Torodial transformer type supplies are bigger,
heavier and usually more expensive but are more robust and forgiving. Just add up all the motor currents and that is the max you will need.
It unlikely that all your motors will draw max current at once so 1/2 to 3/4 would be a compromise that could save you some money.
Thus 3 motor at 3.5A 3 x3.5 =10.5A max, so a supply of 5-7.5A would be adequate, more would be better....

4)There are wiring diagrams and wiring diagrams, no one diagram will apply to all situations. YOU are the machine builder, that's YOUR job.
There may well be material that you can copy or adapt to your installation but ultimately its for you to decide.

5)For a new machine I would use Mach4 instead however you will effectively be required to use an external motion controller (with or without
a breakout board depending on the controller), and you should allow $120- $250 or so for that. Mach3 can be run without an external motion
controller, and hence save you some dollars, but Machs parallel port can be problematic.

The PC to run a parallel port MUST be 32 bit Windows7 or earlier, Windows XP is popular. The PC will require at least one built in parallel port
or a slot to put a PCI card and not all PCI to parallel port cards work. Laptops don't do well, desktops are required. The PC should have absolutely
no other software loaded and even more importantly, running, or Machs parallel port driver will starve of CPU service, it will stutter and/or stall
and wreck your job.

When I started I used Mach3 and a parallel port, and then added a second port with a PCI card. I used that combination for a couple of years
and mostly it worked really well, and of course is cheap! Then I bought an Ethernet SmoothStepper (one of the more respected external motion
controller brands) and it was better, much better again.

One of the advantages of an external motion controller like the Ethernet Smoothstepper is that you can use just about any PC you like,
32 OR 64 bit, Windows 7 OR 8 OR 10, XP, laptop OR desktop. Another advantage is the external motion controllers have much higher pulse rates which
are particularly useful for high resolution encoders increasingly encountered by hobbyists.

All up I would recommend an external motion controller despite the cost. Don't buy Chinese junk, its cheap but it doesn't work properly
and they wont help you to get it going. Suddenly it doesn't seem so cheap when you face having to throw it in the bin......hey it cost only
$20.....but its rubbish...you have wasted your $20.

Craig

[OlfCNC]

Suddenly it doesn't seem so cheap when you face having to throw it in the bin......hey it cost only
$20.....but its rubbish...you have wasted your $20.

This is what always surprises me that most people don't realise this and they really thinking like that.

[ryghar]

joeavaerage , I cant thank you enought for the time you spend in that answer. Invaluable for me.
By "parallel bipolar" you mean connect the coil start and middle tap or the start and end taps and leave the center taped? It has more sense to me use the full coils but most information i got said that use start and middle taps for heating issues. The motors with 4 cables has the same coils or half of 6 cables motors? (I cant get 4 cables motors to avoid this problem but if the coils are equal, I dont see the problem in leave the center tap taped)
Iam the machine builder, Lol, you right. I only wish to be more skilled on this. Im just a java programmer but this stuff blow my head off. I start a project building wood sunglasses, buyed a cnc and now i want one in home and learn more and do some luthier stuff (i make guitars for fun by hand).

Its the first time someone mention a Ethernet SmoothStepper or external controller. I have an arduino one running with printer steppers just for reserach after start making a realone and spend some money. The gcode are interpreted by the external controller or the mach4? I will read more of this, sound interesting.

The motors datasheet specified 3v. Do I need to setup something to this?

Thanks, thanks a lot!!!

[joeavaerage]

Hi,

By "parallel bipolar" you mean connect the coil start and middle tap or the start and end taps and leave the center taped?

Apologies for my poor use of terminology, bipolar parallel is applicable to 8 wire motors, not 6. You are correct, you will achieve maximum torque
(for a given current) by using the complete winds of the coil, that is each end tap and leave the center tap isolated.

The motors datasheet specified 3v. Do I need to setup something to this?

No. What this specification says that if you hooked 3V to one coil then after a short time the current would build up to its rated current. This is in actual
fact just the resistance of the coil.

The stepper driver will apply a great deal more voltage, more like 48V and up to 80V if you get some capable drivers. The high voltage causes the current to increase
quickly. Once the current reaches its rated level, or whatever you set the driver to, the driver will turn the supply on and off to limit the current, the effective average
voltage will be 3V.

Craig

[109jb]

Using half coil (center tap and one end), you will have 1/4 the inductance of full coil, the torque will be (full coil torque/1.414), and the max current will be (full coil current * 1.414)

[ryghar]

Thank you so much guys!!
Last two xD.
1- In other thread i saw that 48v can be "too much" to half coil. Is that true? If I undertand you correctly, as much voltage the better an the driver will limit accordingly.
2- The datasheet of these motor in some sites indicates "4 phase motor" other "2 phase". The current indicates 3A/phase. These 3A are for the full coil or half coil? If I set to full coil i need to config the driver to 3A and for half coil 3*1.414= 4.2A?

Thank you Craig, jb, outstanding.

[joeavaerage]

Hi,

In other thread i saw that 48v can be "too much" to half coil. Is that true? If I undertand you correctly, as much voltage the better an the driver will limit accordingly.

No, 48V is not too much, it maybe enough for the speed you wish to drive your motors but its not too much. The driver limits the current so it doesn't really matter what voltage
the supply is the driver will limit the current anyway.

I use Vexta 5 phase steppers and matching Vexta drivers. The driver doesn't require a power supply, you wire it direct to the 230VAC supply. The voltage it applies
to the motors is a little over 150VDC! It sure make the motor sit up and take notice!

The datasheet of these motor in some sites indicates "4 phase motor" other "2 phase".

I think that refers to the wiring combination that has 8 wires, that is four coils. Two coils on in the same magnetic limb. Your 6 wire motor has identical coils just that
the two coils are joined together already at the center tap.

The current indicates 3A/phase. These 3A are for the full coil or half coil? If I set to full coil i need to config the driver to 3A and for half coil 3*1.414= 4.2A?

I suspect that specification refers to the maximum current in any one coil. So 3A through two coils in series. If you powered just one coil I think it prudent not to go above
3A because it will overheat, Admittedly the other coil on the same limb wont be getting hot because it has no current in it and overall the motor will be a bit cooler but to force
more through one coil may be asking for trouble.

Even at 3A you may find the steppers getting very hot.

As an example my Vexta 5 phase steppers are rated to 1.4A per phase. They go really well but get hotter than I like and so I have them dialed back to 1A per
phase. No doubt I lose a little torque but I can still run them to 2400 rpm without losing steps and staying under 50⁰C. The steppers are mated to 10:1
low lash (<2 arc min) planetary gearboxes so the thrust they can exert on an axis is is over 4500N (450kg force), plenty!!!

Craig

[ryghar]

Thank you Craig!

[reg.miller]

I use the same Wantai motors on 5mm pitch ball screws. They are quite good as far as chinese motors go. Quite low inductance.

You will only get 3A into them are rather low speeds. As soon as pulse speeds get up the inductance stops the current changing and it never gets anywhere near 3A.

I use a stack of STM IHM03A1 "PowerStep" demo boards. ( A little tweeking needed to daisychain 4 motors drivers, since like you I have double drive on one axis ).

Looking at the waveform on a scope it no longer even looks like a square pulse by 3200 mm/min . There is a typical midrange resonance at about half that where phase current and hence torque is very low. That's the downside of stepper motors.

I have tried up 60V using a lead acid batteries, it does not go much faster since waveforms are distorted. They are quite torquey: on a 5mm thread I got about 120kg of linear force at moderate speeds.

Centre wires are isolated as discussed above.

You may want to look at using a 10mm toothed belt to keep the dual drives in sync during power off. Otherwise you may go off square with the gantry.