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View Full Version : Controlling 6 stepper motors and 2 spindles on a budget



freddi
14-12-2016, 03:06 PM
We are group of cnc hobbyists and we were wandering what the best and cheapest way is to control 6 stepper motors that will going going at two different speeds. 4 at one speed and 2 at another.

We want to create a double sided multi functional cnc system. 2 steppers on x, 2 steppers on y and 2 steppers on z. Top and bottom for each axes. We also need to figure out a way to adapt spindle control into all of this. There will be two spindles in the z axis as well. It is part of a uni design project as I am a student.

We are considering using an arduino uno with i/C expanders and considered arduino cnc shields and rapberry pi cnc hat boards.

Further from this, as we lack experience in this area, can someone point us in the right direction in terms of generating g code to control the 6 steppers and 2 spindles. If possible, we want all of this to be under one motion controller.

JAZZCNC
14-12-2016, 07:49 PM
Pokeys 57Cnc will do everything you need. Comes with 8 axis and 4 Analog 0-10V for controlling Spindle speed. Got lots of I/O that can be programmed to work in pretty much any way you need.

USB and Ethernet connection.

https://www.poscope.com/product/pokeys57cnc/

To help with G-code will need more information to what your trying to achieve exactly. If you don't want to post this publicly then feel free to contact me via PM and anything told to me will stay strictly between us.

Doddy
14-12-2016, 10:38 PM
freddi - You obviously consider cost a major issue here but don't indicate how cheap you're looking. What Jazz has linked to is undoubtably a solid CNC solution, but if you're looking at cheap, and IF your stepper drive power requirements are limited, then look at the stepstick drivers commonly used for 3d printer type devices, coupled with an Arduino Mega type controller. I wouldn't recommend the suggestion of a Uno/IO Extender - why bother when a Mega would give you the additional I/O required, more flash/RAM and you don't have the faff and latency associated with the extender. Your spindle controller - up to you but you could use the PWM output from the Mega for an analogue drive (use an integrator to get a clean analogue output). Happy to discuss more.

Boyan Silyavski
15-12-2016, 12:40 PM
It all depends what size are the steppers and what speed they will move at. The 3d printing board are super slow / at least to our standard :-) here/ , but if motors are nema17 this way is better as the drives are cheap and plug and play in the board. But "spindle" and "nema17" are not words to be used in one sentence. So What Dean says is much better

freddi
15-12-2016, 04:00 PM
It all depends what size are the steppers and what speed they will move at. The 3d printing board are super slow / at least to our standard :-) here/ , but if motors are nema17 this way is better as the drives are cheap and plug and play in the board. But "spindle" and "nema17" are not words to be used in one sentence. So What Dean says is much better

Our steppers are Nema 34 on the x,y plane and Nema 23 planetary geared motors on the z. We need to achieve 3.14 KW on our spindle. We thought of buying a 3KW spindle but as this is expensive we are thinking of using the gear to adjust the power for a less powerful spindle. Spindle needs a minimum of 1000 rpm, the steppers need 104.7rad/s basically all motors are going at 1000 rpm. Yes, the ardiuno mega should be of use thank you.

freddi
15-12-2016, 04:10 PM
freddi - You obviously consider cost a major issue here but don't indicate how cheap you're looking. What Jazz has linked to is undoubtably a solid CNC solution, but if you're looking at cheap, and IF your stepper drive power requirements are limited, then look at the stepstick drivers commonly used for 3d printer type devices, coupled with an Arduino Mega type controller. I wouldn't recommend the suggestion of a Uno/IO Extender - why bother when a Mega would give you the additional I/O required, more flash/RAM and you don't have the faff and latency associated with the extender. Your spindle controller - up to you but you could use the PWM output from the Mega for an analogue drive (use an integrator to get a clean analogue output). Happy to discuss more.

Yes, that is the issue for us cost is a major problem. 1500 pounds is our budget is buy all components of the machine, I mean it is give or take depending upon our customer and how he feels about that part of the design. The type of power we are looking at for the motors are between like 83 and 330 W roughly. Ok I will do some research into stepper motor drivers, yes arduino mega controller seems perfect for our project, thank you for suggesting it, will it be able to control 6 steppers motors and 2 spindles though?

The spindles need to move in unison so move at the same time. 4 of the steppers need to move at the same speed and then 2 of the steppers at the same different speed.
Also, in terms of the g code, we have been directed towards using grbl, anyone used this kind of software before? Any tips on how to get the best out of it? So in terms of the spindle controller, it can definitely be controlled by the mega arduino?

freddi
15-12-2016, 04:14 PM
Pokeys 57Cnc will do everything you need. Comes with 8 axis and 4 Analog 0-10V for controlling Spindle speed. Got lots of I/O that can be programmed to work in pretty much any way you need.

USB and Ethernet connection.

https://www.poscope.com/product/pokeys57cnc/

To help with G-code will need more information to what your trying to achieve exactly. If you don't want to post this publicly then feel free to contact me via PM and anything told to me will stay strictly between us.

Thank you for your response. very useful, I have had a look at the pokeys57 cnc, it looks very impressive as it will be able to do the 6 axis movement that we need for our machine. I think though that the arduino mega might be able to do a better job in terms of cost though and I have experience with arduino so would be easier for us as a group to integrate it.
I need to perform FSW and ISF double sided.
So for FSW, the tool will go down towards the work piece then across as it is welding. ISF tool will go towards workpiece on both sides then machine a truncated cone similar to the ones in the julian allwood papers, I hope that helps explain my g code issue

JAZZCNC
15-12-2016, 05:53 PM
T
I need to perform FSW and ISF double sided.
So for FSW, the tool will go down towards the work piece then across as it is welding. ISF tool will go towards workpiece on both sides then machine a truncated cone similar to the ones in the julian allwood papers, I hope that helps explain my g code issue

Ok know I get it.!! Very Ambitious with no CNC experience. . . . Hope you have built it strong.?

To be honest I think your going to struggle on few fronts. Budget Firstly but also on Spec and what your trying to achieve from the motors/drives.

You'll never run nema 34 motor with Arduino drive and get any usable speed/torque from them, if can do it at all.? Nema 34 motors require much higher current than most Arduino drives will probably offer but more importantly you'll need high voltage to have any speed and Torque. Again very much doubt Arduino drive will allow much above 50Vdc.
To get 1000Rpm with any torque left from nema34 will require much more than 50Vdc. Much after 900rpm Torque starts dropping quickly with larger motors. So if you want high speeds and torque you need high voltage. Often this means using Mains voltage drives which are expensive.

Similair story with the Nema23 motor and Gearbox. If ratio is anything above 2:1 then you'll never get 1000rpm on the output shaft from stepper motor. Most Nema 23 motors even when run with good amount of volts (60-70V) will struggle to reach 2000rpm and have any usable torque left.
Again to get good speed and Torque you'll need more volts than Arduno drives will allow I think.? . . . . . I'm not into Arduino's but this is industrial strength stuff your getting into and IMO Arduino's are not going to cut it.!

Be careful because your Budget will be gone in blink of eye.!!! . . . . It's most Common mistake in CNC trying to cut corners by doing it on the cheap with toy setup's only to realise after all the money is spent that got it wrong.

Boyan Silyavski
16-12-2016, 07:39 AM
Better use your chance, call Dean and dont do it the American way.

freddi
07-02-2017, 03:37 PM
Thanks guys.

We have chosen the nema 34 motors and they have suitable drivers and power supplies for them in order for them to be safe and suitable. We are still questioning whether to use arduino uno, arduino mega or uno with the stacking of cnc shields.

There are 6 steppers. We want the motors in the z axis to run independently from the motors in x,y axis. We are planning on using Mach3 to do this as we are aware of this software has the ability to perform 6 axis cnc programmes.

The question now is as I have mentioned before we are on a budget, is it best to run the spindles and steppers with an arduino mega or an uno with the stacking of 3 axis cnc shields? Or are there any other micro controllers that you guys are aware of that might be cheaper or more suitable for purpose

Thank you