Controller / Stepper Driver Help Needed

I need to post a write-up in the projects section but I'm in the midst of assembling my first scratch design/built printer. Mechanically it's coming together but I need to figure out what I'm going to do for the controller and/or stepper drivers. I'm a mechanical engineer by profession so the electrical side of things isn't my area of expertise and hence the procrastination...

Some details on the machine that folks likely need to provide feedback:
- I'd classify the design as a hybrid ultimaker/darwin style printer (X and Y can be moved independently and are fixed in Z).
- It's a reasonably large printer with a max print volume of roughly 420mm (W) x 440mm (D) x 550mm (H)
- The current print bed is a 400mm x 400mm aluminum plate with a 1200W 110-120VAC silicone heater that will be driven by a separate 40A solid state relay (that whatever controller I select will need to actuate)
- Steppers for motion in X, Y, and Z as well as the direct drive extruder are Wantai 2.4A(U) 0.9 degrees/step motors (P/N 42BYGHM810)
- Hotend is an E3D with a 24V 40W heating element and 24V fans. The current design has a single hotend but I designed the machine such that I can somewhat easily add a second hotend in the future (notionally to print water soluble support material)
- Power for everything except the heatbed will be provided by a 24V 15A PSU

I've done a lot of googling and I still can't pick a controller. I've been leaning toward the Smoothieboard v1.1 but given I'm using 2.4A steppers I don't think the onboard 2A stepper drivers will work. It looks like I could easily use external stepper drivers with the Smoothie but this is where I'm really, really, out of my element. Please correct any of the following that is incorrect but here's what I think I've learned/concluded:
- To get the most out of the steppers I've selected I need a stepper driver that has a max capability of at least 2.4A and the onboard smoothie drivers won't cut it
- The nice thing about the onboard smoothie drivers is that they are fully configurable in software (like current limits for example) whereas if you use an external driver you may not have the same capability. With that said, I thought I read somewhere that smoothie has an SDI port which I also read is how you communicate with stepper drivers to configure them. Again, this may not make any sense because I'm basically regurgitating pieces of what I've read on the internet (and we all know the internet is never wrong...)
- I've tried to find comparison lists/tables/charts for external stepper drivers and I haven't been able to find much of anything useful. I'm pretty sure i don't understand the difference between a driver and controller as well. Is the driver the chip and the controller is the integrated package that has has the step, direction, and power inputs?
- I want to maximize speed/performance of this printer and would like it to be as quiet as possible. Since I'm using 400 step/rotation motors and will likely want to use some degree of microstepping I've been assuming that the ATMEGA boards aren't going to work for me. This is tough one to explain since it's also dependent upon the linear motion system design but essentially with 1/16 microstepping I'll need the controller/stepper driver to be able to do ~50kHz (50,000 step commands/second) to hit the print speeds I'm trying to hit (and this would increase if smaller microsteps are possible which i would love to do if it will also bring the noise level down). With 1/32 microstepping this number becomes ~100kHz and this is for each axis/motor.

I definitely don't want folks to waste time educating me on topics that have already been discussed but to be entirely honest I haven't found the reprap wikki on these subjects to be super helpful. I'm happy to do the legwork if folks want to pass links/references my way. I guess my basic questions are:
1) Is my first bullet above a correct assumption?
2) Do folks agree that the Smoothieboard makes sense? I also tried to dig into the Duet, Beaglebone, and the Azteeg X5 GT but it felt like the user communities were a lot smaller and there were more mixed reviews on all of these boards. Smoothie had mixed reviews too but it felt like there was more info/users out there in the weeks of on/off google searching I've been doing.
3) Do folks have any specific recommendations for stepper drivers for my particular setup? As I said, I'm not super knowledgeable about electronics with respect to circuit design but I'm competent wiring and soldering things.

Thanks in advance for the help!!!

Edited 1 time(s). Last edit at 11/19/2017 05:46PM by doubleoerik.

1) You are going to want to run your motors at about 80% current max or they will get quite hot. Probably not a problem for the motors, but that heat might/might not be unwanted, especially if printed parts are going to hold them in place. So 2A will do, but then you are running the drivers at their maximum output. Possibly not a problem but it doesn't sound like a sensible plan. Duet boards can drive 2.8A, so you have a little headroom.

2) I'd have a look through the Duet forum and see if the level of support and responsiveness of the development team (who I know well but who I am not commercially linked to) is what I believe it is - very good, probably the best, certainly the most helpful and polite forum with almost no BS whatsoever. I have a re-arm so have dipped my toe into Smoothie, theres a lot there but I was not as impressed by the support side of things, albeit I was using a Panucatt product (who I am afraid to say, make good electronics but don't offer much support or user interaction - myself and a group of others basically figured out how to work the board for ourselves, though we had a few of the early crowdfunded offerings). I have no experience of Beaglebone.

3) The TMC 2660s on the Duet are the best drivers I've used out of A4988s, TMC 2100 (chinese version) and LV8729 (good but 1.5A max).

They are not cheap boards but you are not building a cheap printer. I was quite sure, before using one, that 32bit was a bit unnecessary and expensive. Now I have 2 and would equip my 3rd machine with one if it would fit into it.

Edited 1 time(s). Last edit at 11/19/2017 06:56PM by DjDemonD.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

This was super helpful - thank you!

I poked around for a few more hours last night and I didn't realize that the Duet Wifi (or Ethernet) was actually a new version of the Duet (notionally equivalent to the Smoothieboard v2). I think you've convinced me to try the Duet Wifi board.

Deleted.

Edited 1 time(s). Last edit at 11/20/2017 05:47PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Both boards seem well built and, like every other product in this world, seem to have their following. My goal in reaching out to the community was to try to get some objective feedback based upon my short write up describing my setup. I’m definitely going to have problems getting this thing up and running so my goal is to limit future frustration by minimizing adding complexity to the thing I know the least about (the controller/electronics). Not having to deal with external steppers seems like a huge plus for me. I also posted some questions on the Smoothie forum a number of days ago and I got crickets whereas it seems like there’s a lot of activity/discussion on the Duet forum.

Long story short is I just picked up a Duet Wi-Fi, the PT100 board, and the 7” touchscreen. I’ll be out of town over Thanksgiving but I’m sure you’ll see some posts from me in a week or two when I start trying to get things set up and get in my own way.

Thanks!