A little off topic but it related in that I hope to machine parts

A little off topic but it related in that I hope to machine parts for a RepStrap…

I have a 12 year old Sherline CNC Mill and Lathe that use a (now defunct) AhHa controller that put out pulses to the stepper motor controllers for the Mill and Lathe. Have not touched either in a decade; I’m just getting into this by way of recent interest in 3D printing. I would like to replace this controller with something more modern. I’m certainly not the first to attempt this, so I thought I would ask here. I like the idea of the Arduino controllers and the host interface of something like Repetier that we use for 3d Printing.

If anyone has a suggestion of a path to explore or a forum that I should follow, I would appreciate it. Thanks.


Cnczone will be your best resource. The controllers we use can’t handle the high amperage on nema 23 motors, and the control software will be different.

Sherline sells relevant control boxes/electronics. Gecko also does, at quite a price but superb reliability and behavior. My Sherline has a set of linistep drivers, which are at the edge of their ability but at $25/axis were excellent; @James_Newton has info on a THB6064-based board that’s easily capable of driving NEMA23’s for $35/axis. There are a bunch of other options as well.

The THB6064AH corrects the design flaws in those cheap junk 6065 drivers you see on ebay and will /actually/ drive 4 amps at 50 volts (200 watts) into a good sized stepper motor.

Thank you, Stephanie, John. I have a high power box that has the stepper drivers in it. So, it’s really down to the interface and software. Mach3 seems the way to go for CNC machining but the reason I posted here was because I know there is overlap with what 3d printers use and I thought it a good question to ask. I don’t want to hijack this forum for CNS stuff. I appreciate the reminder about cnczone. I look forward to staying involved here as I learn more about the 3d printers so that i can build my repstrap.

by the way, I use linuxcnc instead of mach3 and it’s done a great job for me. Most of the real-time-control equipment for cnc mills is still parallel-port-based, for interfacing purposes.

If you really want to stick with a control solution similar to those for RepRap then the German RepRap Foundation has a high power stepper driver.

I use with quite success an Arduino Mega, with Marlin firmware cabled to Chinese high power drivers (depending your need they have 1.5A, 4.2A or 7.6A).

But if your needs are in the low current (2.5A) a straight DRV8825 Pololu can do it with a RAMPS or Sanguinololu boards. Alternatively GRBL shield or TinyG can be other choices in the low power end.

Of course all of it are USB-based, where you do not need a parallel port on your computer and where I do not know how to make it work (if possible) with Mach3 software (not that you need it though).

As I understand it, Eric already has drivers, he is just looking for the motion control part. If he tries to use the Marlin or other RepRap firmware, he may run into an issue with the step pulse width being too narrow for the drivers. Some drivers need a wider pulse, especially the cheap 6560 drivers which need 20uS min! Merlin puts out about a 2uS pulse if I remember correctly. Just something to keep in mind. I made a little video about it when I was testing the RepRap controller with the THB6064AH driver:

Thanks everyone. Yes, as James pointed out, I have the drivers. I simply (ha!) want to replace the AhHa interface card with something modern and use the existing driver chassis and steppers. The configuration as it stands now has 4 drivers for stepper control, the usual assortment of end stops, a spindle motor speed control and an encoder that provides precise feedback about the spindle speed (used when threading). There are companies that sell interface cards and Mach3 is well respected in DIY CNC controllers as far as I can tell.

My purpose in posting this question here was twofold:

a) I want to get a sense of whether there would be benefit in approaching this project from the 3D printer side (controller/software) - is this area more capable? Or, should I find a suitable CNC controller and use Mach3?

b) I want to learn about any current CNC forums I should get involved in to learn more. (Thanks, Stephanie for the CNCZone tip).

Well, since your goal is to build a 3d printer (right?) purchasing a Mega and trying the RepRap firmware wouldn’t be a waste in the long run. If you can verify that your stepper drivers will work with the shorter pulses, the you should be fine. Or, you can use the Teacup firmware, which appears to generate a much longer step pulse. If you have the datasheet for your drivers you can check in advance. There may be other firmware versions available as well…

But the /sure/ shot to get a CNC machine running is Mach 3 (if you like Windows) or EMC2 (if you like Linux) or, and this is my personal favorite, TurboCNC (if you like DOS). DOS!? WTH? Why TurboCNC? Because it isn’t all about pretty screens and bells and whistles. And it will run on an old 486 which you can get for nothing on FreeCycle or your closet if you are like me! And then if you screw up and short something, you didn’t fry a nice computer. You start with that, get it working, and /then/ if you must have bells and whistles, upgrade the PC and run EMC2 or Mach3.

Thanks, James. I think I will either see if I can get the AhHa card working or a controller and Mach3 combination. My real interest now is to build a RepStrap from some X/Y stages I have to experiment and learn. The CNC Sherline is a way to make parts to get there. As I said, I’ve been out of this arena for over a decade so my first step is to connect with the groups that I can learn from and contribute to. Looks like this Google+ group for 3D and CNCZone for the Sherline will keep me busy reading for a while.

I know the feeling. I’ve been working on my repstrap for a few… um… years (wince) now.

Similarly with my mendelmax, @James_Newton

The Gecko G540 is very popular but it still uses the LPT port.
An RS485 version is planned but doesn’t exist yet.
However there are lots of very good and cheap USB controller cards that are really great.
They do their own pulses, keep a command buffer and have proper optical isolators and isolated 5V. So they don’t slow down or stop when your PC enters a different sleep mode or spind up it’s hard drive like with LPT based controllers.

Yes, that is the motion control part that Eric needs. But keep in mind those USB controllers still need a computer. And if you have a computer, why add the extra cost of the USB card? “Cheap” as far as I have seen, is still in the $50 to 100 range at best. Parallel port cards are $15 if your desktop doesn’t already have one, and that’s why I like using TurboCNC on an old machine; they have parallel ports. Also, the USB motion controller cards are one offs, you can’t update them. On the other hand, if you have limited space, don’t want to make room for another old PC, or you are just really tied to the idea of USB connected devices, then they aren’t that much more, and, as Marcus says, many people are quite happy with them.

Parallel port cards are limited regarding timing and the number of inputs and outputs.
And it doesn’t come with a PWM output to control spindle speed.

One can install two parallel port cards, but it’s rare to need more.

The timing issue is up to the speed of the PC and the software, but I agree the USB motion controllers can (generally) run faster.

PWM spindle control absolutely IS supported by Mach3 at least, and I believe by EMC2 on parallel port pins.
http://www.machsupport.com/docs/Mach3Mill_Install_Config.pdf section 4.6.3

Yeah, you can do it with EMC2: I’m working on implementing it. There’s a PWM generator module in EMC2 that can be assigned to arbitrary pins.

Thank you everyone for the feedback. Much appreciated.