Reprap electronics to drive a CNC Mill?

I am considering buying a manual bench-top mill that I can convert to CNC eventually. It will use NEMA 23 motors for the axes, and I was curious as to weather the Reprap electronics would be capable of handling this application? The manufacturer's CNC controller costs $800 alone and uses a parallel cable, so if I can save money (perhaps even more if i learn to SMT solder) that would be great.

... controlling and electronics are the same, you only have to select the stepper drivers accordingly ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

Thank you for your information, the Makerbot stepper controller claims to support NEMA-23 motors, should that be true of other RepRap drivers (i.e. BotMill)? Also, do you think the mill would require significantly more current to cut metal vs. a 3D printer application? I will admit this is all new to me so please be patient as i wrap my head around this fascinating concept. I have wanted to get into CNC machining for over 10 years but it has always been cost prohibitive, now this comes along at the same time that I am going to school to get an engineering degree it just seems perfect.

I think you'll be fine if you can find suitable stepper drivers.. the reprap ones are only good to about 2A and I don't know what the max voltage is- maybe 30v or so? No idea if that's enough for bigger motors on a CNC mill. The mainboard will be perfectly capable of generating suitable signals as long as the drivers you choose accept step/dir 5v logic inputs.

While metal does take more force to cut than extruding, reprap drives its heads directly on all but the Z axis whereas a CNC mill usually has threaded rod or similar, so you'll just have to check out common ratings for your NEMA 23 motors vs what you need. sites like cnczone may help you decide what your requirements are.

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Wooden Mendel
Teacup Firmware

Hi

I have tried this. The stepper motor drives are not up to driving anything other than a very small mill. In the end I bought Chinese 4 amp micro stepping drives from here :- [www.arceurotrade.co.uk]. and built a 40 volt power supply. Secondly none of the firmware I tried had suitable acceleration and deceleration to suit the inertia you get with a heavy table and screw drives. This may have changed in later firmware but I don't think so. In the end I went with EMC2 which is free running under linux. You can control a mill with little more than this, the stepper drives and power supply.

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Regards

Ian

Quote

Secondly none of the firmware I tried had suitable acceleration and deceleration to suit the inertia you get with a heavy table and screw drives.

FiveD on Arduino has acceleration ramping implemented, but you currently have to apply the patch from the Wiki page. There's a config variable allowing to set how steep these ramps are (very lazy acceleration to almost instant speed).

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

This is the mill I am looking at: Sherline 5000/5100. The NEMA 23 motors they provide with their CNC packages are rated at 2A so perhaps the Reprap drivers with some cooling would be enough? My goal is to keep my costs down as much as possible and do as much of the assembly myself as I can. EMC2 is what Sherline uses for their packages so that is a good option, are you saying that with those drivers i wouldn't need the mainboard? Also do you think this setup would have the speed to do 3D printing if I replaced the cutting head with a Plastruder?

EDIT: Also, would the control channel normally reserved for the extruder controller be able to drive a stepper motor as well? this is not crucial but it would be handy if i ever get a rotary table.

Edited 1 time(s). Last edit at 08/28/2010 11:53AM by TbirdMan.

Hi

I have used an extruder bolted on my CNC mill. It did work but was pretty slow. I managed to get up to 300mm a minute where Mendel runs at 3000mm a minute. So build were 10 times slower. I also had quality issues so I have finally after 2 years playing with a CNC Repstrap started to build a Mendel.

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Regards

Ian

That is what i figured, i will probably use the mill to manufacture the parts for a Mendel out of a suitable material. for machining slow is usually better and from what i can deduce 3d printing requires more speed. perhaps i can setup my electronics package to be able to transfer from one device to the other? Maybe just two mobos and use the rest interchangeably.

Hi

The price of the Pololu stepper drives and electronics is pretty low.
[reprap.org]
My guess is you may find it is not worth the hassle of switching electronics.

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Regards

Ian

that is true, however i also am interested in learning some electronics and how to SMT solder. this is a learning experience for me as much as just trying to get a CNC mill going.

That is what i figured, i will probably use the mill to manufacture the parts for a Mendel out of a suitable material. f

TbirdMan, Mendel is sort of a cult object; if you have the tooling I'd suggest doing up a
http://reprap.org/wiki/WolfStrap-English
or
http://reprap.org/wiki/Eiffel

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-Sebastien, RepRap.org library gnome.

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Remember, you're all RepRap developers (once you've joined the super-secret developer mailing list), and the wiki, RepRap.org, [reprap.org] is for everyone and everything!

Those look interesting, and perhaps i might go that way, or make my own RepStrap. but whatever way i go, I think the RepRap spec electronics should work. My biggest concern was weather the motor drivers would take the larger motors and from what i can deduce they should at least with good cooling.