New CNC Controller Design - Feedback wanted

[Zach 'Hoeken' Smith]

Hey all,

I've been working on a design based around the  LPCXpresso dev board to control CNC machines.  Since I'm posting to this list, I'm intending to use smoothieware as the firmware.  I'm relatively new to designing CNCs, but not digital fabrication (been building 3D printers for about 5 years now).  My goal with this board is to make something that is flexible and possibly a bit 'overkill' to allow me flexibility in designing and hacking on low-cost CNC machines.

Once I settle in on a realistic feature set, I'll then pare it down so that it can be as cheap as possible, without missing any critical features.  But lets not get ahead of ourselves. :)

Below is my rough design spec, and you can check out all the design files on github at: https://github.com/Hoektronics/Hoektron-CNC

Please let me know what you think, and if there is anything that I've missed or you think is critical in a CNC controller.  Feedback much appreciated.

Oh, and I'm on the road now, but when I get back home in a few weeks I'll definitely be getting prototypes.  I hope to have everything nice and release ready within 2 weeks.

Licensing	·       Fully OSHW, GPLv3 ·       Developed in the open at: https://github.com/Hoektronics/Hoektron-CNC
Input Power	·       12-24VDC, 24V preferred ·       Internal regulators to 5v and 3.3v ·       Current sensing on main power for POST and realtime current monitoring. ·       Replaceable fuse for safety (5x20 cylinder type)
CPU	·       LPCXpresso from NXP ·       LPC1769 microcontroller ·       512kb Flash ·       64kb RAM ·       100mhz operation
Connectivity	·       USB 2.0 Full Speed (B Connector) ·       10mbit Ethernet (RJ45 Connector)
Spindle Control	·       Isolated Relay for up to 230VAC operation, with option to use built-in 24V supply.
Stepper Drivers	·       5 axes built-in (XYZAB) ·       Supports 2 different types of modular stepper drivers: ·       A4983 based “Pololu” style drivers for NEMA17 size motors (Up to 1A) ·       TB6560 based “HoekStep23” style drivers for NEMA23 size motors (Up to 3A) ·       Step size and other options configurable. ·       Optional support for dynamic current setting on MakerBot “BotStep17” style drivers
Storage	·       microSD slot
Debug	·       3.3v TTL Serial connection ·       JTAG through LCPXpresso board
Extra I/O / Misc	·       10 endstops (min/max for each axis) ·       Tool zeroing input ·       Door open/close input ·       Spindle speed input ·       2 ADC inputs ·       Tentative support for 5 quadrature encoders. ·       3 high-power MOSFETS switching 24v @ 5-10A.  Good for heaters, fans, etc. ·       Buzzer for alerts and simple user feedback

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Zach Smith

[bobc]

Looks great! I like the idea of modular hardware.

This might sound petty, feel free to ignore it. It just seems that Open Source tools would go well with Open Hardware. I know Eagle is "free" and a de facto standard, and Kicad is not really up to a professional standard yet.

I don't want to start a Holy war, just throwing it out there for consideration...

[Zach Smith]

Believe me, if gEDA or Kicad worked for me, I'd switch in a heartbeat.  The sad truth is that I'm an order of magnitude more effective in Eagle so I stick with that.  I revisit them every 6 months, but so far the gap is too big.  :(

[bobc]

That's fair enough, I was interested to get your take on the relative usability of the free tools, seems they have some way to go. I admit I have a similar problem on the software side, after using professional quality tools at work, the open source offerings perform somewhat lower than what I am used to. I think I have found a good balance now though.

Btw, I recently got a cheap CNC 3020 from China to play with, appears to work ok but I haven't tried cutting anything yet...

[Zach 'Hoeken' Smith]

Do you have a link to the actual version you got?  I'm looking to go down that route myself.

Zach

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Zach Smith

[Daniel Dumitru]

Excellent initiative ! and what a pitty that you don't use Kicad...
I can't understand why Eagle it's so spread.
I have hard times to use/learn Eagle and I quit. When I have found Kicad it was very natural for me...

[dave]

good work , but could i mention just a few points ...

 

it would be good to be able to have the encoders with an extra input for the index pulse , and for them to run from 5v by default rather than 3.3v , perhaps link switchable ..

one or 2 pwm outputs would be good for driving inverter type speed controllers as well as the relay , this if using pwm for speed could be utilised as a direction fwd/rev for simple vfd's

ok i know your looking at a simple cnc control , but feel the subtile extras would make a lot of sense for use for example lasers , where the power supplys are pwm controlled etc

[bobc]

On Friday, July 20, 2012 5:14:14 AM UTC+1, Zach Smith wrote:

Do you have a link to the actual version you got?  I'm looking to go down that route myself.

Sure, this is the one http://www.ebay.co.uk/itm/UPDATED-NEW-CNC-3020T-ROUTER-ENGRAVER-ENGRAVING-DRILLING-AND-MILLING-MACHINE-n1-/370550291141?pt=UK_BOI_Metalworking_Milling_Welding_Metalworking_Supplies_ET&hash=item564684bac5
 
There are several apparently identical ones on ebay from different resellers, but they are either sourced from YooCnc or are clones of YooCnc machines. Its hard to tell. There is Yoocnc marking on the PCBs, anyway.

The one I got was packed with generous amounts of padding and arrived intact and seems to be in good working order.

[Zach 'Hoeken' Smith]

Yeah, thats a nice looking one... probably identical to one I was going to buy.  Let me know when you fire it up.

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Zach Smith

[Petmen Petmen]

i have the cnc6040 i love this router.

Op vrijdag 20 juli 2012 06:14:14 UTC+2 schreef Zach Smith het volgende: