A friend of mine recently contacted me because he wants to get/build a cnc.

A friend of mine recently contacted me because he wants to get/build a cnc.
He was considering a $200 ebay special till he looked at the working area of the machine.

Together we decided to build a Root 2 mostly printed cnc…

The big question remaining is the control system.

The default is to go with a GRBL stack, Arduino->Grbl_.Steppers.
I kinda hate that system.
At @Mobile_Makerspace we have a couple of Shapeoko’s and I’ve nearly given up on getting any good use out of them.

The frustration comes down to emergency stops. When there’s something wrong with the code (and somehow there is always something wrong with the code), the mill goes down instead of up and ruins your piece and threatens to ruin the bit and the router, and possibly the steppers and the belts. So you need to stop it, and hitting stop in GCode sender, it takes about as long to stop as this paragraph takes to read.

I have two previous CNC experiences, and unlike G-Code Sender (which I use because our laptops are installed with linux) these other two setups stopped IMMEDIATELY.

With the shapeoko’s the only way to stop it right now is to pull the power. Which means 10minutes of work getting back in place, and probably means scrapping the material you were working against. It’s very frustrating.

The other setups were a linux cnc install (straight out the parallel port) and an ancient (even though it was new at the time) DOS setup in 1998.

I would like to recommend a non-frustrating control scheme. I would like to recommend LaserWeb (in cnc mode) on a smoothie board. So my question is, if we get a smoothie board and CncWeb, does it buffer the stop command like the shapeoko? Or does it know how to stop Immediately?

+Peter van der Walt 10mins is for putting down a new piece, restarting the grbl machine, rehoming, fixing the code, fix the bit… etc…

So does the software stop button in laserweb stop the machine immediately or not?

Well, the shapeoko doesn’t stop right away because it buffers the stop command, it only comes through after everything else that has already been sent.

If is bad firmware if the machine keeps looking at buffered items instead of an emergency stop.
I think the grbl has bad firmware anyways because I realized that it was not honoring all of the gcode that I was giving it from mymcustom gcode making python script which I call bucketmill.

Figure out the spindle or consider the possibilities before making the Z stage. ABS maybe. PLA never or at least only till you can mill replacements.

+Peter van der Walt I am saying the firmware should see the switch triggered with it connected to the grbl board and then tell the software “hey, I stopped”.

@Josh_Rhodes Grbl (actual 1.1e) has real time commands (like ctrl-x, hold, overrides…) that are captured before the buffer and are executed within a few ms. RTFM and don’t blame Grbl for your lazyness!

And sure, LaserWeb does stop the machine immediately. Doesn’t matter if grbl or smoothieware.

@NathanielStenzel Grbl has the option to wire a switch for stop, pause, resume! Check out CNC-Shield.

From my point of view, Grbl is much better suited for diy CNC-machines than smoothieware, because the internal structure takes care of all the security relevant issues (like realtime commands). Smoothieware is overloaded with stuff for 3d-printers, LAN, webinterface…

I would suggest not to build a Root 2 CNC. The rails are crap and belts have too much flex for milling (if not only PCB).
Make something like http://openbuildspartstore.com/c-beam-machine-mechanical-bundle/

@cprezzi I have seen numerous posts about the hardware switch that people installed. I often had immediate stops from CTRL-X. It has been earlier than last may since my last CNC job since my dremel shaft got bent, so I am a little fuzzy on my details. I blame the gcode commands that were not honored for at least some of the bent shaft issue. It was supposed to go up and over, but it just tried to go over with too much of a depth to get an okay cut.

Nice!

As far as an emergency stop, I try to use it to disengage all energy to the machine and spindle if at all possible… Even tho several controllers honor a estop to be wired thru the controller I would never trust that with my life on a hobby machine…

I guess I don’t really know what to do to stop the shapeoko in a hurry.

We’re still deliberating on control electronics/software. Any opinions on what the best electronics are?

I guess I don’t really know what to do to stop the shapeoko in a hurry.

We’re still deliberating on control electronics/software. Any opinions on what the best electronics are?

Use the door switch of GRBL instead of the e-stop. This stops the machine immediately and you can simply hit cycle start after ‘closing’ the door to continue.

@Sebastian_Stetter ​ that would be a good use for a pause/feed hold button…

@Alex_Krause there is a feed hold button, but it does not stop immediately since it empties the buffer, first. The door switch does immedieately, without loosing the position. So it is somewhat between e-stop and feed hold.

Oh!.. door switch like for a laser… of course…