DIY CNC

Hi,

I recently acquired a Sherline CNC-ready mill, and I've been thinking about finally getting around to getting it setup. The problem is that I can't decide on what path I should go down (GRBL or LinuxCNC). I'm quite a novice when it comes to CNC machines, so LinuxCNC seems quite daunting. However, the features the software provides are very enticing. I was wondering what you guys think I should do. Additionally, if I do go down the LinuxCNC route, should I go with a 7I96S or an old computer with a parallel port (I haven't tested its latency, but it should be fine; it is a Dell Optiplex)? The reason I'm considering using my old computer is that I can back out if I get way too in over my head (I figure I won't waste as much money).

Thanks,
Logan

If you have access to a PC with a parallel port, it's a cheap and easy way to get started in CNC using knockoff breakout boards from Amazon and some cheap stepper/driver kits. That's what I did. However, this is not a robust solution. I had many problems with port pins getting fried, for example. Getting any one of the Mesa cards (I used the 7i76E) is a bit more of an investment but the electronics are much more robust, and you get to enter the worlds of "industrial lego". At that point, you'd need LinuxCNC anyway, so might as well start there.

Also, it looks like GRBL is designed to run on an embedded board, not a PC, so if you want the lowest cost-of-entry, go LinuxCNC.

I started with a parallel port for a lathe conversion, it was robust enough to do the job, but eventually went with a 7i76E for it, then a VMC i retrofit with 7i76E+7i84S, then now im doing another mill with a 7i95T, the Mesa hardware is fantastic- so good that china is now knocking it off!

Parallel port to start, then work your way through things. Lots of help here on this forum!!

Logthor wrote:

GRBL or LinuxCNC

GRBL is a good and cheap driver, but only with basic capabilities.
The problem is in communication, the PC sends a full line of g-code and waits for confirmation of its execution.
It is not possible to create loops, conditions or use variables.
(In FluidNC they try to bypass this, but the effect is far from expected.)
LinuxCNC does not have these limitations that will start to irritate you sooner or later.

So if you only want to use some specific CAD/CAM program to generate g-code, then you can use GRBL.
LinuxCNC, on the other hand, offers practically unlimited possibilities.

I feel like making foolish decisions, so I think I'm going to go with the Mesa card. How hard is the setup? I know you can use PnCconf, but is that enough to get you going, or do you need to do anything extra?

If you're using one of the ethernet-connected Mesa cards, you'll want a dedicated ethernet port on your pc to access it - don't share it with a connection to your home router (if you're not using wifi). PnCconf is otherwise sufficient to get you going, although I think you'll eventually find yourself hand-modifying your config files to do custom things

One consideration for the Mesa cards: if you think you'll need more field I/O, you might as well pay a little extra and get a card with that built-in. I.e. 7i76EU instead of 7i96S

My machine is only a 3-axis machine. I'm not sure of how much more I/O I really need. I plan on using the old Dell for LinuxCNC, so I really don't need to worry about having a free Ethernet port. Can you use a Mesa card and a WiFi card at the same time? If not, I'm fine with using the old sneakernet method.

my machine was "only" a three axis machine too, but I just kept adding to it...
Mesa and Wifi should be OK; my machine has two ethernet ports. You just don't want mesa packets on the same wire as other packets.

Different question: if I want to control my spindle's speed, I do this through software, right? My Sherline mill's speed control uses a 0-7V range to control its speed using a potentiometer.

The 7i96S board has an analog spindle out which should work for that purpose - it's implemented as an isolated digital potentiometer.