How hard is Linuxcnc to learn?

Hi, I want to make a 4 axis CNC Mill with AC servos, Linear Encoders and a Tool Changer. The mechanical aspect of the mill doesn't daunt me but the Electrical/Software does. I think I want to use the Mesa cards as they support the high frequency step rates and Encoder Feedback needed. I'm thinking 6I25 Superport FPGA + 7I85S + 7I75 is this correct / enough for what I want?

I'm new to the forums and I've read through some of the Knowledge Base to try and get a better understanding but I'm a little lost. My trouble is I don't have any hardware to just tinker with and figure things out for myself, the hardware is expensive and I want to be sure I've made the right decisions. Would it be worth while buying some cheap stepper hardware just to wrap my brain around it all?

Cheers,

Fenza

FenzaCNC wrote: Would it be worth while buying some cheap stepper hardware just to wrap my brain around it all?

It might be. I made a much better job of my second conversion than my first, and I learned a lot through toasting components during the first build too.

The question is whether you have any use for the "learning" setup. It probably needs to be something at least fun to hold your attention.

Maybe a wall-drawing bipod?
wiki.linuxcnc.org/cgi-bin/wiki.pl?Koppi%27s_Toy

Haha that thing looks strangely brilliant! Maybe a 3D printer would be slightly more useful for me though

I've just checked all the computers I own and unfortunately none of them have a parallel port. What options are there for doing something like a 3D printer on the cheap in Linuxcnc? These stepper drivers are very common in 3D printers ( www.pololu.com/product/2987 ), I'd rather use something like that than a few hundred £££ worth of electronics simply for learning purposes, really all I need is the Mill but a 3D printer would be pretty cool.

Cheers,

Fenza

If you don't have a parallel port then super-cheap options are rather limited.

It might be worth looking to see if there is a parallel port header on the motherboards, but not on the back panel. For example I am currently using one of these:
www.mini-itx.com/store/?c=89#JNF9C-2800
Which has a header, but no connector on the back panel.

You could consider the 7i80DB From Mesa that uses Ethernet for comms, which is compatible with the cheap multi-axis driver boards on eBay. But that immediately takes you out of "cheap".

You could look at a BeagleBone Black and Machinekit. That is quite a lot like LinuxCNC (it's a fork of the project). But that might be a bit of a diversion from the machine you want to build.

I would suggest buying a motherboard known to work well with linuxCNC and which has a parallel port. You can then either keep it on the printer, or use it for the Mill. (There is no reason that the same PC can't control both, depending on which config file you choose to load).

I'll have a look for a parallel port header though I'm not getting my hopes up, it's a 'Dell'.

Hmmm buying Mesa cards would probably be the best option thinking about it, but if I'm going to be buying the Mesa cards I only want to be buying them once. The issue is I don't really understand which cards will be best for my mill, I can be quite flexible as I was intending to buy a dedicated PC when I've got everything figured out. I'm kind of going round in circles thinking like this, I need to understand how it works and the best way to do that is to simply do it, but I don't want to be stuck with an expensive board or have other issues because I bought the wrong thing.

The Servo drives I will be using are these ( uk.rs-online.com/web/p/servo-drives-controls/7701400/ ) they accept Pulse + Direction signals at 4Mpps and the Linear Encoders are Incremental A±, B±, Z± at 15 or 8.3 MHz. Ideally I want to base all my controller electronics decisions around these two components.

If I have to just take the plunge rather than play around with some cheap 3D printer style project then maybe that's what I need to do, I'm just apprehensive buying stuff I know such little about.

Have you got any recommendations for what Mesa cards would suit me best? I'm also assuming Mesa is the option for my needs by the way. I'm open to other suggestions, even none Linuxcnc if it can compete.

Cheers,

Fenza

FenzaCNC wrote: The Servo drives I will be using are these ( uk.rs-online.com/web/p/servo-drives-controls/7701400/ ) they accept Pulse + Direction signals at 4Mpps and the Linear Encoders are Incremental A±, B±, Z± at 15 or 8.3 MHz. Ideally I want to base all my controller electronics decisions around these two components.

There may be more cost-effective sources for suitable drives than RS Components.
That drive seems to assume a specific encoder that is used for commutation. Are you sure that the motors you have are compatible with the drives?

Those drives can be configured to accept analogue-voltage velocity commands. You might find this is easier to configure, as the range of encoder/analogue servo controller cards is more extensive than encoder / step-dir cards.

Specifically, the Mesa 5i25 / 7i77 combination is very popular for such setups. If you find a parallel port you could also consider the Pico equivalent.

The drives seem to work on Modbus, so a third option might be from General Mechatronics.