View Full Version : What do I need to run LinuxCNC???

24-11-2015, 09:15 PM
I am looking at the various options of control for my CNC mill, and LinuxCNC looks very appealing, especially as it has feedback back to the main processor, which I believe gives a true closed loop control system.

I have been looking at MESA boards, and a few other sites on LinuxCNC.

Are there any guides, or can someone give advice as to what I actual require to run LinuxCNC? For example a diagram with the various MESA board for example showing what connects to what.

I see there is a lot more setting up required for LinuxCNC, is this at an in-depth computing level (I'm an engineer!!) or is this more configuring inputs/outputs?

I see there are chinese ethernet boards available

http://www.aliexpress.com/item/LinuxCNC-EMC2-ethernet-4-Axis-max-3MHz-pulse-motion-control-card-20-input-IO-8-output/32468176459.html (http://www.aliexpress.com/item/LinuxCNC-EMC2-ethernet-4-Axis-max-3MHz-pulse-motion-control-card-20-input-IO-8-output/32468176459.html)

Are these any good?

Is setting up LinuxCNC more "plug and play" now? Not as easy as MACH3, but I see there are wizards for setting up things

Many thanks

24-11-2015, 10:22 PM
I can't tell you anything about using external motion controllers with LinuxCNC as I use it via a parallel port (in fact, an add-on PCI card in my case as my motherboard has no native parallel port, like many modern motherboards). However, the motherboard is a fairly basic AMD-based board which works well, within the limits demanded by my fairly ratty CNC router. Installing L-CNC is, in practice, no more difficult than installing Mach3, in my opinion. Find the web site, follow the instructions, and you will have a working L-CNC system. Basically, you download the system image (using any old PC), write it to a memory stick, take that to your target machine, and boot from it. When it's finished, you'll have a working L-CNC system. As you say, there are wizards for configuring the software for a particular machine and from reading this forum, I would say that there are more problems with understanding how your machine is wired and connected, and things like "steps per unit", than there are with understanding the software and configuring it. From this perspective, I don't think that there is much difference between Mach3 and L-CNC.

Sorry I can't help you with comments about external motion control boards and L-CNC; when I first started using it around 3-4 years ago, I don't think that these existed apart from the MESA cards, and they looked complicated and expensive. I haven't really bothered to look since.

So, I don't believe that L-CNC does need particular in-depth computing skills as long as you aren't using the same machine for other software. And you shouldn't do that (or, at least, not at the same time as you are CNC machining! Although I do admit that I might have, say, an MP3 player application running at the same time as I'm using the router and never seen problems with it. But don't tell anyone that I said so or half the membership of this forum will publicly flay me alive...)

25-11-2015, 03:42 AM
+1 to what Neale said. Most any old PC less than 10 or 15 years old will work fine. I have an old PC with M3 and xylotex boad on my router and an old PC with Lcnc and a G540 on my small mill. The Lcnc combo is much snappier. Configuration not much harder or different than M3. My biggest problem was in trying to get the Lcnc to see .tap file extensions. On the Lcnc box I can be running the Lcnc and designing in Vcarve running under vine and have other things up and running. I can't do that with M3 running on windows. That machine is M3 only.

Clive S
25-11-2015, 08:05 AM
I have been looking at MESA boards, and a few other sites on LinuxCNC.
You need to ask the questions on the Linuxcnc site re the Ethernet boards.
Here is the manual for the 5i25 http://www.mesanet.com/pdf/parallel/5i25man.pdf and the link to the mesa http://www.mesanet.com/ if you are using step/dir then the popular one is 7i76 the go to guy on the liniux forum is PCW or andypugh.
if you go with the 5i25 and 7i76 combi then buy them together as the firmware will already be set up in the 5i25 you can also buy the mesa stuff in Europe here http://eusurplus.com/index.php?route=product/category&path=63.

25-11-2015, 01:49 PM
First, read all what you want to know on http://linuxcnc.org/ There are many people, they can help you, the owner of Mesa as well as some ingenieurs who use this parts in their application.
You need a PC with Intel or AMD core not really big performance, but depends from the motion card, it should have a latency, that you can test with a SW that is part of the program.
While the test is running, you should use some processer relative tasks, view some movies, run 3D-Cad or similiar programs, copy bigfiles.
Than you can see, if your PC is good enough for LCNC.

26-11-2015, 09:45 PM
I'd be looking at buying a PC to install into the machine just to run Linuxcnc, nothing else.

So any recommendations, or where I can find PC recommendations would be welcomed

26-11-2015, 11:20 PM
What are you want with PC a complete PC or only a motherboard. If you want a complete PC then you can use nearly any model from the last 3 years, they all should be fast enough for this purpose.
If you want a motherboard, then a fanless board with standard Ramboards is good. The AsrockASR Q1900B-ITX or any similiar board is more than enough. A atom board with 2*1,86GHz is good as well. If you prefer AMD, than thats no problem, the linux version you need can run on both platforms.

26-11-2015, 11:36 PM
... or where I can find PC recommendations ...

Hi Gatesy

Essentially you should be looking for a PC or motherboard with small latency and jitter numbers.
uli12us has given you some answers, but have a look here (https://forum.linuxcnc.org/forum/18-computer/19125-faq-some-latency-solutions) and at part I of the FAQ ('The Latency Problem') for some of the working out.


27-11-2015, 08:09 PM
I was looking at something along these lines, a fan less industrial PC


Ok thanks will have a look


27-11-2015, 08:26 PM
Found this one

Single core processor, but it looks like they can be built to what spec you want

http://www.aliexpress.com/item/XCY-Atom-N270-single-core-thin-client-computer-optiplex-Industrial-Mini-PC/32300434149.html?spm=2114.01020208.3.75.lurDyS&ws_ab_test=searchweb201556_3_79_78_77_80,searchweb 201644_5,searchweb201560_8

27-11-2015, 08:56 PM
Why do you want a complete computer, for much less money you get a COB Board and can add parts you like. Faster or bigger ram, SSD instead of HDD. I recommend Boards, in which you can use standard Ram chips, instead of the SO-DIMM. The board is inside your electric cabinet and don't need some extra housing. Except you want to mount the Computer behind a touchscreen Monitor, you don,t need an IPC. But single core is enogh for LCNC, it can't use a dual or Quad Core.
I use this, but must wait until I have enough money to work an my machines. The Mesa board run with this, without problems. BTW, you should have a LAN Port.


29-11-2015, 04:18 PM
Do not just go ahead with buying new parts to use for LinC without knowing they are fit for purpose.

The single most important thing to run LinC well is the so called latency, for which a test is included with the Linux cnc live cd.

I sort of collect older pc's and test them for this. If the numbers are good, then I keep it.

I now run a pentium 4 2ghz I bought new maybe in 2005 or something.
Ram, ssd and that modern stuff is pretty much irrelevant for the cnc part, but it may be nice for smooth operation for the operator.

With modern boards latency can vary a lot so if you can not test it, or know from others latency is good, do not buy it.

When I started I ran LinC directly from the parallel port.
When I added a 4th axis that did not work so I had to add a BOB.

Once you have the pc, you can just try to run it, if it does not work well, add bob, or add mesa.

29-11-2015, 04:54 PM
I'm not a Lcnc user but I'll just throw this question to those that have posted so far. !. . Do most of you run Steppers or Servos.?

Servo's require much higher frequency than Steppers so I would be speaking or listening to those using Servo's because it may well change the Game regards PP and PC.!

29-11-2015, 05:19 PM
Good point, Jazz. I use steppers, with a BoB and a PCI parallel port adaptor card. My motherboard, bought about 18 months ago, is an MSI A55M-E33 with an AMD processor and 8G RAM. I see from the place I bought it that that MB is no longer available, which just about sums up the problem with PCs and, particularly, motherboards - I've never seen a list of "suitable" MBs that actually has anything on it that I can buy! I did the usual LCNC latency test, and have ended up with a kernel speed of 28KHz (from memory) but my router is not that fast and fastest rapid feed only needs about 8KHz, so there's plenty of headroom.

I wasn't aware that LCNC could support servo encoder feedback directly (but I haven't needed to, so I've never looked for this feature). That would certainly put up the required kernel speed; on the other hand, the OP was talking about a mill where speeds are much lower than a router, so maybe it would be OK. All the same, if you are going to the lengths of using servos and the complications of feeding back encoder output to the motion controller as opposed to a self-contained servo controller, then I'm sure that it would be worth going to the cost of an external motion control card that can guarantee performance.

Doing some simple back-of-envelope calculations for a sanity check - my current router uses a 1.5mm pitch leadscrew (best Screwfix stainless threaded rod and everything...) and 800microstep/rev. 900mm/min max feed (at which point the leadscrew is not quite whipping too much) needs a pulse rate of 8KHz. Go to a 5mm pitch ballscrew and that would give 3m/min rapids with same pulse rate; LCNC tells me that it could run at least twice the current pulse rate so that would give 6m/min rapids and still not be pushing the limits too much. So, with steppers a cheap modern MB running LCNC would comfortably handle a typical "hobby use" router. I'm going to a CSMIO-IP/M for the next machine, but more for peace of mind and general electrical/EMI proofing than real need. Servos - different story.

29-11-2015, 06:36 PM
I'd be looking at using AC servos. I see MESA have a board already configured to output to servo drives which also has encoder feedback as well.

I have a number of old PC's here, so might have to se if I can run the latency test on them and see what I get!

Seems like LCNC is at a bit of a disadvantage here compared to windows based programs like MACH3 etc.

And a bit of a catch22 with what to buy. Not the best situation having to buy something, then test it.

I see Tormach are now using an LCNC based controller, and the Centroid software is Linux based as well. How do these companies get on with what computer to use, or is there software setup different to LCNC?

29-11-2015, 07:19 PM
Any of these be any good for LCNC?


29-11-2015, 08:00 PM
Another though with all this talk of latency, etc and suitable motherboards, etc.

How do/did the likes of Fanuc and Heidenhain work? For my use I just want a small PC fitted into the machine, that will just run the cnc control software, a set up the same as Fanuc and Heidenhain.

Is there any latency with Fanuc or Heidenhain controls, and if so anyone know what sort of values?

Not being a particularly computer literate person, if you have a multi core processor, why is it not possible to use one core to just handle the cnc control, and another core to handle the running of the computer?

Clive S
29-11-2015, 08:15 PM
Any of these be any good for LCNC?

In all fairness these questions would be better on the linuxforum I have just seen this that has been recommended http://www.mini-itx.com/store/?c=34#JNF9C-2800 .
No offence Lee:cower:

29-11-2015, 08:25 PM
For Mesa, you need either a PCI(e) slot or a lan connector. Each actual board should run perfectly with it, if it have one of these connectors. Eventually it should run with a parallel port, but nowadays most computers haven't these stoneaged ports.

29-11-2015, 09:13 PM
Thanks for the replies, have signed up to the LinuxCNC forum.

LAN connector was the one I was thinking of!

30-11-2015, 04:29 PM
How do/did the likes of Fanuc and Heidenhain work? For my use I just want a small PC fitted into the machine, that will just run the cnc control software, a set up the same as Fanuc and Heidenhain.

They use Bespoke Hardware (and Software) designed by them. Pretty much Like Mesa Cards or External Motion control cards for Mach3.
The early ones where based around a crude PC design but mostly just for the I/O interface to access HD etc but there own Bespoke hardware/software does the work.
For instance I've got a HeindenHain Mk3400 Control which under the cover looks just like an old 486PC but that's has far as it goes it's just looks.!! . . . All the Stuff that does the business is on PCI cards and Dedicated daughter Boards in the Main control panel. The PC side does very little other than the display side and Store/pass files to the control.

Don't expect modern Fanuc/Heidenhain performance from Linux Cnc or Mach3 because you won't get it.! . . . . . There is a Reason why they cost and it's not just profit.
Thats doesn't mean Both Lcnc or Mach can't give them a bloody good chase but you have to realise they will always be behind.!

Having the Same PC/Control Style in a box setup is easy enough with both programs and that's all down to you and how it's gone about.

01-12-2015, 11:57 PM
Been having PC problems over the last couple of days. LinuxCNC PC randomly crashing after an hour or two. This has happened a few times in the past with this motherboard although I thought it was fixed after reseating all components. Long story short - don't rely on motherboard graphics adaptors (the LCNC website discusses this) and use a PCI or similar graphics card. Doesn't have to be very high performance but for some reason this gives much, much better latency figures. Also - make sure you update the BIOS before you start using the machine. I think that this is where my problems came from - old BIOS that didn't properly support a rather later cpu, even though it seemed to run OK.

Clive S
02-12-2015, 07:42 PM
This might be interesting for the people that want dual motors to home in Linux https://forum.linuxcnc.org/forum/38-general-linuxcnc-questions/29728-component-for-tandem-stepper-axes-please-test.