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Attempt at LinuxCNC (formerly EMC)

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vtsteam:
This may be a short attempt, too since I don't have any even reasonably modern computer to spare for it.

To start at the beginning, I have run old fashioned TurboCNC on the rare occasions I try to mill something via CNC, so I hadn't hit the snag I did this week with it. Using Sketchup and Sketch-U-Cam I wanted to cut out some 15/16" circles and small screw holes in a 1/16" aluminum sheet panel.

When I tried to run a test, the holes ran way below the proper feed rate and it gummed up the cutter, and well you can imagine, it wasn't pretty.

After checking out the G-code I've found that circles are written as a series of arcs -- Sketchup shows circles on screen as segmented line figures of say 25 pieces, and though SketchUCam writes these as true G3 arcs instead of straight lines, the number of segments stays the same. Because TurboCNC applies its acceleration factor at the start of any segment, the net result is that a 25 arc circle is composed of 25 starts and stops with acceleration applied -- the net result is a drastically lowered average feed rate.

It appears that TurboCNC doesn't use a look ahead buffer and doesn't compensate for this kind of situation, while other CNC programs do -- notably Mach 3, which everyone seems to use. But with Mach 3's cost of $179 it's just not something I can afford now -- I do realize the trial version is free, but I know I'll want the non-crippled features, and I don't want to start down that path and get committed to it.

Also Mach 3  seems to need a computer more modern than I have available, and even buying a used computer would just add to the total cost, as well as make redundant what I already have -- thus more useless storage or another disposal of perfectly usable gear. I hate to do that kind of thing unless I absolutely have to.

So I've been looking at LinuxCNC. I already run Puppy Linux as my standard op system anyway and have for years. It seems there's just a chance that my available hardware can run LinixCNC, so what the heck -- it's free, and open source, give it a try.

It does use Ubuntu as an operating system which I'm not fond of. I started with Linux a 5 years ago running Ubuntu -- but it seemed slow and bloated, wanted late hardware and required frequent updates (which broke my system one too many times). After 6 months I discovered and switched to puppy linux which was light and fast ,easily customized, ran well on anything, could run well as a "frugal" install and wasn't dumbed down. And I never looked back.

So the idea of returning to an even later (and presumably larger) Ubuntu OS for a simple CNC controller doesn't have a lot of appeal for me. But hey, lets try it and see. I do note that the latest version of LinuxCNC seems to be written for a Debian core OS, so that might have more appeal. I tried Debian back in the dark ages, but never got far with it.

Anyway test subject for this (at present) is going to be my 1998 IBM Thinkpad 600E which runs TurboCNC fine now. It's been hacked up to an overclocked Pent 3 with more than stock memory (484 megs if I remember correctly).

 Yes I know, a laptop is generally wrong for any CNC program, etc., and this one is particularly old and abused with soldered wrap wire, cut traces, and a modded bios. But some of the latency reports on the LinuxCNC show similar era Thinkpads actually usable, so I have a slight hope in this. Hey -- this is MadModders, right? Not Sanemodders!  :)


As a start I've downloaded the 2.6 version with the Debian OS, and the 2.5 version with the 8.04 Ubuntu OS with earlier kernel -- hoping that one or the other will run on my old hardware.

awemawson:
I'll be watching this with interest. Some time ago I down loaded it and got horribly tangled up, not being particularly into unix in it's many forms

Brass_Machine:
Hey Steve,

I have no input on the LinuxCNC. I do want to try it someday though. But I can say this, yes generally a laptop is not good for CNC... however, I use one for my mill. I have an old Dell that I use and it hasn't given me any problems.

Eric

awemawson:
I think that the laptop issue is largely one of how the ports are implemented. The parallel port often hasn't a full 5v swing only 3.3v on some, and if you are using it to drive your system break out board you may well be in trouble. Similarly the serial ports very often don't give 12-0-12 which can muck things up.

Brass_Machine:
Yup. I actually have an older dell desktop that I will be moving over to when I start upgrading the mill.

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