LinuxCNC Lathe Build.

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

willburrrr2003

Well-Known Member
Joined
Jun 10, 2011
Messages
113
Reaction score
9
Hello All,

Since I have to start from scratch with LINUXCNC to run my lathe (believe it or not...I lost an entire computer in my move) I was wondering if anyone would like me to do a from the beginning walkthru of setting LINUXCNC up to run a minilathe.

Regards,

Will Riddle , Everett WA. USA
 
Hello All,

Since I have to start from scratch with LINUXCNC to run my lathe (believe it or not...I lost an entire computer in my move) I was wondering if anyone would like me to do a from the beginning walkthru of setting LINUXCNC up to run a minilathe.

Regards,

Will Riddle , Everett WA. USA
Hi <I would apreciate that if not to much work
myght be switching my Taig lathe to CNC

cheers
 
I've arthritis in both hands and am seriously looking into CNc to make life a bit easier.
I've just bought a Raspberry Pi and wonder if there is a possibilty to use it in my very small workshop on a Unimat clone.

So, yes, more power to your elbow( or wherever)

Thank You

Norman
 
I've just bought a Raspberry Pi and wonder if there is a possibilty to use it in my very small workshop on a Unimat clone.

A Raspberry Pi!? Sorry, Linux does run on it, but that doesn't mean it makes sense.

@Will:
I have never set up a lathe with LinuxCNC, so I can't give you specific input on that.

1. Step: Buy a computer. Best if you buy a Intel Mini-IPX-board with a dual-core processor. They are small, they are cheap and they are a perfect match for LinuxCNC.

Questions:
What axis drivers have you planned? Steppers? Servos?
Will you have glass scales?
Did you already decide for interfaces? I strongly recommend to go with the Mesa-cards, they are plug and play for LinuxCNC.

Nick
 
if you use a mesa card the computer details are less important. use a mesa if you use linuxcnc for the feedback loop. if running steppers then don't bother unless you are paranoid about lost steps. with proper machining procedures and good stepper selection you shouldn't need feedback.

there are steppers and servo. servos have matching drives that may have a built in feedback or linuxcnc is also capable of handling the feedback loop though its best combined with a mesa card. there are many standards. position can be controlled by 2 I/o lines with step/direction or digital quadrature or through serial with position/velocity commands and other methods. Linux CNC can handle most of them but may need special configuration.

some things that linuxcnc doesn't like are sandy bridge Intel on board graphics(only applies to new intel other than the atom and not a problem with the graphic but the fact it needs a newer kernel but the realtime components in linuxcnc haven't been updated for the new kernels), nvidea graphics (works with open source driver, don't upgrade to the proprietary version), laptops, some Ethernet and WiFi cards, and multi core and hyper threading can be an issue.

it runs best on old celerons (note the celeron 847 is actually an under clocked sandy bridge and needs a newer kernel) single core with on board parallel. with single core there is less linux configuration to get good latency.

things to look for in a motherboard are a parallel port and amd/ati graphics or intel graphics (not sandy bridge CPU though)

the atom d510 is popular. the amd apu e350 can do the job, there are some low cost via chipsets that work with the use of amd/ati graphics card.

Linuxcnc can potentially turn steppers into a servo feedback system by adding encoders and running the stepgen component in velocity mode and adding a mesa card for faster I/o.

its great for people on a budget because you can start with cheap steppers and a $75 computer and very little else then add as you go to improve the speed and accuracy. it makes more sense than mach because by the time you add the hundreds up from the purchase of a smoothstepper or other needed external hardware a windows licence and the control software it can push you budget near the range of a used cnc knee mill. my friend in north Carolina got a working CNC at auction for $1000. its just a matter of how hard and long you look for one.

when converting a knee mill it doesn't make sense to spend a lot as you may as well find a machine with a tool changer to convert that outlived its usefullness and went to auction cheap. used machines go cheap because they are hard to move and too slow or complicated for most. and when converting a mill with a tool changer it makes a lot more sense to use Linuxcnc because it is more configurable. for people that need windows, or even Mac and are using steppers or servos with step/direction input there is rt-stepper which is $80 and much easier than anything else I've seen and runs over USB 1.1 so even laptops or old computers are happy with it.
 
it runs best on old celerons (note the celeron 847 is actually an under clocked sandy bridge and needs a newer kernel) single core with on board parallel. with single core there is less linux configuration to get good latency.

It's not one of the better tips (to say the least) to use a single core CPU. Since LinuxCNC 2.4 (I think), having a dedicated core is no work at all (yes, I once compiled my own kernel). With two cores, one core is dedicated to the time-critical parts of LinuxCNC exclusively. No matter what you do, the latency (response time) won't slow down.
Also, I strongly suggest to stay away from the Centronics port. It is unsafe (just 5 V) and if it fails due to EMI (not too uncommon on machines) and it is onboard, the whole CPU-board is toasted.
Do it right from the beginning on. Just use 24 V for all digital signals going in and out and isolate the CPU with optocouplers.


Nick
 
It's not one of the better tips (to say the least) to use a single core CPU. Since LinuxCNC 2.4 (I think), having a dedicated core is no work at all (yes, I once compiled my own kernel). With two cores, one core is dedicated to the time-critical parts of LinuxCNC exclusively. No matter what you do, the latency (response time) won't slow down.
Also, I strongly suggest to stay away from the Centronics port. It is unsafe (just 5 V) and if it fails due to EMI (not too uncommon on machines) and it is onboard, the whole CPU-board is toasted.
Do it right from the beginning on. Just use 24 V for all digital signals going in and out and isolate the CPU with optocouplers.


Nick

sorry if i was mis-informed, i was under the impression latency still benefited from disabling all but one core in grub or lilo or whatever ubuntu happens to use now. my brother is the local linux genius and though he said it would be easy to do what you describe regardless of the software version i didn't see any mention of it in the linux cnc forums, though i'm sure it would only be 5 min of searching on the linux from scratch forums. the one thing linux cnc needs is a better wiki. forum based information sharing is great for a hobby but a product needs a real support section even if it contribution based there should be a section of stickied threads on the details of specific types of common configurations, there are too many open ended comments in the wiki and no absolutes which i guess is the nature of something that can be configured for anything (in theory).

good advice about optocouplers.
 
i was under the impression latency still benefited from disabling all but one core

well, one core is isolated/disabled, and this one is dedicated to LinuxCNC.
isolcpus=1


Nick
 
Wow lots of responses so far! i am not starting a lathe conversion from scratch. my lathe was running on linuxcnc before my move, but i hqve not been able to find my computer that was running on it. Since i have to redo my linuxcnc setup i figured people would benifit from a walk thru from a fresh install , and to the point of having a working cnc lathe. i have stepper motors on it's two axis, and a pwm speed controller running my spindle. my control board is a Hobbycncpro board hooked into parallel port. i built a little control cabinet for the boards, power supply, and have an idec plc also for the future tool turret.

Regards,

Will
 
A Raspberry Pi!? Sorry, Linux does run on it, but that doesn't mean it makes sense.


sorry but it does run Linux check this

SOFTWARE

What operating system (OS) does it use?

We recommend Debian as our default distribution. It’s straightforward to replace the root partition on the SD card with another ARM Linux distro if you want to use something else (there are several available on our downloads page). The OS is stored on the SD card.

 
Thank you Luc,
It is basicly making sense. Whilst I am quite capable of making rings around quite a lot of people in 'ordinary old fashioned engineering' , electronics was never on the curriculem.
At my advanced age, merely understanding 'new words' or new meanings for familiar words and 'abreviations' is more than enough.

Way back -in a distant past, a great Brit called Sir Ernest Gowers got fed up with the 'mumbo jumbo' of official forms etc- and wrote something called 'Plain Words' and it even got to a documentary. I spent the rest of my life trying to do this. I'm a Goldstar which is something from my Royal Air Force days, I was running a Technical Library amongst other things. I had a super clerk and we still keep in touch. One day we met up by accident and I was introduced to his wife. 'This is Corporal Atkinson', we go back a long way' She replied 'I Knew a Norman Atkinson, an accountant and I lived in the bowels of headquarters as his audio typist. We never met, but he would always say' Do you understand this,if not bung it back and I'll re-write it' If my typist didn't understand- how would those who really paid my exalted salary understand? Err, uhm and a nice pension which has arrivedregularly for the last 28 years!
 
Nick, as someone who admits to being 'one Teddy Bear Short of a Picnic', thick as two short planks- and has read so many conflicting answers which emulate two little boys with a high wall, could you tell me why a Raspberry Pi will not work or is unsatisfactory.

You see, the English language version of Raspberry Pi suggests that it will work. Morever, it is working but so far, the examples are perhaps low powered or one stepper to drive a rotary table.

Apologies but thank you

Norman
 
You see, the English language version of Raspberry Pi suggests that it will work.

Well, so it will work. But at what price? Is it fast enough? What do you save in money? How is the support? Will you have to recompile LinuxCNC and the kernel or just LinuxCNC? What about the latency?

If you want to play, stay with the Raspberry*). If you want to make chips, buy a Intel board. Insert CD, boot from it, install, configure &#8230; done!

The Raspberry is something nice to play around if you want to automate your coffee-machine, or something similar. Maybe even for a 3D-printer from salvaged steppers out of 2 Epson printers you found at a garage sale.

*)
In my eyes, there are better boards for playing around. But that's just because I like micro controllers, assembler and electronics.


Nick
 
Nick, as someone who admits to being 'one Teddy Bear Short of a Picnic', thick as two short planks- and has read so many conflicting answers which emulate two little boys with a high wall, could you tell me why a Raspberry Pi will not work or is unsatisfactory.

You see, the English language version of Raspberry Pi suggests that it will work. Morever, it is working but so far, the examples are perhaps low powered or one stepper to drive a rotary table.

Apologies but thank you

Norman

linuxcnc depends on a real time kernel componant. linux is not real time by default. even with a real time kernel many things can interfere with the timing from graphics to networking if it uses interrupt signals. the raspberry pi stock kernel is pretty current but rtai (the real time componant used in linuxcnc) hasn't been updated for some newer kernel version thoguh that may not matter with a skilled person doing the compiling. and rtai isn't well tested on arm v6 architecture. not to mention that it may just have a lack of power to crunch the numbers. the linux cnc trajectory planer is quite complex to accommodate a variety of hardware and advanced features like hexapod support, pid feedback and adaptive feed rates (which mach can't do because it doesn't run in real time. yes the mach reps were mis-informed about the outer feedback loop in linux cnc in that last thread, it does more than just the pid that also exists in common servo controls by coordinating all axises together even if one is slow even on steppers it can correct for error if the stepgen is run in velocity mode rather than positions mode). if you wish to use a rasperry pi plan on a big learning experience with kernel .config files and compiling from scratch then debugging when it doesn't work out.

timing tests have already been done with the raspberry pi and it doesn't look good unless you want a slow macine. these issues may be over come in the future but it may be best to buffer the steps externally. for that you may as well just buy an rt-stepper which will likely run with the pi over usb but for the cost of an rt stepper you can buy a mini itx pc that is well tested and proven with linuxcnc. not that i would discourage an rt-stepper or rasperry pi. it depends on what your needs are, it is much simpler to setup than linuxcnc and also less powerful, but if all you need is step/direction output the rt-stepper is great.

the raspberry pi doesn't have parallel or pci (so no mesa fpga cards to assist it) so if the latency issues are sorted and a kernel compiled with rtai or similar module then a driver must be written for the gpio pins to output byte by byte data in a similar way. a driver does exist but it's not very fast, it may need some reworking. and that's all you get for i/o, but even at that point you still just get output, no feedback loop, or perhaps feedback that will limit the step rates and at that point running full linuxcnc is not much better than an rt-stepper.
 
Well, so it will work. But at what price? Is it fast enough? What do you save in money? How is the support? Will you have to recompile LinuxCNC and the kernel or just LinuxCNC? What about the latency?

If you want to play, stay with the Raspberry*). If you want to make chips, buy a Intel board. Insert CD, boot from it, install, configure &#8230; done!

The Raspberry is something nice to play around if you want to automate your coffee-machine, or something similar. Maybe even for a 3D-printer from salvaged steppers out of 2 Epson printers you found at a garage sale.

*)
In my eyes, there are better boards for playing around. But that's just because I like micro controllers, assembler and electronics.


Nick
Nick, I think your a little bit under estimating the Raspberry PI, do you have one? if yes and you can't find support for it
I will gladely give you links . I have DE1, DE2 ,4 Arduino, Raspberry Pi, Atmec board. and I can assure you that the PI
is far from the bottom. If you compare this to an E7 your right but unfair, same thing if you would compare a 16f84 to a 16f877a
cheers
 
Nick, I think your a little bit under estimating the Raspberry PI, do you have one? if yes and you can't find support for it
I will gladely give you links . I have DE1, DE2 ,4 Arduino, Raspberry Pi, Atmec board. and I can assure you that the PI
is far from the bottom. If you compare this to an E7 your right but unfair, same thing if you would compare a 16f84 to a 16f877a
cheers

yeah compaared to an atmel 8-bit or cortex m-3 it has a ton more power for applications but for making little gadgets an arduino has more i/o and will not have any lag time. it all depends on if you need to run an apache server or an x interface or something to do what ever you have in mind. if your project has no real need for a multi user, multi application operating system then a slow 8 bit controller will be much faster.

and if you need linux there are a few dual core and quad core arm v7 cortex a-9 and better boards. some that have no i/o cept for a single usb. and some that have more gpio than an arduino mega and are powered by super fast samsung exynos chipsets.
 
Nick, I think your a little bit under estimating the Raspberry PI, do you have one?

No, I don't have one. I had a short look at it. And I won't have one.
If you think it is well suited to control a lathe, I wish you all the best. You will have to report here.

For me, LinuxCNC on a Raspberry is like CAD/CAM on an iPad. :)


Nick
 

Latest posts

Back
Top