how to make best use of my (unused) 3D touch probe? Linux? Arduino? Raspberry Pi? Mach 3?

Hi,

I'm just looking for a bit of guidance or shared experiences, to steer my llittle project in the right direction before I get too invested in something old hat. The short version of the story, is I have a cnc touch probe, and a Gecko G540 setup, and I don't know which avenue to research to get it working.

I dabbled with a home made CNC mill about 12-14 years ago, I converted a sieg X1, made some cool bits, and haven't used it since! (machine sold, CNC kit in my shed).

I've now forgot everything I knew about mach 3, my Gecko G540 and the then vintage, now ancient, single core Pentium computer that ran it all!

If the hard drive hasn't seized up, it might just fire up.

I also own a Raspberry Pi 2 which is probably much faster than the old pentium but I admit, my Linux skills are "sudo nano beginner/follow online guide!" - I do like it though, I really wish I was better at this, I'm just so unfamiliar.

Does anyone else use a touch probe or CNC software that could offer any help or guidance, perhaps theres a better way to use my hardware, maybe my Raspberry pi could finally be useful to me!?

There are 4 options really, assuming you don't want to use the ancient single core Pentium.

You could just download the last version of Mach 3 which I think is 3.043.062, and pay for a new licence if you can't find the old one. Mach3 hasn't been supported for about 7+ years. Or buy Mach 4 which is the latest product from the same stable. For either of these you will need a new Win PC and, really, a motion controller instead of the old parallel port. But you don't need much of a PC. I use a cheapie miniPC with Win 10 and a UC100 motion controller

Or go the LinuxCNC route, for which you may be able to use the old PC or a new one. I don't think a Pi 2 would support Linux CNC, and I'm not sure if there is any other Pi SW that does.

Or use GRBL that can run on an Arduino, but this is really just a motion controller without the G code streaming so you need other SW, on an additional processor, to do this.

All those options can support a touch probe.

And of course you would need a machine to drive the probe!

I'm having great success with a 'Centroid Acorn' setup - I use a probe for tool setting on my lathe but full 3D digitizing is also available. I find the software very easy to use. Worked well so now onto my second conversion, Mill this time!

It supports the G540 (pre-configured I think?) and also touch probes. The support from the company and other users on the Centroid forum is good. You will need a reasonable PC but nothing special....but it will probably cost a little more than the other suggestions.

Centroid has consistently good reports from users who have spent loads to get it installed and working, it doesn't cost a little more it cost a great deal more especially if you were to go the Linux route.

Emgee

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I may be the only one who had not heard of Centroid Acorn … but that ^^^ intrigued me enough to have a look:

**LINK**

https://www.centroidcnc.com/centroid_diy/acorn_cnc_controller.html

MichaelG.

PostScript:

There are some encouraging Customer Reviews on that site … but this one made me smile:

Matt Doran, Rebco Inc
Rebco custom Vertical Lathe, 53 units running 24/7!
"Using the CENTROID CNC control has allowed us to develop our own specialized machine tool that can produce a high volume of parts with a much lower ROI than purchasing traditional machine tools. In our business the margins are thin and something as simple as an axis drive going bad on our traditional cnc machine tools would blow our profit for that month. With the CENTROID the parts are reliable and when something does go wrong,CENTROID parts are accessible and affordable and we save on expensive traditional CNC service calls by doing the repairs ourselves keeping us running and in the black."

Oops … Presumably he meant to write ‘much higher ROI’

MichaelG.

I don’t want to hog this thread, but I think this is worth watching:

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MichaelG.

A bit more searching around suggests that there is a CNC controller available from the USA that combines an Arduino running GRBL for motion control and a Pi for g-code streaming. Also Linux CNC can be run at least on a Pi4, and the Beaglebone. Google is your friend.

Thanks all for the input, it's really appreciated. Google was overwhelming, there were so many different options, I didn't realise so many would support the use of a touch probe to map out a surface.

John H, Mach 4 is interesting, I found some emails last night from 10 or so years ago between myself and Gecko talking about its imminent release, so I was obviously on the pulse back then at least - I thought it was the first time I'd heard of it when you mentioned it - clearly, I don't have the best memory, I do have a lot of projects over the years, my head clearly has limited storage space, and it's currently recovering and defragging my CNC knowledge!!

After looking into the GRBL I think I might actually start leaning this way, one of the most attractive things about it, is that I can buy a chinese CNC router for under £200 that includes everything I need, and in combination with my 3D printer I can very quickly swap out the questionable looking spindle motor, for a touch probe, and I don't have to cannibalise a 3D printer or modify my mill. Furthermore, I'm wanting to machine very soft, extruded aluminium cooler profile and I think the spindle speeds of a CNC router might actually be what I need, so I'll be keeping hold of that motor (and maybe even upgrade it to something more powerful and IP rated to keep swarf out)

PeteL, Centroid Acorn looks to be a Beaglebone based setup and very expensive from my current perspective! Depending on how I get on with GRBL, might adjust that perspective! Right now, its a solid pass but thank you for the tip, it's impressive hardware and software.

John, I'll check that out before I commit to a GRBL cnc router that seems too cheap to be true......

Well, a Raspberry Pi2 is 'old hat', and I think best avoided for actually running CNC unless the limitations are understood.

The Raspberry's are excellent and wonderfully cheap way of learning Linux, especially programming, and they also provide pins connected directly to the processor. Computers running Apple, Linux, or Microsoft rarely allow that, even though it's ideal for electronic experimenters.

An Pi2 is a perfectly acceptable learning tool, and it might be OK for production work. But a Pi3B is at least 20% faster than a 2, and has more memory and other useful gizmos. I like them because they're reasonably fast and power efficient for always on work - they don't need a cooling fan. The Pi4 is almost fast enough to use as a general purpose laptop, though I find them a little too sluggish for that. Pi's aren't the ideal platform for 3D-CAD! However, they have plenty of poke for CNC and the like. Not difficult to upgrade to a Pi4 after learning on a Pi2.

As a general rule, it's not a good idea to re-use old computers without having a good understanding of them beforehand. Problem being that progress in computing is extremely rapid, making it likely that even a slightly older box will use obsolete hardware interfaces and only run programs of a certain age. Certainly possible to do it, but as a general rule it's much simpler to go with current software running on a modern machine, because doing so avoids shoals of tricky time-related compatibility issues. OK for as long as everything just works, and it might, but it's tap dancing on thin ice. One might end up wasting weeks on the internet looking for second-hand parts, ancient versions of software, and advice on how to fix long forgotten configuration problems. Getting old computers going is a hobby in itself.

Dave

Dave, I think you've clarified something lurking in the back of my mind that I didn't have the experience to convey in words - and it's what prompted this thread, thanks.

My thoughts for Pi was not to run any CAD/CAM software, but rather just as a more powerful alternative to an arduino such as the Atmega328 on the Uno, I recall building a delta 3d printer and using a much more powerful processor than was normally used as it had to translate all the cartesean gcode to delta - and even then, if you threw to much at it, the gantry platform would literally microstutter as it failed to keep up - typically if there was too much precision on a curve (which iirc on 3d printer gcode, isn't a curve, its just lots of little straight lines, why its done like this I dont know....surely a curve would be better, the codes there right!?)

anyhow, I fantasise about using the pi and linux, but I'm not good with it, I'd love to be able to do "stuff" but I can't, I just follow guides, successfully do stuff that's over my head and miss the basic understanding behind what I'm doing, it's a barrier for me and prevents any genuine creativity in this area, I've got too much going on to do everything I want to do, but I will need to crack this at some point as I want to teach my kids the basics, I'll probably buy some sort of robot kit or something when they're old enough and hopefully we'll do a bit of something, structured text maybe, and achieve something from the screen to the real world! I remember doing 555 traffic lights at school, and loved it, I guess its all arduino and linux now, aside from BBC's and Acorns at primary school (which were well past EOL and no doubt just charity give aways), proper IT was just coming into schools as I was leaving - seems to have been a big void in that area though out the 90's

Dave, whats your thoughts on the GRBL/UNO combo, I have a fairly modern Lenovo M710q with an i7-7700 in the garage, it runs my 3d printer, so I have a PC, it's just very small and I don't think it'll run the G540 which as powerful as it is, is old tech.... its made for running a big lathe/mill really, each one of the steppers on that weighs as much as my whole 3d printer!

Edited By Russ B on 16/03/2023 12:05:23

I run GRBL on a Uno for my mill power feed, with a Bluetooth to "GRBL Controller" on my phone. GRBL is a great program for limited CNC, it runs lots of 3D printers and small routers.

The problem with GRBL is that it only takes g-code in on the serial port and turns out stepper pulses - it is in effect a "motion controller". Packages like Mach 3 / 4 nowadays delegate the pulse generation to a motion controller though driven with a more sophisticated set of instructions. The main function of Mach (or LinuxCNC etc) is to manage the g-code parsing, look ahead etc to maximise the efficiency of the system. Also they manage all the stuff like wizards, tool offsets, file management, estop, alarms, and so on. There are programs (like the one I use on my phone) that work with GRBL but as far as I know nothing approaching the functionality of even Mach3. And in my experience integrating them with GRBL is not straightforward. For details see the grbl wiki at **LINK**. Several programs are referenced there. But you could run one of these on your garage PC using an Arduino/grbl for motion control. Note that there is a "CNC Shield" for the Uno that takes 3 or 4 stepper driver ICs and mounts on the Uno - I use one of these on mine.

There are more advanced grbl versions that need a more powerful processor than the 328 and have more features and are much faster - even one that can do backlash compensation. Also there's a "GRBL Lathe" version I think on the Microsoft store. Look for grblHAL - even one that runs on a Pi.

John, thanks.

This is ringing a bell somewhere in the back of my mind, I recall the G540 wanted step pulse and direction info directly, i guess it simply passes estops and limits straight over the parallel port which is picked up by Mach3 on my old setup. I'm sure the Mach3 software was directly generating the step and direction info for the G540, maybe it was a plugin or something.

Inside the G540 its just 4x G250 separate stepper drivers maybe it's time to extract those and put them to use outside the G540.

I think step one.... might be, try and cheat, by a chinese CNC router thats supposedly turn key and see what happens.

backup plan, if i'm grasping this correctly, use my pi2 as a gcode sender (it has a 7" colour touch screen and enough IO to handle estops and limits I guess) and either send gcode to an Arduino motion controller, or perhaps, see if I can make use of a GPIO expansion on the pi2 and have the sender and the motion controller in one package and send step and direction directly to the G540 or G250 drive directly~?! (this sounds like its beyond my abilities, but someone may have done it already online and been kind enough to create a guide!) - All I'd need then, is a PC powerful enough to handle the CAD/CAM and create the Gcode (which my M710q certainly is)?

Chances are, I've miss-understood and I'm certain I've over estimated my abilities, I call it learning.

Well.... pending delivery.... I now own a SainSmart Genmitsu 3018 PROVer V2.

There were loads of different version and "non" brands of this machine, but this one seems a bit more refined, has a better controller with more IO, has limit switches for homing which non of the unbranded ones seemed to have and it it looks to have quite a comprehensive website, guides and a large community who seem to do lots of modding too!

It comes with an offline controller box too, so if I do want to slip the router back in and make something, I can stick a suitable gcode on the included microsd and setup my work coordinates etc without a PC.

They also do a laser add on....... and I've always want to have a go at that!!

So, I guess I now need to look for a suitable piece of software that incorporates a scanning feature, apparently its common but I've yet to see it and my google skills keep showing me the tool height setters in use, I think we can safely say they're straight forward enough!

Yes I noticed the pi4's aren't due back in stock for 6 months, they're powerful for the rrp, but at the prices they're selling for, there are better alternatives if (unlike me) you know a little bit about how to use them and dont depend on the community or generic support

I guess the problem is the ongoing silicon chip shortage where various issues continue to cause havoc in the industry. Sharp price rises and long queues worldwide...

Back to the OP, there's a fairly fundamental objection to using Raspberry as a motion controller. The Raspberry's "System on a Chip" is designed to run a multi-user/multi-tasking operating system sharing resources efficiently between hundreds or thousands of different tasks, and the one thing it's bad at is working steadily at a predictable rate on one job. Instead it delivers high power in short bursts with unpredictable gaps between. The gaps cause serious bother when controlling a fast moving CNC machine because Sod's Law guarantees the machine will need instant attention whilst the control process is in a gap and unable to respond.

A better answer is to use a microcontroller to interact with the printer, router, lathe or mill. Microcontrollers don't have to share. Instead they simply run one program flat out at a predictable speed.

Quite a common arrangement is get the best of both worlds by having a motion controller, such as grbl running on an Arduino, managed by a Raspberry. The Pi sends commands and downloads that aren't time critical to the microcontroller, which drives the CNC machine on the it's own. Then the power of a network connected Raspberry can be used for what it's good at, able to manage several CNC motion controllers whilst receiving new jobs from several CAD workstations, reporting progress, and letting the human play Minesweeper!

Dave

I thought I'd give a little update. I'm going down the GRBL route, it seems to offer everything I need and is free. I will be making a donation to GrblGru if the software does what I need. I watched one of their videos where they used the G38.2 command to scan the surface, setting out an boundary and step over, the software was then able to create an STL file directly from the data if desired, and could even create more points by interpolating the data. This gives me a 3D model of parts I want to scan. I can also use it in the future to engrave or laser 3d surfaces (if I buy the laser attachment)

I've built my CNC machine (it was almost fully assembled right out the box). I've plugged it in and tested it with the included "Candle" GRBL software as well as the built in offline controller. It all seems to do what it said on the tin. It's quite a sturdy machine all round, bar the Y axis which being the weakest link really drags the whole machine down! Given that the included motor is probably only about 75w I really don't think this matters. It is known for being one of the best "3018" CNC routers around, but I can reliably inform you, that it is at best, an engraver, not a router.

None of this matters for me, as it's basically just for metrology but I have put a wanted ad out for a pair of linear slides, ideally a pair of the MGN type, 12mm, with the H type bearings. I'm wondering if I could make use of the MGN9 however, but I don't want to skimp. Once modded the machine will lose some of its Y axis travel as I plan to make the carridge wider to better handle the side load when milling. I just need to be sensible about what I want to use it for, and ultimately, what it's worth. If I want a £1000 router machine capable of machining aluminium plate, it could be cheaper to just buy one!

So, I need to start digging around in storage to find my proper touch probe or 3D print something new with a simple vertical plunger & micro switch

Edited By Russ B on 28/03/2023 12:02:42

Interesting - I was idly wondering about 3D digitising and had had a scout around for suitable software without really finding much. I hadn't come across GrblGru though, so thanks for that!

(Decent looking 3D probes are available from the Chinese direct sellers for about £40)

I also looked at the '3018' type machines, but wanted some (modest) metal cutting ability. I eventually came to the conclusion that I'd need to upgrade / replace every component before I'd be happy with it, so I set off making my own, thinking it wouldn't cost much more - be careful of getting drawn in!

I (foolishly) added up what I'd spent on it - best part of £1000

Edited By Andy_G on 28/03/2023 15:01:39

Too late to edit the above, but you may also like to take a look at bNC which (I think) will run on the Rasberry Pi to use in conjunction with your GRBL controller.

I haven't used it, as it requires python to be installed on a Windows machine.

https://pypi.org/project/bCNC/

Edited By Andy_G on 28/03/2023 15:49:03