[flightfollowing]

Here are pics of a g0704 cnc conversion, very simple, tried to keep it as cheap as possible. Based on Hoss's, but made most of the parts somewhat differently and more simply. Used nylon spacers as standoffs and in place of alum block parts for initial assembly and fit up, but am very happy with them so I will keep them. Used X and Y ballscrews, but left Z as stock screw. Using tinyg is cheap and saves cost, no need for parallel port computer (I use my laptop) and no need for Mach 3.

Attachment 224566
Z axis, used existing M5 tapped holes from cap, did not need to drill and tap new holes.

Attachment 224568
Y axis, with nylon spacers and stock bearing blocks

Attachment 224570
Ballscrew Y, made bracket with two pieces of 3/8 aluminum sandwiched with roll pins.

Attachment 224572
X axis, using 1/4 aluminum plate, nylon spacers, and existing M6 holes holding the end caps on.

Attachment 224574
Y axis with stepper mounted with nylon spacers, note the handwheels to retain manual capability.

Attachment 224576

[SCzEngrgGroup]

I think you're going to find the screws in those Nylon stand-offs come loose on a regular basis, and the motors start moving around, introducing backlash. Nylon is slippery, and
will also tend to "creep" under load.

What is "tinyg"?

Regards,
Ray L.

[109jb]

Interesting approach. As for the nylon spacers, I would think that the screws go through the nylon standoffs and are not actually threaded into then. I could be wrong, but would think the screws are threaded into the aluminum.

I have looked at the G-code controllers based on microcontrollers like the arduino and did a lot of research on them. They are attractive because of the small size. I envisioned a little bitty box on the back of an lcd monitor. That would be ideal and what I was hoping the microcontroller based interpreters could do but decided to pass on them because none of them support some features I feel are very important.

1 - First, all of them only use only a subset of the RS-274 g-code command library. The codes that are incorporated are the very basic ones. Many of the ommitted codes I find very useful. Some examples of ommitted codes are G40, G41, G42 (cutter diameter comp), G43 (tool length offset), G81 through G89 (Drilling and boring cycles). I'm sure there are others, but most of the microcontroller based G-code interpreters don't have enough memory to allow for the program overhead to include these.

2 - Most of the microcontroller based interpreters simply read a g-code file from an SD card, stick, etc. You can stop and start it, but you can't override most on the fly. For example you can't use a feedrate override or spindle speed override with them. Or even simler. Lets say you forgot to program a coolant on command. It would be nice to just hit a button on a GUI and have it come on while the g-code is already running.

3 - You have to load the g-code and start from the beginning. Let's say that you have a program, and you break a tool after finishing 90% of the machining. You can't replace the tool and start where you left off. Likewise, if you want to edit something and restart in the middle of a program you can't. An example would be a part with loose tolerances on everything except a single hole that is milled using circular interpolation with a tight diameter tolerance. You couldn't mill the part, measure the hole and then adjust the G41/G42 compensation that isn't there anyway and recut just the hole.

4 - There is no way to edit the g-code file on the machine. You would have to edit it on a PC or tablet or something and then re-send it to the microcontroller or put it on sd card and re-load it.

5 - IMO they aren't even really attractive in terms of cost since older cheap PC that run LinuxCNC well can be had for next to nothing. Certainly a lot cheaper than even buying an Arduino or similar microcontroller. I actually got 4 PC's for free that only needed hard drives. A cheap tiny hard drive most would consider outdated is more than enough for LinuxCNC. I had a couple already, bought a couple more off e-bay for peanuts and had 4 CNC capable computers. I actually set one up to boot from a USB stick without a hard drive even installed on it as an experiment. Nobody wants 15" LCD monitors anymore and you can get those for free too. I was given 6 of them from a company that upgraded their office monitors. They were happy to see them go because they were about to pay for electronic recycling service to come get them.

Many of these are not a factor on machines like a 3d printer, which is why they are so popular in that realm. I still monitor some of the different sites about these and it is amazing what the little microcontrollers CAN do. It is just that some of the missing functionality is not an acceptable trade off for me. Others may feel that they can live with those missing features and that is OK too. I did see not too long ago that the GRBL group has a new interface that may solve 2, 3, and 4, but would require a separate PC, tablet, etc running JAVA to work. That kind of defeats the purpose though.

I realize this post sounds very negative and it isnt meant to be a total bash. The development of these little controllers is very exciting and I am hopeful that some day they will have the functionality that I need. I think the biggest benefit of them is that they don't have to deal with all the overhead of a bloatware OS, other software and hardware controls, etc. All of that stuff can be troublesome in regard to real-time operation and just controlling the machine. What I would like to see is a full GUI running on a tablet or netbook, or similar that allows all the stuff I mentioned above while allowing the microcontroller to just perform the real time operations required to run the machine. I feel if that happens, the mahcine will be stable with no issues in regard to the real-time stuff, and the GUI could run on just about anything without needing to worry about having that part be real time dependent. The code on the microcontroller though has to be able to incorporate the full RS-274, (or at least the parts I like) and be able to accept changes on the fly (ie: feed and speed override for example). Easier said than done though. I'll keep checking them out and hoping though.

[flightfollowing]

Great feedback gentlemen, much appreciated for a cnc nooby. I'll see how the nylon standoffs work, probably replace them if they loosen or are not stiff enough, using al ones was my initial plan, but had the nylon ones so I used them for the proof of concept. They are not threaded in nylon, long Maxine screws into the aluminum.

I posted your great list of Gcode limitations back to the tinyg developers at synthetos, when I get some answers I'll repost.


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[speed_racer]

Hey, nice work.. Old thread I know but... How did you order the right sized ballscrews? This was the only thing that put me off buying everything DIY.. So I got a cncconversionkit instead.. At $905aud and Chinese ballscrews are $95 each, I couldn't be bothered waiting for multiple ballscrews due to wrong sizing etc.. But no one had the ballscrews size or a defined link to the supplier..

[flightfollowing]

The ballscrews came as a kit, their are several kits, but this is one:
G0704 CNC Update Machine Ballscrew Kit G0704121212, with nut for B-G0704M | Automation Technology Inc

So far the nylon spacers have worked great, the nylon spacers are just unthreaded spacers, threading is in the alumimum, and not loosening a year later. The other advantage of the nylon spacers on the Y axis is they yield and act as a soft stop when running off the table.
The tinyg controller is definitely inferior to a mach controller, but it is a fraction of the price and super simple to install, and can handle many cnc tasks.

[engele]

I know it has been a while anyone posted to this thread, but I have three 425oz Automation Tech steppers and a G0704. How does the 425oz stepper perform on the z axis? What level of reduction did you use? And last but not least, are you still happy with TinyG?

Thanks,

[flightfollowing]

It has been a long time and my memory is fuzzy, but the stepper I have on the Z axis works fine, same as X and Y, but different gearing. I don't remember the gearing, but I just put a ruler to the gears and the small one is a bit under 7/8" diameter and the large one is about 2 1/8" diameter. It is not fast, and I don't remember the details on programming, probably just 1 or 2 half steps rather than 16 steps. I have not been using the tinyg too much recently, I built a full sized bridgeport with mach 3 which is primary at work, the tinyg is at home. Seems like I have not updated the tinyg firmware in awhile, but it is a bit tricky, I have to relearn it now and then when I use it (I use the 704 manually frequently, but CNC aspect rarely since finishing the mach 3 bridgeport style machine). Note that I did not install a ballscrew in the Z axis, only the X and Y, so Z runs fairly slow.

[engele]

I think that mine will likely run slow on the z as well. I have not purchased a TinyG, but had been thinking that it would be a fast way to get the machine moving under its own power.

When you use your machine manually, are you using a DRO? The handwheel indicators are now gone...


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[engele]

Also, did you replace the bearings in the stock bearing blocks with Angular Contact bearings?


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[speed_racer]

Thanks I actually didnt end up using the tinyG, I just used an arduino uno with the grbl software on it and wired it up (at a cost of about $13AUD for the arduino) I did find that using it with Chillipeppr CNC controller it worked well and easy to setup.

I'm now trying with the DB25 breakout board that came with the stepper motors and they run inverted. So in Linux CNC it took a little mucking around but I was able to control the steppers by ticking the invert box during the setup.

Mach3 on win7 on the other hand will not control them at all, So I'm going to try Mach4 with the parallel port driver and see if it works tonight, if not, ill put windows xp on and see how it goes.

The Chillipeppr interface is heaps easier to work with, if only they had a downloaded version with backlash compensation and a couple of other features, it would putarcsoft Mach3/4 in the stone ages..

[engele]

Where would I find a write up on using an Adruino like you did speed_racer?

I understand that TinyG has some amazing acceleration control that GRBL doesn't (though GRBL is getting better).


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[speed_racer]

Where would I find a write up on using an Adruino like you did speed_racer?

I understand that TinyG has some amazing acceleration control that GRBL doesn't (though GRBL is getting better).


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It was actually fairly easy.. What I did was I watched NYC CNC do a video on Chillipeppr ( https://www.youtube.com/watch?v=gzLYNSQEPDk ) and using the stepper motor drivers I got from Long-motor on ebay, I wired all the negatives together and joined to a common negative, then using the GRBL connecting diagram located here https://github.com/grbl/grbl/wiki/Connecting-Grbl I could connect the pulse and direction up (as they only need 5v which the arduino runs natively) and got it working.

I've been thinking I should do a write up on this myself because I didn't see anyone who had done a write up on using Large Nema34 stepper motors with the GRBL software on an arduino to get it to do CNC work. only Nema17's and stuff.. When using the Grbl and Nema34's with external stepper drivers, you can crank up the pulse/step and your acceleration rates, When I first played with the grbl, i was wondering why it would take forever to ramp up and never get to top speed even over a 250mm move using G0x250 for eg. and it was because the parameter #110 and #111 were really low for a nema34. I think I cranked it up to like 1000.. just play with the number, you wont break it, you will just stall the engine and may need to hit the reset button on the arduino.

I do have a video of it running... https://www.youtube.com/watch?v=sxKs9nC7zsI

This was before i started ramping up the speeds.. I got it to spin quite quickly running the speeds at about 7500 (in the parameters at the top)

$110=5000.000 (x max rate, mm/min)
$111=5000.000 (y max rate, mm/min)
$112=5000.000 (z max rate, mm/min)
$120=1000.000 (x accel, mm/sec^2)
$121=1000.000 (y accel, mm/sec^2)
$122=1000.000 (z accel, mm/sec^2)
If you have any issues, just ask,

[datac]

What drivers are you using to push those nema 34's? Does grbl have adjustment for step pulse timing and the like ?

From what I've read recently , the latest grbl release might rival tinyg for motion. Still wholly despise the must have internet connection for cpepper though.....

[engele]

My understanding is that you don't have to run chilipepper online, you can serve it from your local machine, or another machine on your personal network. The downside to this is that you have to update chilipepper on your own rather than dynamically always having the latest version.

Edit: I just read the github page. Running locally isn't a simple thing... https://github.com/synthetos/TinyG/wiki/Chilipeppr

One of the advantages of TinyG is that the stepper drivers are built in (up to about 3A or so with a heat sink).


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[engele]

@speed_racer your YouTube video is marked private.


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[speed_racer]

@speed_racer your YouTube video is marked private.


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My bad.. Should be public now (possibly why i haven't received view for it yet lol..)

[speed_racer]

What drivers are you using to push those nema 34's? Does grbl have adjustment for step pulse timing and the like ?

From what I've read recently , the latest grbl release might rival tinyg for motion. Still wholly despise the must have internet connection for cpepper though.....

Im using the drivers that came with it as a kit. ( UK Ship 3AXIS Nema 34 Stepper Motor 1232oz IN 5 6A CNC Plasma MILL | eBay )
The drivers are DM860A which seem to work fine.

[speed_racer]

My understanding is that you don't have to run chilipepper online, you can serve it from your local machine, or another machine on your personal network. The downside to this is that you have to update chilipepper on your own rather than dynamically always having the latest version.

Edit: I just read the github page. Running locally isn't a simple thing... https://github.com/synthetos/TinyG/wiki/Chilipeppr

One of the advantages of TinyG is that the stepper drivers are built in (up to about 3A or so with a heat sink).


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@engele Thanks for pointing that out. I didn't think it would be that easy.. I'll make a copy of everything and set it up over the weekend and put a zip file up here with the contents(No guarantee's ill keep it updated though). that way I can use a Raspberry PI which I have lying round instead of a full desktop with LinuxCNC.

Thats the other thing, LinuxCNC I could jog each axis easy.. Mach 3 on Windows 7 though, doesn't want a bar of moving anything. I'll try with win xp tonight and see how it rolls.. if not I can always change the wiring and use Arduino & Raspberry Pi with Chillipeppr (I wonder what that would taste like?)

[engele]

You know what would be pretty cool, but might be a pain to set up is an image for a raspberry pi that would serve chilipeppr...

I may play around and see what resources outside of the main site are called by the application.


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