Author Topic: Building Tom's "Easy Mill"  (Read 27633 times)

Davetech

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Building Tom's "Easy Mill"
« on: June 19, 2009, 04:37:44 PM »
I've moved these posts over from the Heliostat section because I felt like I had highjacked the thread.  :-\


Okay, enough of this nonsense of wasted time on trying to get boards etched for my heliostat controls.  You have probably seen this by Tomtechart, but if not, you are in for a treat:



I've been wanting to build his "Easy CNC Mill" for some time, but I put it on the back burner.  Now I have  moved it to the front burner. Just got back from spending $55 on black pipe and threaded rod, so there's no turning back now!




I'm starting to feel like old Don Quixote charging at learning curves.  But it's fun.




Davetech

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Re: Building Tom's "Easy Mill"
« Reply #1 on: June 19, 2009, 04:40:14 PM »
Whew... my eyes hurt....  I've just spent the last 18 hours (literally!) installing and uninstalling demo after demo after demo... cam programs, pcb designers, cnc drivers, etc... 90% of which cost more than my net worth anyway...  and of the few free (or at least cheap), nothing seems to put out file formats that the others can use.

Caution: Long Ramble Ahead.

I had installed PCB Artist, and I really liked it, got used to using it. Produced my Heliostat Motor Control Board with it. But it is free from a board manufacturer and saves to a format that nothing else can import so I can't use its files to make gcode or anything else. The best I can do is print out the top and mirrored bottom and take the prints up to an office supply, get them to copy them on their laser printer and hope the iron-on method would work. I'm building the desktop cnc to get away from having to make boards that way, but I have to make the driver boards for it!

I tried Eagle and hate it. I just got through doing a little board with Diptrace and it exported to dxf but when I fed that to Ace Converter (which is supposed to convert dxf to Gcode, it just produced garbage. And yet Cambam would load it up and display it.

I dunno...  .dxf, .cam, gerber, gcode, .brd, .nc, .cb, .sch, .tap, .dip, .dch, .pcb, .sch, .drl ....  I'm soooooo confused.



There was one bright moment today though. My latest eBay purchase arrived.  Got 3 new 17PM-K103-24v stepper motors for 9.99 plus a little shipping. I think I did good. They are not huge but they should be considerably stronger than the steppers I pulled out of the dead printers.




Here's a link to a partial list of the software out there...  http://www.olimex.com/pcb/dtools.html
It kept me busy for a while!


Gabriel

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Re: Building Tom's "Easy Mill"
« Reply #2 on: June 19, 2009, 05:50:28 PM »
Yeah, there really needs to be a warning label attached to CNCs about how difficult it is to learn the software. I know the time I spent learning how to use it was just a tiny fraction of what I spent building my CNC. It was a complete nightmare.  ::)


I've never tried making PCB boards, so I can't give any tips on software. It's something that I might try out myself one day though, so I'm glad you're getting it figured out first so you can show me what to do.  :)

I just started downloading PCB Artist. I might have an idea for a round about way to export. If it works, I'll let you know.

Take Care
Gabriel

Davetech

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Re: Building Tom's "Easy Mill"
« Reply #3 on: June 20, 2009, 02:35:09 PM »
Making some progress.  Adhering pretty much to Tom's design except for a couple of changes that might be noteworthy.

Tom used channel aluminum for his rails. I had some channel steel that I used. It is the stuff you put vertically on a wall and has slots in it that shelf brackets fit into. It was nice and straight but a bit rusty. I gave it a good working over on the wire brush of my bench grinder and got it where you could run your finger over it and it was smooth to the touch. But when I assembled the X-stage and installed the little bearing assembly, I was concerned over the amount of friction there was. It was a lot harder to push and pull than I expected. In the video, Tom's looked like it slid quite easily.

While I was mulling this development over, my eye strayed to a pile of junk on the side of my workbench in which sat a marble.    Hmmmm...   I put the marble on the slot of the rail and put another piece of channel steel on top of it. It slid practically frictionless. So I hunted down 3 more marbles and tried it again. The top rail still slid easily and there was no discernible latitudinal slop. "Hey... I might be on to something here!" said I. So, as you can see in the pictures, I put it together with glass marbles to act as bearings. It remains to be seen how well it will work in actual practice, but if it works, marbles can be had 100 for a buck at the local dollar store. The bearings Tom used cost a bit more and are harder to find.  I put a screw in the end of each rail to keep the marbles from escaping their duty. (I hate it when I loose my marbles!) :D


(July 18 EDIT):  Okay, it's a month later and though the marbles ~almost~ worked, they had a few small problems.  While the stage was traversing, the line of marbles would hit the stop screw but the ones in back would keep on pushing. This would finally push a marble out of the rail and onto the floor. Also, I discovered that the marbles all looked the same size, but were not. Slight differences caused uneven routing depths.  I've come up with something even simpler than the marbles but I won't present it until I know it works.
_________________



I used 1/4" x 20 threaded rod and found that "3/16" ID Fuel Hose (Lowes #22283) was perfect to join the rod to the 1/4" shaft of the motor.  


In the video, Tom showed how to wrap metal around a nut to make a bracket for the threaded rod to attach to the underside of the stage. I did it a little differently and I think this was easier. I just took a standard size cable clamp, smeared a very thin layer of gorilla glue inside it and inserted two 1/4" x 20 nuts. I threaded the rod into them so their threads were in sync and let the glue cure. I'm sure this looks better than what I would have wound up with trying to copy Tom's metal gizmo.

(July 18 EDIT):  Another good idea gone bad.  Although securely bolted down, the clamp was still slightly flexible and gave me a small backlash. Also, as Gabriel pointed out, steel nuts are not good. The lithium grease has already turned black from metal particles in it.  I really like the picture though.
___________________


So I need to finish up the Y stage. I hope it won't matter if the motor is mounted on the side rather than in the center of the stage. I can see it making a difference if I were routing wood or metal, but I guessing that just buzzing the copper off a pcb won't give any side torque.

I find myself guessing a lot here.  I looked high and low for a cnc noob faq. All the faq's I found were forum rule faq's... not things like "is 1/4 x 20 threaded rod good to use for a pcb mill?" Guess that depends on a lot of variables though.

Haven't even started on the Z stage.  I'm thinking about moving the post over to the corner and having it point out diagonally to the center of the work area.

Oh well, 'nuff fer now.  
« Last Edit: July 18, 2009, 02:04:28 PM by Davetech »

Gabriel

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Re: Building Tom's "Easy Mill"
« Reply #4 on: June 20, 2009, 04:12:00 PM »
Looking Good!

It's pretty clever what you did with the marbles. I've actually attached stepper motors to lead screws the exact same way you did with the fuel hose. It seemed to work out pretty well. Of course, it wasn't in use for very long, so I can't say how it will hold up over the long term.

The 1/4" x 20 threaded rod you used for a lead screw should work fine for what you're doing. I will mention though that the nuts won't hold up very well. It might not ever really be a problem a small CNC like this one, but, for the first CNC that I built, they caused a great deal of aggravation. I personally ended up making some new ones out of plastic, but I've seen other people use brass nuts which I guess must have less friction and therefore less wear and tear.

They should be fine for a fairly long time, but, if you start losing steps one day in the future, try replacing the nuts to see if it fixes it.

It's looking awesome!

Take Care
Gabriel


Davetech

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Re: Building Tom's "Easy Mill"
« Reply #5 on: July 03, 2009, 02:23:56 PM »
Thanks for the heads up on the nut wear. I'll keep an eye on it.

Today two major items arrived.

I just changed the brushes in my Dremel tool (again) and didn't look forward to using it as a router even for light work like pcb etching, so I've been on the lookout for a good router motor. I'd read that some people use Rotozip with good results and I have been bidding on them on eBay. Finally got one that stayed down in my price range. Got it for $12.50 plus $12 shipping!  It's not new, but it looks like it has had light use.




I finally decided to get the chicken first and I'd make the eggs later (aka: making pc boards for the pc board maker).  I think this will drive my three 1 amp stepper motors just fine. Another eBay goodie which I got for the starting bid of about $50.  Hell, it would have cost me close to that just for the parts even if I had made the board for it!




Now that I have the Rotozip, I can continue building the Z-axis stage since I know the measurements of my motor.

Don't think I'll need the marble bearings, but I may use springs to balance out the weight of the motor. It is fairly heavy.

Any luck with saving the output of PCB Artist to other format? 

I think I'll be able to work with KCam.



Gabriel

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Re: Building Tom's "Easy Mill"
« Reply #6 on: July 04, 2009, 07:19:33 PM »
My original idea for for exporting the PCB artist projects didn't work. I just got finished playing around with it though, and I did see that if you go to "Output" on the menu bar you can export to DXF.

If your like me, you tried this and didn't see anything when you opened it. (I opened it in CamBam) After playing around with it though, I did finally manage how to get some circles to show up correctly. A lot of the stuff just doesn't show up though, so I don't know what to do.

Good Luck!
Gabriel

Davetech

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Re: Building Tom's "Easy Mill"
« Reply #7 on: July 17, 2009, 12:22:41 PM »
"IT'S ALIVE!"   Muahahahahaha....

But like Frankie's monster, it's ugly and a bit dumb.  And there's too much slop. I think the marble trick is not going to work out.

Found out a computer power supply won't run it because the sudden current demands scares the switching circuit and it shuts down. So I've been running the motors off my bench supply and just using the regulated 5 volts of the computer supply for the control circuitry. My bench supply has a variac mounted on the front of it, so it is adjustable. The plate on it says 0-8V dc @ 30 amps (yeah, it's a heavy sucker!) but the 8 volts is with the variac only turned half way up. The output will actually go as high as 18v and that's measured under load.  But I'm going to build a 24 volt supply for the mill.

Also, I can see that the #64 (.036") router bits I got are too large for pcb work. After wrestling with software for a day and a half, I finally got a few traces milled into some scrap wood and there's just no way to route isolation grooves around ic pads with that size bit. But I'm learning. Haven't broken a bit or burned a component so far, so I guess I'm doing all right. Thar's a lotta larnin' yet to be done.




« Last Edit: July 21, 2009, 03:00:57 PM by Davetech »

Gabriel

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Re: Building Tom's "Easy Mill"
« Reply #8 on: July 20, 2009, 06:07:55 PM »
Hey Davetech,

Sounds like you are moving along.

It's strange that you are having trouble with the computer power supply. I've always wanted to see if I could utilize one because they really are good, cheap power supplies. I know one site that I like to check out for clever CNC ideas is RepRap.org. The RepRap might not technically be a CNC machine, but the technology is still very similar. When I read your post, the first thing that sprung to mind is their tutorial on adapting PC power supplies.

You might have already seen this, but the link is http://www.reprap.org/bin/view/Main/PCPowerSupply Although, it sounds like you already have plenty of power. :)

On an unrelated note, I put together an instructable. http://www.instructables.com/id/Simple-Ebb-and-Flow-Hydroponic-System/ It was you who gave me the idea.  :)

People always seem to concentrate on generating electricity and getting better gas mileage to try and go green, but they always seem to forget that the food they eat has as big impact on both the environment and the pocket book. I think it's an important issue, hence the hydroponic instructable. [end of rant]

Anyway...

By the way, thanks again for the link from your instructable and also for the one from your site. If you had something on your site that you want me to link to, just let me know. I'll blog about it or something on my homepage.

Thanks
Gabriel

Davetech

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Re: Building Tom's "Easy Mill"
« Reply #9 on: July 22, 2009, 11:10:13 AM »
That RepRap page is a good pinout reference. 

>"To supply higher current, it is a good idea to connect several of the black wires together to provide ground and several of the yellow wires together to provide +12V. "

I didn't do that. Maybe that was my problem. I was using an old AT supply rated at 250 watts. Anyway, I have found that my motors work very well at 8 volts with no ballast lamps. The analog ammeter shows them drawing about 300 milliamps and they stay cool to the touch even after going through a long milling session. The heat sink on the driver card also only gets slightly warm and I have a cpu cooling fan keeping it company. So I'm just going to make a regulator board with a full wave bridge rectifier, LM7805 and LM7808 regulators, and fuses, switches, LED's, and any other bells and whistles I can think of. The LM7808 is rated at 1.5 amp so it should be able to supply the motors without a pass transistor. We will see.


Kudos on your first Instructable!  It looks great. It occured to me this morning as I sipped my morning coffee, that it simulates the way nutrients are delivered to plants by nature. When it rains, more than water is delivered to the roots. The water dissolves nutrients from the surface soil (where all the new dead stuff is) and carries them down to the roots. As we have seen time and time again, nature's way is always the best since the plants have evolved to work best in those conditions. Your "breath of fresh air" simulates a good rain. I haven't read any books on hydroponics, but your system seems to make good sense. 

My mill has undergone a lot of changes in the last few days. Mainly attempts to get more precision and eliminate backlash but also to increase the work area. The steel nuts on the lead screws are gone, replaced by plastic nuts made with your method. I used black 1/4" ABS plastic, sandwiching the lead screw so the "nut" is 1/2" thick.
 
The marbles are gone. I'm using galvanized steel electrical conduit as a rail for the channels to slide on. It seems to be working very well. I'll have pictures soon.

Right now I'm having the most trouble getting the platform perfectly level. I don't see what is causing it but the depth of the cut varies slightly on different areas of the platform and with thin pc board, cutting on both sides, there is no room for error. A cut on one side easily cuts through to a cut on the other side if there is the slightest variation. I need thicker pc board too.



Davetech

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Re: Building Tom's "Easy Mill"
« Reply #10 on: July 22, 2009, 02:06:30 PM »
Hey Gabe,

Let's see some pictures of your now-working heliostat!  I wanna see!  Better yet, you mentioned you had a new video camera...  YouTube time!  :D


Here's some pics of my z-stage in its present reincarnation:



That's a limit switch just to the left of the motor. Notice the clamping ring at the bottom. It came with the RotoZip to clamp on an adjustable depth dooma-flotchie. I mounted it up to hold the Rotozip on the stage.




The Rotozip mounted up and ready to scream... literally.   




As luck would have it, the diameter of the mount happens to be exactly the size of a toilet paper tube... thus the home-made plotter pencil holder.
Works real good. The pencil can slide up and down but is held in place by a spring hot glued to it close to the point. Thus the stage can be lowered enough to put spring pressure on the pencil. You can just barely see the spring in the picture. I thunk this up all by myself.  :P




Even better... the mount diameter also happens to be the same as my Dremel tool!
A single wrap of friction tape makes it a snug slip-free fit. I've been using the Dremel for most of my testing because it works pretty good and I don't have to wear hearing protection!




Here's the Z-stage plastic nut I made from your directions on your site, Gabe.
I used two pieces of 1/4" black ABS plastic from a plastic pipe I flattened after heating it. 
Damn, I'm good.  Looks like someone would give me a job, don't it?




Gabriel

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Re: Building Tom's "Easy Mill"
« Reply #11 on: July 22, 2009, 07:56:56 PM »
Wow! It looks like it is really coming along. You're doing a lot better than I did when I built my first CNC.

Sadly, I spoke too soon when I said that I had my heliostat working. I thought that fixing the misalignment caused by the compass would make it work. It is still doing the same thing though.

If you check the homepage of this site, you will see that I do have time lapse video (made with my new camcorder :) of a small test heliostat working beautifully. The fact that the test heliostat works does at least prove that the calculations I programed are correct.

I have ruled out just about everything that I can think of. I am beginning to wonder if the gimbal idea is throwing things off. I might have to add even more calculations to take it into account.

Right now, it's been cloudy out, so it tends to slow things down.

Oh well, hopefully it won't be too much longer now before it's finished.

Take Care
Gabriel

Davetech

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Re: Building Tom's "Easy Mill"
« Reply #12 on: July 23, 2009, 01:23:11 AM »
Well, I went and watched your movie.

And then I watched it about 20 more times.  That is so cool!  I'll bet it was really satisfying to see your work turn out so well.

Seeing the full sized one work will really be a treat.



  for inspiration. I was expecting the ground to smoke and rocks to explode!



« Last Edit: July 23, 2009, 01:29:00 AM by Davetech »

Davetech

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Re: Building Tom's "Easy Mill"
« Reply #13 on: July 24, 2009, 08:46:18 PM »
Okay, forget everything I said about the power supply.

I've changed my mind... again.  ::)

I played around with some higher travel and feed rates, thinking that I might want the speed if I were cutting foam or plotting. At higher feeds, my motors started sounding like they were crushing gravel and they were loosing steps like crazy. I added some voltage (keeping a close eye on the ammeter) and they smoothed out. Then the stuff that I have read about needing higher voltage for more speed started making sense (sometimes you just have to clobber me between the eyes with the obvious).

So I spent the day making a ballast lamp board. My first milled printed circuit board. Yay!  I wrote the g-code for it, so i got a little experience there too.



I wished I had a bunch of those wire screw posts like came on the driver board, but I did have these nifty lamps that look like fuses. I have a handfull of them in 6v, 8v and 12v. I'm using 6-wire motors wired for bi-direction so just using 4 wires each. That meant 2 lamps per motor since the coil circuits have to be totally separated.

Got it all hooked up and test-jogged it around a bit at 14v and it looked and sounded good, so I loaded up Tom's G-code for his easy driver board and turned it loose just for laughs.


I should have sharpened the pencil first.  This stuff is so crowded and small I don't think I could mill it with my .036 tool. Guess it would have to be etched. It's not perfect but I think I have just about licked the backlash and slop problem (there's a little wiggle in the pencil holder).
 



Gabriel

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Re: Building Tom's "Easy Mill"
« Reply #14 on: July 27, 2009, 04:03:45 PM »
That's looking really good. It seems like it has really good precision.