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Forum Index : Other Stuff : just another CNC project
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| Dinges Senior Member  Joined: 04/01/2008 Location: AlbaniaPosts: 510 |
Nothing much to report from this part of the world w.r.t. progress on the 10hp motorconversion. Have been busy the past month with another project, the construction of a CNC router. About 20 years ago I played around with stepper drivers and interfacing to the PC too (even wrote my own 'CAD/CAM' software for it in Turbo-C; wish I could refind it; probably somewhere in that stack of 5.25" floppies...) but interest shifted halfway through the project back then. Anyway, reading about Glenn's (and other's) CNC projects on this site gave me the itch again. Decided to start with the (for me) easy part, the electronics controller. It's a basic design around the L297 & L298 (schematic stolen from Glenn's projects files, but it's a straight copy from the L297 datasheet anyway; full and half steps, 2A per phase) with some very minor improvements as more/better reverse-polarity protection and adding plenty of LEDs to indicate status of the power lines and outputs. One can never have enough status indicators in complicated systems like this. Decided to settle for 4 channels (I really wanted to go for 5, but I only had 4 each L297s and L298s in the parts bin; that, plus the cabinet didn't have enough room for 5 driver boards). 
Threw together a simple interface circuit (straightforward, just a few 74HCT244 buffer ICs), some relay drivers and again plenty LEDs to indicate status of the various signal and power lines. 
The power supply is (of course!) another Oztules-conversion job, a PC PSU modified to 24V/10A. But don't tell him... or he may want even more royalties. 
All combined and wired up it starts looking like this: 
After final testing ready to box it up: 
(for those interested, more and high-resolution images can be found here: http://picasaweb.google.com/motorconversion/CNC#) It passed all testing so far. Everything remains nice and cool (L298s, voltage regulators, computer power supply, etc.). The only things that get hot are the stepper motors themselves. Hot enough to cause burns. Also gave the software (Mach3) a quick try-out, but my initial fears were confirmed: there are too many timing-jitter problems using this windows laptop with Mach3. The included 'drivertest.exe' software already hinted that this would likely be an issue with my configuration. Will soon give KCam a try; if that doesn't work, it will either be a dedicated PC with Linux EMC2 or some old DOS software. We'll see. Next step will be building the actual router/engraver. I have plenty of ideas and plans on that too, but nothing solid yet. Apart from the CNC controller I've also experimented with laser diodes from old CD and DVD burners. VERY impressive, those laserdiodes... driving them with 150mA and properly focused with a collimator they easily burn black plastic (or even through it, if it's thin) and burn wood (and skin). More powerful technology at our fingertips. Truly exciting times we live in! ...so the above explains why progress on the 10hp conversion has been slow... 
Peter. |
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oztules Guru  Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Fiendishly evil of you ..... now I'm thinking I might need one of those... dammit. I trust the cheque is in the mail as usual... I will be a something-aire soon if I don't watch it 
Very nice 1 off looking device. Do you see it doing prototype circuit board "etching"?. You may draw the conclusion from seeing my high tech EV, that mine would not look anything like that.... (more like a rats nest with hot bits in it.  )
Nice project, look forward to seeing what you make with it. ...........oztules Village idiot...or... just another hack out of his depth |
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vasi Guru Joined: 23/03/2007 Location: RomaniaPosts: 1697 |
Wow! I like how they look, very professional. I have also a stepper driver in construction (only half step, because the pics are 8 pin). Friday I will have my pics to test with. Hobbit name: Togo Toadfoot of Frogmorton Elvish name: Mablung Miriel Beyound Arduino Lang |
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| Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510 |
Oztules, One idea is to mill printed-circuit boards. Another to engrave frontplates and nameplates. Laser 'scribing' and dot-peening are other ideas to play with. Milling wood and plastic parts wood be nice too, though I don't really have the intention (yet) of milling windturbine blades. (why bother with CNC when a chainsaw can do it too, with much more noise and chips flying about your head... )
Vasi, looks nice. I decided to go with standard stepping ICs, but the downside is I can only do full and half stepping. With PICs, it should be just a matter of software to go to microstepping? One thing I've noticed is the huge improvement (in vibration and torque-ripple) of half stepping over full stepping. If microstepping gives the same improvement over half stepping as half does over full, then the next controller (no one I've seen gets a CNC machine right the first time, so it'll be a question of 'when', not 'if' a new machine will be built) will definitely be a microstepper, preferably with more driving capability (4-5A). And 5 channels, of course, just to be on the safe side w.r.t. future expansions. One thing that continues to surprize me is the overlap of interests I see in this board and the IRC on subjects other than windturbines. CNC machining is definitely a topic I've noticed a lot of RE-ers have been playing with (or are interested in) too. Peter. (and for some *very* strange reason, growing peppers also seems to have more than its fair share of RE enthusiasts) |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5030 |
Good work Peter, very neat. Yep I think they need that. Both the modules I bought have failed, the L298 blowing its top for no apparent reason. Umbuntu EMC2 runs very fast and smooth compared to the Windows based offerings, but is much more compicated to configure and use. Keep us posted. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
You might find that just putting some shottkey diodes between each stepper output and the supply and ground will solve most problems. This will not replace good power supply bypassing. H-bridge drives have a way of letting the smoke out. become more energy aware |
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| vasi Guru Joined: 23/03/2007 Location: RomaniaPosts: 1697 |
Yes, is a matter of software when you have enough memory space. That's encouraging. I'm advancing step by step (half steps, as usual  )
Then maybe I should modify my schematics too, adding LED's on all four outputs... will look nice for sure.. at least. on testing board... Hobbit name: Togo Toadfoot of Frogmorton Elvish name: Mablung Miriel Beyound Arduino Lang |
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| Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510 |
Vasi, I just counted (from memory) 43 LEDs in the device: 6 LEDs on each stepper board, one in the PSU, and 18 on the interface card. What can I say... I like blinking lights
(in hindsight, I would have added 2 more LEDs per stepper board, to indicate direction and step pulse signals; at the time I didn't include them because I wasn't sure if the buffer IC could drive them (I even didn't know whether I would add buffers at all...); in hindsight, the 74HCT244 can take the extra load. There are step/dir LEDs on the interface card, but it would've been handy to have them on each stepper card too) I figure they're not important in normal use... but when it's time to debug a problem it may provide a lot of immediate information at a glance, without having to resort to the multimeter or oscilloscope. And credit where credit is due... Ron reminded me of the benefit of this (when I was still doubting whether to add them myself; guess he convinced me of something I already knew) The LEDs also make it immediately obvious when (slowly) stepping whether the mode is half step or full step. But the most important reason is, of course, that they look cool. Maybe I should've used blue LEDs too... 
Peter. |
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| Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510 |
Just built a dedicated PC for the CNC project and installed Linux/Ubuntu 6.06LTS EMC2 on it. In line with the rest of the project, no bought parts were used (neither hardware nor software). The PC is made from various bits of hardware that others threw away. The specs: P4, 2.0 GHz, 512 MB RAM, 40 GB HDD. The software with OS, EMC2 in Linux/Ubuntu, can be downloaded from here: http://www.linuxcnc.org/. Works off a live-CD too (even on a PC without a harddrive... how I ran it initially, from CD...) Timing jitter of the system (even using the onboard video) is less than 17us, which puts the system in the 'excellent' class according to the EMC2 manual. Timing jitter must be as low as possible when you want to use a PC as steppermotor driver. The reason I went with EMC2 and moved away from TurboCNC (DOS) is that it doesn't have a simulation mode to 'virtually' run the G-code. This was nearly a must-have requirement for me. I know myself too well... without simulation I'd be ruining more workpieces and tools than producing good products... Setting up EMC2 to drive the steppers was a piece of cake. After playing around a bit with the software I made a custom machine driver file with properly defined lines of the parallel port. Don't think it took more than an hour from installing the live-CD till ending up with moving stepper motors. Of course I'm only using just a fraction of the possibilities of EMC2 at the moment, and most likely it isn't set-up optimally yet, but so far it does what I ask of it (unlike Mach3 for example). Gotta love this Linux thing... after half an hour of installation (everything went automatic; *all* hardware being recognized) I actually have a complete system, without needing to install any extra drivers (audio/video/network cards) or software (Open-Office tools all included; chat client too. Firefox webbrowser present.) Once more, the ease of use of Linux Ubuntu is impressive. Actually, I find myself using this EMC2-PC for 'normal' tasks now (such as reading and posting on the backshed ), not just driving the stepper controller.
</ EMC2 advertisement> Peter. |
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| vasi Guru Joined: 23/03/2007 Location: RomaniaPosts: 1697 |
Hi Peter, Ubuntu 6.06 LTS was replaced by 8.04 LTS (Long Term Support). 8.04 will be supported for two years I think ... At the end of these years, it will became the most stable Ubuntu distribution, as 6.06 is (6.06 is no longer supported). I mean, an updated 6.06. After installation you must update it... and I don't know if this is possible anymore..., And you have access at new and useful applications (e.g. KiCAD). Plus, the new .iso for Ubuntu 8.04 LTS from www.linuxcnc.org have a new version of EMC2. I think your PC specs are good for 8.04 ... Hobbit name: Togo Toadfoot of Frogmorton Elvish name: Mablung Miriel Beyound Arduino Lang |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
My comment is not specifically CNC related. Hi Dinges, When I made my dual X-Yaxis CNC foam cutter for model plane wings, I used a basic stamp II as the stepper controller. I buffered the outputs with D469 mosfet drivers, that drove the totem pole N-P mosfets, that connected to each of the stepper coils. I used stepper systems from a scanner on each end for the dual X directions, and used the head movement mechanism from a 3.5" floppy drive for each of the Y-axis. The micro, with 2k ram, held the code for each airfoil section and the cutting rate was adjustable within the program. I also am still using a P1-50MHz, 16MB ram, 200MB hard disk, vintage 1996 I think, 9W power consumption, PClaptop on my weather station. I cannot think how parts of a a 2GHz PC could be considered junk and thrown away. Gordon. become more energy aware |
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| Dinges Senior Member Joined: 04/01/2008 Location: AlbaniaPosts: 510 |
[quote=Vasi]Ubuntu 6.06 LTS was replaced by 8.04 LTS (Long Term Support). 8.04 will be supported for two years I think ... [/quote] I know, Vasi, but I used 6.06 for its proven stability; 8.04 is still pretty new. Once it has proven its stability too I'll make the switch. The PC hardware should have no problem running 8.04. KiCAD would not be an argument for me for switching, as I've been using another CAD package for a long time and don't fancy switching to other software with a new learning curve. [quote=Gordon]I used stepper systems from a scanner on each end for the dual X directions, and used the head movement mechanism from a 3.5" floppy drive for each of the Y-axis.[/quote] Interesting, Gordon... In the past I cut out styrofoam wings using a hot-wire knife and plywood templates. It worked too, pretty well actually once you got the hang of it. But one of the major advantages of CNC would be the ease to change the wing profile. [quote]I also am still using a P1-50MHz, 16MB ram, 200MB hard disk, vintage 1996 I think, 9W power consumption, PClaptop on my weather station.[/quote] Good to see such old systems being put to good use. And you can't beat the power consumption... My main computer is a notebook, P3/1GHz, 512MB, 30GB HDD, consuming 25W of power. It does everything I ask of it. Before that, up until about a year ago, I used a P1/200MHz/3GB notebook-PC for all light-duty stuff (reading books, surfing the web). The reason I switched to notebooks is purely for power consumption reasons, I do not need or use the portability. By simply moving away from a desktop PC to a notebook I'm saving 100 E/yr worth of electricity. The investment in the P3 notebook has paid itself off within months. It's not the fastest system, but it does all I ask of it. [quote]I cannot think how parts of a 2GHz PC could be considered junk and thrown away.[/quote] Same here Gordon. I actually find this throw-away attitude repulsive. Sometimes I can't help but wonder if an economic depression wouldn't actually be a good thing for people, to make us realize again what enormous prosperity we live under and not to squander it. Peter. |
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