Building a CNC machine from ordinary items.

Anything else around the house.
Jarod
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Building a CNC machine from ordinary items.

Post by Jarod » Sun Nov 27, 2011 2:52 am

Heres my progress on the build of this cnc machine idea


Currently I'm at the point where I need to attach my 1/4-20 threaded rod to the tables and build the motor holding z axis parts, still working on a good way to do that.

I found a old printer with a uln2003a stepper driver and stepper motor, so I can do at least one motor right now, hopefully I can find another so I can have 2 axis travel, then I can manually adjust the z axis at least until I've etched a new driver pcb with it.

The machine still needs tweaking and loads of adjustments to get everything straight and true, then I'm hoping to find a welder to borrow/buy/use to weld all the rails to the pipes, all the pipes to the fittings and generally make everything permanent so it can't go out of adjustment.
Attachments
IMG_20111126_212922.jpg
X and Y Axis tables attached
IMG_20111121_122622.jpg
Base and x axis rails attached.

foxmiles
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Re: Building a CNC machine from ordinary items.

Post by foxmiles » Mon Nov 28, 2011 2:31 pm

For the rod to table - How about a 1/4-20 nut with a half inch of 1/4-20 rod welded to it at 90*? or a wood screw or 2 nuts welded at 90*?
I know someone with a welder. :)
Digging with a spoon will accomplish more than leaning on a shovel.

Jarod
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Re: Building a CNC machine from ordinary items.

Post by Jarod » Mon Nov 28, 2011 3:15 pm

My thoughts on attaching the table to the threaded rod was I could weld a 1/4-20 nut to a small piece of sheet metal and drill a hole or 2 through the sheet metal and put wood screws into the table.

I attempted to botch something together last night so that I could have proof of concept and have it all work and move properly and get it all adjusted to be accurate then worry about making it work perfectly later on, but i think that's a bad idea. I overheated a nut and seized it to the rod and snapped my lead screw in half... not a happy moment lol

so I figure I'm going to have to build it properly now or perhaps go hunting at the hardware store lol. I go there so often they said they're going to start charging me for coming and walking around the store because they'd make more money lol

If we come up in December I'll bring it with me and maybe we can mess with it a bit, weld the pipes and stuff.
Eventually I'll replace the dremel I'm planning on using as a motor with something more like a router motor or something that won't have the run-out a dremel does.

I'm hoping to find another printer to recover some better stepper motors and a driver chip or two.
Need to go bug the radioshack guy to let me rummage through his garbage pile.

foxmiles
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Re: Building a CNC machine from ordinary items.

Post by foxmiles » Mon Nov 28, 2011 6:36 pm

You could braze (permanent) or solder (temporary) it instead of welding. Do it off the rod and wait for it to cool (don't dunk it in water, it may shrink). if you've got a 1/4-20 tap run it through to clean the threads up too.

I've got the free version of eagle (Schematics and pcb layout). Apparently does autorouting and will export to something some cnc software can use.
http://www.brusselsprout.org/PCB-Routing/
Digging with a spoon will accomplish more than leaning on a shovel.

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Re: Building a CNC machine from ordinary items.

Post by Jarod » Mon Nov 28, 2011 10:50 pm

Can you Solder steel? I know you can braze it but idk if I even have any solder that's not rosin core.

If only i could find my brazing stuff! I've looked everywhere for that stupid little thing of safety-silv, I paid 30 bucks for probably 6 feet of 15% silver brazing rod. and I can't find it... ridiculous.

I've got eagle too, no idea how to work it though.
I'll go mess with some nuts and solder and stuff, maybe I can get something rigged up well enough to work as a test.

I'm also thinking of using a standard dc motor with a h bridge so both directions could be used plus gear reduction and an ir encoder to count the rotations of the threaded rod. idk how well it'd work but I've got several encoder/receiver thingys laying around.

foxmiles
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Re: Building a CNC machine from ordinary items.

Post by foxmiles » Fri Dec 02, 2011 8:50 pm

I think you can solder steel, it just has to be clean (sanded)

I've been thinking on the stepper motor controller, I can build a really nice one for around $75-125 (parts, no labor). I'm thinking seriously of building two. It does a lot more than the one you linked to, it will run 3 axis plus a stepper extruder feed and temperature controlled extruder head, connects via USB. The expensive bit is the actual stepper drivers - $14ea x 4 pre built (shipped, including a heat sink), drop in place. About $8-10ea x 4 (total) all smd components, it's doable though. Controller PCB's run $13 shipped, Stepper driver PCB's $1.50ea plus shipping. Should be able to build 2 controllers in a day. I still haven't decided between the prebuilt and bare stepper PCB's yet (it's like $60/board pre built, probably build them too)

http://reprap.org/wiki/Sanguinololu

If you haven't figured it out, it's designed to control the Reprap 3d printer. With the addition of an extruder (and power supply) you're cnc would double as a 3d printer. (and print me the parts to build one). I was thinking I'd like something that could do isolation routing on PCB's and I think the reprap could (slowly). Plus it can build plastic stuff (cases, etc).

http://reprap.org/wiki/Main_Page
Digging with a spoon will accomplish more than leaning on a shovel.

Jarod
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Re: Building a CNC machine from ordinary items.

Post by Jarod » Sat Dec 03, 2011 4:39 pm

foxmiles wrote:extruder feed and temperature controlled extruder head, connects via USB. The expensive bit is the actual stepper drivers

As soon as I saw Extruder I thought reprap.

I've got 3 small steppers and enough driver chips to drive 5 stepper motors :)
1 uln2003a (7 output) and 2 Toshiba uln2803 lookalikes (8 outputs each, 2 motors per chip)

I've been working on the cnc along, got tables working and fairly smooth, i want to see if these steppers will be big enough, they're just little fellas out of inkjet printers.

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Re: Building a CNC machine from ordinary items.

Post by Jarod » Sat Dec 03, 2011 8:37 pm

I forgot what I was going to say so heres a random thought instead:

I got one stepper motor working, however it only turns counter clockwise no matter what I do.

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Re: Building a CNC machine from ordinary items.

Post by Jarod » Sun Dec 04, 2011 5:20 pm

Ground your Logic Chips Gentlemen!
I discovered why my stepper only turned one way. the uln2003a was not grounded. after grounding it it works in both directions but draws an awful amount of power... 1.5A at 12v is not nearly enough. kills the transformer as soon as the motor trys to turn.

12A at 5v works, however I get the feeling there isn't the same amount of torque as there would be at a higher voltage but I really don't know if thats true, probably not, as a higher voltage would reduce the current draw.

Anyway, I have 2 Unipolar steppers which I can control very nicely, and one Bipolar stepper that I need to build an H-Bridge to drive.
The problem I've just discovered is that every G-Code interpreter I can find doesn't work with a darlington array setup like I've built.

foxmiles
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Re: Building a CNC machine from ordinary items.

Post by foxmiles » Sun Dec 04, 2011 8:39 pm

Those numbers sound wrong. 12A@5v for a little stepper motor doesn't sound right. You'll burn them up.

The (big) NEMA 17 motors from ebay are rated for less than 1.5A
http://www.ebay.com/itm/4-Stepper-motor ... 336ef25cf4
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