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Adam Munich

Sat Feb 12 2011, 04:55AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Anyone know of any good CNC plans? I'm looking for something small, maybe a 12"^2 working area. It needs to have very little backlash because I plan to mill PCBs with it, possibly even SOP chip surface mount. It also needs to be powerful enough to mill plastic/wood.

So... anyone know of some good CNC plans? Also, my working material is going to be wood or mdf.

Hmm... so many projects at once. flamethrower, X-ray, now a cnc possibly.

Patrick

Sat Feb 12 2011, 05:05AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

I was disgusted with the crap plans for sale in the back alley's of the net so I enginneered my own, entirely of my own design. my advice---build a stiff quill with a motor thats variable from 4k-15k, 1Hp or better.

Also, use servos if you can affford it, steppers if you cant, that is my one great regret. Shouldve used servos, such a fool I was.

or copy Dr.H.'s ->

if you plan to do PCB's id build his.

His is better then even mine, at least talk to him before you buy/build anything!

Carbon_Rod

Sun Feb 13 2011, 05:37AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155

Unless you plan to build something as a learning exercise it will cost you more.

These are actually quite nice, and if you are lucky a 4-axis mill can be found used on ebay.

The PCB island tool path generator for Eagle PCB:

Cheers,
Rod

Adam Munich

Sun Feb 13 2011, 06:41AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

More than $700?

And I don't use eagle, can't figure out how to. I use diptrace which supports dxf export. I can turn the dxf into g-code or something using one of those fancy programs.

Patrick

Sun Feb 13 2011, 07:56AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Grenadier wrote ...

And I don't use eagle, can't figure out how to. I use diptrace which supports dxf export. I can turn the dxf into g-code or something using one of those fancy programs.

I use Kcam, AutoCAD 2007. But I dont make many PCBs.

Dr. H.

Sun Feb 13 2011, 08:18PM

Registered Member #931 Joined: Mon Jul 30 2007, 05:25PM
Location: Bulgaria
Posts: 486

Good day guys

achieving SOP accuracy is quite a challenge - furthermore you are planning on using "wood" .... you will have to use anti - backlash nuts (witch won't be a big problem to make or buy) but accurate linear bearings is a must (and when you spend money for such bearings you could easily afford to use aluminum for building material (also it is quite a small mill). The motion drive - steppers are best for first project (and you CAN achieve great accuracy with them). For driver - I have build quite a few of the "Linistepper"s and they work perfectly. Also have used chopper type ICs but are harder to find. But if you want real accuracy - servos (and you have a closed loop then) - but be prepared to spend much more cash on good servo (motor + encoder) and driver.

All in all - it is always a compromise between working area accuracy and milling power when you build a budget mill.

Cheers

Patrick

Sun Feb 13 2011, 09:12PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

I use the L297H ic, and the L298 ic from STmicro. I've never had a problem with either for stepper-motor control, guess you could buy ready made gecko's which are nice, for rich people. The L297H is the power ic, driven by the l298 which is the logic ic. You can make your circuit as complcated with many fucntions, or as simple as only step/dir.

Martin King

Mon Feb 14 2011, 10:56AM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

Bosch Rexroth extrusion is good stuff to make small CNC machines from. Quite expensive new but there are people selling bundles of if (from old dismantled machines or off-cuts) on EBay e.g.

It also has the advantage that if you want to make a bigger machine later you can dismantle the old machine and re-use many of the parts it's a bit like big boys Meccano

. The T-slots and nuts also make adjustment and squaring up easy although you still need to be able to cut it squarely and accurately to get good results.

Martin.

doctor electrons

Tue Feb 15 2011, 02:58AM

Registered Member #2390 Joined: Sat Sept 26 2009, 02:04PM
Location: Milwaukee Wisconsin
Posts: 381

you can also check out 8020 and frameworld, its all pretty much the same stuff. If youre interested i have some polyphase steppers with
the drive and a few robocylinders with the drive as well. I also have some plcs and power supplies. I was going to do exactly what your plans
are with them. Shoot me a pm and i can give you more details about the goodies. OR i can post them in the sale and trade thread.

Adam Munich

Tue Feb 15 2011, 05:41AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Hmm....

Well my main goal is to mill PCBs as cheaply as possible, and I figured building a CNC would be cheaper then that buying that zen kit. So you guys are convinced that it'll cost me more?

I suppose I could always start a PCB milling service to make the money back though... mill a PCB for $5 + the cost of the copper clad or something.

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