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I have found the people at the mailing list for the LinuxCNC.org EMC CNC software very very helpful and encouraging while seeking guidance and information on building my home-made CNC machine. I am posting the my all of the replies from those guys in this document.
I was wondering if anyone has ever tried a do-it-yourself CNC project like this. http://www.instructables.com/id/Easy-to-build-CNC-Mill-Stepper-Motor-and-Driver-ci/ and this http://www.instructables.com/id/Easy-to-Build-Desk-Top-3-Axis-CNC-Milling-Machine/ . If so, any pointers or words of knowledge before I dive in?
Also, I'm still looking for some stepper motors to use if anyone has a good source.. I'm a college student, so I'm obviously broke and starving. So, inexpensive would be good. Thanks guys.
Sean
Sean,
The stepper driver looks OK at a first glance but I did not have a detailed look at the schematics.
It looks to be a full-step driver which is nice since full step drivers tend to have a higher torque than microstep ones.
But I would stay away from the easy to build desktop thingy from instructables.com, it's just too weird a design and these funny piping and aluminium profile parts do cost money, there are other design on instructables that I think make more sense:
http://www.instructables.com/id/How-to-Make-a-Three-Axis-CNC-Machine-Cheaply-and-/
http://www.instructables.com/id/Build-a-CNC-Router-from-Scratch-Part-1%3a-Complete/
make more sense, I prefer the top one since it contains a more detailed description on how to build it (instead of videos showing how to handle a saw) and some links to stores selling parts.
Rockcliff Machine sells the plans and parts for a home-made CNC router but if you have a look at the photos in the gallery you'll get a fairly good idea of its construction.
Using aluminium L strips to do the linear guidance looks nice and cheaper than the round steel axes. Before building/buying anything I would advice to make some detailed drawings of what the linear support should look like and then make a price calculation. When I started drawing and building my machine I made a rough guestimate of around $4,000 but on the go I updated the plans and got to a total of $10,000 and now I want to buld a second (small) one much like the Rockcliff design but from aluminium instead of MDF board. Since the first machine left a nice hole in my savings account this second machine needs to be low-cost, but I still want to be able to use it to do some real work in plastics/foam/wood and maybe later even aluminium.
You'll find rockcliff at http://www.rockcliffmachine.com/cnchome.htm
Some words of advice for going cheap:
Use MDF board, it is easy to work with, and select standard threaded rods from the DIY store that will fit in roller-skating bearings so you can fix the bearing using standard nuts instead of having to make special mounts. Use thick-walled (not to thick, not to rigid) plastic hose with hose clamps as motor couplings this is by far the easiest and cheapest coupling I could think of.
If investing any real money, invest it in a milling spindle that does not make too much noise. When I started I used a Dremel tool but it makes just too much noise to let it run for more than 10 minutes - I defenitely did not want to be in the same room as a constantly running Dremel...
This may build you a working CNC milling machine but it will only do some light milling and I would be surprised if it gives you an accuracy as good as 0.02 inch
Just my two cents worth - and don't spend it all at once ;-)
Rob
Sean,
An easy way to go for a first project is to us drawer slides for the
guide ways.. Look at http://www.cnczone.com/forums/showthread.php?t=15768 and you may get some
ideas. You can usually pick up suitable drawer slides fairly cheaply and
all you need to do then is to mount them parallel to each other - you
can use hot melt glue for initial positioning before screwing them
down.. You do need to be aware that a machine like this will only be
capable of cutting foam or wax as it won't have the rigidity for
anything harder. If you want to make a more serious machine, you could
consider one of the X-Y table vices from Machine Mart or whatever it is
called in your part of the world, or you could do as I did and look out
for the cross slide/topslide assembly off an old lathe in a scrap yard.
This gives the basis for a very rigid and useful machine. If you can
build your own driver boards I would suggest using a basic L297/L298
chip design which will give you a rugged and reliable half step drive. I
have found Futurelec hard to beat on price for components although they
can be a bit sluggish at dispatching them.
--
Best wishes,
Ian
Sean, I started down the path of building the Instructible you mentioned. I
even have the metal framework built. However unless you scavenge
everything, the costs will add up. For example, look up the cost of each
of the stepper driver chips mentioned in the instructible. Times that by
three (one for each motor).
I bought a HobbyCNC controller board and motors for $170. A 10A power
supply that I built myself cost another $80. I guess I could have gone
cheaper, but if you scavenge motors from things then you don't know the
torque and you have to work out the wiring yourself (there doesn't
appear to be a standard). I happen to think the HobbyCNC package was a
good deal.
Even getting threaded rod from a place like Ace Hardware is a pain. I
bought a nut and it doesn't go down the rod smoothly. The solution I
suppose is to re-tap the rod, which means buying a tapping kit.
My suggestion is to look at www.fireballcnc.com. The machines are hand
made in the USA, are made with quality parts and are cheap for the
price. Still need to add motors and electronics. These machines have
been used to create PCBs. Currently the maker is offering a nice
discount for the "beta-testers" of his new machine.
There are also plans you can get from people, for example look on
cnczone.com. Check for recommendations/good reviews.
Andy
Sean,
If your on a budget then go with one of the Allegro chipset based controllers (Hobbycnc etc..)
Try to get motors that are rated at 2.5-3 amps (about the max that an Allegro chip can drive) and are rated around 3-5 volts.
Also, make sure you run the highest voltage the controller can handle (usually around 36-42volts with an Allegro base controller).
These means hunting down a good 30VAC 10 amp transformer.
Don't waste your time or money with anything that is not a constant current, pwm type controller.
There are schematics for Allegro based controllers to be found on the web if you want to roll your own.
If you don't mind spending a bit more then go with the Geckos. You won't regret it. Dean
Sean, If you're going for the cheap, and dont need to really cut anything more than wax or foam, i would think some of these motors could do nicely for less than $10 each. http://www.allelectronics.com/cgi-bin/category/400600/Stepper_Motors.html
I think we could provide some better direction if we know exactly what you're going for. you tryin to get your toes wet with cnc stuff, or are you wanting to produce parts? what tools / supplies / resources do you have available? if you happen to have access to say a school or employer's machines, that could be very handy in building your machine. im assuming you have at least bsic electronics skills if you're wanting to build those stepper drives.
I've seen that instructables, and thought about trying something like that but decided I'd come up with my own design using mostly MDF. Jim
sean,
i'm slowly (in my very spare sparetime) working up a small (12"x12"x3") low tolerance cnc machine for light wood and plastics. it is also serving as a general teach-myself-cnc project. i chose to go with a pre-config'd electronics / servos package from keling inc. (http://www.kelinginc.net/ThreeXCNCPackage2.html ). after reading lots of cnczone entries and doing lots of chipset / board / wiring research, i figured it's 329$ well spent by saving me time, and it's a pretty complete set of items for a good price. also, this site has some helpful info on wiring (http://www.robertguyser.com/ ). i am next building up the machine using basic 8020 or minitec extrusions and linear accessories. lovejoy couplings will round out the basic bom. i'll use whatever i have as a cutter head - dremel, trim router, etc. it should turn out to be a fairly cheap machine without eating up too much time reinventing the wheel. cam environment: emc2 packaged with ubuntu. it was a smooth install and the forums are great. so, i cannot say that this route is flawless and worked out yet since i'm still in the process, but i can say that i've spent a bunch of time running cnc machines, spent lots of time reading everything i could find on the internet and printed about various diy cnc options. i think this route seems like a pretty efficient and solid starting point. i'll let you know how it comes out - if i ever get the time to complete it!
have fun regardless of which direction you choose. good luck.
-seth |
