Look what I can do! (First CNC Project)

[cp8071]

Sorry for the cheesy title but I’m pretty excited about my new CNC mill. It’s a home built job with eBay parts and some skeptical help from a machinist friend. It’s just finally starting to turn out real parts and I’m at a few crossroads with some of the components, but it works pretty darn well for what it is!!!



The computer is just old parts (I think it’s a P2/300) running Win98. The “drives” are crappy built-it-yourself stepper drivers that are full-step only. I’m running them from an old rebuilt supply at 13.8 Volts, I wanted to run at 30 Volts but the resistors were too expensive for an untested system. The steppers and lead screws came off eBay and step at 6400 ticks per inch (for X&Y) and 2540.9 ticks per inch for the Z (metric). The rails were a special find but required rebuilding (and still need new balls), they are overkill for the PCB routing that I want to do, but overkill is fun. Right now everything is held together with MDF and it’s actually kinda straight, I’d have it run new aluminum parts for itself … but I’m having too much fun right now. All the parts you see were created with a Rotozip running about half-speed off a Variac and a 3/8” dual straight flute wood bit running at 2 IPM and 0.050” DOC.

The first parts I made were for an engraving spindle for doing PCB work. The results were poor because I was trying to create my own TINY cutters (0.005”), so I’ve ordered the proper cutters and I’m waiting for them … (tapping foot). Until then I’ll play with other stuff.

So the idea here was to create a mount for a standard size wood router. I picked up an old router at the local Pawn for $14.95 then started my work. The finger trigger switch was removed and the motor rewired so that it’s ON all the time (it will be controlled separately.) Then toss the base into the trash and start anew. The diameter of the motor is 3.51” so I did some drawing and created the two motor cradles using DXF conversion software, the other parts were created by writing the G-code directly. The metal is 2.5” x 3/8” and 2” x 3/8”. So here are the pictures.







If you think this is cool or would like some more info just ask. I need some more motivation to finish the project so any good words you could say could be helpful. Also, anyone doing PCB work I'd like to hear what method you use for going from Gerbers to G-Code ... I've tried ACE without good results. Right now I'm doing Protel to Gerber to DeskCNC(which seems smart) to KCAM4(easy windoze application.) I'd like to use TurboCNC(DOS) but the viewer sux and I don't trust it with the "unclosed circles" that my Gerber and DXF outputs seem to have. Any input about this kinda stuff?

(edit): Looks like I was limited by the number of files I can include.

CP

[pen25]

looks good.. goto the galary and upload them there. i just might have to build something like this instead of a moving gantry for right now. what is your cutting area?

[JRoque]

CP, nice! It reminds me of my own machine when I started it - mounted on 2 x 4 pieces of wood and held down with C clamps.

I also use Protel for my PCB prototypes. I export to .DXF and then manually trace it on AutoCAD. I recently purchased Rhino so will be trying that route next. It didn't work for me but many folks use Eagle to isolate Gerber files and export a routable DXF. Halfway down this posting on my machine log are a couple of pics of one of my prototypes. I've gotten them to come out sharper now by trying different types of cutters, as you also suggest.

Later,
JR

[cp8071]

Thanks, I've uploaded a few images, I guess you can find them under my name? Here's another quick shot of some milling in process:



Although the important parts are held together with MDF, the "head" and table base are made of 4"x4" 1/4" steel square tube ... so I think that should be strong enough for whatever I want to do. The steppers are undersized and the drives really keep the speeds from being impressive (rapids of 10IPM and cutting of 6IPM.) But since I don't have the spindle or end mills to actually cut worth a dang it doesn't matter much right now. I've got my eye on some Automation Direct steppers, but not sure which chopper driver to go for ... guess I need to figure out all my software before finalizing the H/W.

The linear slides can move 14" X&Y, and 16" for the Z(which isn't needed of course but sure makes tool change easy.) But my lead screws are only 9" X&Y so that's the table limit right now.

Sounds like you have the same Protel to Gerber to G-Code (or PCB export DXF to G-Code) headache that I have right now. The boards I'm planning are pretty complex, so no "hands-on" conversion is practical. DeskCNC seems to handle my Gerber files pretty well and generate good G-Code which automatically creates a "trace out" cut (kinda a trace negative if you'd like.) So I guess that's my method for now until the trial runs out. KCAM can't seem to do anything useful by importing Gerbers.

Next on my list is to button-up the computer and get spindle and coolant (vacuum) outputs working ... that'll be pretty cool!
CP

[JRoque]

Hey CP. Listen, you can't get away with posting a picture of metal cutting operation and not telling us what speed the router spins, what is the depth of cut and the feed rate. It's right there on the Zone's "noobs want to know" golden rule.

Not a bad machine at all if you are able to cut like that. Is that aluminum? What kind? How'd the finish come out? I'm asking because I can't seem to get a decent aluminum cut with my Porter Cable router. It starts cutting fine but at random it will throw a fit and start vibrating which ruins any precision cut. I had better luck with my 1/2 HP, highspeed spindle than I get out of the 3.25 HP Porter Cable. I'm actually building my own spindle right now which is coming along nicely.

Later,
JR

[cp8071]

I had almost all that info scattered throughout the post. It's 6061 Aluminum 3/8" thick in bar stock form. The Depth of Cut was 0.050" and the feedrates were between 2-4 IPM. This was using a straight flute wood bit (3/8"). The Rotozip is rated at 30,000 RPM ... but I slowed it down using a Variac. Since voltage and RPM aren't directly related it's hard to say what the actual RPM was ... I just turned it down as low as possible to achieve good cuts. My guess is that it was running 8,000-10,000 RPM ... slower made cleaner cuts until it started chattering, then a little extra RPM would prevent the chatter (especially on deep cuts.)

The Rotozip bracket is pretty cheesy. Although it has bearings, the plastic body really flexes, so I hope that's were my chattering problems were from. The new router bracket and router is very rigid and has some "Umpff" behind it, so I'm hoping for cleaner cuts. Of course this is also I high-speed motor so I'll need some way of slowing it down while keeping SOME torque. So today I'm pulling an old project out of the closet which did phase controlled speed for large inductive motors ... kinda like what I need here. If that'll work then I'll need an RPM sensor on the router to "close the loop."

I'm interested in the spindle project!
CP

[CNCezee]

Hi Guys i am new to the group and over the pond in UK

CP, Looks Good, I am impressed with the shot of cutting the ali sheet, i am also part way through building my first machine albeit a little bigger, i hope to be posting some photos later when it is in a more altergether state.
I am also soursing my bits from new and ebay but in the UK a bit more of a limited market, so bits are a bit harder to find.

Keep up the good work

CNCezee...call me EZEE

[buscht]

cp, great job. I agree, if you can cut aluminum like that you should pat yourself on the back.
Trent