[TheBakachan]

Thanks. I'm glad to be getting so much constructive feedback! For sure, I'm going to have to fit the pieces together and see how sturdy it is. I'm unsure what kinds of forces are going to be put on it, so I'm really going to have to wait and see.

The rails are solid chrome steel shafts. 20mm on the X and Y and 12mm on the Z.

It's going to be another week before I can put it together, it turns out I'm actually short a couple pieces of 80/20. But other than that, I'm ready to go.

At this point, my biggest concern is still that I need another motor/screw for the Y axis.

I found a solid solution for mounting the delrin nuts to the stages, but it's going to require machining, heh. So I think I'll do it with L-channel just to get the machine running, run some tests, and if all goes well, make the parts. I have little blocks of 6061 that are just the right size. I figure that's fine, even though it means I have to pull the screw assemblies apart to replace the mounts. Since I expect to have to tear it all down to make refinements anyway.

Now for some New-B questions:
Is there a handy resource for getting an understanding of different bit types?
Is there any really basic machining stuff I should know, and is there a good resource for that sort of thing?


With the exception of a couple months of woodshop in high school...over a decade ago...I really have very little experience with power tools. I'm more the soldering iron and multimeter type, than the drill and circular saw type.

[Jack000]

another tip about the motors:

consider your power supply and drivers when choosing the motor. I also bought the 425oz/in motors from keling, which turned out to have an 80v operating voltage. The geckos I bought only supported 60v, and most power supplies are at 36~48v. I'm running my machine at 36v right now, making it seriously under-volted.

I would have gone with their new 2.8 mH 318oz/in motors if I could do it over, apparently it's compatible with the geckos.

[stevespo]

There's a lot of good information on the site here about unsupported rails. Here is one thread from a few years ago. Naturally, deflection and vibration depend on the spans involved, but it is definitely something to consider.

http://www.cnczone.com/forums/showthread.php?t=14045

As far as machining goes, there are some calculators online that will give you a rough idea of feedrates for a given material, RPM and cutter design. That's a good starting point when you begin to mill wood, plastics, metal, etc. With your setup, any work you do in aluminum is going to need to be ultra-light cuts and moving at a fairly fast speed.

Steve

[TheBakachan]

Thanks for the info, guys. Hopefully I'll be able to put it to use in the not-so-distant future.

Finally making some new progress. I've been acquiring some of the tools I would need to assemble the actual machine, but I also bought what I would need to prep the old computer and build the wiring harnesses and stuff.

Tonight, I started working on disassembling and cleaning the computer.

I bought some nice shielded wire rated for my needs, to hopefully mitigate the EMI problem that running all that wiring around in the computer represents. Ordered various things from Digi-Key, such as limit switches (More on those later, I didn't take a picture), D-Sub connectors, various housings, and other odds and ends.

One of the design considerations I made was that I wanted everything to be as compact and self-contained as possible. To that end, I re-purposed my old friend, the Yeong Yang YY-0221 'server cube' case I bought in like '02.

It is an absolutely cavernous case, as you can probably see in this picture. With that kind of space, I can keep the computer in one half, the CNC drive and power hardware in the other, and it's even on casters! I was more than happy to put this great old case to work, since I've been agonizing over what to do with it for quite some time. It doesn't cut it for the kind of hardware I run now, but I didn't have much need for the old machine that was in it. (And of course there's the fact I paid like $350 for that case in 2002)

I'm really rather proud of my wiring harness though. I wasn't sure how much amperage a D-Sub could handle, but the DB-15 connectors I got from Digi-Key are rated for like 5A, supposedly up to 500V (But not for extended periods of time), so I think I'm covered. I got the idea to use DB-15 connectors from a couple old AUI network cables I have laying around, it's some real heavy-duty stuff. The main feature that interested me though, is the locking mechanism that old AUI stuff uses. Instead of having threaded standoffs and screw-down knobs, you have these little studs, and a sliding lock mechanism. Seemed like it'd be quick and easy to hook up or disconnect, and quite safe from getting unplugged.

Here's what one of the completed PC-side connections look like, along with one of the housings from the PC-to-CNC cable. Since I have a crapload of old AUI network hardware to scavenge the clasps off of (I didn't even bother looking for new ones on Digi-Key) it was really a no-brainer.

Anyway, I'll go into more detail on the computer and the wiring when it's finished. I was hoping to have the machine at least partially assembled in the next week or so, but there are more pressing issues that demand my attention (deficit)...not the least of which is the prospect of a sudden move.

[ahren]

Jack,

I wouldn't worry too much about your motors and power supply. A "lack of voltage" for stepper motors isn't that big a deal until you get to high speeds. It does affect how fast you can go, as the voltage you run at is basically the voltage available to overcome back-emf as the motor runs faster. However, it has no influence on low-end torque provided you're several times above the motor's rated voltage. At 36V, you aren't losing too much.

Bakachan, your wiring job does look good. I wouldn't worry about the amperage a D-sub can take. While it may have a rating of some sort, the distance the current is traveling through the connector is very short, so you shouldn't see much voltage drop (or much in the way of heat). What I would worry about is the extension cables you build for the motors. Make sure these are sized properly, especially if they are longer than 3 or 4 feet. For 3.5A of current, you should be using at a minimum 24 AWG wire, and these will warm up (and lose power for your motors). 22 or 20 AWG is preferred, and required if you are pulling more current.

Ahren
www.cncrouterparts.com

[TheBakachan]

What I would worry about is the extension cables you build for the motors. Make sure these are sized properly, especially if they are longer than 3 or 4 feet. For 3.5A of current, you should be using at a minimum 24 AWG wire, and these will warm up (and lose power for your motors). 22 or 20 AWG is preferred, and required if you are pulling more current.

Yeah, thanks for the tip, I tried to look for guidelines on what gauge wire I should run, and ended up sort of defaulting to going by what the leads on the motor were; 22 AWG. And the shielded multi-conductor wire I'm using is 18AWG. I was hoping for 20 or 22 to keep the bulk down, but the place I was getting it from only had 18 AWG for that, and 22 AWG for the shielded limit switch wire.

Speaking of the limit switches, I mess around with a lot of microswitches, because one of my other hobbies is arcade hardware. But I decided to do something interesting with the switches when I came across a neat switch on Digi-Key.

Omron makes these nice low-profile chassis mount microswitches in any combination of NC/NO, roller/simulated roller/no roller/no lever, but instead of having terminals on them for disconnects or the like, they have a tiny locking plug. I'm just a huge nerd when it comes to elegant solutions, and so I had to get them. :P

So far it's been a total FLOCKING BUSTARD crimping the pins for the connectors though, despite having a MOLEX pin crimping tool. They're just so tiny! But I'll persevere!