starting a hobbycnc homebuilt & looking for pointers

[RynoSLC]

Since I'm just getting my feet wet in the CNC pool, I want to see if anyone has any pointers etc. to make sure I'm on the right path.

Hi, forum! I just started building my CNC for cutting thin aluminum and plastic. It's based on a bunch of 8020 aluminum and the 305oz hobbycnc 4 axis driver kit. The x-axis is 5/8x22", y-axis is 1"x18" (y-axis it's thicker because they were spare bars I found). The x-axis bearings are based on a 3-point skateboard bearings. Y and z-axis a bushings.

So, on to the questions:
1) Can I use 2 motors in parallel for the x-axis based on the hobbycnc 4-axis board? (I figured that doing this will promote even movement).

2) Is it ok to use screw rod from home depot in order to get my project up and running considering that is will be used to cut aluminum? Should I worry about backlash on my axis'?

3) Any reason why my cnc will not be able to cut aluminum?

4) Any pointers on general setup? Things I should watch out for? Any things to keep in mind when setting up the z-axis?

5) Am I in over my head?

Thanks,
RynoSLC

[m1911bldr]

Congrats on "jumping in" with us. If you're anything like me, the CNC world will intrigue and consume you beyond your imagination. I have two CNC projects going - a hot wire foam cutter and a CNC router for alum, plastic and wood. I, too, want to run 2 motors on the same axis but have had no luck finding a way to do that so far. I believe I have seen Dave or someone else advising strongly against trying to use one channel of the HOPPYCNC board to run 2 motors. Several have advised that Mach 3 can slave two axes (sp?) together but for my application, I also need the 4th asix to run a rotary. Someone used to sell a "parallel" board to run tow motors off one axix channel but I can't find it now. I doubt you'll be happy with "all thread." It's OK for "loose parameter" drives but if you want accuracy and smoothness, at least use ACME rod and nuts. Nook sells a rolled ACME product that is pretty nice for anything less than a ballscrew setup. You can get 6' of 3/8-10 for about $60.00. Backlash can be compensated for in many of the g-code interpreters but building to eliminate as much as possible aslo yields rigidity and reduces vibration, etc. If you build your table and linear rails/ways with as little play and as much rigidity as you can achieve, you can easily cut aluminum but you'll have to monitor feeds, speeds, etc, to keep from overloading the structure and getting chatter. The bushings will eventually cause you fits - maybe get bearings or manufactured slides for those axis as well. If you're using polished or ground or even good quality drill rod for the rails, VXB Bearings and other companies sell "traveling ball" slides for almost any diameter of railing. As long as the rails are round, straight and good quality, you can fit real ball bearing slides to them. Look at the VXB website and find "linear motion" in their index (http://www.vxb.com/page/bearings/CTG...rMotionSystems). Keep things as tight, straight, smooth and rigid as you can. Think about rigidity and smoothness at every step - it will pay great benefits. Yes, you're in over your head, but the drowning is lots of fun and will give you a life-long addiction.........

[RynoSLC]

Wow, thanks for all the info. That's like the last three weeks of questions packed into one reply. I can't thank you enough.

That's too bad about the hobbycnc not being able to run two motors on one channel. I'll look into the mach3 slaving. Is there another simple way to incorperate two screw drives on the x-axis without getting into belts and gears?

I will definitely take your advice with the screw drives from acme and start looking for some more bearings for the y and z axis'.

Just checked out VXB and am impressed. He's got some great prices on sealed linear bearings. Maybe I'll modify the initial build

[m1911bldr]

I just found that "parallel stepper driver" I thought I remembered. It's a "sister" card to the ARCSIN that used to be available through "BuildYourIdea.com". Dave Kush is the "proprietor" but he has a note on the Order tab that says he's taking some time off. The idea of two motors on one axis without using the "Slave" feature as found in ArtSoft's Mach drivers is, I believe, a valid one and it intrigues me why no one else is looking for the same thing.

[beone]

I believe mcmaster-car's price for acme is better. also check out Dumpstercnc's acme nuts etc for a good anti backlash solution. Excellent product
Dave

[RynoSLC]

Originally Posted by m1911bldr I just found that "parallel stepper driver" I thought I remembered. It's a "sister" card to the ARCSIN that used to be available through "BuildYourIdea.com". Dave Kush is the "proprietor" but he has a note on the Order tab that says he's taking some time off. The idea of two motors on one axis without using the "Slave" feature as found in ArtSoft's Mach drivers is, I believe, a valid one and it intrigues me why no one else is looking for the same thing.

I agree. It seems like a complicated effort to run belts or something like that in order to get symmetrical movement on an axis..? Maybe I'll build one and make millions

[RynoSLC]

So, I found that I can get a 3/8x12 from McMaster for $30. If I get the 3/8x10 it's almost $60. Why the difference? Plus, it seems easier (on McMaster's site at least) to find 3/8x12 nuts.

Do you think it would hurt to use 3/8x12 instead of 3/8x10?

[m1911bldr]

Hhmm, I never considered using 3/8 x 12. It doesn't give "even" divisions of tenths, hundredths and thousandths. I would work OK, but you would never get even thousandths. The price of the 3/8 x 10 is a little puzzling..........