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jdholbrook
05-26-2006, 04:54 PM
Hello,
I've been lurking on this forum for a while, gathering ideas and parts.
Finally I'm ready to start building something.
I'm looking to cut foam, balsa, carbon fiber and maybe some light aluminum

I choose 80/20 as my building material for several reasons.
1) It goes together like a "kit".
2) I don't have any woodworking tools but have a small machine shop including 2 lathes, Taig CNC mill, metal cutting band saw (2), large and small drill press and lots of aluminum stock laying around.
3) I've accumulated 80/20 over the past 6 months or so and have enough for several routers. 80/20 outlet on ebay knows me by my first name :rolleyes:
4) I can build something and if I don't like it I can re-use most of the parts on another.

My first design will use the 80/20 linear bearings in the interest of keeping cost down. I know people have cursed them but I've got several sets of THK rails for later as this is mainly a way to get my feet wet.
I'll be using some ACME 1/2x10 with AB nuts from Dumpster, preload bearings on the motor end, floating bearing on the other end to control whip.
HobbyCNC driver board.
Vexta 5v 1.4amp steppers. Not the best for the job but were on hand.
A linear slide assembly I got off ebay with 4.5" travel (nice unit that I got for around $50. Has some small linear bearings and a nice ACME screw with preloaded bearings etc..)

On order are:
Lovejoy couplings.
ACME rod, nuts and bearings.


My ultimate goal is to have a nice machine with 48x48x6" cutting space.
This one will have around 30x29x4.5"

Costs....
1530 x 33....... $12.95 each x 2 $26.90
1530 x 36....... $16.95 each x 2 $33.90
1530 x 42....... $23.99 each x 2 $47.98
6834 Bearings.. $35.99 each x 2 $72.98
Steppers........ $17.50 each x 3 $52.50
9x15x0.375 plate $14.99
Fasteners...... $10.00 estimated

Total... ~$260

Anyway.. here are some pictures of things I'll be using today.

jdholbrook
05-26-2006, 04:58 PM
After bolting frames together.

Waiting on ACME parts to arrive to start building bearing holders and end plates.
Drawing doesn't show it but I'l have another 1530 across the bottom of the gantry for stability and to attach the AB nuts to.

Comments and suggestions are wholeheartedly welcome.

James

jdholbrook
06-20-2006, 12:24 PM
My job took me out of town for a few weeks but I'm back and ready to get busy.

I cut the side plates out of the 9 x 15 x .375 plate. Marked and drilled the holes.

The large drill press is one of the HF jobs that went on sale from $299 to $179. I immediately chucked up a dowel and noticed a LOT of run out. After working the MT2 to JT3 arbor over, honing out the MT2 spindle and some fussing with the chuck I was able to get this down to 0.0015"

With the holes drilled and the slides/bearings mounted I measured for the Y axis and found I needed 36.8".
I cut the 42" 1530 to length using an 80 tooth carbide blade in my miter saw. I wanted to use the new band saw but had yet to square it up and didn't want to spend a day doing that just for two cuts. I did try to square up the miter saw but wound up with the cut being 0.010" short on one side. A few minutes work with a mill file and a machinist square got that straightened out.
Next came the tapping of the ends of the 1530.
Other than using a tap handle that was a waste of money that went well and I was able to get the holes tapped over the length of the tap. Very handy having the holes already sized for the 5/16 x 18 threads.

On to making the supports for the motor, bearings and AB nut.

Comments or criticisms welcome.

jdholbrook
06-20-2006, 12:34 PM
As it stands now it takes around 12 pounds to move the gantry. That's pretty high I think.
The reason is that I shimmed the inserts in the bearings a little tight so as to allow for some "wearing in" hopefully. Good thing is that there is no play in the whole thing and by my measurements it's pretty straight.
I can tell that the Y axis beam is a little long as it's got the side plate bowed out just a tiny bit.
Back to work with the file and machinist square..

The 3030 you see for the legs are some that I found on ebay for a killer price.
5 pieces at 30" each for $99 shipped!!

I will put some 1515 lite across the inside of the frame to support the spoil board as well as give some extra stiffness to it. Although it's pretty stiff as it is.

Total so far around $360.00

ACME rods, AB nuts, lovejoy couplers and assorted hardware came in so will be installing that over the next few days.

Stay tuned :banana:

diarmaid
06-20-2006, 01:00 PM
Very very nice. Please do keep us updated. You make it look so easy! :) The pics are great. One question: What is the problem people have with the 80/20 bearings?
I like the T-Slot aluminium, it seems to fit together really well and without too much trouble.
L8rs

jdholbrook
06-20-2006, 01:13 PM
Thanks for the kind words.
It is a lot like a kit after you figure out the dimensions.

From what I've read (no experience yet) the 8020 slides/bearings have too much play unless they are adjusted tightly then they have too much drag :(
I have read where people have had good luck with them at low speeds such as below 40ipm rapids. (I read somewhere that someone was using 8020 and 80ipm rapids and it worked OK)
I'm using 1/2"x10 ACME rod so expect my rapids to be in the 100ipm range.

I spent several hours adjusting the pads in an attempt to get the slides tight but not too tight and eliminate all play. Lots of trial and error.

We'll see..

jdholbrook
06-23-2006, 09:57 PM
Update:
I've spent the past few days with my tools to the grind stone.
I went over the gantry and squared up the top and bottom braces, straightened out the whole thing and made some mounts for the AB nuts as well as some bearing holders for the bearings on the leadscrew.

Two of the cheap bearings ($2.65ish) from Enco squeezed together to act as thrust bearings are working great. No play that I can detect and the rotate nice and free.

More pictures..

dertsap
06-24-2006, 12:01 AM
i think you will be fairly impressed in what those little motors can put out , i had the same ones being run with a stepperworld driver @ 24v and it moved my 24 x 48 table fairly well , had them connected to a 3/4-6 tpi lead screw and was cutting at 30ipm with no real problems rapids were about 45ipm max , i was surprised such a small motor was so strong , the hobby board should push those motors much better than my fet3 board did ,ive since upgraded motors and drivers table (everything), i will be interested to see how you make out , your doing good so far