Colibri Hummingbird Dynamic Sculpture - WIP

[kvom]

With the mill back in operation, I finished the B side frame.  Then it was time to drill and tap mounting holes for the base.




Just enough room to clear the Bridgeport table.

[Vixen]

Hi Kirk
What is that red anodised frame we see in some of your photos? It sure looks interesting.

Mike

[kvom]

It's an adjustable vise stop.

http://www.edgetechnologyproducts.com/pro-vise-stop-single-side/

[fumopuc]

Also available in the UK.
https://www.machine-dro.co.uk/edge-technology-single-pro-stop-4-inch-vice-stop.html

[kvom]

I got the vacuum chuck set up on the  mill.



I needed to put the sub table on setup blocks to raise it 2" so that the spindle can get within an inch or so.  The air connections are from my compressor (nominal 125 psi) through the adjustable valve (to 85 psi) to the vacuum generator and then to the chuck.  The silver knob on top of the generator locks and releases the stock.  The picture shows a 12x12" sheet of .236" acrylic mounted on the chuck.  With the vacuum applied I couldn't budge the sheet with my hands.  The gasket forms a square about 10x9" so a theoretical holding force of over 1200 pounds.

I trammed the front edge of the chuck plate parallel to the X axis motion, and the top of the chuck is flat within .001" side to side.  Now I just need to figure how close without breaking through or cracking the acrylic I can go.  This sheet should yield the flower petals and the body of the bird.

[crueby]

Slick setup with that chuck! Well, apparently more sticky than slick. Anyway - are there independant slots/chambers spaced around the surface of it, or is it one set of slots with holes? Not sure how it is set up, does it work for smaller parts as well? Maybe a close-up shot of the table would help?

[kvom]

The slots are precisely cut in a grid fashion.  The area of the vacuum is sealed off by tubular rubber gasket material inserted in the slots, and there are 9 threaded holes over the table to introduce the vacuum inside the "roped off" area(s).  You only need one hole open in an area, and all the rest are closed off with screws.

The holding area can be fairly small, but the holding force is 14psi over the roped off area, so the best usage is wide and thin material, just the type that's hard to hold in a vise.

I'll post a photo of the top of the plate tomorrow.

[crueby]

The slots are precisely cut in a grid fashion.  The area of the vacuum is sealed off by tubular rubber gasket material inserted in the slots, and there are 9 threaded holes over the table to introduce the vacuum inside the "roped off" area(s).  You only need one hole open in an area, and all the rest are closed off with screws.

The holding area can be fairly small, but the holding force is 14psi over the roped off area, so the best usage is wide and thin material, just the type that's hard to hold in a vise.

I'll post a photo of the top of the plate tomorrow.

Clever, thanks!

[kvom]

Here's a pic showing the gasket material in the slots:



And here's the first cuts using the chuck:



Since the acrylic sheet and paper covering varies in thickness, I set Z0 to the surface of the chuck.  Then it was a question of setting the target depth as the thickness of material to leave.  On the first part I set it at .015", and it had no indication of wanting to move.  The other 3 were at .01".  I probably could have done a little deeper, but probably not necessary.  I measured the back of the chuck plate as .003" higher than the front, although side to side is flat to less than .001".

Cut with a 1/8" 2-flute carbide endmill .05" deep at 10 ipm.

Five other parts remain to be cut from the sheet before trying to break them out.

[kvom]

Got all the parts cut from the sheet:



Parts made here are 5 halves of the petals, 2 sides of the body, 2 sides of the head, and a possible candidate for the central gear.  I'll have to see if the color is a poor visual choice within the mechanism.

It turns out that the .01" flashing remainder made it very easy to cut the parts out and then deburr with a small deburring knife.  The first piece I did with a .015" remainder was quite a bit harder.

I used the same amount for drilling in the hope that I could finish the hole by merely pushing the drill bit through by hand, but that didn't work.  So I'll need to drill them manually.  I think that for other parts I'll got deeper, probably to .005" above the chuck surface.  The few 1/8" holes that were drilled with an endmill were easy to push through, so obviously the conical bottom of the other holes was the problem.

[b.lindsey]

Those look fantastic Kirk. Sounds like the vacuum chuck worked out very well for this too. Once the vacuum is applied, how much clearance is there between the underside of the material being cut and the actual surface of the chuck?  Just wondering if the vacuum compresses the gasket material until the clearance is virtually nil?

Bill

[kvom]

I suspect clearance is zero.  I can't see any at the edge of the stock.

[kvom]

Today I did the same type of machining on the green acrylic for the flower's stem.  Since that's the only other part that's green, I decided to cut out green read petals in case I like that look better than the red ones.



These petals need to have two 2-56 threaded holes in the ends for assembling the flower.  Here is the setup for doing so.  By using a vise stop and spindle stop, I was able to do the drilling in assembly line fashion.  I was only able to tap one of them before I had to leave for a family obligation.



The two holes the stem are overlarge due to a CAM error on my part (3/8 vs. 1/4).  I'll make a couple of brass bushings to compensate.

[Hugh Currin]

Kirk:

Good stuff, like the project. Thanks.

I've been thinking how to use the vacuum chuck and machine through. Suddenly realized today that you can't. Once the cutter plunges through the vacuum is lost. A non-starter but took me awhile to come to my senses.

Thanks for the writeup.

Hugh

[kvom]

If the work overhangs the chuck you can plunge through.  In addition to losing vacuum otherwise, you also end up with a hole in the chuck.