How to run 4-5 bits per part?

[sheldon@dingwallguitars.com]

I don't have my shopbot yet, so am trying to plan machining strategy. I need to run 4-5 bits per part. The cheapest solution would be to run one bit at a time and run a number of parts through. I would like to be able to machine the entire part with one set up and switch bits or... Is it possible to mount a fixed router base to the Z column so that a series of router motors with bits permanently installed could be swapped out and just zero the first bit?

[cmrtom]

Changing bits is not a problem. Also, a second Z axis would cut the bit changing in half. I had not thought about a fixed router base before. That has some merit and would be pretty easy to accomplish. Getting an accurate x and y with the Z height has been easier since I have started mounting cheap dial indicators on my tools. 7 dollars at Harbor Freight and they work pretty good. Once you established tooling length and Proofed out your program you should have a pretty easy run. Another idea is to make a bigger ShopBot table to hold a number of parts. I modified my first unit to 5 ft by 9 ft but my second unit is 6 ft by 12 ft. The ShopBot does not care how big your table is at all.

[birdsofplay]

If your bits are long enough, what about adding a collar-stop to them so they are always at the same height ?

[sheldon@dingwallguitars.com]

Bob, that's a good idea. I could apply that to drill bits too.

Thomas, I'm not sure I understand how you are using your dial indicators.

[birdsofplay]

IF ! we could find a GOOD snap action chuck AND
IF ! the Z axis had enough force to "make it work"
THEN ! we could design a tool bit changer.

I have fiddled with this notion using a 3D
CAD design and rendering to help visualize.

BUT ! I stopped the effort when I realized how
flaky the Jacobs was. sigh ... :-(

If ya wanna see the design just lemme know !

[gorrington@iafrica.com]

Bob, I am curious about your design. Could you e-mail in .dwg or .dxf format?

I am toying with the idea to (quick)change the whole router, though not automatically.

[sheldon@dingwallguitars.com]

Gerald, I was thinking the same thing last week. Using vacuum, a master mounting plate with a cross hatch pattern bordered by a vacuum gasket and a couple of alignment pins mounted on the second Z axis and a set of mating plates holding each spindle.

[Gerald D]

Sheldon, I don't think that I would trust vacuum to hold the dangerously spinning tool.

A master mounting plate, dowelled (pinned) to a variety of mating plates, is okay. However, I was thinking of using a pair of "over centre" latches to hold them together. On short notice, this is the first site that I found illustrating the style of catch:

http://www.southcoipsg.com/prd/hierarchymain.Showhierarchy?par_nNodeID=2116&par_n Lang_ID=1

Our local suppliers/agents have these catches holding up to 1 ton! (but no digital catalogs!)

[birdsofplay]

The four views of my Jacobs design are at these URLs
Front
http://www.birdsofplay.com/sbpix/bitchangf.jpg
top
http://www.birdsofplay.com/sbpix/bitchangt.jpg
right
http://www.birdsofplay.com/sbpix/bitchangr.jpg
iso
http://www.birdsofplay.com/sbpix/bitchangi.jpg

The whole thing depends on the following ...
Bits have to "fall out" after release, unless
they are held by YET another mechanism, see later description.

The whole bit tray has to move back against the
purple Tray spring to engage the Jacobs release pins for engage and release.
I envision a couple of low friction slides.

The other NECESSARY issue is that the bits will
have to be EXACTLY in the right place for the
pick up action. The Jacobs is not exactly tapered
enough to ensure this.

That is why I have abandoned the idea.

Operation "was" envisioned to work like this ...
1. Move over to the exposed bit
2. Z down to engage.
3. move back into the horizontal pins and then
4. Z down again to snap the chuck closed
note: that the action of the bit closure is between the Ring and the BACK HALF of the bit.
5. Then move back out or the pins.
Lift away and go to cut .

6. return to original bir holder position
7. Move back to engage pins
8 Z UP to SNAP / disengage the bit
9 Move back to pickup position
10. Z up and away from the bit
11. then over to the next bit and repeat 1 thru 5

I suppose a bit clamping mechanism could be designed for each type of bit to HOLD it tight
while in the Pickup/Release position.

All this was using the SB X,Y,Z axis ONLY and NO added channels or mechanisms.
A better chuck with a somewhat tapered collar
for "centering" or engagment would be the KEY.
Mabe a taper grind on each the end bit shaft too.

Hope this answers some questions and Piques some
new and better ideas as well :-)

[sheldon@dingwallguitars.com]

Gerald, you may be right, but even if you were drawing only 10 psi of vacuum, a 6" x 10" vacuum area would generate 600 lbs of pressure.

Bob, what if precision aluminum or plastic collars were pressed onto each bit shaft. A matching recess or cup in the bit tray would accept the collars, holding the bits centered and vertical. A chip blower would be needed to keep the collars and cups clean.

[Gerald D]

Bob, are you happy with the Jacobs in all other respects (except for taper lead in)? I am not familiar with this "jacobs" at all - can you point me to some pictures or data?

[birdsofplay]

Do a keyword search in THIS FORUM for Jacobs.

You will see thaT I am NOT a Jacobs fan.
There is a Pic there also.

[sheldon@dingwallguitars.com]

Here is a link to another review:
http://www.woodworking.org/WC/GArchive99/8_23powercollet.html

[jack@maui.net]

Regarding multiple bits/tools...
I am a new 'botter' with a dual Z axis machine. I would like to use one Z for the primary router, and have have maximum versatility on the other one. I envision a rack of four identicle small routers - such as the tiny bosch trimmer - for round-over, ball, rabbit/undercut bits and whatever else comes to mind. They would all be aligned to the same depth, and each would be deployed by a single toggle that would trigger a solenoid powered sliding mount to drop them a few inches into cutting position and also turn that one on.
Could this be done within the Shopbot software, indicating the sub channel in the part file by using the 'auxilliary switches'?
Where could I buy sliding solenoid powered actuators that would be appropriate for this?