Can the SB cut parts with tenons out of boards?

[justjohn]

I make small oak mortise and tenon tables. I
don't have a SB, but am considering it.

1) I'm wondering if I can start with a 7"w x 3/4"
x 6' board and cut a number of pieces which are
2"w x 3/4" x 12"long, with TENONS at each end?
I'm assuming the board would need to be flipped,
so that the tenons are centered depthwise; is
registration of the board a problem when doing
this? Has anyone been sucessful at cutting
tenons?

2) How does the SB cut out pieces? Is the work
suspened above the table surface, or does the
router head cut groves into the table?

3) When the last bit of material is removed, and
the piece is free, can it interfear with the
blade, and possibly damage the freahly cut piece?

Thanks

[parlee@island.net]

1) As you mentioned, the most difficult procedure will be flipping your work over while ensuring correct allignment. Other than that, multiple passes may be necessary to cut throught your oak which will need a light sanding afterwards. Many Shopbotters are cutting 3/4" ply in a single pass though I doubt anyone is achieving this in hardwood.

2) The easiest holddown for your application will be clamps or screws. Yes, the piece is held directly onto a sacrificial surface which is replaced from time to time.

3) Unless you are using a vacuum table or have screwed down the piece you are cutting out, you will need to leave a few "tabs" on your final pass. A few passes with your Japanese saw will release the parts.

Having said that, I would question whether you wouldn't be better off with a table saw and a good set of jigs? The circular saw is so much more efficient at cutting straight parts (and with less waste) than a router. Just my opinion.

Regards,

Robin

[jimt]

I use my shopbot to cut tenons for projects all the time. I mount the piece vertically through a hole in the table ang clamped to an angle plate above the table to keep things vertical. I find this is easier than a table saw and much more accurate as all the shoulders lin up perfectly all the way around and any adjustments to the tenon are done by changing a few numbers in the program. I also use it for mortising too - usually only when there's a bunch to do though.

Jim

[justjohn]

Robin and Jim,
I'm planning on cutting a lot of these (3,500/wk
initally) of varying widths and lengths, and I'm
looking at reducing the set up time (i.e. labor
$). I also like the safety aspects of the SB. I
am more concerned with wasting time, than wasting
materials, this is a production enviroment. By
using table saws, there is always a chance that
the setup was wrong, resulting in wasted time and
materials. Also the minor inaccuracy in the
cutting require additional work during assembly.
While the cutting time may be slower, the overall
productivity should be higher. Also a worker
using the SB shouldn't require a lot of training
just to place the board, and tell it to "go".

It should be possible to cut 1/4" of solid oak in
a single pass, right? This is all I need. Any
guess how long it would take to cut a 12"x1/4"
groove in oak?

Can the router by turned on and off by the SB?

Assuming that the SB program file is known to
work, can the SB be left unattended while it cuts?

Are there any techniques to ensuring correct
registration of flipped boards? I don't think I
can guarantee that either edge of a board is
perfectly streight. I don't need .001" of
accuracy, but 0.05" would be nice.

If the SB were to drill 2 holes straight thru the
board which corresponded to fixed alignment pins
of the same diameter, on another part of the
table, would this work?

Other than the bits, what part is most likely to
wear out on the SB?

Does the SB need to be horizontal to work? Could
it work vertically with the same accuracy if the
wood was held securly? Will it hurt the motors?

Can the SB be made shorter than 48"? I'm thinking
of something like 18"x 84".

Thanks for your help!
John

[SaintJohnBosco@yahoo.com]

I have cut sucessfully through 3/4" ash in a single pass. I don't remember the speed though.
You could cut 1/4" pretty fast though. At that depth you could probably go 2" per second at least. If you had the new gear headed shopbots you could probably go faster.

Yes the router can be turned off when you add a relay I put several on my one for the dust collector to turn on one for the router and one for the vacuum pump. ShopBot doesn't like to encurage hooking up routers to turn on by themselves (I guess for safety reasons), but It can be done.
You can leave the SB unatended, but it could be dangerous. Once I had a work piece come loose and jamb up the SB so it couldn't move within a few seconds I had a small pile of red hot glowing coals on my table. Luckly I was in the room at the time. If you wanted to really go crazy you could rewire a smoke detector and have it turn on one of the imput switches and then an output switch could be used to open a solinoid valve and dump the contents of an extinguisher down into the cutting tool. I have been know to say a prayer and walk away from my SB even after my glowing coal experiment.

I have used dowel pins as a means of registration of my engravings and been very accurate. Much closer than .05". I put my holes equal distant from the center and then fliped the board over using the same location on the table. You should be able to relocate some where else though.

The driver board amplifier on my bot has blown a few times. I finally just bought some replacement amps and soldered them in.
You might replace your table top ocasionally.

I think gravity would cause major problems on a vertical mount. Every time the motors were turned off you would risk damaging the controller and motors. I wouldn't try a vertical mount. Too risky.

You could make the SB 18"x84", but you have to pay more for it unless you do it yourself.
There are some ShopBotters who have made very long machines.

[Jay Meadors]

I put my router on its own power strip, and recently connected the dust collector to the same strip - I can now turn them on and off independently of the SB itself.

As for letting the machine run unattended, well, I do that, occasionally, when I am using a cut file that I have used sucessfully before, but I do check on progress of the work frequently, and usually try to stay within earshot so that I can hear any changes in pitch of the router or drive motors. But being careful and keeping an eye on the running machinery is always a good thing.

[beacon14@home.com]

In a production environment like you mention, unless floor space is a major problem, you may not want to be so quick to limit the size of your machine. I have several files which I use for multiple parts which repeat themselves, first on one area of the table, then on another area. While the machine works the first area, I load the second, and vice-versa. The result is near-continous operation, which you will likely need to create 3500 parts/week. In your case, you could cut the "top" half of a group of parts on one end of the table, then flip them and run the "bottom" half on the other end of the table while reloading the first half of the table for the next set of parts.
I insert a pause in the program between halves, to ensure that the machine does not move to the next set of parts before I am ready.
I only rarely leave the room unattended by either myself or my partner during cutting, since although the machine might run 12 hours without a hitch, something could (and occaissionaly does) go wrong at any time. I tend to have more problems with small waste pieces catching between the workpiece and the dust skirt than with the workpiece itself.

[justjohn]

Thank you, all for your answers they were very
helpful.

Joh