Sanity check...

[geneb]

I've got the air-drill option installed on my 'bot, but I've never really needed to use it until recently.

I'd like to get it aligned as precisely as possible to the spindle - to the point if I drill a hole with the air-drill I could drop the same sized cutter into the hole with the spindle and not scrape the sides.

My thought is to drill a 1/4" alignment hole with the spindle and then jog the air drill around so that a 1/4" bit in the air drill will drop smoothly into the existing hole with the bit NOT spinning. From there I would take the offset measurements needed for the control software.

Is this a reasonable way of performing the alignment task?

Thanks all.

g.

[harold_weber]

Search for this file -

S_Set2spindleoffsets.sbp

It comes with the newer versions of SB3.

They expect you to install pieces of 1/4 inch drill rod into both heads, then the program runs a little routine using the drill rod as a touch probe to find the center of an exiting larger circular hole in a metal plate (you must supply the drill rod and the metal plate with the circular hole in it).
It does this for both heads, and so the differences in the two X's and Y's are the offsets.

I believe you'll need need to modify the routine to determine the offsets between a spindle and an air drill - but I'm not familiar with the air drill z-plunge commands so I'm not sure what would be involved.

[harold_weber]

Oops - in my previous post please change the word "exiting" to "existing"

Sorry.

[geneb]

The air-drill is an on/off kind of thing - you can't control the Z depth by computer.

Does anyone know if the method Harold describes would work for the air-drill?

g.

[chuckster]

Has anyone ever cut 1/2" thick polypropylene? I have an opportunity to pick up a job cutting parts out of 3 sheets of this material.

[Gary Campbell]

Gene...
Harold is exactly right on the the S_Set2spindleoffsets.sbp file being the best way to set the drill offset.

I am assuming that you have the drill mounted on a PRT? Read the instructions on the S_Set2spindleoffsets.sbp file and then release the switch that runs the air motor on the drill. Then turn on output 5 manually to plunge the drill. You may have to adjust the depth stop to get the drill rod in the circle. Now you should be able to get an accurate offset.
Gary

[geneb]

Thanks Gary & Harold. Now the only trick is to find something with a big enough hole in it.


Does the metal plate with the hole in it have to be of a known size and the hole be of a known size or will any chunk of metal with say a 2" diameter hole work?

g.

[Gary Campbell]

Gene..
A 3/4" hole drilled thru the Z zero plate will also work, if you can get your drill rod to just above the spoilboard.
Gary

[harold_weber]

You do not need to know the diameter of the hole. I use a piece of aluminum I got a machinist friend to make for me. It has a 3 inch hole, and there is a piece of Plexiglass at the bottom of the hole with scribed cross hairs so I can also use it to set X&Y to be zero where I want. The red you see at the bottom of the hole is an O-ring to hold the Plexiglass in.

You can get 3 foot lengths of drill rod at any machine shop supply house.
8833

[geneb]

Thanks guys. Drill rod is kind of hard to come by in my neck of the woods, but I'll bet that an up-ended drill bit may do the trick.

g.
(I'm absolutely gobstopped that the "ing" variant of "bet" is a forbidden word in the forum. *stunned look*)

[harold_weber]

It occurred to me that some folks may not be comfortable modifying the code. The program as written by ShopBot makes two critical assumptions which are not plainly spelled out::

1. Program assumes that moving 1 inch from the center of your hole will put you over solid metal. If you are using a 2 inch diameter hole, that's not a good assumption and you will need to change to a larger distance.

2. The program will move your test probes down by 0.130/2 inches from the top of your metal plate and attempt to find the center of the hole using that depth. Your probe or your hole (or both) may not be "clean" at that dimension.

Since I use a 3 inch hole, and sometimes use spherical ended touch probes, I've modified the code to take care of these issues. Your mileage may vary.

If you are not comfortable changing the code, then you need to make sure that the end of your probe is not chamfered or rounded. And you probably would be best to use a 3/4 inch hole.