Laser alignment tool

Metalworkers use "wigglers" or "edgefinders" but they have to be used at quite a low speed. Link.

I'm wondering if he scraped and trued the "Uni-Strut" before he mounted the laser.

On a real note, if one did want to know where the center of bit is they could mount two line-casting lasers, one to the "X" cariage and one to the "Y".

And yes, metal workers do use "wigglers". They also use stops and dial-indicators to find lines and centers.

Imagination, trial and error have taught me more than instructors ever could. I still have "stops" at certain known points on my table. Dowels fit in holes and become locating pins.

There is a saying about more than one way to skin a cat. Trust me, one wants to make sure the cat is dead first. It is also helpful to have a reason and a sharp knife.

My table has a "grid" that acts as a place for vacuum gaskets and vacuum channels. the grid is a on a 2" x 2" pattern and the channels are 3/8" wide. I can usually "spot" a piece within 1/8". The "next time" I rebuild my table I will probably dye sections of the table various colors so I can tell where the bit is without looking at the screen.

Ron

Don't get me wrong here. I'm certainly aware of the limits of accuracy in the Bot, and my instructions were really not meant to draw anyone to the conclusion that the Torpedo laser will provide any more accuracy than the Bot inherently has (which is pretty good in and of itself!)

I just see it as a more convenient way of finding an X-Y zero-point than eyeballing down the X and Y axes with a V-bit chucked up, which I found incredibly tedious and time consuming, not to mention inaccurate because it's hard to sight down the Y-axis.

The Torpedo Boy comes with a magnet attached, and I've discovered that by just placing it snug againt the Z gantry that this provides a fairly reliable point of reference every time (it's plumb). No jigs to build for the laser, etc. I've had the extreme privledge to work under shop foremans who believe that "simpler is better", and I've used that philosophy here as well.

You're right, dropping a V-bit down to -0.005" does produce a VERY small dimple (I guess -0.010" would have been better advice!), but once I got the offsets for the laser relative to the bit, it works every time. It's not rocket science, and I wouldn't recommend using this technique if you require more accurate tolerances than most woodworkers need, but for a "quick and dirty" X-Y zeroing routine, this works for my money.

Again, my apoligies for any confusion or seemingly misleading information.

Dan,

Actually, my math was rusty, or I was not thinking right. The dimple diameter would be twice the depth. The "length along cut" would be square root of 2 times depth or diameter. And you weren't the one asking if a level was accurate enough.

If the goal is to find "Center Bit" you are on track. One might also think about using the "line generating lens" and put two plates on the "Y" carriage and have a "Cross" where the center of bit is.

The accuracy question is raised many times. I remember an argument with a supervisor about me using the 3-4-5 triangle for "square" and the supervisor insisted I use a 6-8-10 triangle. Some of the folks raise the questions and don't have the tools to measure the results.

There are certain truths in layout and engineering. Braided lines are more accurate than twisted line. A knife cut is more accurate than a pencil line. A fish quits growing if you take a picture.

It is hard to guess where the bit will hit....

We all know that the z-zero plate works for positioning the SB in the z-direction. Why don't we develop that principle to the x and y directions as well?

Instead of just a flat alu plate, let's take an alu "cup" (or "ashtray") with a viewing hole cut in the bottom. Put crosshairs across the hole (scribed clear plastic) so that the "cup" can be put on your workpiece accurately in the x, y and z directions. The cup is electrically connected the same way as the one-dimensional z-zero plate.

Now we bribe Bill Young to modify one of his edge-finding programs to probe the bottom (next to the window) and rim of the cup and automatically zero the SB in the x, y and z directions. Sounds too easy, doesn't it?

Why haven't I done it yet? Well, we normally don't need that type of accuracy in our particular line of work. Also, we use mostly single flute cutters that are not symmetrical. And lastly, we don't know if Bill will take a bribe.

Ron-

Haha. You could have REALLY torqued off your supe and insisted you use a 9-12-15 triangle, then walked of muttering about the postulate of similar triangles (with a few explectives thrown in just out of the audible range).

Some folks you just can't reach.

"Now we bribe Bill Young to modify one of his edge-finding programs to probe the bottom (next to the window) and rim of the cup and automatically zero the SB in the x, y and z directions. Sounds too easy, doesn't it?"

I believe I might have a copy of a file similar to that if you would care to see it......

Ron

after 2 1/2 years, there's still this much interest? well, I guess relating some experiences are in order.

the accuracy of the laser is not an issue. it's not accuracy but precision that's the issue. it could be off by 10 degrees, but if it hits the same place every time, the offset to the bit will be the same. the laser will fit snuggly on my z-axis such that it can be reliably placed every time.

when I use the laser (which isn't often) I use the line attchment and align the laser to a cut in the table. that gets the line parallel to the axis of interest. I can then check that a piece is aligned correctly. there are easier and faster ways of checking stock alignment. my primary use for the laser is for aligning stock that has pre-existing patterns. either materials partially done by someone else or a job that had to be removed for intermediate processing then replaced. usually some forethought to establish keys and work template minimizes re-alignment concerns.

I generally 'zero' the table with contact switches bolted to the rails. the x-y-z zero program works fine for that purpose. when I need to move the table zero, I generally zero the table, apply an offset with the M2 or M3 command then reset the table zero.

occasionally, I'll throw some stock on the table and want to set the table zero to the corner of the stock. to do that, I picked up a machinist's square and mounted it on a block of wood so that it can be clamped to the table but still sit above the stock and aligned to the corner. the square has a wire on it, like the zero plate, I again use the supplied program to zero the x and y axis with the bit contacting the machinist square instead of the frame closing the contact switches.

sometimes I get anal and want to re-zero, either between bit changes or after the system's been turned off for a while. the square works, but I need to check that the outer diameter of the bit is making contact and not the valley between flutes. to eliminate that concern, I mounted contact switches on magnets that I can position along the rail to set a variable system zero. they're also useful if you want to set variable limits in order to protect a job in progress elsewhere on the work table. (remember, the switches and zero plate/square trigger the emergency stop input.)

so after all the high tech and gadgeteering, I'm back to the original SB design of using contact switches and thinking ahead.

da

David Allen, that was a great post! And it puts your recommendation of a simple laser perfectly into perspective.

Thanks to David Allen and the rest of the gang...
I asked about the accuracy of the laser, not to cast aspersions on it... but for education, which I'm getting. In my book .2" or almost a 1/4 inch in 1.1 yards seems pretty bad, but I now know that is the level, rather than the laser. And if you are using it on the Z axis mounted magnetically to project a dot relatively close by, I can see the repeatability would be quite adequate. I'm new at all this, so am mostly asking out of imagination rather than experience, but what about just using the home command and prox. switches? Bill P. uses variations on the program with different offsets to place him repeatedly in differenct quadrants or on the mark on different jigs... are we talking about being sure the jig is in the right place? I like registration pins, and the wired square that contacts the bit idea as well. Has anyone wired simple aluminum x & Y stops to jigs with calculated offsets from the Zero home spot and used them like the Z plate? Seems that would circumvent all the eyeballing - they could even perhaps be firmly affixed to the edge of a jig, and pivot up and down on a bolt say, to keep clear of router bits. Perhpas jacks could be wired into the control box, or into each jig to allow for quick connect & disconnect? Am I being too anal here? I do make musical instruments, so I lean that way, but it seems the Shopbot specs are way better than my old eyes.
Thanks again for all the ideas.
David Beede