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  #1  
Old 11-25-2000, 09:11 PM
david allen davidallen is offline
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Location: , Ewing NJ
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Default Laser alignment tool

just got a laser alignment tool from Northern Tool and Equip. that looks like a good addition to the ShopBot. it's their Torpedo Boy Laser Level w/ tripod for $24.99. it has a magnet mount on it and can be fixed to the Z-axis to provide an offset for the tool's x-y zero. it has a small spot size as well as a line generating lens. you can use the line to set zero as well as align stock.

da
  #2  
Old 04-16-2003, 02:04 AM
danbrewer@attbi.com
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That's a great idea, David. I bought one myself and am looking forward to trying it out. It sure beats running a v-bit down to .005" and sight-aligning.

One question: since it's attached to your router (assumption here) has it withstood the vibration test? Has the laser ever gone out of alignment (or just plain "gone out")?
  #3  
Old 04-16-2003, 06:27 AM
ron_cleaver
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How do you use it to set (0,0) and align stock?
  #4  
Old 04-16-2003, 09:55 AM
david allen davidallen is offline
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since it has a magnetic base, I mount it on one of the vertical channel pieces of the z carriage. this gives an offset line for either the x or y axis.

table zero is best set using your table stops. you can then use the laser (with the line attachment) to align stock and calculate or set the edge offset from the system zero. if you want, you can then use that offset to reset the table zero to the stock zero.

I usually remove it while the router is running
  #5  
Old 04-16-2003, 11:05 PM
danbrewer@attbi.com
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Ron

It depends on where you mounted your laser. Looking at the cutter head from above, you can split the area around it into four quadrants. Knowing which quadrant your laser is mounted in will determine the offset values you'll use when zeroing out the Bot. When standing in front of your Bot, the 3rd and 4th quadrants will be nearest to you.

Here's a top-level view of the cutter head and the laser mounted in the 3rd quadrant (this looks best when viewing this message in Courier font)


|
2nd quadrant __|__ 1st quadrant
/ \
----- | |------
\_____/
3rd quadrant * | 4th quadrant
^ |
|
Laser mounted here


My approach would be to move the cutter to 0,0 (wherever that may be; it really doesn't matter), chuck up a v-bit and then drop the head down to -0.005" to produce a small dimple. Turn on the laser and arrow the head over until the laser is pointing straight into the dimple.

Make a note of this X-Y location. These values will be used as your offsets.

Then set up a custom cut file (like CUSCUT5.SBC) to offset the ShopBot and Z2 the bot.

Depending on what quadrant you mounted your laser in, you'll need to adjust your offsets accordingly; one, both or neither offset may be a negative value. The rule of thumb for determining which values would be negative, which would be positive, is this:

Laser mounted in the....
1st quadrant: X and Y offsets are both positive
2nd quadrant: X is negative, Y is positive
3rd quadrant: X and y are both negative
4th quadrant: X is positive, Y is negative

For example, let's say your laser is mounted somewhere in the third quadrant, and after moving the laser into the dimple your ShopBot is at X-Y coordinates 6.212, 3.019. Write this in your custom cut file:

'Zero X-Y at Laser
'Move the bot to the NEGATIVE offset of the laser
'for 3rd quadrant mountings
J2 -6.212, -3.019
'Now zero out X-Y
Z2
'Now move to the new X-Y zero
JH
'Done!

Of course, your results will vary, depending on the quadrant your laser is mounted in and how far the laser is from your cutter.

Hope this helps.
  #6  
Old 04-16-2003, 11:12 PM
danbrewer@attbi.com
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Thanks for the quick reply, David. I saw a posting of yours in another forum that discussed creating a mount for the laser. I'll take that advice to heart as I REALLY don't want to chunk down another $25 for another laser!

The laser works beautifully. Again, thanks for the fantastic suggestion.
  #7  
Old 04-18-2003, 10:56 PM
david@fools.net
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David,
I saw at the description of the Torpedo Boy that its accuracy is rated at +or- .2 inches at 1.1 yards... is that acurate enough?
David Beede
  #8  
Old 04-19-2003, 06:13 AM
rgbrown@itexas.net
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Let's do a little simple math here. The specification for "the rest of the world" might read +/- 5mm @ 1 Meter.

My ShopBot has a "Z" of 6" (150 mm) but, to make the math simple I will say it is 200mm - near 8" from the end of our level to the top surface. Now, our accuracy would be +/- 1mm @ .2 Meter. This is the "outside" of the envelope. In reality it is probably much closer but, if you advertise, you must take everything in account or some user will come back and say "I used this level and it was off 1/8" in 100 yards. I want my money back!"

I have one of the older ShopBots with self installed Rack and Pinion up-grade and "home-made" gearboxes. It is more than visually accurate.

The tool is more accurate than most woodworkers. Dan is lowering his tool to "-.005" and making a small dimple. The dimple, if one is using a 90 V-Bit will be .01414". Overall cutting accuracy is advertised on the new models as +/- 0.015". Let me get my "Opto-comparator" and find those last six tenths.....

My point is I hear all this talk about accuracy and the most accurate tool I have seen used on a ShopBot is a dial-caliper or digital caliper. And, how many of you folks wondering if an "X-Y" location of .020 is accurate enough have checked their "Z" for true square with the table? Did you check the table for flat with a "straight-edge" ? A good 48" straight edge is about $150 or more these days. Did you sweep that table off before you placed a "square block" on the table? Did you scrape the table to assure you were on an "average" of the table. Did you do the necessary analysis for temperature compensation of your tools?

Or, as I suspect, are you folks trying to split hair with a sledge-hammer?

Ron Brown

Diplomacy is the art of saying 'Nice doggie' until you can find a rock. - Will Rogers
  #9  
Old 04-19-2003, 11:09 AM
Gerald_D gerald_d is offline
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David, don't let Ron's maths confuse you!


The other posters were only talking about using the laser to make a dot. You have looked at the spec for the "level" part. i.e. when you have to level a playing field. That spec tells you how level the field would be afterwards. And quite frankly, 0.2 inches in 1.1 yards is disgustingly bad. But, if you want to use the laser part like the other posters have described, you are not going to use the level part. In fact, a keyring board pointer will probably do that job just as well.

If I really had to, I would buy an industrial quality laser unit, like this or this and make a small adaptor to fit it directly in to the router collet. These laser units are only around 3/8" diam x 1"~1.5" long. I have used them on other applications and they are quite tough. They should withstand being permanently mounted on the z-axis.

But, quite frankly, I don't think that I ever would mount a laser on a ShopBot - I just don't see the need for it. If I really needed to find edges and spots that accurately, I would first call on a metalwork shop and find out more about the tools that they use in their milling machines for this purpose.
  #10  
Old 04-19-2003, 11:17 AM
papadaveinwy
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Ron, great narrative! I have always stayed away from theads like this because I always thought this is "splitting hairs" Lets all get real, if you need that kind of accuracy then your work must be for NASA or you are trying to develop a new atomic tunnel for the DOD. Or are you tring to use your bot for calculating quantum physics. David in Wyoming
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