Sorta Woodworking - New Sight Glasses for My Table Saw

I don't CNC cut a lot of polycarbonate, but I thought folks might like seeing that with sharp cutters it cuts very nicely. This piece was from a piece of scrap left over from building the table top enclosure on my big mill. The math said I could have taken a much deeper depth of cut and made these sight glasses faster, but I don't CNC cut a lot of polycarbonate so I wanted to take it easy on my cutter without slowing down the feedrate and risking melting the edges. It came out perfect. The edges look as good as the edges on uncut sheets. A razor knife cleaned up the holding tabs.
Video
https://www.youtube.com/watch?v=YqF56m31TYo

Picture
http://yumabassman.com/forums-new/gallery/2_22_05_16_5_24_01.jpeg
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Bob La Londe
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As soon as I hit send I knew I said that wrong. The stock was just held to the backing with packing tape, and I didn't want it to come loose and go flying.
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On 5/22/2016 7:35 PM, Bob La Londe wrote:

Pretty cool!
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On Sun, 22 May 2016 17:35:15 -0700

what about magnification
mine has a magnifier bulge on it
seems like cnc is the way to go these days
the right setup can be very versatile and replace a lot of conventional machinery
a while ago i saw a video where a guy moved out some of his old stuff and built a new platform for a cnc rig
he had provisions for handling vertically or horizontally placed materials for maximum flexibility
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wrote:

That would be nice, but the old ones are totally 100% unuesable.

A flatbed CNC router large enough to handle sheet good will eliminate the need for a lot of things. It might not be as fast as a panel saw for ripping shelves out of plywood, but once you have it programmed you can do an entire sheet while you are on the other side of the shop sweeping up from your last project. I want one, but the metal woring is what is paying the bills. It will be a year probably before I like at large format CNC routers again.
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On Tue, 24 May 2016 12:37:50 -0700

wonder if a small magnifying lens could be glued onto one
not sure of there are any adhesives that dry clear and stay clear
there are hemispherical lenses
i guess the trick would be getting the proper magnification

plus it is probably safer

one thing i wonder about is the depth of cut
how to make sure the cut is clean through
you would not want to cut into the table and how do you keep the material flat for large sheets
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On Tue, 24 May 2016 16:44:24 -0700, Electric Comet

Sure there are. They're used in photography and in making touch screens (the "touch" part is a separate piece from the "screen" part). They're also used for cell phone protective glass sheets.

I'd think you'd want a cylindrical lens.

The same way you do it with a saw.

Sacrificial backer (someone here, I think it was Swingman, uses foam insulation sheets. A CNC machine should be able to cut precisely, so the backer will last a while.

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wrote:

One of the neatest tricks I've seen is to surface your sacrificial backer, and then use your tool height setter to set that as negative the nominal thickness of your sheet goods. Then you throw your stock on the table align it, and lock it down. This way you just scuff the back, regardless of the varying thickness of the sheet goods. If you are good at setup your sacrifical backer should last for hundreds of jobs.
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On Tue, 24 May 2016 18:21:17 -0700

here is the problem that i imagine could be encountered
you lay a 4x8 sheet down let us say it is 1/4 or 5/16 it does not lay perfectly flat so you get a different depth of cut over the area
it seems to me you would need to have wheels on the cutter head that applied consistent downward force while cutting to provide even depth of cut and not cut into the sacrificial backer
with thicker sheet goods i would not expect much warping over the 4x8 area but with thinner i would expect a problem
maybe i misunderstand what you mean by lock down
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wrote:

Ok, first off if you are cutting through, which was the question then you don't give a flying rip about varying thickness of the sheet goods. You cut based on the surface of the table. Second if you don't lock it down in some fashion its not going to stay on the table. Third, if it was me I would "lock it down" with a vacuum table if I was doing a lot of sheet goods. Only small parts will go flying. Larger ones will remain in place just fine.
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On Wed, 25 May 2016 11:42:24 -0700

yes i understand the material has to be secured but that has to be at the perimeter of the material
the vacuum table would do it for sheet material as you said so there is the answer
have you done any research on the most bang for the buck for a cnc setup for wood
being budget conscious i am interested in looking at solution
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wrote:

If you are up for builiding your own you can invest a little at a time by starting with one of Ahren Johnson's kits from www.cncrouterparts.com , but by the time you get done building the cost will be the same to build a solid heavy machine of decent quality, plus a lot of your time. There are noname Chinese Imports for around $4800 to $6800, but I have yet to talk to somebody who owns one. The most basic machine I would consider as decent will run from about $12.8K to $15K nearly complete. (may still need computer and control software) The really nice sheet goods size machines start at around $16k and go up. I'll probably go with the $12-13k range machine and build my own vacuum table when I am ready to add that machine to my arsenal.
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On Thursday, May 26, 2016 at 1:45:51 PM UTC-4, Bob La Londe wrote:

I'm not positive, but I think I just heard EC hit the floor somewhere :)
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On Thu, 26 May 2016 10:45:46 -0700

i will probably do it myself but just wanted a starting point for inspiration
there is a lot of opensource cnc stuff out there my big concern is getting caught up in putting one together and enjoying this fiddling around stage too much
fwiw i would probably do 4x5 or something like that or some other optimal size that is less than 4x8
i have noticed some equipment sellers/makers have fewer conventional machine offerings and more cnc stuff
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On Thursday, May 26, 2016 at 2:21:51 PM UTC-5, Electric Comet wrote:

Maybe search the IRS (Industrial Recovery Service) auctions for a used pin router, to start with, if you want to play, first.
Example: In York, Pa, the bidding for a few are $200-$500 at the moment. Lots 417, 422, 435: http://www.irsauctions.com/index_lots.asp?pg tails&tot=&id 325
Check the other listings for an auction near you.
Sonny
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On Wed, 25 May 2016 10:51:57 -0700, Electric Comet

You lay it on a table that is flat. If you're not cutting on a flat table, you're screwed before you start.

See above.

Exactly the opposite.

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wrote:

I love what you did. Looks great.
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On Sunday, May 22, 2016 at 7:35:25 PM UTC-5, Bob La Londe wrote:

Pretty neat, Bob.
When making/replacing my sight glass, I used a small plastic rectangle box, that fish hooks came in. I trimmed 3 sides of the box off, leaving the b ottom and one perpendicular side (the attaching portion). Back then, Delt a wanted $9 for a replacement glass. Today, my fabricated glass has dulled , become scratched, etc., again.
Sonny
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