Scoring Glass and Toolpath Solution

I've had my machine for several years now, mostly cutting wood products, plastics, and some aluminum. I've been wanting to try some stained glass projects for a while, and, naturally, I want my CNC to help me out.I've been digging around the web for a few days, and it seems that scoring with a blade like what you would use to do it by hand is going to be the best option. There is a scoring attachment on ebay for about $80 that has something like a shock absorber that "automatically" applies the correct amount of scoring pressure on the glass using a carbide wheel offset from the centerline.I'm running Vectric Aspire as my design software, and they have a drag knife gadget that creates tool paths. The way it handles sharp corners is that raises the Z enough to where the blade is barely touching the material so it can move XY to reposition the blade to start next line and create the sharp corner.The thing is that I don't know if that will work for glass. I recall seeing something in the past where a solution to sharp corners for drag knifes was to go past the corners and make a small loop to reenter the vector.Does anyone have experience with this? Any help is much appreciated.

Not with glass but, fusion has a draft knife plugin that allows more control than the vectric one. I would assume that you wouldn't want to do the loop at all. You could set the lip size too something very small. You could not have it run that loop at all and instead, extend the line past the cut to travel. Then hope that starting that far out would turn the tool.
I've seen several stepper controlled drag knife setups as well. I guess, if you had the correct post processor, you could use that as a rotary axis and lift/turn the tool for the next cut.

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I saw a YT video yesterday where the scoring blade went beyond the corner and made and an arc in the direction toward the next line, rises, moves, and makes another arc to finish positioning the blade before starting the next line. Seems like a great solution, and it would be nice if I knew how to easily program those moves when creating the tool path.

Oh, that should be one of the units available with the dragknife vectric plugin. Have you tried a toolpath to see what it generated? I believe the tip offset is the key factor of the size of that arc. Meaning, the tip is offset from the center by whatever amount.
When you do use it, you have to play around until you get the results you want though. Then stick with it.

That being said, applied science in YouTube used a cnc router that he then built a little water table to put a very expensive single surface mirror on. Then used a diamond rotary bit and then pumped water over it continuously. He cut very shallow passes and was able to get a clean finished edge on a circle. Been wanting to try with stained glass ever since. I will at some point.

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What about using a diamond engraving bit which is a tool with a diamond point which you can use to score along a toolpath, as the point is in the center there is no offsets required, try googling diamond engraving bit to see what I mean. https://www.amazon.co.uk/Dremel-9929.../dp/B00004UDJU
The one I have shown refers to it as a rotary tool but it doesn't be spinning when you are drag engraving, I've used these bits to engrave names into the clips of pens held in a spring loaded holder so you don't have to be to worried about exact height.



In fact I had forgot I had it and I also do some stained glass work so must try it myself sometime

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Originally Posted by apewrangler

The way it handles sharp corners is that raises the Z enough to where the blade is barely touching the material so it can move XY to reposition the blade to start next line and create the sharp corner.The thing is that I don't know if that will work for glass. I recall seeing something in the past where a solution to sharp corners for drag knifes was to go past the corners and make a small loop to reenter the vector.Does anyone have experience with this? Any help is much appreciated.

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Have you ever tried cutting glass by hand? It's not the same as cutting profiles with a router bit. There's no way to create a sharp outside corner except by scoring across another scored line, breaking one piece off, then the other. (Sharp inside corners don't work at all - if you need one, use a diamond saw or abrasive waterjet.) So making it create sharp corners without doing that isn't going to help. Think in terms of pieces that you can break off one by one, with scored lines that go all the way to the edge of the piece you're cutting.

I have looked at the spring-loaded diamond engraving bit, but there are a lot of reviewers who say the bits just can't hold up very long on glass.

I have never cut glass by hand. That's always an option, but I'm just going by the "work smarter, not harder" approach at this point. I don't want to invest a lot at this point, either. I'm just putting out feelers to see what could work.

https://youtu.be/HyI111Tn0Cs

This is the video I referenced earlier. Cheap method that for sure works. He cut a first surface mirror that costs an incredible amount to have made. If you're cutting cheap glass, this seems doable. Cheap diamond bits, the only thing diamonds are with anything for and water.

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I have a diamond set just like that that I use in my dremel.

Exactly. Dirt cheap.
Not sure if it's a 1/8th collet or not. I'm sure you can find a holder for not much if you do not have a collet of the correct size. I have used extensions from amana that have been good. I have so much air passing down from the spindle that I would print a deflector to make sure the water isn't going everywhere.

Small tabletop water fountain pump with a reservoir. Maybe some acrylic sheets welded to make a table that can catch the water and drain back to the reservoir with a strainer. I'm sure you could use some plastic container though.

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I worked in a glass factory for several years that made glass bottles. We had to cut the bottles periodically to gauge the wall thickness. I bought a diamond point glass cutter and used it for a couple of years with no problem. One of the diamond point engraving tips (spring loaded) as is available on the Vision Max engravers (I have one) should work as I have used it on glass bottles doing engraving on wine bottles. Scoring and breaking an inside corner will be nearly impossible as someone said. Using a rotary diamond bit like available for Dremel like tools could work but you will need to flood the work with water and travel very very slow. My dad did some stained glass as a hobby for several years, every once in a while heard some cursing when a cut didn’t go right. Best of luck.