Vector table works suprisingly well

[dave cox]

245879245880

Recently vector cutting double sided 4mm veneer I was spending more time cleaning the pieces than anything else.

I tried an oven rack which was ok except when the laser beam reflected off the shinny rack gave bad damage so tried galvanised 100mm nails glued into laser cut holes in 6mm acrylic and it works very well. A couple of photos may give you an idea.

[Steve Busey]

As we say around here, necessity is the mother of invention - well played, Dave!

[Dan Hintz]

There have a been a number of bed-of-nails designs over the years... I think my favorite for simplicity was sticking golf tees in the standard vector table. No reflection, and since they're wood, hitting it with the beam meant no more smoke than what was already being generated.

[Mike Berndt]

Wow,
Golf tees??? I think that is my next purchase for a vector cut table?

[Glen Monaghan]

I have a similar "bed of nails" that I use for larger pieces but found it a pain for smaller cutouts. If the pieces can fall down the way many of your circles have done, they all too often seem to land where the beam cutting a neighboring piece makes an out-of-focus burn across the dropped piece. One particularly unlucky batch of approximately 1" shapes had more than 1 in 4 ruined that way... but making a large BON with less than 1" spacing is a time consuming PITA. Now I tend to use a honeycomb with a few scrap L shapes of 1/8" ply at the corners and a narrow scrap ply strip or two near the middle as spacers to raise the work piece and prevent any back burn or melt from the honeycomb.

-Glen

[carl stevenson]

what about the plastic golf tees, then hardly any smoke at all...?

I sometimes put a sheet of perspex on the honeycomb and then cut paper on top which minimises reflection and smoke, seems to work.
Also I use expanded foam (the blue stuff from model shops) as a base over thehoneycomb, the beam doesnt reflect off it at all and it generates no smoke. Even if it gets cut slightly by the beam, its still supporting the work.

[Chuck Stone]

I have a similar "bed of nails" that I use for larger pieces but found it a pain for smaller cutouts. If the pieces can fall down the way many of your circles have done, they all too often seem to land where the beam cutting a neighboring piece makes an out-of-focus burn across the dropped piece.

maybe a bed of cribbage pegs would work better for small items? More of a pain to make
a tighter table, but someone with a CNC could probably whip one out pretty
quickly. And 1,000 wood pegs are under $50, so it isn't terribly expensive either.

(wood sheet full of holes.. big bag of pegs? Add some popcorn and get the kids involved!)

[Keith Outten]

At CNU we recently made the second generation Corian vector table based on the first one I made a couple years ago. This time we used a 60 degree vbit to cut the rows of prisms, there is much more depth and the table works so much better. I use the Corian table to cut engravers plastic, it works ok with acrylic but it is superior to any table I have used cutting thin plastic.

I can post some pictures later if anyone is interested.
.

[Mark Ross]

Keith,

I would like to see a picture of it. Thanks.

[Stephen Sullivan]

At CNU we recently made the second generation Corian vector table based on the first one I made a couple years ago. This time we used a 60 degree vbit to cut the rows of prisms, there is much more depth and the table works so much better. I use the Corian table to cut engravers plastic, it works ok with acrylic but it is superior to any table I have used cutting thin plastic.

I can post some pictures later if anyone is interested.
.

Would like to see those pictures of the Corian table.

[Frédéric PARROT]

Hi Keith,

I would like to see pictures of it too :)

[Ernie Martinez]

Another solutions is to use Cleco fasteners. They are used in the aircraft industry to hold aluminum sheet together for riveting, but they would make excellent stand offs. Just take a piece of aluminum .060 sheet, and drill a grid of holes. The you can position the Cleco's specifically where you need them.

http://www.amazon.com/Allstar-25-Qty-Cleco-Fasteners/dp/B000GHEZ4Y

[David Rust]

Hi Ernie, the head of the Cleco is probably 1/4" in diameter. If you vector over one you will get a reflection. Also When the Cleco is fastened it will extrude through the bottom of the aluminum sheet. You may have to put it on a piece of corrugated cardboard so you can seat the Cleco bottoms into it in order for it to sit even.

[Keith Outten]

Corian Vector Table.

The table and the support pieces are all 1/2" thick Corian.
This was a very simple CNC machining job using a 60 degree Vbit.
It is perfectly flat and we can pressure wash it when it gets dirty.
It absorbs the laser energy and does not produce any smoke at all.
The pics aren't the best quality and the first one is upside down....took them with my cell phone.

Oh yeah I forgot to add that I did not make a fence for either the X or Y edges. I prefer to be able to lay thin plastic on the table and wrap tape around the edge. This seems to keep thin plastic laying very flat even when we cut hundreds of letters from a sheet for ADA signs.

Any questions?
.

[dave cox]

Great thing about SMC, you think you have a good idea and someone has a better one, the corian looks like a great answer and it is available to us in the far flung corners of the world.

I have found cutting anything that isn't effected by water, wet brown paper on the back is good, usually it is impossible to see any clue how it was cut.

[Frédéric PARROT]

Hi Keith,

Thanks for the pictures.

I think in my case the clearance under the material to be cut is not large enough.
I cut paper or cardboard and colored smoke stains often the back of my cutting table despite the honeycomb.
The ULS-PIN TABLE KIT is very expensive so I think I'll try the solution with the golf tees indicated by Dan.

[Keith Outten]

Fred,

When I made the first Corian table I was concerned about the height of the prisms and whether I would be able to push enough air under the plastic. As it turns out the table performs well but it requires a bit more air than a standard fan. Since I use a dust collector attached to my laser engraver I have plenty of air and the flow under the material is better than my standard aluminum honeycomb table because the air comes in contact with the bottom of the plastic when I use the Corian table much the same as the golf tee system works.

The new Corian table has more depth, the prisms are taller because I used a 60 degree bit so the performance is even better than the first table. Although I haven't measured them the new table prisms are about 1/4" deep, the downside is that they are very sharp so the table is best handled by the frame. The supports on the bottom keep the table flat and provide space for tape to wrap around the edge to secure the plastic to the table and keep it flat when vector cutting.
.

[Dan Hintz]

Although I haven't measured them the new table prisms are about 1/4" deep, the downside is that they are very sharp so the table is best handled by the frame.

A quick pass with a belt sander, maybe? Faster than trying to knock the tips off using the CNC, though the CNC would ensure it remains level.

[Mark Ross]

Keith,

We cut a ton of 1/8 to 1/2 inch acrylic (8-10 hours a day). Are you saying we could lay the material right on the corian and vector cut through it? Wouldn't the corian get damaged in the areas we do the cuts in? Thanks for your reply. I never thought of doing it this way. I'll post a picture of the last attempt we did using bolts when I get a chance.

We also cut a ton of plastic (styrene) that is 1/16 of an inch thick and that stuff is gummy, sticky, you cant clean an aluminum vector grid without destroying it and to boot, the residue loves to catch on fire. If this would work and we could power wash it, that would be awesome.

[Mike Lysov]

I have a similar "bed of nails" that I use for larger pieces but found it a pain for smaller cutouts. If the pieces can fall down the way many of your circles have done, they all too often seem to land where the beam cutting a neighboring piece makes an out-of-focus burn across the dropped piece. One particularly unlucky batch of approximately 1" shapes had more than 1 in 4 ruined that way... but making a large BON with less than 1" spacing is a time consuming PITA. Now I tend to use a honeycomb with a few scrap L shapes of 1/8" ply at the corners and a narrow scrap ply strip or two near the middle as spacers to raise the work piece and prevent any back burn or melt from the honeycomb.

-Glen

the pin or nail raised cutting works great but it's really a pain for small and sometimes for big cutouts. The solution is simple. You do not need these pins/nails to raise material too high. 2-3mm is more than enough to get rid of reflection at the back of material. I have found that using a honeycomb table with short pins that raise material above it just 1-3 mm leaves no much space for the cutouts to fall down under to be hit by the laser beam.

It's better to be used with the honeycomb because this way there will be a lot of airflow through honeycomb cells for fumes extraction.

[Keith Outten]

Keith,

We cut a ton of 1/8 to 1/2 inch acrylic (8-10 hours a day). Are you saying we could lay the material right on the corian and vector cut through it? Wouldn't the corian get damaged in the areas we do the cuts in? Thanks for your reply. I never thought of doing it this way. I'll post a picture of the last attempt we did using bolts when I get a chance.

We also cut a ton of plastic (styrene) that is 1/16 of an inch thick and that stuff is gummy, sticky, you cant clean an aluminum vector grid without destroying it and to boot, the residue loves to catch on fire. If this would work and we could power wash it, that would be awesome.

Ross,

Yes, you can vector cut all day long using a Corian table. The last time I cut letters and numbers for ADA signs I spent ten days cutting 8 hours per day on our Corian table. There is a small amount of damage to the Corian prisms but it should last for many many years before it has to be replaced. Pressure washing is a great way to clean Corian, you can even soak it in a degreaser for awhile before you power wash it if you need to.

[Stephen Sullivan]

Keith, thanks for the photos!!

[Frédéric PARROT]

Keith,
Very thanks for the explanations :-)

[Ian Wilson (AUST)]

Hi Keith,

Could I pls see your pictures?

Thanks Ian

[Sandy Henry]

Keith, What is the purpose of the support pieces. Why not lay the 1/2" sheet directly on laser bed? Thanks, Sandy

[Keith Outten]

Sandy,

If you look closely you can see that I glued two pieces of half inch thick Corian together to make the table surface. I did this because a single sheet tends to warp a little bit when you machine so much of the surface away. The supports on the bottom help to keep the table perfectly flat and they lift the vector table off of the engraving table so it is easy to install and remove. The additional height that the supports provide also makes it easy to tape thin engravers plastic around the edge to hold it flat.

The reason that I leave the sharp points on the prisms is that the table needs to be perfectly flat if you want to engrave materials like laser lights or AlumaMark. There is just enough space for air to move under the material to be engraved or cut and there is plenty of support under the material to keep it in place. Another nice thing about this design is that small pieces that I vector cut don't drop down inside the table so it is easy to place a piece of matte board on top of the vector table and flip it over to unload hundreds of letters and numbers when we cut them for ADA signs.

Ian, my pictures are attached to post number 14.
.

[Albert Nix]

May have to try that Keith..Thanks

[Sandy Henry]

Thanks Keith, This will keep me from scrapping my 1st attempt at making one of these. Do you glue the 2 1/2" pieces together before or after milling? Thanks Again!

[Ken Dolph]

Keith,

Two things will keep the cupping down when doing machining in Corian.

First keep your feed rate down 30 to 60 ipm. This lessens the uneven heating from friction.

Start in the center of the material and spiral out. This balances the heat build up. Since Corian anneals with heat it will be slightly smaller after heating and cooling. This is the most common cause of cupping.

I know that both of these suggestions will slow down the processing but sometimes it is worth it.

[Keith Outten]

Sandy,

Yes, I glue the two half inch sheets together before I machine the prisms. Make sure you have a good flat table or you can use to keep both pieces flat while the glue dries.
I cut the two pieces just a little oversize so I can machine them to size on my CNC Router, in this case 12" by 24".

Ken, thanks for the tip. I always machine Corian at a slow speed (routing or sawing) based on your recommendations a long time ago. The CNC machining doesn't produce any measurable heat to the best of my knowledge.
.

[Michael Kowalczyk]

Ken,
In my experience that is way to slow for me. A good sharp bit at the proper RPM and IPM to generate the best chipload is the formula to use, IMHO. Unless your RPM is slowed down to make the correct chipload, you might be generating more heat than going faster. Also a Rule of thumb is once you use a bit for solid surface don't use it for wood and vice versa. I use Avonite poly blends more than Corian 100% acrylic so there may be a different factor but a sharp SC bit is a must. Depending on what I am doing would determine the bit also. I use single flute spiral, double "o" flute, 2 flute compression, chip breakers and they all have a little different settings and the diameter of the bit also changes the feed and speed settings to get proper chip load. What do you think?

Check this article out. It recommends to start at 200 IPM at 18,000 RPM and increase until you get the best finish.

http://www.plasticsmag.com/ta.asp?aid=2588

(after thought)
Just got an Amana 90 degree V-fold insert bit set and it would make it possible to have 1 side of the insert used for wood and the other for composite/acrylics. Or even a separate set that can be marked with a sharpie or possibly laser engraved :D.
Just thinking out loud.

[Ken Dolph]

Michael

With Keith's indulgence, I will try to explain each of the points you questioned.

The article you referenced is for plastics. Corian is not considered a plastic because it is about 70% mineral. Chip loads for plastics, metals or wood are calculated to eliminate a binding effect where tie chips are wedged in the gullets during cutting. Corian chips or shavings will tend to powder in the gullets at less than half the maximum chip load. While this does not effect the cut, the fine dust has a high static charge. This is not just a nuisance. Because of the charge, the dust will attract oils even out of sealed bearings. Most, who experience bearing failure, assume that Corian is abrasive. It is not. It is the drying of bearings that cause the failure.

The term 100% acrylic, when used with solid surface materials refers to the binder which is about 30% of the weight of the material. This does not mean that it will cut like acrylic. It does mean that it has a coefficient of thermal expansion close to that of pure acrylic. And that it anneals like pure acrylic. Avonite products are all over the spectrum as far as their composition. Originally they were all pure polyester filled with styrene, no mineral at all. Some of their recent lines have been nearly identical to Corian and still others are somewhere in between.

As to heat build up during cutting. Of course, the heat is from friction. Scientifically speaking, the heat of friction is dependent on two factors: a constant that is dependent on the two involved materials multiplied by the force between them. The faster you feed the material the greater the force. This is further exacerbated by the thermal expansion of Corian. The heat of friction causes the Corian to expand, shrinking the slot as your cutter moves through it. This increases the force on the cut and increases the heat. So temperature, at the point of the cut, increases exponentially with a linear increase in feed rate. I know that you do not seem to experience this. The effects are normally small. But you will see an increase in the quality of the cut if you move slower. One can go too slow. In this case the bit causes less heat per unit time but it remains too long over the Corian causing excessive localized thermal expansion. This expresses itself in a whitening of dark materials. This is micro-fracturing not a change in pigment.

Increased force can also set up standing waves in your tooling. The frequency of these waves increases with force. At 30 to 60 ipm the waves are so long as to be straight lines. Again these effects are usually very small but can be noticeable as chatter with some tooling.

As to not using the same bit/blade for wood as Corian: the reason for this is that trees absorb silica in the water they use. Some trees more than others. Think quartz. This causes abrasion to the fine cutting edge. This is what you notice when later cut Corian.

Finally, we experienced a blade life increase of 11 times when we slowed our equipment down. We did this at the suggestion of our tool sharpener. He also sharpens the tooling for DuPont's Corian plant and had studied the geometries and other factors in cutting Corian. It appears that the carbide experiences cavitation at higher feed rates. This is like the cavitation that boat propellers experience when spinning too fast in water. I have gone over this with cutting tool metallurgists. Though we have not done any micrography on this, it seem to be the best explanation since there is nothing in the Corian to explain this.

Sorry about the long post but I wanted to be thorough.

Ken

[Vicki Rivrud]

I tried an oven rack which was ok except when the laser beam reflected off the shinny rack gave bad damage so tried galvanised 100mm nails glued into laser cut holes in 6mm acrylic and it works very well. A couple of photos may give you an idea


Hi Dave,
I've been doing alot of research on making a nail bed. I have a question about the galvanised nails.

When the laser hits these does it give of a plume? I've been told that anything galvanised will give of a poison gas or plume when hit with the laser.

Any idea?

Thanks
Vicki

[Michael Kowalczyk]

Thanks Ken for that articulate explanation. Though I have not had any major issues using our currant settings, I will try your suggestions, at some point, to see if there is a noticeable difference in what our needs are. But cutting down the feed rate by 70-90 % is going to be tough. At that rate it may not be profitable. Thanks again for clarification and ...

[dave cox]

Hi Vicki,
Didn't seem to be a problem, there isn't much to hit with the laser and the chances of hitting many on any one job is low I think.

[brian fithian]

Keith, have you ever cut clear or transparent acrylic on this jig ? does it create enough reflection to scar the acrylic ?

[Keith Outten]

Brian,

Sorry for not answering your question last month I missed your post. The answer is that the original Corian table did not work well with acrylic, the new one that we used the 60 degree V bit might fair better but I haven't tried it yet. I hope to make a couple of these tables this weekend and implement another small modification to the design. Once completed I will test it with both engravers plastic and acrylic and share the results.

FWIW my goal is to make the tables lighter by eliminating the double thickness of the table surface and redesigning the support structure under the table. In order to do this I will install the supports first then machine the prisms in the top of the table.
.

[Marijus Petraitis]

Hi Keith,

how do you think, would the Corian table be good for wood, plywood cutting? I cannot find the solution for clean cutting of 3-9mm plywood. Tried honeycomb, pin table - and always getting burns on backside of material. Cleaning of honeycomb and pins is not an easy task...

[David Somers]

Keep in mind I am suggesting this as someone without a laser? But....

When I would worked gluing laminates to counter tops I often used venetian blind slats to hold the glued laminate above the glued substrate while I got it lined up. Then I will pull the slats out and firmly put the laminate in place as I went along.

Would making a cutting surface using venetian blind slats, either aluminum or vinyl, work in this case? Damaged blinds can be had free all over the place. Cuts in it from the laser wouldn't matter. And you could simply lay the slats directly on your existing table surface to make it free form for some jobs and perhaps lightly glue the slats down on a substrate for other, repeated uses. I am not sure which would work better, concave side up or convex side up. Easy enough to test it though. If it worked you would not have such a deep area to have to pick up pieces from. And you would have plenty of air flow to help move smoke and fumes.

Just a' pondering while I read this and sipped some stout coffee.

Cheers everyone!

Dave

[Rolf Randby]

I used truss plates, painted black with epoxy paint, they are dirt cheap :-)
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