Which is best way to cut pexi stock that will be glued together as a box, CNC router or table saw with a good carbide blade? The surface doesn't need to be extremely smooth but I'm new to the CNC thing and am trying to figure out which way to go.
BOth are fine to cut plexi, however if yor going to be using weldon solvent to make your joints you want a nice smooth finish on the cut ends for a good optically clear joint if appearance means anything. I have been quite busy of late making a lot of acrylic stuff for use with aquariums and also aquariums as well and use a table saw with a carbide tooth blade and still finish mill or route and edge to get a good clear solvent weld joint. The saw cut alone does not make it for a "nice" clear joint.
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You'll have much less waste with a table saw.
I've seen fish tank manufacturers use the table saw to bring the material to within a few thousandths then finish with router for that super clear and good adhesive surface. I think the CNC router will clog on you that's why the double work.
The router will be much slower but has the benefit of much better finish possible. If you want speed then the table saw will work well. Keep all oil away from the plexiglass. Water makes a good coolant but needs to be kept away from the motor. I have cut, in one pass, using a skillsaw, two inch thick plexi using a spray bottle to apply water to the cut surface. Bad finish, but no way could this have been done with a router. ERS
For straight cuts (rectangular/square pieces) you might consider a printer's saw, providing the cuts are less than about 18" long or so. Someone on the OWWM Yahoo group advised this type of saw to me for that sort of application. Woodworkers seem to like them for "fine" work.
This type of saw was used by printers to cut lead slugs to fairly accurate tolerances (+/- 1/144 in). It's basically a table saw that features a sliding table with a fence and perpendicular finger that presents the work to the blade. The fence is perpendicular to the blade and the finger perpendicular to the fence. The finger positions the work for the width of the cut piece and is adjustable via a leadscrew and detents to a resolution of 1/2 pic (1/144"). They typically take a 6-1/4" blade, though some will take a 7" blade with minor modifications.
I ended up with a Hammond G4B TrimOSaw from Ebay, which is apparently one of the more desired brands for this class of saw. It's pretty heavy at a little over 400 lbs. This model features a ball bearing slide on each side of the saw which imparts a nice solid, but easy action to the sliding table. Other brands or models may have a different table sliding design approach. You can see some details on it here:
Forrrest sells a 7" carbide-tipped blade that is "optimized" for cutting plastic but gets around $165 for it. Tenryu sells a blade advertised for non-ferrous for around $100. Both did a good job on my acrylic and PVC test cuts with fairly clean surfaces and no melted "boogers". A much cheaper Endurance blade also seemed to do a fairly decent job.
I used the saw for the first "real" job the other night for some roughly 4x6 albs of 1/4" acrylic sheet. The edges on a couple of the pieces seem to be parallel to within 0.001 to 0.002" which should be plenty good enough, though I'll probably finish the edges on a knee mill for final size and appearances sake.
Mike
I used two methods: With a hand-saw and a very sharp carbide blade. Slow feed, cool with shop air. If the plastic melts, you will get cracks that show up _after_ glueing. The hand saw was a FESTOOL with a guide. A _very_ good and precise saw.
The other method was in the mill with a slitting saw (HSS) and lots of water for cooling. This gave the best results.
After sawing, I sanded the cut with 240 grit and then with 400 grit _whet_. Sanding with 400 whet is good enough for glueing. Do not clean with alcohol, you will get cracks.
At least that was what I found out to work.
Nick
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