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Routing Lexan/Plexi

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38K views 33 replies 22 participants last post by  BigJimAK  
#1 ·
I know lexan and plexi aren't the same, but I need one of them for a small project (holding a parking pass that I transfer between vehicles, a bicycle, and my backpack) and I'll purchase whichever I can find cheapest.
I'll be using 1/8th or 1/4" thick and just cutting out a small recess to hold the pass.
To make things interesting, and because I don't have a "real" router yet, I'll be using a dremel with a 1/4" straight router bit...
Any retrogradations for the speed to run it at so I don't melt plastic and wreck the bit (granted, it's only $8, but I'm cheap)

Hopefully in a few more weeks I'll have a bit more $$ saved up and I'll make up my mind on a starter router.
 
#2 ·
Your problem is challenging. The biggest problem you will confront is the plastic melting as you cut. For real routers there are dedicated O-flute router bits but as far as I know they are only straight non-plunging bits. However, the wood-cutting bits can also be used if the right speeds are chosen. You will simply have to try in order to find the best speed of rotation (rpm) and the best speed of feed that allows cutting without melting.
Lexan v. plexi. Lexan has much greater mechanical strength than plexi; NASCAR windshields are lexan, and Formula 1 is considering requiring that their cars have windshields of lexan. On the other hand, plexi has much better chemical resistance.I have not been able to check which is less expensive at this time. There are several online stores that sell each.
Good luck. Keep us posted on your progress.
 
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#4 ·
I checked at my local big box and they have 8X10 sheets of lexan for about $5. I'm going to run down to my local Ace in a bit to see if they have anything and peruse their reconditioned tools for good luck. I've helped my dad bend/mold lexan in the past. He got tired of the sand and salt in the trucks getting wet and freezing so we made some tarp supports out of some rather large pieces of lexan he had laying around. You can do amazing things with lexan and a heat gun (don't use a torch, it scorches easily...)

jschaben said:
I wonder if you are going to get what you expect though. Routing the stuff will remove the surface polish and, unless you have a means or knowledge of how to polish the stuff, it will leave a hazy/milky appearance where it's been routed. Picture is a shot of a zero clearance dado insert I made for my table saw. The hazy areas are where I had to relieve the bottom to provide clearance for the arbor bearing and riving knife bracket. Material was 3/8 Macrolon (lexan with scratch resistant coating).

You may have better luck using two pieces of thinner material glued at the edges.

Just some suggestions:)
Click to expand...
I hadn't thought of the polish and haze. I'll have to poke around online or just buy a piece of lexan and see what happens. If I'm out $5 or less, I can happily chalk that up to play and education.
 
J
#3 ·
Hi Bill, lexan also has a lower melting point but is virtually unbreakable. Not sure how large a piece(s) you need, it is available on eBay in various sizes. Mostly cutoffs from sign making or display mfg businesses. If you have one in your area you may be able to do some dumpster diving for what you need.
I wonder if you are going to get what you expect though. Routing the stuff will remove the surface polish and, unless you have a means or knowledge of how to polish the stuff, it will leave a hazy/milky appearance where it's been routed. Picture is a shot of a zero clearance dado insert I made for my table saw. The hazy areas are where I had to relieve the bottom to provide clearance for the arbor bearing and riving knife bracket. Material was 3/8 Macrolon (lexan with scratch resistant coating).

You may have better luck using two pieces of thinner material glued at the edges.

Just some suggestions:)
 

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#7 ·
When I cut either material, I leave the paper on for the cut. I don't know how or why, but the paper seems to dissipate the heat and I get less melting.
 
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#9 ·
I use a lot of Lexan for my routing templates. Why not make a template and rout the actual card holders. You can saw and file the template and leave square corners if you don't rout it. Drill out the waste, scroll/jigsaw to line and file up to size. When you do rout, be prepared for Lexan flakes everywhere.
 
#12 ·
I do know acetone discolors lexan and chloroform can be a very effective glue for both lexan and plexiglass (at least the plexiglass I use in my day job). Thus I a certain chloroform would smooth the edges of cuts. However I have no idea how easy it is for someone not with my day job to obtain chloroform.
 
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#15 ·
Here's a thought (disclaimer: I haven't had my morning coffee yet)--why not make the bulk of it from wood, and just use a thin piece of plastic on the face to cover the pass? Or you could use thin plastic for both the front and the back (if the back needs to be visible too), and enclose them in a wood frame? A scrap of nicely figured hardwood would be more attractive than routed plastic.
 
#16 ·
LexB said:
Here's a thought (disclaimer: I haven't had my morning coffee yet)--why not make the bulk of it from wood, and just use a thin piece of plastic on the face to cover the pass?
Click to expand...
That's my thought for if I can't get the plastic to work. Working with the acrylic I picked up is kind of a "just because" project...

I did find out that I can route the plastic at about 18,000 without melting the plastic...
That was just a quick test. I accidentally signed myself up to work 75 hours this week since the kids are with the Grandparents so my dreams of spending time in the shop fooling around probably won't happen until Saturday afternoon/evening when I'm hopefully done with it.
 
#18 ·
Lexan is GE's version of polycarbonate and it is somewhat softer than acrylics such as Plexiglass, Perspex, Lucite, et. The big plus of polycarbonates over acrylics in certain applications is its' greater impact resistance, which is why it is often chosen for machine guards, etc. Machining is best done with either spiral cutters or O-flutes (see Onsrud Cutter's web site) but the best approach in trms of feeds/speeds is the fastest fed speed you can manage but with a reduced spindle speed (12,000 to 14,000 rpm if you can manage it). this produces a true curl chip rather than just dust and reduces the amount of "churning" (where waste is cut then recut before being expelled from the cutter flute). "Churning" increases the friction causing the waste to heat up and potentially melt-back onto the surface. If at all possible arrange for extraction by a vacuum cleaner (which will also help cool the cutter), use larger diameter cutters if possible (bigger cutters and cutters with larger diameter shanks help dissipate heat) and consider either an air blower or a water spritzer bottle to cool the cut. If you use a spritzer make sure it doesn't go into the router motor and try to use either a 110/120 volt router or arrange to be on a RCD (residual current device) circuit to be on the safe side. Wherever possible retain the plastic/paper coating on the material for as long as possible as it reduces the number of scratches you'll get on the end piece.

Edge polishing of acrylics can be done using a propane torch (work quickly and try not to spread onto the edges), but you do need to peel back the cobver films for this. Not sure it works so well on polycarbonates, though. You can also sand the edges (to get a frosted edge finsih) or wipe with MEK (metyhl eythyl ketone) thinners - but be careful with these as they are a health risk as well as being highly inflamable.

Hope this helps
 
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#20 ·
What I have learned thus far...
Edge guides are my friend. I freehanded a few tests and got close, but it looked off.
When the acrylic chips come out, they're hot. they then quickly melt to the surface and if you're using a dremel with the basic cutting guide (15k rpm), it will get stuck on the chips. So you'll frequently need to pull it out, brush off the chips, then get going again.
Even at lower RPM if you let it sit still for more than a second or two you'll melt a hole through the acrylic and it will smell horrible in your garage for a long while. Also, your daughter will blame the smell on you and ask you if you're sick because you smell really bad.

So now that I've had my fun I think I'll just route a small cut out in a piece of 1/2" stock, put the pass under that, and secure it to the stock. Maybe not as pretty, but not quite as headache inducing. And I have a lot of 1/2" stock sitting around in various scrap sizes.
 
#21 ·
As a former aircraft mechanic and inspector I have a plastic polishing kit that uses sandpaper in step by step applications down to paper that is practically smooth. It is mainly used to polish out dings and imperfections in aircraft windshields.

Unless memory fails me the kits can be purchased at Graingers. You could Google acrylic polishing kits also.
 
#22 ·
To polish try your Dremel polishing/felt wheel and jewelers rouge after various stages of wet sanding (very high grit count)........I sometimes use a micro polishing compound....auto body guys use it for final buffing and I also have a friend that restores pianos that uses it on his final finish buff for that High gloss sheen.
 
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#24 ·
I've cut quite a bit of clear plastic product with a band saw, table saw and a hand held jig/scroll saw. The band saw resulted in too much heat and the material would partially fill in behind the cut. Because of the variable speed, the hand held jig saw was able to be adjusted to produce better cuts than the band saw. For straight cuts, the table saw always won out. In each instance, I used a fairly fine tooth blade.

I seem to remember scribing and snapping a few pieces too. Of course, the more brittle the material, the better this would work.

I've used a router to clean up edges and as long as I kept removal to a minimum, produced nice edges.

Information on cleaning up edges wasn't easily found back then, so I just tried sanding the edges using my pad sander. Depending on the severity of blade marks, I'd start with 220 or 320. Next, I'd jump to four hundred, then 800 grit. You could jump to fifteen and 3000, or go to cheap buff wheel on a drill press (about 1,000 RPM) and some stainless steel or other fine polish did a pretty good job.
 
#27 ·
Gary

Have I missed something here? Just asking
 
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#28 ·
If I understand correctly what your parking pass is, it's just a piece of thin cardboard.
Why go to all of this routing trouble with thick plastic? Go to a print shop near you and have it laminated. You will get back a vacuum packaged parking pass with a thin layer of flexible plastic on both sides with a clear boarder around it and rounded corners. For a small item they usually only charge a couple of bucks for this service.

Charley
 
A
#31 ·
Why not a table insert of like materials? Milling and/or routing phenolic or any of the above mentioned plastics? Clarity of material perhaps being not important for such, but as a suggestion to this thread, along with trying acetone or a torch (NOT together, of course) to smooth out cloudiness how about passing over it with a heat gun?
There are plastic polishes that supposedly remove scratches ala headlamp repair products, and I've also heard that furniture polish can act similarly.
 
#32 ·
Autre said:
Milling and/or routing phenolic or any of the above mentioned plastics?
Click to expand...
Phenolics certainly rout in a similar way in that they require a low-ish spindle speed with a fastish feed speed to obtain a true chip (or at least thick dust) as opposed to fine dust. The difference is that phenolic dust doesn't weld back, in extremis it just catches fire. As with all plastics good dust extraction is essential to ensure personal safety (the dust, especially phenolics, can be extremely unpleasant to breath in) as well as providing extra cooling

Autre said:
Clarity of material perhaps being not important for such, but as a suggestion to this thread, along with trying acetone or a torch (NOT together, of course) to smooth out cloudiness how about passing over it with a heat gun?
Click to expand...
The problem is temperature and heat dissipation. Whilst a good heat gun will produce air at up to 550°F (288°C) the actual amount of heat it can put into the edge of a piece of acrylic is actually quite limited when compared to a propane flame (3625°F/1995°C) or better still an acetylene flame (5800°F/3200°C). I mention this because the approach when polishing acrylics is to get the edge alone to melting point very quickly rather than the surface (typical acetylene polishing speeds are measured in metres/yards per minute, the thicker the faster) . Make the surface too hot at one edge whilst the rest of the acrylic is still cool (which is what a hot air gun can do) and the differential expansion will possibly cause your acrylic to craze or even shatter. I'm not saying it won't work, but it certainly will be difficult to do consistently. For large scale use propane (or butane) generate a relatively dirty flame which includes a percentage of soot particles which is why professional acrylic polishing gear uses acetylene. I've manufactured acrylic components for retail shop displays and flame polishing is the best and quickest way to achieve a result, but the idea of in effect dissolving the edge by using a powerful solvent is still commonly practiced in plastics engineering, signmaking, shop interior work, etc. for one off pieces

Autre said:
There are plastic polishes that supposedly remove scratches ala headlamp repair products, and I've also heard that furniture polish can act similarly.
Click to expand...
There are indeed, but before you start to polish you'll still need to either scrape or sand out the edges to at least P180 grit or you'll simply waste a huge amount of effort to polish the edges. I make a number of Corian counters, vanities, etc every year (they are fundamentally acrylic) but on that you need to work up through the grits from about P120 to P500 without skipping to many steps) so P120 - P150 - P180 - P220 - P280 - P320) and this is best done with a coarse orbit random orbit sanding machine (for speed) before you start to polish out with P320 grit (fine orbit). Final polishing out can then be achieved using a car body shop polishing compound such as Farecla on a clean, uncontaminated lambswool mop.

In reality this is all getting a bit complex. Surely if all you need is a safe edge then that can be achieved by scraping it with a cabinet scraper (as suggested by another poster) then sanding through a range of grits (say P120 to P180- also suggested earlier). Remember that with plastics cleanliness is next to godliness, so every tiime you change a grit vacuum off both the work and the sander to avoid cross-contamination of larger (lower number) grits which will show up as indellible scratches
 
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