I occassionally need to cut acrylic shapes from a template, and would like to get some type of router or laminate trimmer or dremel setup that would let me follow the contour of the template to make the acrylic copy. The originals are usually around 1/8" thick, and the copies are 1/16" or 1/8" thick, and they are usually fairly random shapes (not many straight lines or continuous curves, etc).

Currently I trace the pattern on the acrylic backing paper, cut close with a dremel tool using a 1/8" rotozip drywall bit, then sand/file to get the correct shape/size. This generally works well, but since I find this tedious work, I wouldn't mind spending a few bucks for a simpler way. Hence my thoughts of using a router.

I know that routers use small bits with a little ball bearing on them, but the smallest straight bit I could find with this bearing is 3/8" dia, with a 1/4" shank. That shank size seems to be pretty common for routers. But there is a relatively large gap (http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&productId=100082013&langId=-1&catalogId=10053&ci_sku=100082013&ci_src=14110944&cm_mmc=1hd.com2froogle-_-product_feed-_-D25X-_-100082013) between the bearing and the cutting flutes. This is significant for the thicknesses of materials I am using.

My other discovery was this flush-trimmer router bit (http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&productId=100324728&langId=-1&catalogId=10053&PID=1609763&cm_mmc=CJ-_-1499621-_-1609763-_-Flush%20Cut%20(Solid%20Carbide)%20Carbide%20Router%20Bit&URL=http://www.homedepot.com/webapp/wcs/stores/servlet/BuildLinkToHomeDepot?linktype=product&id=100324728&cj=true&SID=tfc_-_9_1_080619_3eb8e80a677b369ac7a7eaf910812537&AID=10368321&cj=true) that did not have the bearing, and I'm wondering if it's for *flush*trimming, then is the non-cutting part of the shaft expected to rub against the edge of the the template piece? At 20k-30k rpm, wouldn't this damage the edge of the original template piece? And if not, then can I find a similar bit in 1/8" diameter (so I can use a dremel or roto-zip tool instead?) Anything else I should be aware of that can make this easier?

Thanks,
-Neil.

Neil,

First suggestion would be to go with the Bit with the bearing. Only thing you forgot was to put a filler board (1/4" thick maybe) to bring your work piece away from your pattern. Make the filler smaller so it is not quite the size of the pattern so it doesn't rub or get cut during the process.

However, building a CNC would be MUCH more fun. :D HTH

Rance

Rance,

Yes, I can add a filler. I was thinking that it would be nice if the second bit (without the bearing) would've worked, then I could've just avoided that. Also, a 1/8" bearing bit would save me from purchasing another tool.

I'm probably going to cut a hole in a workbench and mount a dremel or router to make it a table-router. No more space to fit another (actual) router table.


I do have a CNC mill, and I do cut acrylic with it (albeit slowly due to the 1500rpm spindle), but for the amorphous shapes for which I only have templates, it would be a lot more work to scan, convert to bmp, then to dxf/outline, then cam it to g-code, then mill.

I see the word "pilot" on some of these routers -- any idea that that means?

Cheers,
-Neil.

Another thought -- use the router bit on my mill. The wood base would be mounted onthe mill table and fixed in one position. I would use a melamine shelf or similar so that the pieces being worked on slide easily. Yes, the mill runs relatively slow, but perhaps this would give me more control.

http://www.narwani.net/neil/mech/mill/Acrylic_Router_Mill_01.jpg

I see the word "pilot" on some of these routers -- any idea that that means?

Neil, it looks to be like your link to the flush trim router bit. There's another setup though. Think of a table router with a straight cut router bit. Just above that is suspended a steel pin, the same diameter as the router bit. It is suspended using a bracket of sorts. Sorry I couldn't find a pic for you (any one else able to find a pic?). Does this make sense to you? You still need to have the sandwich as before with the filler in between. HTH.

That flush trimmer bit is for laminate (Formica), and is usually used with a lubricant to prevent damage to the surface it's riding on. Even with lubricant, it'll still leave a markj if you pause in one spot for more than a second or two.

If you get a router that accepts guide bushings (most porter cables, including their laminate trimmers), It's a better way than using bearing guided bits. The downside is that your templates need to be slightly smaller than actual size. Usually 1/16" or 1/8" smaller on all sides works well. The only problem is that you usually need a 1/4" thick template, but you can shim the template up higher with spacers.

http://eagleamerica.com/solid-brass-router-template-guide-set/p/400-1419/

Cutting templates to a different size is a problem, because I don't actually make the templates -- I'm taking them from an existing product, then making a copy (and usually only one copy) out of my special-colored acrylic.

Leaving a mark on the original is not such a problem, but I'd prefer to avoid damaging it.

BUT... I had another brainwave, which requires nothing to be purchased. I just need to turn a small aluminum cylinder as the guide, and adjusting for the thickness of the original would be very easy (better than anything purchaseable so far). This will be a bit slow until I finally get around to upgrading to a faster spindle on my mill, but for now I can test the concept, and I can run a multi-flute larger-diameter endmill to effectively speed it up a bit.

Rance, if I understand you correctly, this is an upside-down version of your idea...???

http://www.narwani.net/neil/mech/mill/Acrylic_Router_Mill_02.jpg

I tried this last option that I drew up, and it works beautifully! I found that by changing the spindle height, I was able to adjust for the thickness of the template very easily.

Some caveats though...
- Rather than turn down a piece of aluminum to the diameter of an endmill, but I realized that I could use a round PCB spacer instead. Since the ones I had were 0.25" OD, I used a 0.25" endmill (4-flute) for now. But I used a nylon spacer and found that the nylon flexed enough that the endmill cut a bit into the template -- really just milled the paint off the template. I should switch to an aluminum spacer, or machine something with an adjusted diameter as appropriate.
- I need to use a larger diameter endmill so it can be longer (without flexing), so that I have more clearance for holding/moving the parts. BUT... I need to use a smaller diameter endmill so that I can get into more corners as per the original template pieces. Perhaps a 1/8" endmill with a 3/8" shank might be a good compromise.
- This thing is sloooowwww. I get the equivalent of around 5ipm. Really this is limited by my spindle speed, but I do this occassionally enough that I won't complain for now.

Cheers,
-Neil.

I don't know how big the objects are that you are copying, but maybe
a router pantograph is something you could use.

This is a Sears model that is only $55
http://www.sears.com/shc/s/p_10153_12605_00925187000P?keyword=roiters

Very interesting device. I'll have to see if they have it in stores so I can see clearly how/if it would work. The pieces I'm reproducing are the clear-ish plastic/acrylic pieces from older instrument clusters, so usually no more than say 18" x 7", but they're usually a handful of smaller pieces. Here's an example, this one is about 3.5" across, with the original being about 0.1" thick and the copy (dark red piece) being 0.060" thick...

http://www.narwani.net/neil/mech/mill/Acrylic_Filter_Sample_01.jpg