ACRYLIC HELP

[terryb]

Hi Shopbotters...If anyone has any hints on getting the best cut on colored cast or extruded acrylic,1/4" 1/2"(bits speed, feed rate, etc.) also how to get rid of the white haze that is left on the edge after the cut would be helpful...

Terry B
Impact Sign Co.

[artisan]

Hello Terry. Your problem is generally a feed/speed issue where experimentation is the only cure. The enemies here are heat and chip removal. Also, be aware that extruded and cast acrylics behave differently with cast acrylic being the more friendly of the two.

First, try a spiral upcut bit for quick chip removal. The excess chips will "weld" back to your acryic if they are not removed quickly.

Second, you might also try a straight bit as this sometimes works well on plastics that are 3/16 or less.

Third, you'll need to experiment with speeds and feeds and keep a notebook handy to write down your own formulas. I ususally work around 2ips at full speed with the big 3.25 HP PC router.

Fourth, try taking a spray bottle with water and bit of murphy's oil soap and spray where your bit makes contact for a few inches to observe the effect. If this cures the problem, then heat is your major concern and you will need to play with your feed speed. Slower is not always better....some plastics you want to move through as quickly as possible to avoid heat build-up. Multiple passes that remove less material may also cure this.

In summary.....there are so many formulations of plastics that vary from vendor to vendor that there is no blanket answer....thus the experimentation. Polycarbonates and PVCs machine best.....and it's all downhill from there. Having said that, know that acrylic can be cut beautifully ( we cut and carve the 1 inch cast stuff here, multiple passes, twin spiral upcut bit and flame polished edges, water clear ).....but strategies will vary according to the formula and process that the piece is manufactured by....D

[don]

Darrell, is correct in being a feed and speed issue.

Just an added note for acrylics and soft metals such as aluminum and brass.
I've use 2 different sizes of bits on acrylics, .250 and .500. I have the luxury of taking my tools to work and resharping them, and I make sure I have plenty of rake ground into the flutes and an extra degree of relief on the primary diameter and end lands.
But before I sharpen them. I polish inside the flutes to make them smooth and really slick. This does a very good job and keeps the soft heated acrylics and soft metals from sticking to the flutes and reduces build up and possible from ruining a job.
For small jobs I also blow compressed air at the tooling while cutting, and on large jobs, I use my cold air gun to blow cold air and to help evacuate the chips.

[terryb]

Thanks Darrell ...all is understood and I continue to learn as I cut different types of Polycarbonates...I've had a chance to cut some acrylic thus moring with good results ...could you explaine a little more on getting a nice clean or clear edge (flame polished edges, water clear ) in piticular I'm working with black 1/2 cast at the moment.

I really apperciate your time and helpful tips
Terry....

[terryb]

thanks don ...i may look into some sort of coolant add on ...in the future ...any suggestions ...I'm running a Alpha 96 colombo spindle

[coolhammerman]

Terry:
I have used a simple consumer grade propane torch to "flame-polish" the edge with great success, although it is not without its pitfalls. I have used this technique on fairly straight cuts or non complex edges. You have to move the torch quickly and generally with the edge instead of across the cut. If you overheat the edge it will distort, i.e. melt, bubble, droop, etc. It does tend to round the edge over in any case so if you need a square edge, this is not a good option. Practice on some scrap until you get the technique right then try your hand.

Good Luck,
Cool Hammer Man

[terryb]

this is such a Cool....forum
i'll give it my best shot......

Thanks Mr. Cool Hammer Man ....

Terry B

[wcsg]

I do a lot of sign fab with acrylics.

Cast is the best of course. My common bits are upspiral bits (Belin) 1/4" & 1/8"

1/4" CED bit 15,000RPM / 2.5"IPS Z@.40 (mailto:Z@.40)"IPS

1/8" CED @ 18,000RPM / 1"IPS

As with anything, black is always hard to work with. Sometimes if I want a real nice edge i'll program my tool as being a .27 diameter bit instead of .25, then reroute calling it a true .25" bit.

Also I'll use a little hand sprayer filled with WD-4o and shooot the bit as it's cutting every once in a while, helps with a nice finished edge. I have a mister but have yet to hook it up as I have a MDF spoilboard

[terryb]

Thanks Eric ...Looks like I'll be a little busy this weekend giving all these techniques
a try...

thesignsyndicate.......looks like a great place to hang out .....

TerryB

[wcsg]

Terry Thank you. It's like hanging out in a bar

[jhicks]

I saw a program on the science channel about how they make screw driver handles. They use Acetate in assorted colors, machine/turn/ and cut ends of the handle ends from extruded rod stock on a screw machine, then to clear/polish the machined areas/ends simply pass them though an acetone bath and its done. Anyone machining acetate? Looks like nice colors are available and seems like a neat option for letters, shapes and even multi layered, multi colored art.
I'm calling around for samples but thought I would ask.