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by Ken Weiss, krweiss@ucdavis.edu This
information is extracted from a pamphlet published by CYRO Industries,
manufacturer of Acrylite acrylic sheet. I did my best to keep the
information accurate to the source, but hey, I don't do this for a
living or anything. I got the original brochure from my local acrylic
dealer (Is that a transparent drug lord? Why are drug lords bad, when
drug czars are good?).
Characteristics of the material
- Half the weight of glass
- Impact resistant
- Unaffected by sun or salt spray
- Temperature range of -30 to 160 degrees F for continuous service
Cleaning
Wash with mild soap or detergent, with plenty of lukewarm water, dry
with soft cloth or chamois.
Grease, oil or tar can be removed with hexane or kerosene. Solvent
residue should be removed by washing immediately.
Do Not Use window cleaning sprays, scouring compounds,
acetone, gasoline, benzene, carbon tetrachloride or lacquer thinner.
Masking
When working with the material, leave the paper masking film on the
sheet as long as possible. Except for intricate detail work you should
remove the masking only when your project is completed.
Working with acrylic sheet
DO
- Keep masking on as long as possible.
- Use metal cutting saw blades and drills which are ground for
acrylic sheet.
- Make sure all tools are sharp.
- Use water or drilling oil as a coolant when cutting sheets over
1/8" thick or drilling sheets over 3/16" thick.
- Wet the material before cleaning.
DON'T
- Use saw blades with side-set teeth. Saw teeth ideally should
be ground with 0 degrees of rake and be of uniform height and
shape.
Cutting Acrylic Sheet
- Cutting with a knife or scriber
- Acrylic sheet up to 3/16" thick may be cut by a method similar
to that used to cut glass. Use a scribing knife, a metal scriber,
an awl, or a utility knife to score the sheet. Draw the scriber
several times (7 or 8 times for a 3/16" sheet) along a straight
edge held firmly in place. Then clamp the sheet or hold it rigidly
under a straight edge with the scribe mark hanging just over the
edge of a table. Apply a sharp downward pressure to break the
sheet along the scribe line. Scrape the edges to smooth any sharp
corners. This method is not recommended for long breaks or thick
material.
- Cutting with power saws
- Special blades are available to cut acrylic. Otherwise use
blades designed to cut aluminum or copper. Teeth should be fine,
of the same height, evenly spaced, with little or no set.
- Table and circular saws
- Use hollow ground high speed blades with no set and at least
5 teeth per inch. Carbide tipped blades with a triple chip tooth
will give the smoothest cuts. Set the blade height about 1/8"
above the height of the material. This will reduce edge chipping.
When using a hand held circular saw, clamp the sheet to the
work surface and use a length of 1x3 wood to distribute the
clamping pressure and act as a guide for the saw.
Feed the work slowly and smoothly. Lubricate the blade with
soap or beeswax to minimize gumming from the masking adhesive.
Be sure the saw is up to full speed before beginning the cut.
Water cooling the blade is suggested for thicknesses over 1/4",
especially if edge cementing will be performed.
- Saber saws
- Use metal or plastic cutting blades. The blades you use to
cut acrylic should never be used for any other material. Cut at
high speed and be sure the saw is at full speed before beginning
the cut.
- Hand saws
- Good results are possible, but very difficult. Be sure the
acrylic is clamped to prevent flexing. Flexing at the cut may
cause cracking.
- Routers and shapers
- Use single fluted bits for inside circle routing and double
fluted bits for edge routing. At the high speeds at which routers
operate it is critical to avoid all vibration. Even small vibrations
can cause crazing and fractures during routing.
Drilling
For best results, use drill bits designed specifically for acrylic.
Regular twist drills can be used, but need modification to keep
the blade from grabbing and fracturing the plastic. Modify the bit
by grinding small flats onto both cutting edges, so the bit cuts
with a scraping action. If the drill is correctly sharpened and
operated at the correct speed, two continuous spiral ribbons will
emerge from the hole.
Finishing Acrylic
- Scraping
- The first step in getting a finished edge is scraping. The
back of a hacksaw blade is perfect for scraping. Simply draw the
corner of the square edge of the blade along the edge of the acrylic.
- Filing
- A 10 to 12 inch smooth cut file is recommended for filing edges
and removing tool marks. File only in one direction. Keep the
teeth flat on the surface, but let the file slide at an angle
to avoid putting grooves in the work.
- Sanding
- If necessary, start with 120 grit sandpaper, used dry. Then
switch to a 220 grit paper, dry. Finish with a 400 grit wet/dry
paper, used wet. Grits as fine as 600 may be used. Always use
a wooden or rubber sanding block.
When removing scratches be sure to sand an area larger than
the scratch. Sand with a circular motion, and use a light touch
and plenty of water with wet/dry papers.
Almost any commercial power sander can be used with acrylic.
Use light pressure and slower speeds.
- Polishing
- Final polishing will give acrylic a high luster. Power-driven
buffing tools are recommended without exception. Buffing wheels
are available as attachments for electric drills.
A good buffing wheel for acrylic consists of layers of 3/16"
carbonized felt, or layers of unbleached muslin laid together
to form a wheel. Solidly stitched wheels should be avoided.
The wheel should reach a surface speed of at least 1200 feet
per minute. Speeds of up to 4000 feet per minute are useful
for acrylic.
Acrylic should be polished using a commercial buffing compound
of the type used for silver or brass, or you can use a non-
silicone car polish that has no cleaning solvents in it.
First, however, tallow should be applied to the wheel as a
base for the buffing compound. Just touch the tallow stick to
the spinning wheel, and then quickly apply the buffing compound.
To polish, move the piece back and forth across the buffing
wheel. Be careful not to apply too much pressure. Keep the work
constantly moving to prevent heat buildup.
Never begin polishing at the edge of the sheet. The wheel
could easily catch the top edge and throw the piece across the
room or at you.
Forming Acrylic
Acrylic can be heated to make it pliable. It will become rigid again
when it cools. Never heat acrylic in a kitchen oven. Explosive fumes
can accumulate inside the oven, and ignite.
A strip heater is the best tool to form acrylic. This tool will
only form straight line bends. Buy one from your acrylic dealer.
The strip heater will heat just the area to be formed.
Heat the sheet until it begins to sag at the bend line. The bend
should be made away from the side exposed to the heating element.
Sheet thicker than 3/16" should be heated on both sides for a proper
bend. Use forming jigs or clamps for best results, and wear heavy
cotton gloves when handling heated acrylic.
Forming other than straight line bends will generally require
specialized equipment and jigs.
Joining Acrylic
Solvent cement is recommended for joining acrylic. There are two techniques
for solvent cementing, capillary and dip or soak methods.
- Capillary cementing
- This is the most popular method for joining acrylic. However,
this method will not work at all unless the parts to be joined
fit together PERFECTLY.
Make sure the parts fit properly. Then join them with masking
tape or clamp them in a form to hold them firmly in place. It
is important that the joint be in a horizontal plane, or the
cement will run out of the joint.
Apply the cement carefully along the entire joint. Apply from
the inside of a box-corner joint, and on both sides of a flat
joint. A needle-nosed applicator bottle is recommended. The
thin cement will flow into the joint through capillary action
and form a strong bond. Maximum bond strength will not be reached
for 24 to 48 hours.
- Soak or dip cementing
- This sounded like a real pain in the butt, and is suggested
only for thick joints.
- Viscous cementing
- Viscous cements are used for joints that can't be cemented
with capillary or soak cementing, either because the joint is
difficult to reach or because the parts don't fit properly. Viscous
cement is thick and will fill small gaps. It can make strong transparent
joints where solvent can't.
You can make your own viscous cement by dissolving chips of
clear acrylic sheet in a small amount of solvent.
Apply a small bead of cement to one side of the joint, join
the pieces, and tape or clamp in place until cured.
Disclaimers
Neither CYRO Industries, Ken Weiss, or anyone or anything else connected
with this posting really know what they are talking about. If you
believe a word of this posting, it's at your own risk. Hey, if you
had any sense you wouldn't be spending all your spare cash and time
on a box full of water anyway, would you? |