Sanding Acrylic sheet

Acrylic sheet can be joined with solvents to form strong durable, transparent joints.
Abrasion Resistant Acrylic sheet can be cemented on the non-coated sheet surfaces using the same procedure as the Cast and Extruded acrylic sheet. If solvent cementing on or to the coated surface is necessary, the coating must first be removed by wet sanding with 500 grit or finer, sand paper.
The ingredients in most solvent cements are hazardous materials, and extreme care should be observed using proper ventilation and handling techniques as recommended by the manufacturer of these products. Always follow the manufacturer’s recommendations and instructions when using these and any other products.
The ultimate strength and appearance of your joints will depend on how carefully you make them. Getting really good joints requires a lot of care, and considerable skill. Practice on scrap pieces. The more experience you have, the better your work will be.

Observe some basic precautions when working with acrylic solvents.
-         Always work in a well-ventilated area
-         Do not smoke-solvents are highly volatile and flammable

-         Protect skin from contact with cement
-         Do not attempt to cement acrylic sheet in temperatures under 60°F (15°C). Temperatures from 70° to 75°F (21° to 24°C) are ideal.
-         Always follow the cement manufacture’s recommendations

 

Preparation of the joint

All surfaces that are to be joined should fit together accurately without having to be forced. Flat, straight surfaces are the easiest to work with. Any area that is part of the original surface of the sheet should be left untouched.

A smooth cut made with a cooled power saw also should be left alone. However, if the area to be joined has a saw cut that is rough, it should be wet sanded or finished with a router to get a flat, square edge. Do not polish edges that are to be cemented. Polishing leaves a highly stressed, convex edge with rounded corners. It will make a very poor joint. Always remove the masking from around the area to be joined.

 

Capillary cementing

Capillary cementing is probably the most popular method of joining acrylic sheet. It works because of the ability of a low-viscosity solvent-type cement to flow through a joint area by capillary action. Properly done, it yields strong, perfectly transparent joints; however, it won’t work at all if the parts do not fit together perfectly.

First, make sure the parts fit together properly. Then hold the pieces together using a jig that will support the pieces firmly but will permit slight movement as the joint dries.

It is important that the joint be kept in a horizontal plane, or the cement will run out of the joint.

Apply it from the inside edge, whenever possible on a box corner type joint, and from both sides, if possible, on a flat pieces. A special needle-nozzled applicator bottle can be used for applying the cement.

If the cement does not flow completely into the joint, try tilting the vertical piece very slightly (about 1°) towards the outside. This should allow the solvent to flow freely into the entire joint.

Always let the joint dry thoroughly (usually 10-30 min.) before moving the part. Maximum bond strength will not be reached for 24 to 48 hours.

 

Dip or soak cementing

This method of cementing acrylic sheet involves dipping the edge of one of the pieces to be joined directly into the solvent. It is very important that only the very edge be dipped. Exposing too much area to the solvent will result in a weak, slow setting joint.

You’ll need a shallow tray in which to dip the acrylic. The tray can be made of aluminum, stainless steel, galvanized sheet, of glass. Do not use plastic-the solvent may dissolve it.

Place short pieces of wire, pins, or brads into the tray to keep the edge of the acrylic sheet from touching the bottom of the tray. The tray must be level. Pour solvent cement into the tray so that it just covers all the brads-and covers them evenly.

Now carefully place the edge to be cemented into the tray so that it rest on the brads. You can hold the piece upright by hand, but it is better to use some kind of support to hold the piece in place while it soaks. A couple of padded clamps attached to the sheet, and resting on the edge of the tray are fine. Heavy pieces of wood placed against each side of the sheet and resting on the edge of the tray are fine. Heavy pieces of wood placed against the each side of the sheet will also work. Slotted wooden supports are usually used for production work, but anything that will hold the piece firmly upright is sufficient.

The acrylic sheet should be left in the solvent from 1/2 to 2 minutes, depending on the thickness of the sheet, the type of solvent used, and the bond strength required. Soaking time should be long enough to allow the edge of the sheet to swell into a “cushion”. As soon as an adequate cushion is formed, the piece must be removed. Hold it for a few seconds at a slight angle to allow the excess solvent to drain off. Then carefully, but quickly, place the soaked edge precisely into place on the other part to be joined. Hold the parts together for about 30 seconds without applying any pressure. This will allow the solvent to work on the surface of the other piece.

After 30 seconds you can apply some pressure to squeeze out any air bubbles. But be careful not to squeeze out the cement.

When the pieces are joined, the part should be placed in a jig to maintain firm contact for 10 to 30 minutes. Do not allow the parts to move during this critical time.

Allow the joint to set for another 8 to 24 hours before doing any further work on it.

 

Viscous cementing 

Viscous cements are used to cement joints that can’t be easily cemented using the capillary or solvent soak methods-either because they are difficult to reach, or because the parts don’t fit properly together. Viscous cement is thick. It will fill gaps, and can make strong, transparent joints where solvents cements can’t.

You can make your own viscous cement by dissolving chips or clear Acrylic sheet in a small amount of solvent. Let the solution stand overnight.
Apply the cement like glue with a brush, spatula, or directly from the applicator tube.

Remove the masking material from around the joint area, and carefully apply a small bead of cement to one side of the joint. Then gently join the pieces as described under “Soak cementing”.

Masking tape may be applied to protect the area around the joint, but it should be removed carefully after about 5 minutes, while cement is still wet. Don’t touch the parts at all for the first critical 3 minutes, or the joint will not hold. The part may be carefully moved after 30 minutes, but don’t do any additional work on it for 12 to 24 hours.

Article Title:
Sanding Acrylic sheet
Article Summary:
Information on hand and power sanding acrylic
Article Date:
4/9/2009
Article ID:
581
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