Soak or Drip Cementing Techniques
1. Machine pieces with sharp tools so the parts to be joined fit without forcing or flexing. Do not polish edges to be cemented. Apply masking if required.
2. Dip or soak the parts until the desired amount of cushion is obtained.
Tank cover (made from any material not affected by solvent) to minimize solvent evaporation.
Cutout for part
Support part on nails, wire frame, inverted angle iron, etc.
Soak tank made from any material not affected by the solvent.
Tightly applied tapes such as 3M #670 or equivalent may be used.
Masking may be required in this area to prevent attack by the solvent vapors.
Solvent depth about 1" deep
Basic Cementing Techniques
The two basic cementing techniques using unthickened cements are:
The capillary action method.
The soak or dip joint method. The soak or dip joint method is not recommended for Plexiglas® MC acrylic sheet, because it dissolves rather than softens the sheet.
To use the capillary action method, the parts must be closely fitted, with no visible gaps. The parts to be cemented are either unclamped or very lightly clamped together. The cement is dispensed (from a hypodermic needle, eye dropper or similar instrument) along the edge of the joint. Capillary action draws the cement between the parts. The time for the joint to set will vary from two to five minutes (sometimes longer), depending on the solvent used and temperature and humidity conditions. Figure 15 illustrates this method.
Do not flow or drip solvent cement on a flame-polished laser-cut, strip-heated or dry-belt-sanded surface, since these conditions show the maximum amount of fabrication stress possible in plastic sheet. With Plexiglas® MC acrylic sheet, use a minimum amount of solvent and pressure in the joint, since it is more readily attacked by solvents, resulting in longer set times, lower joint strength, whitening in the joint and increased risk of crazing because the solvent takes longer to evaporate.
In the soak or dip method, the parts must also fit closely. One of the parts is placed in a container holding a solvent cement until the edge softens into a cushion. When the parts are assembled, the cushion from the first part forms a cushion on the other part by solvent action.
Masking may be required near the edges to be cemented, to prevent excessive softening. The parts should be allowed to set for 24 hours before handling. Figure 16 illustrates this method.