Seelye’s Step-by Step Welding Procedure
1. Preparing materials for the type of weld
- Determine whether the type of weld requires a beveled edge.
- If beveling is required, perform the beveling with a grinder and/or table saw. Bevel a 60° angle.
- Clear dust and dirt from material to be welded. To remove oily substance, Methyl Ethyl Ketone (MEK). Be sure materials to be welded are dry before starting.
2. Tack Welding for work Fit up
- After you have installed the Seelye Tacking Tip, start the air flow, plug in the electric source, and allow the welding tip to heat for several minutes.
- While the tip is heating, line up pieces to be welded. By this stage, you should have prepared the plastic pieces carefully, made the necessary bevels if required, and cleaned and dried the pieces to be welded.
- No rod or strip is required for tack welding with hot air. Apply the hot Tacking Tip to the area or seam where the plastic pieces are to be joined; moving the tip along both pieces at the same time, until the plastic fuses (joins) at that point.
- Do enough tack welds to hold the weight of the piece together. With large pieces, it may be necessary to draw the tacking tip along the entire seam, fusing the work continuously. This will hold the work together properly for accurate permanent bonding which will be performed during the next phase of work.
- Avoid overheating the tack points. This causes the plastic material to discolor, char, or warp. If you are not satisfied with the welds, or the work is not properly fitted, start over. Tack welds are easy to break. Before doing a new tack weld, grind the tank points down to smooth edges.
3. Permanent Welding with Hot air.
- Before starting the permanent weld be sure to select the right type of welding (or strip). It must be the same type of plastic as the materials you will be bonding together. Usually the manufacturer of the plastic material will label the plastic type of easy identification. If you do not know what type of plastic you are welding, refer to a burn test chart to identify the material you are going to weld. (call factory)
- For maximum welding economy, select a rod diameter size close to the thickness size of the base material. For base material thickness greater than 3/16”, more than one rod will be necessary. Example: to weld fill the beveled area between two base material sheets of ¼” thickness, three 5/32” rods will be required.
- Select the proper welding temperature and air flow setting.
- Install the proper Round tip for permanent welding. Allow the Round Tip to heat properly. If you change from the Tacking Tip to the Round Tip while welder gun is hot be sure to unscrew the Tacking Tip and screw in the round tip using pliers. Do not overtighten; it should be snug only.
- Cut the end of the rod at a 60° angle. Hold the cut end of the rod just above the weld starting point. Apply heat to rod end just above the base material seam at the same time until both are tacky. Press the tacky end of the rod down into the tacky starting point of the base materials. Only the surface of the rod and base materials will be tacky, but will bond properly. The rod will continue to hold its basic shape, for the most part, throughout the welding work.
- Continue the weld, holding the rod at a 90° angle directly above the weld seam, pressing firmly and evenly, down into the weld joint as you apply heat in the direction of the weld seam with short fanning motion. As the rod and base material becomes tacky, if you are welding at the proper temperature, a loop will form where the rod joins the base materials and small beads will form where the rod joins the base materials and the small beads will form on either side of the completed weld.
- At the end of the weld, cut the rod with a knife or pliers at a 30° angle. Cut the end of the new rod at a 60° angle to continue.
There should be no charring, discoloring, or warping if proper heat is applied. There should be no stretching of the welding rod. This will weaken the rod bond and can be avoided by taking care to press directly down on the rod rather than pushing the rod along the direction of the weld seam.
A few hours of practice welding will give the “feel” for maintaining the right even pressure on the rod straight down into the weld area.
4. Weld Quality Analysis
A. Check the quality of your weld. You can tell much about the quality of the weld
It’s appearance. A good weld will not pull apart when hot.
A weld that was too hot will have a scorched area around irregular bead.
A weld that is too cold will have a poor bond.
A stretched weld will break at thin stretched points.
A good weld has a fine bead on both sides of the weld.
B. If you require less heat, increase air pressure. Do not go below 3 PSI.
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