Heat Welding Sheet Vinyl, Step by Step

A heat-welded seam fuses a vinyl rod into a groove cut along the seam, sealing it against water and dirt. It's a staple in healthcare, labs and food service. The steps are simple; the skill is in groove depth, gun temperature and welding speed.

Before you weld

Welding too early or with the wrong rod undoes everything that follows, so check these first.

• Wait for the adhesive to set, about 24 hours after installation.^[1] Check your adhesive's instructions.
• Use the weld rod made for your flooring line and color. Rod from another line may not fuse or match.
• Keep the space at the conditions the flooring maker specifies. AHF calls for 65 to 85°F for 48 hours before, during and after installation.^[2]

Groove depth depends on the sheet

Homogeneous and heterogeneous sheet groove differently, so check which one you have.

Groove width should match the weld rod and nozzle.

Step by step

With the adhesive set and the groove sized right, the weld itself follows a steady routine.

1. Groove the seam with a power groover, keeping the blade centered on the seam. Use a hand groover in doorways and at walls where the machine can't reach.
2. Vacuum the groove clean.
3. Pre-heat the gun with a speed nozzle (Forbo specifies a 5 mm speed tip).^[1] Test on scrap: the rod should melt without scorching.
4. Feed the rod through the speed nozzle and weld at a steady pace. A good weld shows three signs: the melted rod reaches the bottom of the groove, the top flattens slightly, and a small bead forms on each side.^[1]
5. First trim while the rod is still slightly warm (not hot), using a crescent (spatula) knife with a trim plate to take off most of the excess.^[1][2]
6. Let the rod cool to the touch, then make the final flush trim with the crescent knife alone.

Common mistakes

Most weld failures come from timing, groove depth, heat or trimming too soon.

• Welding too soon. Wet adhesive under the seam lets the edges move.
• Grooving through the wear layer on heterogeneous sheet. The backing shows and the weld can't bond properly.
• Too hot or too slow. Scorched, discolored rod and burned edges.
• Too cool or too fast. The rod sits in the groove without fusing and pops out later.
• Trimming flush while hot. The rod shrinks as it cools and leaves a dip. Trim in two stages.

Tools we carry

These are the welding kits, groovers and trimming tools we carry.

• Leister Triac AT Heat Welding Kit and Triac ST Advanced Kit
• Turbo Master Kit and Crain No. 989 Economy Kit
• Accutrack 380 Precision Floor Groover and blades in 3.5 mm and 4.0 mm
• Leister Spatula Knife
• Nozzles and tips: see Which tip for which job

References

1. Forbo: Heat welding guidelines for vinyl products
2. AHF Contract: Heterogeneous sheet vinyl installation instructions

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