A successful weld forms a slightly raised, smooth, even bead across the component surface. Welds must be flatted only when they are cold; warm welds clog the sanding disc.

Remember that plastic is a soft material that yields easily to abrasives. For this reason use a 120 grit disc first then progress to 180 and finally 320 to produce a smooth finish. Always use new clean, sharp papers. All a 7 to 10cm margin around the weld area for dressing to provide a key for painting.