Nearly all power supplies for stick arc welding (SMAW), are designed to provide a "constant current." Changing the arc length changes the voltage to a certain degree. Note that the arc should never be longer than the width of the electrode. Too low current produces not enough heat input to sufficiently melt the base metal. The weld will be narrow and tall, and will poorly fuse with the base metal. Lack of fusion, overlap, and slag inclusions will be common problems. Too much current causes too much heat input. The bead will look wide and low and flat topped, with a wavy, irregular ripple. Arc instability will be more frequent when welding. Typical weld defects caused by this are undercut, porosity, burn through, and excessive spatter. Hot cracks are likely on some steels. Also, the electrode will tend to overheat while welding, beginning to glow and fuse before it is completely used up. Having too fast travel speed may look similar to too low current. Fast welds tend to have an irregular, wandering, globular, or inconsistent size and shape. Typical problems associated with this are undercut , excessive spatter, and lack of fusion. Traveling too slow causes a larger than necessary weld, with an inconsistent width and irregular ripple. Note that in the flat position such welds may still be serviceable. Typical weld defects here are porosity, undercut, overlap, and burn-through. Traveling too slow in the horizontal, vertical, or overhead positions makes it very difficult to make a good weld. It will cause the molten metal to literally drip out of the weld leaving an empty crater behind. t A good weld has a constant width and a constant shape. The ripple should be neatly rounded and highly regular. The edges of the weld should smoothly tie into the base metal, without overlap, sharp corners, or undercut.