Proof Loading: Wednesday's Word Of The Week

Proof loading refers to inline testing done to the finger joints of critical tension plies. Tension plies (typically the bottom 5% of beams) are the most highly stressed zone in glulam, so the finger joints in these plies are of utmost importance.

Just after these finger joints are cut, glued, and rapidly cured (and before the ply is cut to length), the board runs through our proof loader. The proof loader puts constant downward pressure on the board and watches for variation in how much deflection this pressure causes. As long as the deflection is less than calibrated limits, the edge of the board is marked to show that it passed proof loading. If deflection exceeds limits (a "soft spot" is detected), this could indicate a poor finger joint, so that ply is rejected and replaced. 

*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.