Aluminum extrusion for windows and doors is only half the battle—dimensional tolerance determines whether fabrication runs smoothly or turns into a nightmare. Wall thickness variation beyond ±0.15mm creates uneven thermal break insertion, leading to compromised insulation performance. Twist and camber, often overlooked during incoming inspection, cause cumulative misalignment across multi-panel sliding systems. I've seen perfectly cut profiles refuse to assemble because a 0.3mm bow accumulated over a 6-meter length. Die design, quenching uniformity, and stretch-straightening all influence these outcomes. The best fabricators I know don't just measure cross-sections—they track straightness per meter and verify web flatness before machining. In this industry, "close enough" isn't. A profile that looks straight on the rack may fight you at the cutting table. Precision upstream saves rework downstream, and in aluminum windows, rework is pure margin erosion.
