Clearance groove machining method and 3D substrate product

The invention discloses a clearance groove machining method, a 3D substrate product clearance groove machining method and a 3D substrate product. The clearance groove machining method comprises the following steps that the length D1 of the long side of a product to be machined and the width D2 of the short side of the product to be machined are detected, the center point and the center line of the product to be machined are fitted according to the length D1 and the width D2, a CNC rough cutting curve is fitted according to d2, d2 = d1 + sigma, d1 is the distance between the groove long side of an L-shaped clearance groove and the center line, and sigma is tolerance; and the distance d4 between the long side of the L-shaped clearance groove roughly cut according to the rough cutting curve and the long side of the 3D product is detected, the allowance d needing fine trimming is calculated, a CNC fine cutting curve is fitted according to the allowance d, and the L-shaped clearance groove is cut according to the