Positional Accuracy and Repeated Positional Accuracy of Color Coated Aluminum

Manufacturers of machines processing color coated aluminum usually list repeated positional accuracy in hand manuals yet no positional accuracy. Some users, therefore, tend to regard the former as main index deciding processing precision. As a matter of fact, high repeated positional precision does not necessarily mean high processing precision, key index for which should be positional precision instead.

Repeated positional precision of machines for color coated aluminum show ability of machine tools to get back to a same position. The measuring method is to set a fixed percentage in the measure equipment which is considered as the beginning point. Then move the principle spindle to a random position and make it go back to the original position. Check the error on percentage meter. Repeat the activities for several times. The largest error is repeated positional precision. Based on current technological level and matching method of machines (servo meter–rotary encoder–ball screw), the error can be kept below two pulse equivalent, far smaller than 0.01mm. Positional precision of machines for color coated aluminum refers to moving ability of the principle spindle to a given distance accurately. Machines in our workshop can move as far as seven meters precisely controlled by a laser interferometer. Many factors influence results of positional precision, including form and position error of guide rail, machinery gaps, lead screw or gearing errors, machinery parts deformation and electronic equipment errors. To get high positional precision, operators can put error figures obtained by laser interferometer into the digital controlling system which has error compensation function.