Portable CMM - Articulated Measurement Arms

What is a poly articulated arm and what can it do

The poli articulated arms are 3D dimensional inspection instruments that can measure the position of points on the probe’s contact with the mechanical part to be inspected. They are manual dimensional control instruments and need to be handled by a trained operator.

The precission of the articulated arms  is usually lower than a laser tracker's, but in certain 3D control applications they also have some advantages on the trackers.

Poly articulated arms - Operating principle

A poliarticulated arm is a 3D portable dimensional control equipment, basically made of a series of tubes joint together by very precise articulations. Each joint allows the 2 succesive tubes to rotate in only one direction, constantly recording the angle between the tubes, by means of highly accurate optical encoders.

By precisely measuring the angle between the tubes, and knowing the base position, the position of the stylus (contact probe that touches the part to be measured) can be determined. Further probe radius compensations and the point’s projection onto the part lead to the actual position of the point taken on the sample part to be inspected. Based on the 3D measurement specifications and on the part’s characteristics, a series of probe types can be chosen from.

The articulated arm’s accuracy is directly dependent on the the encoders’ precision and the tubes’ thermal stability. Mod de utilizare The articulated arms are manual, mobile 3D inspection instruments, requiring a trained dimensional control operator. The articulated arms’ operating principle is very similar to a 3D contact CMM (portal, gantry), determining the 3D measurement points by touching the probe against the part to be measured.

The operator positions the probe against the part, and the probing is generally manually performed, triggered by an operator pushed button. The 3D inspection software determines the 3D position of the probed point by Comparing the measured point with the 3D cad nominal value.

3D inspection articulated arm’s advantages

• Relatively low acquisition price;
• Highly mobile, fast and confortably operated – allows for on site 3D inspection;
• Ease of handling and setting;
• No need to warm up and wait for a thermal stability, once installed they can be readily used;
• They can be handled by a single operator;
• Unlike the laser tracker, poly articulated arms can reach and measure “hidden points” (points that are not in the direct line of sight);
• Satisfactory precission for a wide range of on site 3D inspection applications;
• Relativelly small and light, making it easy to transport, install and handle by a single operator;

Typical applications for 3D articulated arms

• 3D inspections of molds and dies;
• 3D control of automotive jigs and fixtures;
• Tri dimensional measurement of aerospace fixtures and tools;
• Small parts and fixtures 3D inspection;
• Reverse engineering points acquisition;
• Point clouds aquisition for reverse engineering;
• Machine alignment and calibration;
• General CAD based 3D dimensional control;
• General dimensional inspection and analysis;
• In process inspection;