ACR3 system description

Renishaw’s ACR3 is a four port rack that facilitates fast, automatic probe exchange without the need for probe re-qualification. The ACR3 is a four port mechanical design that traverses the MRS rail. Driven by the motion of the CMM, it locks and unlocks the autojoint between the probe and the probe head.  In addition, the ACR3 provides covered storage and protection for up to eight probes and extension bars (two four port systems can be linked to provide an eight port system).

Mounted within the CMM’s working envelope, the ACR3 is combined with the modular rack system (MRS) to form an automatic change rack for probes and extension bars that incorporate the Renishaw autojoint.  Each rack port is of modular design to permit easy replacement should wear occur during the operational life of the ACR3.

 ACR3 not on MRS

Fast probe exchange cycles are achieved by the probe head docking the original probe and selecting a new one. The autochange system consists of a four port autochange rack (ACR3) and the modular rack system (MRS) as shown below.

MRS with empty ACR3


The autojoint (shown below) is a highly repeatable kinematic joint, one half of which is attached to the probe head, the other half to a probe, extension bar or adapter.

Ph10 & autojoint

Locking and unlocking of the autojoint is achieved either manually, using an autojoint key, or automatically, using the autochange rack system. In all cases, the repeatability of the autojoint eliminates the need for probe requalification after each probe exchange.


The MRS is the common mounting platform for the ACR3, SCP600 (stylus change port for SP600) and FCR25 (flexible change rack for SP25M). It is available in a number of different overall lengths and heights. For a detailed explanation of this system, please refer to the MRS installation and user’s guide (part no. H-1000-5088).