# The Off-Line Simulation on Measuring through Software PC-DMIS CAD++ V4.3
## 4 Discussion  
Before the direct running on the CMM, the measuring program has to be verified not only in terms of the kinematics of the movements during the measurement but also in terms of compliance with the correct technological procedure of the measurement. Measuring and evaluating software PC-DMIS enables starting the prepared measuring program in the off-line simulation regime, during which collisions of the scanning system with the measured part, occasionally incorrectly placed contact places of the touch point with its surface, are identified. Simulation off-line in the work environment PC-DMIS was carried out for both prepared measuring programs (measuring program for measuring position 1, also for the measuring position MP2). During their simulation, a detection of collisions of the scanning system with the measured part was activated, which in the case of any collision will stop the operation of the measuring program and mark the point of its origin. Another function used not only during the off-line simulation but during the programming of the measuring task itself is a graphic display of the trajectory of the scanning system (Figure 13). Activation of this function has enabled to visually check the presence of excessive movements of the coordinate measuring machine based on the estimation, and the origin of possible collisions of the scanning system with the worktable of the device or with the measured part. Off-line simulation of the measuring program has pointed to the need to tune the prepared measuring program for the measuring position 1 as well as for the measuring position 2. On the basis of estimations, the coordinates of the position of several positioning points have been adjusted, and for the reason of removing excessive movements of the coordinate measuring device, the transfers of the coordinate system into the package plane have been removed in the cases where there was no threat of collision of the scanning system with the measured part. A debugged and collision-free measuring program for verification of observed geometric specifications of the device part in the measuring position 1 and 2 was verified on the coordinates measuring device DEA Global Performance 12.22.10. It was done at a considerably lower speed, as is the set measuring speed, and after confirmation of its faultlessness, a measuring in the measuring positions 1 and 2 was carried out on the stated coordinates measuring machine. Figure 12: Geometric cylinder element designed by construction. A, B, C, D—order of selection of the elements measured directly (first element is element A, last is the point D); E—designated geometric element is represented by an axis and a directional vector, the direction of which stems from the order of selection of elements measured directly. The principle of coordinate measuring is based on this assumption: \"Each machine part consists of different geometric elements, such as e.g., plane, cone, cylinder, etc.\" On coordinate measuring machines, points whose position is unambiguous in the defined coordinate system are sensed by contact of the touch tip of the sensing system with the surface of the measured part. The read coordinates of each scanned point are sent in real-time to the measuring and evaluation software. If the scanned points represent basic geometric elements, they are replaced by a corresponding substitute geometric element. To ensure the correctness of substitute geometric elements identification, it is necessary to observe the minimum number of scanned points for each of them (e.g., circle 3, line 2, etc.). As the number of scanned points increases, the substitute geometric element gets closer to reality, which increases the accuracy of the measurement. On the other hand, the measuring time increases, which causes an increase in the costs related to the measurement.