# The Off-Line Simulation on Measuring through Software PC-DMIS CAD++ V4.3
## 1 Introduction
### Problem Description
In the case in which the position of the calibration ball in the work environment of the machine has changed since the last calibration, it is necessary to scan the first point on its pole manually (Figure 1). As the measuring program includes a command file, based on which the device performs a particular measuring task, under the phrase \"programming of the measuring task\" we mean all activities leading to the creation of a functional measuring program of the controlled part. Nowadays, construction and technological preparation of the production is carried out by use of the software packages CAD/CAM (computer-aided manufacturing) like NX, Creo Parametric, CATIA, etc. Pro. Therefore, a great advantage of the PC-DMIS software is its ability to import a prepared parametric model of the measured part in the CAD system, which can be used for the programming of the measuring task, as well as for the presentation of the measured results. Measuring programs for the coordinate measuring device DEA can be created in the programming environment of the PC-DMIS by two means:  
* On-line programming--During the on-line programming of the measuring task, the computer with the installed measuring and evaluating software PC-DMIS is directly connected with the coordinate measuring device. A so-called learning creates the measuring program, when the user with the help of a manual operation unit estimates entry-measuring points on the surface of the controlled part, necessary for the identification of the position and type of the scanned geometric element. For the required accuracy of the measurement to be the highest, the device then repeats the strategy learnt in an automatic cycle and scans at least those same points, defined by the user. An indispensable condition for programming of the measuring task on-line is the presence of the controlled part in the work environment of the device, whereas its imported parametric model can be used as well, depending on the need. In the case of use of the imported parametric model, programming of the measuring  
Figure 1: Point (1) scanned on the pole of the calibration ball. task is carried out in a way so that the operator clicks on the required place on the surface of the parametric model in the programming environment of the PC-DMIS. The coordinates measuring device will realize the given task by scanning the point on the surface of the real part in the same place the operator required. Considering that during the programming it is not possible to administer any other measuring activities on the device, the disadvantage of measuring programs created in this way has mainly economic importance, particularly when the measuring device represents large purchase costs. * Off-line programming--The creation of the measuring program takes its course on a remote computer with an installed measuring software PC-DMIS off-line, which is not directly connected with the coordinate measuring device. Programming of the measuring task always stems from the imported parametric model of the measured part. Individual points needed for identification of the position and type of the geometric unit are entered by clicking on the surface of the imported model, whereas the value of the dimension of each geometric element represents a nominal value of the dimension of the same element on the real part. A program created off-line can be simulated in the programming environment of the PC-DMIS, which provides an option to remove the created collision of the scanning system with the measured part (Figure 2). A considerable advantage of the off-line programming of the measuring task is the removal of auxiliary unproductive times of the device that originate in programs created directly on the coordinate measuring device. The next chapter will describe the procedure of component measurements with emphasis on compliance with the accuracy of measurement procedures.