scope:

The interactive optimization of a mechanism on the screen calls for a rapid analysis of the complete mechanism using efficient algorithms. The calculation modules in VDI 2142 Part 2 were developed especially for the kinematic analysis of any transmission cam mechanism and guide cam mechanism. In contrast to VDI 2729 the complex number method is used here, which makes a very compact and clear representation possible and also permits a reliable and fast computational assessment. In this way the kinematic variables of transmission cam mechanisms with roller lever, roller follower, flat lever and flat follower can be determined and their cam disk profiles calculated. Furthermore, any guide cam mechanism can be kinematically analyzed which normally contains elements of linkage mechanisms and, where applicable, of gear mechanisms.

By means of selected practical examples, the present standard provides the user with assistance in the correct use of the module methods introduced in VDI 2142 Part 2. New subject areas here include the admission of "higher kinematic groups" in the mechanism structure - which previously could not be covered by the module method (VDI 2729) - as well as including the topic of the "electronic cam disk" in the design of servo drives. The practical examples have been selected such that on the one hand as many as possible of the modules listed in VDI 2142 Part 2 appear and on the other hand the mechanism presented will be of interest from the point of view of technical application. Since standard VDI 2729 already gives numerous examples of the occurrence of two-bar linkages with prismatic links, examples of such two-bar linkages will be dispensed with here. In each example the user of the standard is provided with a way of checking the numerical values and function sequences.

First of all, Section 3 gives a basic description of how a mechanism should be systematically described such that all of the data required for using the calculation modules are made available. Taking the straightforward example of a cutting mechanism, the application of this procedure is demonstrated in detail. In the examples which follow in Section 4 to Section 7 this procedure will also be used - but in a more compact form.

The "Gear-and-cam indexing mechanism" example in Section 4 describes a combination of a gear mechanism and a cam mechanism such as is found in, for example, a chain conveyor. In this example particular emphasis is placed on showing how limit curves for transmission angles can be calculated with the modules and thus suitable roller centres or lever lengths can be selected interactively.

The "Glass bottle handling" example in Section 5 describes a flat-follower mechanism with a fixed cam disk and also a rack-and-gearwheel combination. Movement takes place on two orthogonal planes although a planar equivalent mechanism can be used for the calculation. Mechanisms of this kind are used when a relative motion is superimposed on a primary motion.

The "Die cutter" example in Section 6 describes a linkage mechanism with a higher kinematic group. This example should demonstrate how with the aid of the modules additionally specified in this standard it is even possible to calculate mechanisms which cannot be resolved into elementary two-bar linkages. This addition means that a large number of other mechanisms which were not originally accessible to the module method can now be covered.

Section 7 describes a "Transport mechanism for a synchronous phase with servo drive", whose main assembly is a linkage mechanism. Here the module method is used first of all to design, on the basis of technical inputs (synchronous movement, transfer position of the transported material), a linkage mechanism which would offer a suitable path of movement. To ensure synchronous operation, a drive function ("electronic cam disk") then needs to be found. Two different ways of performing this task are shown. Firstly, the drive function is calculated using "classic" iterative methods in which the module method is used in calculating values. Secondly, the problem is formulated as calculation of a higher kinematic group and then solved with extensive use of the module method. In this case a calculation module specified in the Annex for a higher kinematic group is used. From the application point of view the example looks at a problem which often crops up in the synchronous transportation of an object.

The Annex contains calculation modules for two higher kinematic groups of practical relevance and thus supplements the collection of modules in standard VDI 2142 Part 2.