The "CAD-CAM process chain" is a frequently mentioned and recurring buzzword in the field of production-related design. But what is this anyway? And who benefits from that? We want to address these questions together and try to find some answers.
Let's first look at the use of computers in design and manufacturing. The use of CAD software (Computer Aided Design) has been widespread in the field of design for many years. For this purpose, the software market offers a wide variety of products from different manufacturers. The user is therefore spoilt for choice. Usually the selection of a CAD software takes place under economic aspects with consideration of the individual requirements of the enterprise. A company from the automotive sector naturally has different detail requirements than a steel construction company. Common to all users and applications is the generation of design data for the respective purpose. With today's common 3D systems, the generated data can be directly viewed on the screen and, if necessary, adapted. This is the main focus of each of the systems, because no parts can be manufactured or even sold without design. Many company-internal strategies and procedures concentrate accordingly on the construction range and the tasks directly connected with it. Improvements to increase efficiency, to accelerate processes or to save work steps also focus on this point.
But how does the designed part become a marketable product? Only by converting the design work into an end product it is possible to offer the customer the desired object. As a rule, we call this step "production". Now this is a very broad term. Mechanical engineering alone already knows six main processes here, including primary forming, forming, joining and separating. The general task of production is to use these processes, possibly including several intermediate steps, to create a product from various starting materials that conforms to the design specifications. The greatest challenge here is to extract the defined properties from the design and reproduce them in a real workpiece. This requires a flow of information from design to production.
The use of production drawings is classic and still widespread today. Although the profession of technical draughtsman no longer exists in its original form, drawings are still created and handed over to the production department by frequently specialised employees. Experience has shown that companies invest considerable resources in the form of time and money in the creation and implementation of processes for drawing in accordance with standards. Existing CAD systems are customized, external software connected and PDM systems extended. Once the drawing has been created, it is printed - often in several copies - and transferred to production.
Figure 1: Classic process chain
Production, which is often run as a separate department within the company, is now faced with the challenge of preparing the documents provided in paper form for the mostly highly mechanized and automated production process. Different processes are used for this purpose. Small companies with a usually small number of production machines manually enter the required data into the corresponding systems, generate the NC code on the system and manufacture the corresponding parts. This process takes a considerable amount of time, but there is still considerable potential for errors due to incorrect entries or interpretation errors. The latter are then often attempted to be countered with further refined production drawings.
The use of an independent CAM system (Computer Aided Manufacturing) in manufacturing is also similar. The data flow from design often reaches the affected employees in paper form as well, sometimes supplemented by 3D models in the form of proprietary formats. The exchange of data via formats such as Iges, Step or others alone again causes a media discontinuity, which not least leads to an increased effort in data maintenance.
During the subsequent NC programming, existing information is re-entered into a computer system, the CAM system. CAM systems are also offered in large numbers on the market. They also handle different types of data and can process them more or less well, depending on their individual characteristics.
The aim of this work is to generate an NC program and to design it in such a way that the desired product can be manufactured in the specified quality with the aid of one or more production machines. But this sounds much simpler than it seems at first glance: The transition of information regarding quality - for example, the surface quality - is inhomogeneous and potentially faulty due to the system. Frequent coordination between the departments and the resulting change loops become necessary. An essential part of the NC programmer's task is therefore often the procurement of information on the desired product in order to be able to select the suitable material and manufacturing process.
Once all the information has been obtained, the actual NC programming, the original task, can be started. The result is a command set for the machine tool, with which the desired product is produced from a defined blank. This finished part is the product of all the efforts of the production department. The following figure shows an overview of the exemplary data formats involved.
Figure 2: Example of data formats used in the process
An external observer often notices the confusing amount of different data formats, file repositories and responsibilities, which often ties up valuable resources and obstructs the workflow. Let's be clear: CAD files are updated in the design department, exchange files are created and drawings are created and printed. The transfered data as well as CAM and NC files are now stored in production. All of these have to be stored, revised and made available - quite an effort - and one that not least needs to be well administered.
Now an important question arises: Is the media break between design and production really necessary or even desirable?
In the next article we will therefore deal with the question of what possibilities exist to reduce or even completely avoid media disruptions.