Mass production is shifted towards the countries with lower factor cost (human and natural resources are cheaper). European industry, though, must search for a chance in customized and hi-tech products, trying to take advantage of its supremacy over emerging countries (China, India, etc.) regarding new technologies development. Aerospace industry, automotive industry, medical implants, hi-end equipments industry, consumer products, protection and safety are the target sectors –which include more than 1.200.000 European enterprises in real need of customized product.
Additive Layer Manufacturing (ALM), also known as Free Form Fabrication, is a novel fabrication method of parts right from the electronic model by layer manufacturing. Layer manufacturing is a building process that consists of plastic/ceramic/metallic 3D printing using layer-by layer approach. An electronic model of a part is sliced into thin layers that, when “physically printed” one over each other recover the physical, solid form of the part.
At present, ALM is the first and the best option for short series of customized products. The advantages of these technologies vastly outnumber its limitations. However, currently, when ALM is planned, an experienced technician must invert several hours to study all criteria and orientate part manually so as to get out the best result in all parameters. Therefore, it is desirable to provide an automatic planning for such production, independently from human operation.
KARMA project ( Knowledge Based Process planning and Desing for Additive Layer Manufacturing) has been conceived to respond to these challenges with a knowledge-based engineering system (KBE) that will perform an automatic analysis and optimization of the build-up direction searching for the best impact on processing parameters (surface quality, build-up time, support structure, etc.), thus being an Expert Process Planning Tool for ALM.
The KARMA end-user will be able to choose material and then certain technology capable of processing this material. Also, if he has a given ALM technology, he can just choose the material. Anyhow, he is assisted by the database wizard. When the choice is done, the end-user chooses a build scenario (a set of machine parameters) for the combination of material and machine he selected.
Processed material properties – both in build direction and layer direction - will be available in the database as a result of machine/material/build scenario set up. If the triple combination results in no result, the wizard suggests him the proper testing procedure to get the results on part properties. It is meant that the database grows together with the experience of its users.
In addition, KBE database contains design considerations (geometrical limits and ranges) for each technology. These values are used as an input in KBE tool (algorithms). The KBE tool uses these values in the surface roughness estimation algorithm to find the part orientation that minimizes surface roughness. The same is done with support volume estimation and build-up time estimation. Therefore, the result of these algorithms implementation is a series of n build directions, each one being the most favourable regarding certain manufacturability aspect.
Algorithms will use both empirical models (that accumulate the know-how and knowledge on ALM) and theoretical models to get the best n directions from different points of view.
When the KBE tool has finished, the part is sent to a FEM analysis tool together with proposed n build-up directions, part properties in build direction (PP BD) and in layer direction (PP LD) and thermal and mechanical loads specified by the end-user. Finally, only m directions that have passed the resistance test are valid and are offered to the end-user. Using the cost estimation algorithm, fabrication costs are then estimated for the part fabricated in all m directions. Finally, the end-user analyzes the m solutions and chooses the one that fits best his principal criteria.
The following repercussions on the ALM users are foreseen:
- The availability of the KBE database will help them in choosing the most appropriate technology, material and build scenario for the product they are launching;
- Full mechanical and thermal characterization of ALM parts. There will be no uncertainty regarding what a ALM part can or cannot withstand depending on their build parameters.
- Efficiency in designing for ALM – a KBE tool will do an efficient and automatic process planning that will analyze the critical issues (surface finish, build time, costs, material waste, etc.) before the part production is launched.
- Give a boost to ALM certification for crucial sectors (biomedical, aerospace, etc.)