D IAGRAMA DE C LASES DEL D ISEÑO

Current manufacturing technologies are very well optimized for mass production; however, they face many issues to produce mass-personalized products. Guidelines were proposed and evaluated, in the presented research study, as requirement for manufacturing processes allowing mass-personalization. It was shown throughout this thesis work, by a case study for high-precision glass parts, how the micro-machining process SACE can be developed towards a manufacturing process for high-precision glass mass-personalization, respecting these guidelines i.e., reducing manufacturing overhead introduced by the four key drivers of manufacturing costs related to a specific part design (calibration, tooling, processing steps, complexity).

Thus far SACE process was never deployed for high-precision glass mass-personalization by industry and academia. Three main issues of current SACE technology are preventing its use for this highly flexible manufacturing approach:

1. No models are available for glass cutting and milling, relating SACE process input parameters to a desired output such as MRR (feed-rate together with depth-of-cut per machining pass). Such a model is a key requirement for setting up efficiently (i.e. low setup time) manufacturing systems with a high degree of automation. Currently, it takes a significant number of trial and error runs before the process parameters (machining voltage, feed-rate, depth-of-cut) for appropriate cutting and milling operation settings are found;

2. Extensive calibration is needed for tool-workpiece alignment and tool run-out elimination to achieve the desired high-precision (~ 1 µm);

3. Part specific tooling is required for proper clamping of the glass workpiece (almost each production cycle demands changing dimensions in the case of mass-personalization) to attain high precision.

These issues are progressively addressed throughout the outlined research study, resulting in the main contributions of this work:

▪ Glass mass-personalization by SACE technology

SACE technology was progressively developed from mass-fabrication technology towards a process for mass-personalization of high-precision glass parts by addressing the challenges of

the four key drivers of part related manufacturing costs (calibration, tooling, complexity, processing steps);

In order to achieve this transition of SACE technique towards an Industry 4.0 manufacturing process, the following milestones were accomplished;

− Development of a process model for SACE cutting and milling

A model for SACE cutting and milling process operations was developed and empirically validated allowing direct relation of the machining input parameters (e.g.

voltage, feed-rate) to the desired machining outcome (e.g. feature depth), enabling a considerable increase of automation across the manufacturing process workflow from desired design to establishing of machinable code containing all necessary manufacturing execution information (e.g. toolpath definition, machining voltage settings, feed-rate, depth of cut, machining time, achievable quality), which is key for suitable manufacturing processes for mass-personalization. Application of this established normalized model could be extended to other heat-driven processes as well;

− In-situ fabrication methods and low-cost rapid prototyping for tooling were developed

An in-process fabrication method for the needed tool-electrodes is developed, eliminating the need of cumbersome and lengthy calibration procedures, reducing costs and lead times compared to conventional SACE machining approaches.

Low-cost rapid prototyping technology is deployed for part specific tooling fabrication for precise clamping of the workpiece to obtain the required high precision and allowing a consistent, smooth electrolyte flow across the glass workpiece;

− Spark Assisted Chemical Polishing (SACP) was introduced

A strategy was developed to reduce the surface roughness of cut (down to Rz ~ 1 µm) by introducing Spark Assisted Chemical Polishing (SACP), which is carried out on the same setup as machining, avoiding alignment and tool calibration issues;

To show the viability of the developed mass-personalization approach some case-studies towards industrial applications were performed using glass in a non-traditional, indirect way.

Novel applications were proposed and fabricated using glass as substrate material and SACE

technology for rapid prototyping of templates to process polymers and metals with high-precision in the microtechnology field:

▪ Fabrication of glass imprint templates for microfabricating devices by hot embossing. This technique had the advantage of rapidly and accurately introducing features into glass substrates, with good control over all three dimensions.

▪ Manufacturing of glass tools (dies) for micro-forming of metal micro parts. Micro deep drawing of thin metal sheets (thickness 25 µm) was successfully performed without showing significant tool wear of the fabricated glass dies.

The proposed manufacturing process criteria as presented throughout this research work can be used as a first step to assess a given technology on suitability for mass-personalization. It was shown that addressing the proposed four part related manufacturing cost drivers 1) calibration, 2) tooling, 3) complexity, 4) multiple process steps is essential:

1. Calibration runs increase dramatically the setup times for each different workpiece jeopardizing effective manufacturing process work flow as needed for mass-personalization;

2. Part specific tooling add significantly to machining overhead increasing drastically the cost per product;

3. As mass-personalization demands manufacturing of a wide variety of geometries, compatible processes need to be able to handle complex shapes;

4. Each new manufacturing step demands transfer of parts from one manufacturing system to another resulting in new overhead and error introduction due for example to alignment or tooling.