Measurement / Metrology

G. Bissacco (a), T. Gietzelt (b), H.N. Hansen (c)

(a) Department of Mechanics and Innovation (DIMEG), University of Padova, via Venezia 1, 35131Padova, Italy
(b) Forschungszentrum Karlsruhe Institut für Mikroverfahrenstechnik, 76021 Karlsruhe, Germany
(c) Department of Mechanical Engineering (MEK), Technical University of Denmark (DTU), Produktionstorvet 2800 Kgs. Lyngby, Denmark

Abstract

This paper discusses the issues related to force measurement in micro milling and presents the results of the experimental investigation performed in an on going Cross Divisional Project within the 4M network of Excellence, aiming at force analysis and process characterization in micro milling. Reliable force measurement in micro milling is shown to be a challenging task. Measured forces are affected by contributions coming from the machining system. Based on the performed measurements, tool engagement has been demonstrated to occur at each tooth passing, even at feeds per tooth as low as 2 μm.

K. Hofmann (a), L. Staemmler (b), H. Kück (a), (c)

(a) Institute of Micro- and Precision Engineering (IZFM), University of Stuttgart, 70569 Stuttgart, Germany
(b) now: Greiner Bio-One GmbH, 72636 Frickenhausen, Germany
(c) Hahn-Schickard-Institute for Micro Assembly Technology (HSG-IMAT), 70569 Stuttgart, Germany

Abstract

The electrochemical milling with ultra short voltage pulses (ECF) displays an important progress in micromachining of hard materials. Machining a workpiece with conventional milling the removal takes place by shape cutting. Therefore mechanical forces are applied to tool and workpiece. In contrast, using electrochemical milling, the material removal occurs by an electrochemical reaction. Therefore the workpiece as well as the tool are submerged into an electrolyte and the surface of the workpiece is etched by a galvanic current. Hereby the so called working distance is formed between tool and workpiece, which goes linear with the pulse amplitude and pulse on time in a first approximation. As a result, there are no mechanical forces applied to the tool. This allows the use of very thin tools. To achieve the highest precision with this technique, it is necessary to manufacture very precise tools and to verify their shape and dimensions. In addition the use of rotating tools could be a promising strategy to speed up the ECF process and reduce the roughness. Therefore we introduce a method to produce very thin rotation-symmetric tools with high precision using the ECF technique. While the tool rotates the diameter is reduced by a one sided removal of material similar to machining with a turning lathe.
To verify the shape and the dimensions of these tools a commercial laser measuring system for tool setting and breakage control was integrated into the ECF machine. Algorithms to determine the tool diameter and the toolshape are installed. Further algorithms have to be developed to characterize more details of the tool like tilt and run-out error.

Richard Thelen (a), Joachim Schulz (a), Pascal Meyer (a), Volker Sailea (a)
(a) Institute for Microstructure Technology, Research Centre Karlsruhe, 76646 Eggenstein, Germany

Abstract

Reproducibility and precision of LIGA structures has been claimed in many publications, founded mainly on brilliant pictures. Because of the poor accessibility to the sidewalls many publications are based on surface measurements without including information about z depending aspects [1] and focus on reproducibility as measured close to the top.
Often this neglects operator’s influence, short time and long time reproducibility, environmental effects on the CMM and others. Tactile optical metrology might help to overcome 2D measurements. Repeatability of tactile optical metrology at IMT was proven to be less than 0,3 μm over some months using ultra fine probes with less than 25 μm diameter. In addition DoE was used to determine the minimum deviation for best possible machine settings. Standard Deviation between 50 and 30 nm was measured. Compared to that, uncertainty remains about 1-2 μm for 3D measurements even with z maximum restricted to 1 mm [2]. Not enough to measure sub-μm product variation that is a typical benefit of LIGA products.
Investigations were started at the Research Centre Karlsruhe to find out more about the effects influencing the measurements to explain why repeatability and capability do not match. Interaction between sample and sensor was the main reason. This was simulated and the results were used to reduce the uncertainty of the system. IMT elaborated a new strategy that improves the capability of a coordinate measurement machine CMM with tactile optical sensor for LIGA parts with sub μm variation.

R. Teti, P. De Santo
Department of Materials and Production Engineering, University of Naples Federico II, Naples, Italy

Abstract

The main objective of this work is the investigation on micro-nondestructive evaluation (micro-NDE) metrology for dimensional measurement and quality control of multi-material electronic devices consisting of chipset tablet assemblies. The micro-NDE approach is based on ultrasonic (US) sensors in pulse-echo testing mode applied according to the full-volume immersion scan method that provides for the US axial tomography of the chipset tablet. The thickness of the multi-material chipset tablet assembly layers was evaluated through micro-US 2½ D geometrical measurements and the chipset tablet inter-layer integrity was critically assessed via micro feature US image analysis.

L. Mattsson (a), P. J. Bolt (b) , S. Azcarate (c), E. Brousseau (d), B. Fillon (e), C. Fowler (f), E. Gelink (b), C. Griffiths (d), C. Khan Malek (g), S. Marson (h), A. Retolaza (c), A. Schneider (f), A. Schoth (i), A. Temun (a), P.
Tiquet (e), and G. Tosello (k)

(a) KTH – the Royal Institute of Technology, Department of Production Engineering,School of Industrial Engineering and Management, SE-10044 Stockholm, Sweden
(b) TNO Science and Industry, 5600 HE Eindhoven , The Netherlands
(c) Tekniker Technological Center, 20600 Eibar, Spain
(d) Cardiff University, Manufacturing Engineering Center (MEC), Cardiff CF 24 3AA, United Kingdom
(e) French Atomic Energy Commission (CEA), Laboratory of Innovation for New Energy Technologies and Nanomaterials (LITEN), 38054, Grenoble, France
(f) Science and Technology Facilities Council, Rutherford Appleton Laboratory (RAL), Technology – Central Microstructure Facility, Harewell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK
(g) FEMTO-ST Institute, CNRS UMR 6174, LPMO Department, 25044 Besancon Cedex, France
(h) School of Applied Sciences, Cranfield University, Cranfield, Beds, MK43 0AL, UK
(i) University of Freiburg, Institute of Microsystem Technology (IMTEK), 79110 Freiburg, Germany
(k) Technical University of Denmark (DTU), Department of Manufacturing Engineering and Management (IPL), 2800 Kgs. Lyngby, Denmark

Abstract

Surface roughness of tiny micro machined features is not easy to verify. The statistical variation of the surface itself can be the limiting factor that hampers tolerance verification. In this paper we have studied this effect and we also test the performance of 10 different surface profilers over a very well specified surface area. For this area 6 profilers yielded the same result within a standard deviation window of ±6%. For other areas, on top of narrow bars and in narrow and deep channels, a much larger spread in the Round Robin results was found.