Application of Ultra-Small Micro Grinding and Micro Milling Tools: Possibilities and Limitations

Abstract

Current demands for flexible, individual microstructures in high quality result in high requirements for micro tools. As the tool size defines the minimum structure size, ultra-small tools are needed. To achieve tool diameters of 50 µm and lower, we investigate the complete manufacturing chain of micro machining. From the development of the machine tools and components needed to produce and apply the micro tools, the micro tools themselves, as well as the micro machining processes. Machine tools are developed with the possibility of producing the micro geometry (cutting edge design) of micro tools as well as plating processes to produce super abrasive micro grinding tools. Applying these setups, we are able to produce ultra-small micro grinding and micro milling tools with typical diameters of 50 µm and down to 4 µm. However, the application of such tools is very challenging. The article presents possibilities and limitations in manufacturing the micro tools themselves as well as microstructures made with these tools. A special emphasis will be on the influence of the tool substrate in micro milling and grain sizes in micro grinding.

Keywords: electroless plating; micro end mills; micro pencil grinding tools.

Figure 1

Micro milling center (MMC) after [18].

Figure 2

Precision 4-axes machine after [19].

Figure 3

Schematic of the Tool grinding process and nomenclature after [15,17].

Figure 4

(a) Schematic of electroless plated MPGT tip; (b) schematic of electroless plating setup.

Figure 5

Electroless plated MPGTs with grit sizes (a) 1–2 µm; (b) 2–4 µm; (c) 3–6 µm; (d) 5–10 µm; (e) 6–12 µm, and (f) 8–16 µm.

Figure 6

Micro grinding process kinematics.

Figure 7

MPGTs after machining (left column), entry area of grooves (middle column) and process conditions (right column), for case 1 (a), case 2 (b), case 3 (c) and case 4 (d).

Figure 8

Bottom surface roughness of first 100 µm groove length.

Figure 9

Micro End mills with different diameters (a1 and a2) 10 µm (b1 and b2) 50 µm at different magnifications.

Figure 10

Specifications of cemented carbide for the different grain sizes of (top) 0.3 µm, (middle) 0.6 µm and (bottom) 3 µm

Figure 11

Influence of cemented carbide specifications on tool quality and wear in dependence of the grain size (from left to right: 0.3 µm, 0.6 µm and 3 µm) before (top) and after machining (bottom).

Figure 12

Etched cross-section (left) and properties of commercially pure (CP) titanium grade 2 (right) after [35].

Figure 13

Forces in dependence of the cemented carbide specifications (top left: 0.3µm, top right: 0.6 mm and 3 mm (bottom left) when micro milling (process specifications bottom right).

Figure 14

Bottom surface roughness in dependence of the cemented carbide grain size (from left to right: 0.3 µm, 0.6 µm and 3 µm).