machining
Bore processing for small components can present a challenge;
specialised technology provides the solution.
Precise processing
MINIATURISATION of manufactured products is
not simply about making everything smaller;
conventional manufacturing processes cannot
always be simply scaled down. For example certain
workpiece characteristics become more critical,
and this has a knock-on effect on the
manufacturing process. The need to avoid burr
formation on ductile materials, generally
unacceptable in 'micro-technology' applications,
means tungsten carbide, ceramic, silicon or
polycrystalline diamond (PCD) are becoming more
important; brittle/rigid materials on the other hand
are machined mainly by a grinding and polishing
procedure, using diamond as cutting material.
Processing bores with diameters 0.015 to 4mm
represents a special challenge, particularly with
regard to access, and what are often large aspect
ratios (bore length:diameter). There is not an
abundance of manufacturing processes for
machining small bores, which deliver to the
tolerances (on form, position, measure, etc) and
surface quality required within the sub-micrometer
range; while EDM, laser, and ultrasonic methods
have been developed, finishing remains a problem.
Diameters below 1.2mm are beyond the practical
economical and technical limits for conventional
procedures such as internal cylindrical grinding or
honing; and reliable measuring of the bores in itself
represents a challenge within this diameter range.
With its Micro Bore Sizing (MBS) machine range
Microcut addresses this, offering specialised and
economical solutions for processing of bores down
to 0.015mm diameter, and in particular for hard
materials. The method is devised to deliver
diameter, roundness and cylindricity to close
tolerances plus high surface quality.
Specialised and accurate abrasive tooling plus
stable processing conditions are at the heart of the
process: with the conical part of the tool the raw
bore is enlarged and with the cylindrical part
Enquiry Number: 30
48 MWP november 2007
consistent geometry is achieved over a large
number of pieces. It is claimed that surface and
accuracy are comparable to those achieved by
lapping technology; and the cold process does not
affect the microstructure of the workpiece material.
Choice of the tool governs surface roughness
and metal removal rate; processes with two
alternative types of tool can be performed on
Microcut’s UniBore 800:
■ Lapping process (loose grit) - suitable for brittlerigid
materials.
■ Honing process (bonded grit) - favoured for
softer materials such as steel
Applications range across the toolmaking, fibre
optics, medical, semiconductor and automotive
industries. Typical work pieces which can benefit
from the process are nozzles, tubes and bushes;
specific examples include ferrules for fibre optic
connectors, where roundness of <<0.5μm has been
achieved. www.microcut.ch
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