Nylon abrasive filament
brushes have been used in deburring applications for many years.
However, their use has been largely restricted to offhand operations
and custom deburring machines. As a result, deburring was viewed
as a secondary operation instead of a part of the machining process. Recent
changes in manufacturing philosophies and machine tool capabilities are
creating a shift in thinking. The advantages of consolidated machining and
deburring operations can be significant.
In today's tight labor
market, competent manufacturing personnel can be difficult to
attract and retain. This is especially true in jobs such as manual deburring
that can be perceived as dirty and demeaning. In addition, secondary
deburring operations always add incremental direct and indirect labor
costs to the finished product. Reducing these labor inputs can offer significant
financial justification for a consolidated machining-deburring process.
In many manufacturing
processes, parts are shuttled from CNC (computer numerical control)
machining centers to "deburring" or "cleaning"
departments that are responsible for these operations. A major
disadvantage of this type of part flow is that the personnel
responsible for the machining may not consider burr size to be
a factor in selecting cutting tools and toolpaths. While they
are appropriately focused on important issues like cycle time and dimensional
accuracy, machine operators may choose tools and parameters that
increase burr size and subsequently increase downstream processing
costs.
The drive toward "lean
manufacturing" and "single-part flow" has highlighted the
expense and inefficiency of conventional "batch-and-queue production." The
existence of secondary and tertiary processes is a major contributor
to manufacturing costs relating to lead time and WIP (work in progress). Eliminating
these operations can improve customer responsiveness and help reduce
the financial burdens created by long manufacturing cycles.
The first step toward
successful implementation of an in-machine deburring operation is
burr minimization through optimized machining. The selection of
proper cutting tools, machining parameters, and tool-change frequency can
significantly reduce burr size. Although these adjustments may create additional
costs, they can frequently be justified with the advantages of a consolidated
process.
Once the burrs have been
minimized, additional steps may be required to eliminate remaining
burrs, produce required edge radii or improve surface finish.
Nylon abrasive filament brushes are extremely effective tools for these
applications.
The compliance of nylon
abrasive filament brushes makes them ideal for automated applications.
It is essentially impossible to damage a part due to inaccurate programming
or part fixturing. As lean manufacturing philosophies continue to
demonstrate their merit, manufacturers are looking for opportunities
to implement these ideas. Consolidating machining and deburring operations
is typically easy to implement and generates immediate financial results.
Implementation assistance is readily available from the producers
of nylon abrasive filament brushes.
Details
of a Typical Case Study
In the following application,
a manufacturer of screw compressors implemented an in-machine deburring
solution to their manual deburring problem. The company set the
following objectives at the outset of the project: eliminate labor cost
and reduce scrap/rework associated with manual deburring; improve consistency
and repeatability in the deburring operation; and implement a deburring
operation that would not damage painted surfaces
Three nylon abrasive filament
brushes were required to deburr the part. The implementation of these
brushes was achieved very quickly. The brushes were mounted in existing
open spaces in the toolchanger, and the toolpaths for deburring were
developed by making slight alterations to the cutting tool paths.
Parts mounted on tombstone.
A disc brush
is used to deburr flat surfaces where all of the burrs are in
the same plane. The top and the bottom of the housing are
deburred in this manner. The disc brush is run immediately
following the face milling operation because the burrs are easy
to access while the parts were still fixtured in the same position on
the tombstone.
A small
wheel brush is used to deburr and improve the surface
finish on the bores in the housing. Like the disc brushing
operation, the bore deburring is done while the parts are
still fixtured for boring with the brushes interpolated in the
bore. The brushes are run in the direction opposite to that of
the cutting tool to provide maximum aggression on the edges
where the largest burrs are created.
An end brush
is used to deburr confined areas where larger products would
not fit. The surfaces inside the housing that had been milled
are deburred using end brushes that follow a toolpath offset
slightly from the path of the endmill.
The selection of the right
brush speed for each operation was also critical to the success
of the application. Unlike conventional abrasive products, increasing
the spindle speed does not enhance the aggression of a nylon
abrasive filament brush. In fact, higher speeds normally reduce
the cutting action of the brushes. Because these brushes work
with a wiping and filing action, they are best operated at speeds that
allow fairly deep penetration of the part into the brush filaments.
Finished Part.
The
results of implementing the change to in-machine deburring are as
follows:
All burrs produced by the machining process were removed, eliminating
the need for manual deburring and the associated cost of about
$10 per housing or $60,000 annually.
Placing the deburring operation in the CNC machining center increased
the cycle time by 3%. The incremental cost associated with this
longer cycle time was justified by economic and quality advantages
created by eliminating the manual deburring operation.
The consistency of the deburring process was significantly improved,
and the scrap/rework previously created by manual deburring was
eliminated.
Finish on the rotor bores improved from an. approximate starting point
(Ra) of 60 micro inches to a final finish of 35 micro inches.
Because of their conformability, nylon abrasive filament brushes did
not have any detrimental effects on the part. This is due to
the nature of the interaction between the filaments and a machined
surface, which has a profile similar to a mountain range. As brush
filaments move across the surface, they file away the peaks of the
mountains, removing microns of material. This selective filing
action improves the surface finish without changing part specifications.
As manufacturers continue
to look for new ways to improve productivity, in-machine deburring
operations are being adopted as a means to increase throughput and
lower deburring costs.