|Electro discharge truing|
Koyo Machine Industries Co., Ltd. is represented in Europe by
Company Products Grinding machine Centerless Surface Shoe Grove E-dt Semi
Electro discharge Truing
Grinding wheels need from time to time dressing and truing. This is done with a special dresser often consisting of a diamond tool. It is pulled over the grinding wheel in order to re-estabilish the original form of the grinding wheel, which is lost during grinding procedure over the time. The shape of the grinding wheel depends on the grinding application. Sometimes it is necessary to structure parts by grinding. For centerless grinding a concave shape is necessary in order to ensure the automatic transport of the parts through the grinding machine. The truing of the grinding wheel has to be done in order to excavate new abrasive grain to the surface. This is done by removal of the binder between the grain. A diamond dresser does dressing and truing at the same time, but the fresh grains on the surface are damaged during this operation.There is one way to avoid such a damage: electro discharge truing. Electro discharge truing is a is a precise, non-contact truing method which improves grinding accuracies while increasing productivity and quality. E-dt makes truing possible while metal-bonded diamond wheels remain on the grinder. It removes only the metal bond with no damage to the diamond grain.
Koyo realizes the advantages of using
diamond wheels. They are non-conductive and extremely hard which
makes them excellent for grinding applications with materials such as
ceramics, carbide, cast iron, and sintered metal, as well as hardened
steels. A diamond grain is also less expensive than cBN and has a
longer life, thereby lowering tool cost.
So why aren’t diamond wheels more popular?
Koyo has the solution....... Electro discharge truing (E-dt)
Truing (or dressing) is required to achieve highly-accurate grinding whether using cBN, diamond, or conventional aggressive wheels. However, truing of these wheels was difficult due to the materials hardness, so these super-aggressive wheels were made with soft bonds for ease of truing or dressing the grinding face. This resulted in a shorter life for the grinding wheel.
Down time for dressing is reduced by 1/8 to 1/5 from that of
resin-bonded cBN wheels. According to our test results on a Koyo
KVD-300, it took only 15 seconds to remove 0.76” of grinding
surface using with E-dt.
Comparatively, the dressing time for resin-bonded cBN wheels using a WA
dressing stone was 120 seconds.
The dress frequency using diamond wheels with E-dt is 3 times less than with cBN wheels. Cycle time is decreased by 28% for sintered metal parts. This enables dressing to be done between shifts.
By maintaining the integrity of the grinding wheel surface
after truing, the quality of size, flatness, parallelism,
roundness, cylindricity, and surface finish is dramatically improved on
high-precision parts. Using a finer grit diamond wheel,
mirror-finish (0.2µm) quality can be achieved.
E-dt trues accurately since there is no resistance between the dressing tool and the grinding surface.
cBN wheels are
dressed by using a method which fractures the cBN grit, producing a
sharp edge on the tool. In comparison, with E-dt there is no
damage caused to the
grinding wheel grit. This can be seen in the following pictures.
|cBN dressed with WA
(white aluminium oxide) stone
E-dt available on the following Koyo Grinders:
Centerless: C3015F, C4520FS, 4515C, 4515CS, 4520C, KCL-50
KVD-580, HD-3, HD-5, HD-7, HD-10, R-031, R-431, R-631, R-632
|Crystec Technology Trading GmbH will be pleased to further discuss details with you.|
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