is Cryogenic Treatment?
can you expect?
Industries - Plastic Industry
The plastics molding industry is extremely
competitive. Any advantage that can be had can make the difference
between profit and loss on almost any job. You cannot allow your
competition to have the advantage of greatly reduced mold wear and
higher profits due to molding runs that are uninterrupted by
Cryogenic processing is very successful in reducing wear on runners
and in cavities, even when highly abrasive materials are being molded.
Cryogenic processing has shown to stop the seizing of ejector pins.
Side actions show reduced wear, and parting lines stay sharp.
One of the biggest costs of a mold is polishing. The cost of polishing
is up to 30% of the total mold cost. Cryogenic processing reduces the
time required to polish a mold. The process produces a more evenly
hard surface that is easier to polish.
Cryogenic processing of extruder barrels and screws reduce wear in
these critical areas.
Treating pelletizer knives increases their life an extraordinary
amount. At one major household products supplier, cryogenic processing
increased the life of pelletizer blades and screens from two months to
over two years. This company had over 50 pelletizers at one plant
alone. The potential savings in labor, sharpening, purchasing costs
and new parts are enormous.
A huge plastics container company has tested cryogenic processing on
the blades of their scrap pelletizers. Before cryogenic processing,
they could run the pelletizer for 3 months before they needed to
remove and sharpen the blades. The treated blades have been running
over two years now. This gives this company a decided advantage in the
highly competitive plastics industry.
Molds are a primary area for the application of cryogenic processing.
Virtually all parts of the mold should be processed. The advantages
1. Less cavity wear
Cryogenically treating metals increases their abrasion resistance
greatly. Therefore, molds used with highly abrasive materials such as
glass filled plastics or titanium dioxide filled plastics will wear
2. Reduce wear on gates and runners
3. Reduced wear on ejector pins and core pins.
One of the chief causes of ejector pin wear on molds is that the
heat, pressure, and vibration of use of the mold cause the retained
austenite in the part to transform to martensite. This transformation
causes the pin to grow. Because of the close fit needed to prevent
flash between the pin and the hole, this growth is enough to cause the
pin to seize in the bore. The seized areas will locally weld and pull
apart and a tiny piece of the weld will often fall in between the two
moving parts, and we then have a galling situation which leads to the
failure of the pin.
Another problem occurs due to the transformation of retained austenite
to martensite. This causes the part to have residual stresses due to
the change in size locally. This residual stress and the fact that the
martensite is primary martensite can cause the part to be brittle and
to crack. Cryogenic processing prevents these problems by converting
retained austenite to martensite.
4. Reduced wear resistance on cams, side actions, etc.
5. Better polishing
Cryogenic treatment has a unique effect on metals. The hardness of
the metal becomes less variant after treatment. Typically, the
standard deviation of the hardness of treated metals will one third
that of a similar untreated metal. Cryogenically treated metals are
easier to polish and resist orange peeling more. The net result is
that less labor is required to polish the metal and the polish holds
6. Higher precision
As stated above, cryogenic processing stabilizes the metal. There
is less chance for residual stresses to deform the metal during
cutting or when the mold is in service. This causes the mold to run
truer and not bind.
7. Better grinding finish, easier to grind
Treated metal is easier to grind. The metal is more stable so it
does not warp as it is being ground. This makes it easier to achieve
flatness. The fact that there is little or no retained austenite makes
it easier to grind without grinding burn. The more even hardness makes
for a smoother finish. Some of our customers get such a good finish
with their initial grind that they have eliminated the need for making
a final pass with a finer grain wheel.
8. Better machinability of the metals used in the mold making
9. Treating grinding wheels make them last about 20% longer.
Plated type diamond wheels have been tested by an automotive company
and show two to three times the life. We've done a lot of vitrified
grinding wheels with similar results.