FOUNDRY TECHNOLOGY - Zollern

Flat surfaces
Although it is possible to cast relatively large surfaces, these
should be avoided where possible, as they can only be executed
with a dis-proportionate effort. They should consequently
be ‘broken up’ by ribbing effects, recessing or breakthroughs.
This simplifies the casting process, increases the
form strength of the casting under certain circumstances,
and often also reduces the weight.
Knife edges in the tool
In cases where knife edges would be created in the tool or
on the core slide, for example where boreholes with varying
diameters collide tangentially with each other, then watersoluble
or ceramic cores must be used. However, where this
type of transition in the cross-sectional area can be avoided,
with a slight adjustment it is often possible to use core slides.
This presents a particularly economical solution.
Unfavourable
Favourable
Knife edge in both
core slides
Unfavourable
P
P
P
P
P
P
Possible
Core
Unfavourable
= Knock-out direction of core slides
Knife edges at the casting
Due to the surface tension of molten metals, it is not possible
to cast knives or sharp edges. These must be produced
with a machining allowance and then finish ground.
Division plane and ejector marks
Where patterns are produced using automatic tools, it can
happen that marks are created at the division plane and
ejectors; As these are raised areas, as a general rule they
can be ignored.
To be avoided
Favourable
Ideal
Machining allowance ≥ 3 mm
INVESTMENT CASTING