U.S. patent application number 14/190117 was filed with the patent office on 2014-08-28 for casting device and casting method.
This patent application is currently assigned to SCHULER PRESSEN GMBH. The applicant listed for this patent is SCHULER PRESSEN GMBH. Invention is credited to TOBIAS SCHWARZ.
Application Number | 20140238633 14/190117 |
Document ID | / |
Family ID | 50156612 |
Filed Date | 2014-08-28 |
United States Patent
Application |
20140238633 |
Kind Code |
A1 |
SCHWARZ; TOBIAS |
August 28, 2014 |
CASTING DEVICE AND CASTING METHOD
Abstract
A method for manufacturing a cast component with a casting
device includes providing a casting device. The casting device
comprises a filling chamber, a mold cavity comprising a hollow
space, runners comprising at least one of a different length and a
different cross-section, and a plunger arranged in the filling
chamber. The metal melt is provided in a fluid state in the filling
chamber. The metal melt is advanced via the runners from the
filling chamber to the mold cavity by advancing the plunger in the
filling chamber. Electromagnetic fields are provided. A flow
velocity of melt currents in the respective runners is increased or
decreased via the electromagnetic fields so that a melt front in
each of the runners reaches the mold cavity when the filling
chamber has been completely filled by the plunger.
Inventors: |
SCHWARZ; TOBIAS; (VAREL,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SCHULER PRESSEN GMBH |
GOEPPINGEN |
|
DE |
|
|
Assignee: |
SCHULER PRESSEN GMBH
GOEPPINGEN
DE
|
Family ID: |
50156612 |
Appl. No.: |
14/190117 |
Filed: |
February 26, 2014 |
Current U.S.
Class: |
164/500 ;
164/147.1; 164/271 |
Current CPC
Class: |
B22D 18/08 20130101;
B22D 17/2272 20130101; B22D 17/32 20130101; B22D 27/02 20130101;
B22D 45/00 20130101; B22D 35/04 20130101; B22D 17/10 20130101; B22D
17/30 20130101 |
Class at
Publication: |
164/500 ;
164/147.1; 164/271 |
International
Class: |
B22D 18/08 20060101
B22D018/08; B22D 45/00 20060101 B22D045/00; B22D 35/04 20060101
B22D035/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 27, 2013 |
DE |
10 2013 101 962.5 |
Claims
1. A method for manufacturing a cast component with a casting
device, the method comprising: providing a casting device
comprising: a filling chamber, a mold cavity comprising a hollow
space, runners comprising at least one of a different length and a
different cross-section, each of the runners respectively
connecting the filling chamber with the mold cavity, and a plunger
arranged in the filling chamber, the plunger being configured to
advance a metal melt from the filling chamber via the runners into
the mold cavity; providing the metal melt in a fluid state in the
filling chamber; advancing the metal melt via the runners from the
filling chamber to the mold cavity by advancing the plunger in the
filling chamber; providing electromagnetic fields; and increasing
or decreasing a flow velocity of melt currents in the respective
runners via the electromagnetic fields.
2. The method as recited in claim 1, wherein the increasing or
decreasing of the flow velocity of melt currents in the respective
runners via the electromagnetic fields is performed so that a melt
front in each of the runners reaches the mold cavity when the
filling chamber has been completely filled by the plunger.
3. The method as recited in claim 1, wherein the electromagnetic
fields are configured to be at least one of controlled and
regulated as a function of at least one of the mold cavity, a
temperature, and a melt composition.
4. The method as recited in claim 1, wherein the electromagnetic
fields are configured to reduce a hydrodynamic resistance of
sections of the metal melt with a small cross-section so as to
reduce a closing force of the casting device.
5. The method as recited in claim 1, wherein the electromagnetic
fields are configured to reduce a hydrodynamic resistance of
sections of the metal melt with a small cross-section so as to
decrease a casting drive force.
6. The method as recited in claim 1, further comprising at least
one of heating, decelerating, and accelerating the melt currents in
the respective runners to a different degree via the
electromagnetic fields.
7. A casting device for a metal melt to implement the method as
recited in claim 1, the casting device comprising: a mold cavity
comprising a hollow space for a cast part; a filling chamber
configured to serve as a reservoir for a metal melt; a gate unit
comprising at least two runners, the at least two runners being
configured to connect the filling chamber with the mold cavity; and
a flow velocity device configured to influence a flow velocity of
the metal melt, the flow velocity device being configured to act on
at least one of a part of the gate unit, a part of the at least two
runners, and a part of the mold cavity.
8. The casting device as recited in claim 7, wherein the flow
velocity device influences the flow velocity via an electromagnetic
field.
9. The casting device as recited in claim 7, wherein the flow
velocity device comprises coils configured to create an
electromagnetic field, wherein each of the at least two runners is
surrounded by a coil.
10. The casting device as recited in claim 7, wherein the mold
cavity further comprises at least one coil arranged in a surface
area.
11. The casting device as recited in claim 7, wherein the casting
device further comprises an electromagnetic retaining device
configured to retain the metal melt.
Description
CROSS REFERENCE TO PRIOR APPLICATIONS
[0001] Priority is claimed to German Patent Application No. DE 10
2013 101 962.5, filed Feb. 27, 2013. The entire disclosure of said
application is incorporated by reference herein.
FIELD
[0002] The present invention relates to a manufacturing method of
cast components with a casting device, a metal melt in a fluid
state being brought from a filling chamber into a mold cavity
comprising a hollow space via several casting runners, and the
casting runners having different lengths or different
cross-sections. The present invention further relates to a device
for implementing the method.
BACKGROUND
[0003] A metal melt, usually in form of a liquid alloy, is provided
for primary shaping. The melt is stored in a filling chamber
serving as a reservoir and is maintained in a liquid state by
supplying heat. By way of a gating unit, the melt reaches a mold
cavity, which forms the negative form of the cast part to be
cast.
[0004] An important criterion for high quality cast products is a
turbulence free, gas free and uniform feeding of the liquid melt.
In order to provide a uniform transport of the melt,
electro-magnetic pumps have previously been described which produce
a laminar movement of the liquid melt in the pump tube.
[0005] The flow velocity of the melt can be influenced in several
ways. DE 10 2009 035 241 A1 describes, for example, a deceleration
and acceleration of electrically conductive melts which is based on
electromagnetic alternating fields.
[0006] During the entire filling process, it must be ensured that
the melt does not solidify. The runner therefore requires a minimal
cross-section which depends on its length and the flow velocity of
the melt to prevent it from solidifying without an external energy
supply. On the other hand, the cast mass increases along with the
runner cross-section so that a greater part of the melt is
lost.
[0007] Large-scale cast parts with several gate areas or
particularly thin-walled cast parts require several runners to
prevent solidification in the casting mold before it is completely
filled. Several runners must be disposed in such a manner so that
as little turbulence as possible is created during the casting
process. In order to ensure a uniform filling, the individual
runners therefore generally have different lengths and
cross-sections. The proportion of the circulating material or the
cast mass is thereby disadvantageously increased and a simultaneous
start of the second casting phase cannot always be ensured. High
casting pressures and high temperatures of the melt are also
required that are conform to the runner with the smallest
cross-section and to the most thin-walled structures of the cast
part.
SUMMARY
[0008] An aspect of the present invention is to improve the prior
art and, more specifically, to provide a method for influencing the
melt which avoids the above-mentioned disadvantages. An additional
aspect of the present invention is to develop a casting method
which avoids an uncontrolled filling of the mold even for complex
casting products, and to create a device adapted to implement the
casting method.
[0009] In an embodiment, the present invention provides a method
for manufacturing a cast component with a casting device which
includes providing a casting device. The casting device comprises a
filling chamber, a mold cavity comprising a hollow space, runners
comprising at least one of a different length and a different
cross-section, and a plunger arranged in the filling chamber. Each
of the runners respectively connect the filling chamber with the
mold cavity. The plunger is configured to advance a metal melt from
the filling chamber via the runners into the mold cavity. The metal
melt is provided in a fluid state in the filling chamber. The metal
melt is advanced via the runners from the filling chamber to the
mold cavity by advancing the plunger in the filling chamber.
Electromagnetic fields are provided. A flow velocity of melt
currents in the respective runners is increased or decreased via
the electromagnetic fields so that a melt front in each of the
runners reaches the mold cavity when the filling chamber has been
completely filled by the plunger.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The present invention is described in greater detail below
on the basis of embodiments and of the drawing in which:
[0011] FIG. 1 shows a schematic representation of a device for die
casting a metal melt.
DETAILED DESCRIPTION
[0012] In an embodiment of the present invention, a generic method
is provided in which the individual melt currents in the casting
runners are heated up, decelerated or accelerated to different
degrees, so that the melt front in all runners reaches the mold
cavity when a casting chamber is completely filled by an advancing
plunger.
[0013] In an embodiment of the present invention, the melt is not
subjected in its entirety to an electromagnetic alternating field
of the same strength, but is influenced in accordance with the
geometry of the melt current and only in certain areas so as to
modify only the properties of one or several melt currents in
relation to other melt currents. More specifically, the flow
velocity of individual melt currents in the runners filling the
mold cavity or in the mold cavity itself can thus be increased or
reduced so that the filling can be favorably influenced.
[0014] The varying electromagnetic alternating fields induce eddy
currents in each melt current forming an electric conductor. The
magnetic field exerts forces on the eddy currents, the strength of
which depends on the spatial variation of the magnetic flux
density. The melt thus experiences a force aligned on the lesser
magnetic flux density. Analog to a Lorentz force acting on a solid
body, displacing it in space, the melt current is accelerated or
decelerated depending on the flux density gradient.
[0015] In an embodiment of the present invention, the
electromagnetic fields can act contactless on the respective melt
current. A direct electrode contact with the melt current, which
would be subjected to considerable wear, is thus not required.
[0016] An electromagnetic field is to be understood as a
time-varying electric or magnetic field. The electromagnetic fields
can, for example, be generated by coils. When an electric current
passes through the coils, the coils generate a magnetic field which
locally induces eddy currents in the melt. One or several coils
can, for example, surround the individual runners, for example,
along their entire length. They can alternatively only surround
sections thereof. Areas of the mold cavity having thinner diameters
can also be surrounded by coils.
[0017] In an embodiment of the present invention, the
electromagnetic alternating fields locally reduce the flow velocity
to a point where the melt front almost or completely stops. A
contactless operating valve is thus created. Stopping the melt
front does not have to occur at all runner cross-sections, so that
not all the runners are necessarily provided with such a valve.
Such valves can be provided in addition to or instead of coils
modifying the velocity of the melt. In the first case, they can act
as a securing mechanism and prevent a premature filling of the form
cavity. In the second case, they constitute an adapted mechanism
for runners of similar lengths which do not require a complex
control or regulation.
[0018] In order for the coil dimensions of the coils surrounding
the runners or the surface areas of the mold cavity to not become
too big, field generators can be used that concentrate the action
of the force on one specific area. A field generator can, for
example, be designed as a conductor which is cut in the
longitudinal direction of the coil axis and is charged with short
current pulses. Due to the skin effect, the short impulses barely
penetrate the conductor itself and can thus act on the densely
flowing melt with very high field strength.
[0019] In order to accelerate the melt in a runner, a traveling
electromagnetic field can be achieved by means of an inductor
according to the principle of a linear motor. The respective melt
current thus forms the secondary part of a linear motor, i.e., the
rotor.
[0020] In an embodiment of the present invention, the melt is not
slowed-down in any of the runners. The individual runners are thus
accelerated or do not experience any modification of their velocity
by the alternating fields. This embodiment is advantageous for a
rapid casting. The coils can also act particularly effectively on
the outer surface areas of the runner because of the skin effect
and thus accelerate the melt current particularly in those places
where the hydro-dynamic pressure is smallest. Their effect is
therefore particularly effective. Due to the inner friction caused
by the eddy currents, they also counteract the temperature gradient
in the melt cross-section and therefore counteract surface area
solidification. As a rule, the viscosity drops because of the
higher temperature, which indirectly improves flow properties.
[0021] In an embodiment of the present invention, particularly big
electromagnetic fields allow for a very steep temperature gradient
between the melt edge and the runner wall. This can have positive
effects on the durability of the runner wall.
[0022] In order to slow down or stop the melt flow, the strength of
the electromagnetic fields should be adjusted to the center of the
runner where the hydrodynamic pressure is greatest and the
penetration depth of the fields simultaneously decreases. These
fields are relatively big, which generally requires relatively
strong currents and large coils.
[0023] The eddy currents causing the acceleration or deceleration
of the melt also increase the melt's temperature because of the
inner friction of the melt. The generated heat has a positive
impact on the casting in that premature solidification can be
prevented. In runners having a very small cross-section or with
thin-walled sections of the cast part to be cast, this effect can
also be used to prevent premature solidification without intending
a modification of the flow velocity. More specifically, a primary
shaping of cast parts with a wall thickness under 3 mm or with long
flow paths can take place with a high level of process
reliability.
[0024] The flow velocity can also be increased to the maximum value
suitable for the cast part, which allows for a reduction of the
runner cross-sections. The thereby increasing influence of the heat
transfer at the wall surface compared to the heat input by the flow
rate can thus be counteracted. For example, a runner with an
ideally round configuration, which is reduced to half its diameter,
has a cross-sectional area of only 25% of the original
cross-sectional area, the wall surface decreasing by 50%. The
doubled temperature loss at the wall surfaces at the same current
velocity is completely or overcompensated by the increased flow
velocity from the flow rate of the melt.
[0025] As mentioned above, the local temperature increase not only
prevents premature solidification, but also locally reduces the
hydrodynamic resistance in thin runners. The centrally defined
casting pressure should be sufficiently high that a uniform filling
of these critical areas is always provided. By locally reducing the
hydrodynamic resistance, the central casting pressure can be
considerably reduced, which allows for less complicated casting
devices.
[0026] If the hydrodynamic resistance is overcome merely by the
electromagnetic force, a central casting drive can also be
completely dispensed with as necessary. The electromagnetic fields
thus provide a direct electromagnetic casting drive.
[0027] The hydrodynamic resistance can be reduced by means of the
electromagnetic fields at least so that the required casting
pressure drops and the closing force required for closing the mold
cavity is also reduced. The casting device can thus be manufactured
at considerably lower cost. This effect is advantageous for
manufacturing large-scale and thin-walled structural parts.
[0028] The coils can be powered permanently or according to an
algorithm stored in an electronic control system. A control or
regulation of the coil current can alternatively occur depending on
specific input parameters or, in case of a regulation, also on
output parameters, such as casting speed, geometry of the casting
system, gate system, shape of the cast part, location of the melt
front, type, temperature or temperature gradient of the melt. In an
embodiment, a regulation can be advantageous which adjusts the
speed of the melt currents so that the mold cavity is filled
simultaneously or substantially simultaneously through all runners
and that an optimal heat is everywhere provided. The filling amount
can also serve as a regulation parameter. The melt supply velocity
can, for example, be adjusted depending on the gasification of the
foam model volume.
[0029] The metal melt is brought in a liquid state from a filling
chamber via several casting runners into a mold cavity comprising a
hollow space with several gate areas. The several runners serve to
fill the mold cavity of a single cast part. In order to provide a
fast filling of the mold and a simultaneous start of the second
casting phase in all the gate areas, the individual runners can,
for example, have different lengths and/or different geometric
shapes. The flow velocity of the melt in the individual runners can
be modified by means of the electromagnetic fields so that the melt
front in all runners reaches the mold cavity, for example, when a
casting chamber is completely filled by an advancing plunger.
[0030] The casting method is more specifically adapted for casting,
such as die casting, large-scale components. A synchronization of
the individual fronts of the melt currents based only on the
geometry of the runners is difficult when many runners fill the
mold cavity. The present invention therefor also allows for complex
gating units with many runners.
[0031] In an embodiment of the present invention, the individual
runners can, for example, be shorted or their cross-section reduced
so that a simultaneous filling of the mold is not possible without
the action of the electromagnetic fields. By separating the flow
velocity and the cross-sectional area traversed by the flow, there
is no longer a need to put up with a lengthening of individual
runners and therefore with an increase of the amount of circulating
material. An undesired increase of the cross-section, which would
lead to a greater weight of the cast, can also be dispensed with.
By using the electromagnetic fields in a targeted manner, the
respectively shortest runners with a small cross-section can be
chosen. This simplifies the configuration of the casting
device.
[0032] In an embodiment of the present invention, a direct casting
occurs into a casting mold, which comprises a horizontal or a
vertical separation plane. During the first casting phase, the
casting chamber is filled with the melt. The melt front is held
back until the advancing plunger has increased the fill level of
the casting chamber to 100%. A premature filling of the mold cavity
is prevented before the casting chamber is completely filled. A
wear-free retaining device is provided therefor which holds back
the melt by means of electromagnetic fields instead of a shut-off
plate. At the same time, the eddy currents generated by the
electromagnetic fields and the temperature increase produced by the
eddy currents counteract premature surface layer solidification.
Once the second casting phase has started, a rapid filling of the
mold can occur by acceleration of the melt.
[0033] The presented methods and casting devices can in principle
be adapted for all electrically conductive melts. Examples include
aluminum or magnesium based melts. The melt to be cast can, for
example, be a hypereutectic or hypoeutectic Al--Si-alloy.
[0034] The present invention is also usable for different casting
methods such as, for example, hot-chamber or cold-chamber die
casting methods. Due to the different flow velocities, more
specifically, to a possible acceleration of melt currents, the
present invention allows for a more flexible configuration of the
gating unit and a shortening of the runners. The casting result is
improved and the weight of the cast is reduced.
[0035] The present invention is usable for different casting
methods. The present invention will now be described in greater
detail based on an exemplary embodiment for die casting.
[0036] FIG. 1 shows a casting device 1 for die casting magnesium or
aluminum melts. The melt 2 is fed from a melting furnace serving as
a storage container 7 into a filling chamber 4 by way of a supply
line 8. The filling chamber 4 forms a reservoir for a predetermined
amount of the melt 2. The melt 2 can leave the filling chamber 4
via several runners 10, 11, 12 and flow into a mold cavity 3. The
mold cavity 3 is formed as a hollow space 13 by two casting mold
half-shells 14, 15 and forms the negative form of the die cast
product increased in size by the shrinkage value in a known manner.
Both casting mold half-shells 14, 15 have a vertical separation
plane 9 for subsequent removal of the cast part.
[0037] In the first casting phase, the filling chamber 4 is filled
with a dosed amount of the melt 2. An exact dosage provides that
the mold cavity 3 is subsequently completely filled and the
remaining material thus formed does not burst.
[0038] A plunger 6 forces the melt 2 via the runners 10, 11, 12
into the mold cavity 3 by applying flow pressure. The slow forward
movement of the plunger 6 provides that the air is displaced out of
the runners 10, 11, 12 until the fronts of the melt reach the
gate.
[0039] The runners 10, 11, 12 have different lengths and
differently sized cross-sections, so that, without additional
measures, the individual fronts of the melt currents 20, 21, 22 in
the runners 10, 11, 12 would reach the gate areas at different
points in time.
[0040] Sections of the runners 10, 11, 12 are surrounded by coils
30, 31, 32 with respectively different configurations, which are
adapted to be energized by way of a control or regulation unit (not
shown) and can generate eddy currents in the melt 2. As part of the
gate unit 5, the runners 10, 11, 12 and the coils 30, 31, 32 are
configured so that, with a suitable current feed, the individual
melt currents 20, 21, 22 can be slowed down or accelerated so that
they reach the gate areas at the same time.
[0041] As an additional safeguard, one of the runners 12 has a coil
32 which acts as an electromagnetically operating retaining device
33. With the retaining device 33, the front of the melt current 22
can also be effectively retained when it prematurely reaches the
gate area. By means of the inducted eddy currents, the melt front
is simultaneously heated up so that its surface layers do not
solidify prematurely.
[0042] Once the gates have been simultaneously reached, the second
casting phase begins, during which the mold cavity 3 is filled. The
controlled filling of the mold takes place relatively quickly and
under high pressure, a uniform filling being also provided with
thin-walled and large-scale cast products due to the plurality of
runners 10, 11, 12.
[0043] In thin-walled surface layer areas, coil 34 are disposed on
or around the mold cavity 3, which locally causes a temperature
increase in the cast part and thus lowers the hydrodynamic
resistance. An acceleration or deceleration of the melt current
front within the mold cavity 3 is also conceivable. Due to the
hydrodynamic pressure, the melt 2 uniformly and precisely fills the
mold cavity 3.
[0044] The schematically showed coils 30, 31, 32, 34 respectively
represent one set of coils, which respectively acts on the
individual melt currents 20, 21, 22.
[0045] The present invention is not limited to embodiments
described herein; reference should be had to the appended
claims.
LIST OF REFERENCE NUMBERS
[0046] 1 casting device
[0047] 2 melt
[0048] 3 mold cavity
[0049] 4 filling chamber
[0050] 5 gate unit
[0051] 6 plunger
[0052] 7 storage container
[0053] 8 supply line
[0054] 9 separation plane
[0055] 10 first runner
[0056] 11 second runner
[0057] 12 third runner
[0058] 13 hollow space
[0059] 14 casting mold half-shell
[0060] 15 casting mold half-shell
[0061] 20 first melt current
[0062] 21 second melt current
[0063] 22 third melt current
[0064] 30 coil
[0065] 31 coil
[0066] 32 coil
[0067] 33 retaining device
[0068] 34 coil
* * * * *