Note: Descriptions are shown in the official language in which they were submitted.
~086683
A METHOD OF AND AN APPARATUS FOR PRODUCING EXTRUSION PROFILES
The lnvention relates to a method of and an appara-
tus for producing extrusion profiles having a desired
extrusion length, in particular from cast metal billets.
In the extrusion of rods, tubes, profiles, and the
5 like from metal such as aluminum, normally an extruded 'f
profile is produced from a billet having a certain length.
The length of the extruded profile depends on the billet
length extruded and on the press ratio, i.e. the ratio
between the pressing pad cross section and the extrusion cross
section. The extruded billet length then corresponds to
the billet length minus the length or thickness of a
remainder to be discarded, the so-called butt thickness.
The butt retains impurities contained in on or
at the billet and protects the die from overload. The butt
thickness is in the order of from 3 to 5% of the billet
length and forms part of the waste produced in extrusion
processes.
It is an aspect of the invention to produce
extruded profiles of desired extrusion lengths, at a given
approximately known press ratio, from billets having such a
length that the butt thickness is as small as possible
and maintained at the optimum rated thickness value
which still contains some reserves as compared to the minimum
permissible butt thickness with regard to the quality
of the extruded profile
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and the permissible loading of the die.
Accordingly, this invention provides a method for
producing from a series of billet blanks a plurality of
extrusion profiles each having a given first longitudinal
dimension, and a plurality of corresponding billet remnants
each having a given second longitudinal dimension, comprising
the steps of
(a) severing a first billet (11) to a predetermined
length (l);
(b) initiating longitudinal extrusion of said first
billet, thereby to progressively form said billet
- into an extrusion profile portion and a billet
remnant portion;
(c) continuously measuring during the extrusion
process the longitudinal dimensions of both the
extrusion profile and billet remnant portions,
respectively;
(d) interrupting the extrusion process when one
of said dimensions reaches its predetermined value;
and
(e) adjusting the predetermined length to which the
next succeeding billet is severed in accordance
with said measured dimensions, whereby the
extrusion profile and billet remnant produced from
the next succeeding billet will have dimensions
more closely approximating the given first and
second longitudinal dimensions, respectively.
Further, this invention provides apparatus for
producing a series of billet blanks a plurality of extrusion
profiles each having a given first longitudinal dimension,
and a plurality of corresponding billet remnants each having
a given second longitudinal dimension, comprising
(a) adjustable billet severing means for severing
a first billet to a predetermined length,
(b) extrusion means receiving said first billet to
progressively form said billet into an extrusion
profile portion and a billet remnant portion;
(c) first measuring means for measuring the longi-
tudinal dimension of the extrusion profile portion;
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~086683
(d) second measuring means for measuring the
longitudinal dimension of the billet remnant
portion; and
(e) computer means receiving the measurements from
said first and second measuring means, said
computer means including
(1) comparison means for generating a first
signal representing the difference between
the first measurement and the given first
longitudinal dimension and a second signal
representing the difference between the
second measurement and the given second
longitudinal dimension; and
(2) control means responsive to said first and
second signals to adjust the predetermined
length of said severing means for the next
succeeding billet, whereby the extrusion
profile and billet remnant produced from the
next succeeding billet will have dimensions
more closely approximating the given first
and second longitudinal dimensions,
respectively.
The method and apparatus according to the invention,
on the one hand, permit a correct preselection of the extrusion
length, thus avoiding the extrusion of unnecessary lengths
of material. On the other hand, a minimum of billet length
or original billet weight is required to obtain the desired
extruded profile length. Together these two aspects afford
the possibility of extruding under optimum utilization of the
material, with the smallest possible amount of waste. Thus
the method and apparatus according to the invention permit
more economic operation than heretofore possible.
Conveniently the individual steps mentioned are
repeated so many times, always using the newest billet length
determined instead of the preselected billet length, that
finally the actuating signal which represents a difference
from a rated value or reference input value of the butt thick-
ness becomes zero. This procedure is typical of a feed-
back control system. In the present case the butt thickness
or the profile length represent the controlled variable,
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depending on whether the desired extrusion length is
reached or failed to be reached during the first pressing,
in other words whether the reaching of the minimum permissible
butt thickness is signalled previously. In the latter event
the deficiency in billet length, i.e. the enlargement of the
billet length required to obtain the desired extrusion
length is determined on the basis of the press ratio which
is defined by the ratio between the pressing pad cross
section and the extrusion cross section.
The feedback control may be effected in consideration
of a correction ratio between the butt cross section and the
- billet cross section of the hot billet.
The controller is connected with a computer in
which the actual data detected by the length recorders are
compared with the reference input values at the end of an
extruding process and processed to form the positioning or
actuating signals. A third length recorder is provided to
detect the billet length. The output signal of this recorder
is also applied to the controller.
Conveniently each length recorder comprises a rota-
tion pulse emitter with counter. Here the longitudinal dis-
placement, which has been converted into rotation in per se
known manner, is sensed in digital manner and transmitted to
the computer in the controller as the actual value.
The positioning element conveniently comprises a
positioning motor which adjusts the longitudinal feed stop by
way of a screw spindle upon receipt of a positioning signal.
The invention and advantageous details thereof will
be described further, by way of example, with reference to the
accompanying diagrammatic drawings, in which:
Fig. 1 is a diagram of the various component parts
of an apparatus according to the invention and their combination
to cooperate in accordance with the method of the invention,
Fig. 2 is a block diagram of a feedback control loop
according to the invention,
Fig. 3 is a flow chart illustrating the course of
the process in an easily understandable sequence of the
individual steps taken.
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In fig. 1 the three principal component parts of the
apparatus, namely a billet hot shearing unit 1, a press 2,
and an extrusion drawing unit 3 are shown only diagrammati-
cally, since they are known per se. The billet hot shear may
be of the design described in detail in German patent
application DE-OS 26 04 418, laid open. From a preheating
furnace 4 a billet 5 is fed to the billet hot shearing unit
by a roller guide means comprising rollers 6 and then passed
through a stationary shear ring 7 and a movable shear ring 8
up to an adjustable longitudinal feed stop 9, including an
abutment roller 10. The vertically movable shear ring 8
serves to cut the material supplied into billets 11 of pre-
determined length "1".
As the longitudinal feed stop 9 i5 adapted to be
displaced in longitudinal direction on a spindle 12 by means
of a positioning motor 13, the length "1" of the billet is
variable. An electronic rotation pulse emitter 14 is coupled
to the positioning motor 13. In combination with a counter
(not shown) it serves for digitally sensing a change in
position of the longitudinal feed stop 9 and thus a
variation in length "1" of the billet, which length "1"
is measured from the shear edge designated O and located
in the vertical plane between shear rings 7 and 8. A first
billet length "1" can be preselected by means of a selector
15.
The sheared-off billet 11 having a length "1" is
supplied to the container 16 of the press 2 where it is pro-
cessed by means of a ram 17, constituted by the extrusion stem
and the pressing pad ahead of the same (not shown), extruding
the billet through a die 18 which has an orifice 19 corres-
ponding to the desired cross sectional shape of the extruded
profile. It is not the entire length "1" of the billet which
is being extruded, but instead a length reduced by the
thickness of the butt Px which corresponds to the press
stroke hx. The butt thickness must not be less than the
minimum permissible butt thickness pO. The optimum rated
value of the butt thickness p which still warrants satisfac-
tory quality of the extruded profile 20 and, moreover,
guarantees that the die 18 is not subjected to undue stress
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1086683
is somewhat greater than the smallest permissible butt
thickness pO.
A length measuring instrument 21, including a
screw spindle 22 which is rotated by advancing the ram 17,
a rotation pulse emitter 24, including a counter (not shown),
a linear scale 25, an indicator 23 moved along with the ram
17 all are associated with the ram 17. Thus the actual
value p of the butt thickness can be determined which is
derived from the press stroke h, as illustrated by block
26 in fig. 1.
The extrusion drawing unit 3 comprises a carriage
32 which is supported on rollers 31 for movement along a pair
of rails 30 arranged in parallel with the extruded profile 20.
The carriage is driven by a motor 34 acting through a chain
33. The extruded profile 20 is grasped by the carriage by
means of a fixed jaw 35 and a parabolic jaw 37 adapted to
swing about a pivot 36, the jaws taking along the extruded
profile until the desired extrusion length Lx has been
reached or the press stroke hx has terminated upon reaching
the minimum permissible butt thickness pO. The actual
length L of the extruded profile is detected by a rotation
pulse emitter 38 associated with the motor 34 and forming
the actual value L (block 39 in fig. 1). The actual values
of the butt thickness p ( from block 26 in fig. 1) and of the
extrusion length L (from block 39 in fig. 1) are applied
to a controller 40 and an associated computer. The controller
and computer also receive the output signal of the rotation
pulse emitter 14, which signal is representative of the
respective billet length "1".
Furthermore, reference input values Px and Lx f the
optimum butt thickness and desired extrusion length,
respectively, are applied to controller 40, these values being
adjustable, for instance, by potentiometers at reference
input adjusters 41, 42. Additional inputs into the controller
40 and computer are fixed adjustment values of the minimum
permissible butt thickness pO, the pressing ratio defined
initially, and the correction ratio likewise defined initially,
the input of these values being effected through corresponding
input means 50, 51, 52. Based on these values the controller
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~086683
40 and computer form a quantitative controller output signal
which is applied from output 43 to positioning motor 13 of
longitudinal feed stop 9 for a corresponding change of the
billet length "1" in a follow-up open loop control. The change
made is reported back to the controller and computer through a
"feedback 1" so as to terminate the adjustment of the longi-
tudinal feed stop 9 as soon as the calculated value has been
attained.
The functioning and mode of operation of the method
and apparatus shown in fig. 1 will be understood by reference
to figures 2 and 3. The block diagram of the feedback control
- loop according to fig. 2 shows the individual blocks of the
feedback control loop with the same designations as used in
fig. 1. The controlled variable is the actual butt thick-
ness p or, in case of insufficient billet length "1", theextrusion length L. The controlled system is formed by the
press 2 and the drawing unit 3. The actual values of the
butt thickness p are determined by the length measuring
instrument 21 or in block 26, while the actual values of
the extrusion length L are formed by means of rotation pulse
emitter 38 in block 39. These values are applied to the
controller 40 and computer to which the reference input
values Px and Lx of the butt thickness and extrusion length,
respectively, are applied as well from reference input
adjusters 41, 42. Further inputs into the controller and
computer are the additional data mentioned, namely the
minimum permissible butt thickness pO, the press ratio, and
the correction ratio. The customary comparison between
rated or reference values and actual values is made in the
controller and computer and, based on such comparison, an
actuating signal generated at the output 43 is applied to
the positioning motor 13 to adjust the longitudinal feed
stop 9 of the billet hot shearing unit 1 and thus vary the
billet length "1" so as to eliminate the actuating signal.
The reference input values Px and Lx are used alternatively.
If the desired extrusion length Lx is reached without
- failure of the press to reach the minimum permissible butt
thickness pO, the reference input value Px Of the butt
thickness is compared in the controller with the actual
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~086683
value of the butt thickness. The billet length "1" then
is increased or decreased in dependence on the actuating
signal~ i.e. in response to a positive or negative difference
between the reference input values and the actual values.
If, on the other hand, the minimum permissible butt
thickness pO is reached before the desired extrusion length Lx
is obtained, the extrusion length Lx is taken as the reference
input value and compared with the actual value of the ex-
trusion length L. In this case the controller and computer
determine the lacking billet length on the basis of the
difference between the actual extrusion length and the
- rated extrusion length, utilizing the press ratio, to
generate a corresponding signal to be applied to positioning
motor 13 for enlargement of the billet length "l".
In detail the course of the individual steps in
applying the apparatus according to fig. 1 may be taken
directly from fig. 3.
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