Extrusion die

Details Extrusion die Extrusion die

2001-11-02

2004-06-15

Tolan, Ed (Department: 3725)

Metal deforming

By extruding through orifice

Pressure or velocity conditioning

C072S269000, C072S467000, C076S107400

Reissue Patent

active

RE038534

ABSTRACT:

TECHNICAL FIELD
The present invention relates generally to extrusion dies and a method for designing extrusion dies. More particularly, the present invention relates to a method for designing and manufacturing an extrusion die that permits faster extrusion speeds. Specifically, the present invention relates to an aluminum extrusion die having a variable, continuous bearing and a pocket that cooperate to improve material flow into the die to allow faster extrusion speeds.
BACKGROUND OF THE INVENTION
Extrusion is the process of forcing material through a die having an extrusion profile to form a product having a cross section that matches the extrusion profile. The length of the extruded product is determined by the amount of material forced through the die. A typical aluminum window frame may be fabricated from extruded rails and stiles. A typical rail or stile has a relatively complicated cross section including a plurality of arms extending from a common spine. Additionally, each of the arms may have a plurality of members extending therefrom. In the past as the extrusion profile became more complex, the speed of the extrusion process had to be reduced to maintain a high quality product.
A depiction of a typical extrusion die known in the art may be seen in FIG.
1
. The prior art extrusion die, indicated generally by the numeral
210
, generally includes a die body
212
having an upstream face
214
and a downstream face
216
with a cavity
218
extending toward the upstream face
214
from the downstream face
216
. An extrusion profile
220
is cut from the upstream face
214
through the die body
212
to the cavity
218
. A wall
222
parallel to the upstream
214
and downstream
216
faces extends between the extrusion profile
220
and the cavity
218
. This wall
222
can also be referred to as the undercut
222
of the die
210
. The depth of the extrusion profile
220
is referred to in the art as the die land or the die bearing
224
. The die land or bearing
224
is the portion of the die
210
that the material contacts as it is force through the die
210
. Such contact causes friction that creates heat and negatively affects material flow.
The length of the bearing
224
and the length of the undercut
222
affect the strength of the die
210
. The strength of the die
210
is important because the die
210
is subjected to high pressures and high temperatures during the extrusion process. If the material surrounding the extrusion profile
220
is weak, the quality of the product is negatively affected. To increase the strength of the die
210
, a longer bearing
224
and a small undercut
222
may be used. A long bearing
224
, however, decreases the speed of the die
210
because of the friction created by the long bearing
224
.
Thus, it is desirable to minimize the length of the bearing so that the maximum extrusion speed may be achieved while maintaining adequate strength for the die. Maximizing extrusion speed is extremely important to the extrusion industry because a die may be used to create miles of product over its lifetime. Thus, even a small increase in extrusion speed yields large benefits to the manufacturer.
Another feature of known dies
210
is a cavity
230
formed in the upstream face
214
of the die
210
to facilitate consecutive billets. Consecutive billets are required when the desired length of the product is longer than the capacity of the extrusion processor. To allow consecutive billets, a cavity
230
is carved out of the upstream face
214
of the die
210
around the extrusion profile
220
. When the ram of the extrusion processor approaches the upstream face
214
of the die
210
, the billet is cut and a portion of the extrusion material remains in the cavity
230
. When the billet is cut, the act of cutting creates a force that tends to pull the material remaining in the cavity
230
back out of the die
210
. To prevent the material from being pulled entirely out of the cavity
230
, the cavity
230
is relatively deep. The depth is such that the angle indicated by the numeral
232
is typically less than 45 degrees. The depth of the cavity
230
prevents the cutting force from pulling the material all the way out of the die
210
. Once the material is cut, the ram is then pulled back and another billet is inserted. The new billet welds itself to the material left over in the cavity and the extrusion process is continued.
The depth of the cavity
230
negatively effects the performance of the extrusion die
210
. When the angle
232
formed by a line normal to the upstream face
214
at the corner of the cavity
230
and a line taken through that corner and the corner of the extrusion profile
220
and the bottom
234
of the cavity
230
is less than 45 degrees, the flow through the die
210
is restricted. As the material is forced against the die
210
in the extrusion processor, areas of material are forced into the corners and essentially stay in the corners during the extrusion process. This area is known as a dead area of flow and is indicated generally by the numeral
236
in FIG.
1
. The dead area
236
creates friction between the rest of the flow and itself. A deep cavity
230
causes an additional dead area to form, as indicated by the numeral
238
. The deep cavity
230
also acts as an additional length of bearing where the flow may flow against the cavity walls, as indicated by the numeral
240
. The additional friction created by the dead area
238
and the extra bearing
240
is undesirable because it creates heat which degrades the surface finish of the final product. To reduce the affects of friction, the extrusion processor is run at slower speeds.
To design such a conventional die, a die designer typically relies on a trial and error method. The success of the die design often depends on the knowledge and experience of the die maker. A die is currently manufactured by first determining the desired profile of the final extruded product. The profile is then cut out of the die body. When the die designer first cuts the profile, the designer intentionally leaves the bearing longer than desired so that bearing length may be removed. If needed, after a test run. The die is then placed in an extrusion processor and run through a series of tests. If the die functions properly, the die is then used to create final products. A problem with this method is that the bearing of the die has been left intentionally long and the die must be run at slow speeds.
If the designer discovers problems with the die during the test runs or desires a faster die bearing, the designer takes the die out of the processor and makes adjustments. The magnitude of these adjustments often depends on the knowledge and experience of the designer. One typical adjustment that may be made is the removal, or shortening of the bearing. The known methods for removing bearing are to shorten the entire bearing or to shorten a portion of the bearing to create a stepped bearing. Once this has been done, the die is repositioned and additional tests are performed. One problem with creating a stepped bearing is that a die having a stepped bearing forms a product with surface lines at the location of the bearing step. Such lines are undesirable and must be removed by a further process.
The reconfigurations and tests are repeated until a satisfactory product and extrusion speed are attained. It should be noted that bearing length cannot be added back to the die after it has been removed. Thus, if too much bearing is removed, the die must be scrapped and the process repeated. For this reason, the die bearing is always left longer than necessary. The added length causes the extrusion processes to be run slower than possible. Even a knowledgeable die designer with significant experience typically requires approximately three tests to create a satisfactory die. The number of runs and the labor required to perfect the die undesirably increases the costs of forming the die.
SUMMARY OF THE INVENTION
It is therefore, a primary object of the present invention to

Affiliated with

Also associated with

Rating

Extrusion die does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Extrusion die, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Extrusion die will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3324877