Information
-
Patent Grant
-
6516645
-
Patent Number
6,516,645
-
Date Filed
Wednesday, December 27, 200024 years ago
-
Date Issued
Tuesday, February 11, 200321 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 072 53
- 072 57
- 072 60
- 072 40
- 451 38
- 451 39
- 029 907
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International Classifications
-
Abstract
Equipment and methods for the rapid and easy cleaning of metal forming dies while in a press and operating at elevated temperatures. The invention features the physical removal of excess lubricant collecting on the hot surface of the forming dies under operating conditions so that no lubricant-induced flaws occur on the show surface of the formed part for optimized production of high quality parts. Special and effector tooling is supplied with high velocity air which draws in solid CO2 which sublimes into pressurize streams of gaseous CO2 that is discharged through nozzles onto the forming surfaces of hot forming dies after a number of lubricated parts have been formed therewith to physically sweep foreign matter including lubricants from the die surfaces. A robot is employed to move the activated end effector in predetermined paths across the dies for fully sweeping and cleaning the forming surfaces. The gas then dissipates.
Description
TECHNICAL FIELD
This invention relates to the art of cleaning hot forming dies and, more particularly, to new and improved processes for the rapid and contaminate-free cleaning of lubricants and other foreign matter from hot working surfaces of superplastic and quick plastic forming dies to enhance the production of formed sheet metal parts with high quality show surfaces.
BACKGROUND OF THE INVENTION
Prior to the present invention, various processes and types of equipment have been developed to form sheets of alloys of aluminum and other suitable metallic materials into panels or other parts for vehicles or other constructions. Among such process and equipment are super and quick plastic forming processes and equipment in which a ductile metal sheet of suitable metallic material is heated and stretched onto the forming surfaces of a hot die to improve production of high quality parts. Examples of such processes and equipment are found in U.S. Pat. No. 5,974,847 issued Nov. 2, 1999 to Saunders et al. for Superplastic Forming Process, and U.S. Pat. No. 5,819,572 issued Oct. 13, 1998 to P. E Krajewski for Lubricating System For Hot Forming, both assigned to the assignee of this invention and both hereby incorporated by reference.
While such hot plastic forming processes and equipment provide improved parts, production efficiency has at times been diminished because of rejection of some parts for indentations and other irregularities occurring in the show surfaces thereof. Such surface imperfections are primarily caused by the accumulation of foreign matter and particularly dry lubricants used on the blank sheets of material on the hot die during the hot superplastic forming processes. Such matter accumulating on the precision forming surface of the hot die deforms the hot outer surfaces of the part being formed under the loads of the superplastic or quick plastic processes.
SUMMARY OF THE INVENTION
In contrast to the prior art, the present invention provides new and improved methods and mechanisms that meets higher standards for cleaning hot superplastic and quick plastic forming dies while in the press and operating at elevated temperatures. More particularly, the invention is directed to the effective removal of accumulated foreign matter and particularly dry lubricants so that such foreign matter does not effect the formation of flaws such as lubrication marks in the outer surfaces or tears in the bends of the parts formed by the die.
This invention provides new and improved CO
2
hot die cleaning methods with the controlled discharge of dry ice which at least partially sublimes and impinges on the surface of a heated forming die to contact and displace foreign matter from the surface of the forming die so that the forming die can be quickly operated to again produce parts with Class A part surface quality. This invention eliminates lubricant and oxide build-up on the die surfaces and provides a significant improvement in the efficient and quantity production of Class A quality surfaces on metallic parts and panels formed by the dies. Importantly, there is no liquid residue or other consequential pollution produced by this process. The cleaning procedure for dry cleaning forming dies reduces cleaning frequency with minimized CO
2
consumption to provide improved operating efficiency.
This invention further provides a new and improved hot die cleaning unit comprising a special end effector for discharging streams of CO
2
gas and solid mixed into streams of pressurized air onto the hot surface of the die operatively mounted in a press when the press is open. The unit features the quick attachment and release of the end effector to a programmed robot operable to move the discharge end of the end effector across the die in a controlled pattern and at a predetermined distance from the forming surface with optimized discharge of the carbon dioxide and air cleaning mixture to decrease the cycle time required to complete effective cleaning of hot die surfaces during the production cycling of such dies.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features, objects and advantages will become more apparent from the following detailed description and drawings in which:
FIG. 1
is a pictorial view of an opened forming press with forming dies to be cleaned by cleaning equipment according to this invention;
FIG. 2
is a diagrammatic side view of the robot and the attached cleaning unit of the present invention cleaning the profiled hot dies as operatively mounted in the forming press of
FIG. 1
;
FIG. 3
is a pictorial view of a portion of a blank sheet of metallic material to be formed by the die set of
FIGS. 1 and 2
;
FIG. 4
is a pictorial view of the head portion, partly broken away, of the cleaning unit of
FIGS. 1 and 2
;
FIG. 5
is a cross-sectional view taken generally along sight lines
5
—
5
of
FIG. 4
; and
FIG. 6
is an end view of the head of the cleaning unit of
FIGS. 1
,
2
,
4
and
5
.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Turning now in greater detail to the drawings,
FIG. 1
illustrates a forming press
10
comprising a lower bolster plate
12
on which lower steel forming die
14
is mounted in addition to a reciprocating ram plate
16
, which carries an upper tool chamber
18
which basically corresponds to the upper tool of the above-referenced U.S. Pat. No. 5,819,572. Both of the plates
12
and
16
are electrically heated to establish the required heat energy levels in the die and the sheet metal blanks
20
for superplastic forming or quick plastic forming as is known in this art. Moreover, the die steel
14
can be mounted on the upper plate instead of the lower plate and the chamber
18
operatively supported on the lower plate if desired and depending on the characteristics of the part to be made.
The ram plate
16
is moved by hydraulic cylinders
22
to cycle the ram plate from the open position for blank loading to the closed blank forming position and then back to the open shown in
FIG. 1
for formed part removal. The blanks
20
utilized with one preferred embodiment of this invention are flattened sheets
24
of aluminum alloy coated with a dry lubricant
26
such as boron nitride to function as a release agent to prevent the formed panel
30
from sticking to the die and furthermore to enhance the stretching and formation of the part during forming operation. As the parts are being serially formed in the press, quantities of dry lubricant
26
as well as other foreign matter may accumulate on the forming surfaces of the die. This material is diagrammatically illustrated as collected matter
32
in FIG.
6
.
Because of the progressive accumulation of lubricants on the forming surfaces, panels
30
subsequently formed by the dies will likely have surface flaws or imperfections in the form of dimples, streaks, or other blemishes formed thereon. These flaws are diagrammatically illustrated as visible imperfections
33
in FIG.
1
A. Such flaws are generally found by visible inspection and the part scrapped and recycled. In any event, when the part is subsequently cleaned in a wash line, the visibility of such deformities is exacerbated and the part will fail inspection and have to be scrapped.
To eliminate accumulations of lubricant on the die surfaces, the present invention provides a new and improved cleaning tool or end effector
40
comprising a rigid and elongated tubular support
42
having spaced support brackets
44
extending transversely from fixed points therealong. The support brackets fasten to a cylindrical air conducting tube
46
disposed in general parallel relationship with respect to the support tube
42
. A second elongated tube
48
for conducting generally cylindrical pellets
50
of CO
2
(dry ice) is also supported by these brackets or by additional support brackets
51
(
FIG. 2
) extending transversely from fixed points along the air conducting tube
46
to mount pellet conducting tube
48
in general parallel relationship to the rigid support and air tubes.
The support tube
42
of the end effector
40
is provided with a conventional quick release coupling
52
at the inboard end thereof for selective operative connection with an arm
53
of a programmed robot
54
which is capable of moving to any position along rails
55
supported by the floor. After moving from an out-of-way station to a predetermined position adjacent to the press in a die cleaning operation, the robot arm activates to move the end effector
40
into an operative cleaning position relative to the forming die. More particularly, the discharge end or cleaning head
62
at the free end of the end effector is pointed to and is located at a given height above the forming surfaces of the die and in the limited space between the lower steel forming die and the upper tool chamber supported in the opened press.
The end effector with its cleaning head operating is then longitudinally and laterally moved in a predetermined sweeping pattern and at a predetermined and variable distance with respect to the varying contours of the forming die. This movement is in accordance with the programmed robot to effect the dry cleaning of the hot die with the ejected streams of CO
2
and air as will be further explained hereinafter. Moreover, the robot can turn the end effector and the cleaning head to any angular position about the horizontal axis A of the support tube so that any tooling supported by the plates of the press can be readily cleaned as needed. After such cleaning, the robot withdraws the end effector from the die and out of the press. The robot then takes the end effector to a storage station and releases it from the arm
53
by operation of the quick release coupling
52
so that it is available for further duties.
The air tube
46
has a connector
56
at its inboard end for releasable connection with a flexible air supply hose
58
leading from a pressurized and controlled air supply source
60
to the cleaning head
62
fixed to the outboard end of the air tube. As shown, the head
62
extends at a given angle such as 90 degrees with respect to the air and pellet conducting tubes
46
and
48
to afford improved support and improved aiming of the cleaning head
62
with respect to the forming surfaces of the forming die for augmenting the cleaning of the forming die.
More details of the cleaning head
62
are shown in
FIGS. 4
,
5
and
6
in which the outboard end of the air conducting tube
46
is rigidly secured to a transversely extending manifold
64
, in turn fastly secured to the inner side of a thick and flattened base plate
65
of the head
62
. The manifold pneumatically connects to and feeds high velocity streams of air into the four laterally-spaced inlets
66
formed in the base plate that further connects into four finger-like internal cleaning agent flow passages
68
,
70
,
72
,
74
that generally extend along the length thereof. The internal flow passages respectively terminate in laterally spaced discharge openings or nozzles
68
′,
70
′,
72
′,
74
′ at the outboard end of the base plate for discharging mixed streams of pressurized carbon dioxide gas and pellets and air onto the surfaces of the dies set for cleaning purposes. The cleaning head is closed by a bottom plate
76
secured to the base plate by suitable fasteners
78
.
The elongated pellet conducting tube
48
of the end effector
40
transmits CO. pellets
50
from a pellet supply container
82
and connecting hose
83
into the head
62
of the end effector. The outboard end of the CO
2
pellet conducting tube
48
operatively connects onto the head
62
by four pellet feeding tubes
84
,
86
,
88
and
90
that operatively connect to fittings
92
of a connector block
94
mounted on the head
62
and then through vertical passages in a portion of the base plate
65
of the cleaning head and respectively into corresponding flow restricting or venturi sections
96
of the cleaning agent passages
68
,
70
,
72
,
74
.
With high velocity air being fed into the cleaning head
62
from a pressure source
94
, a low pressure occurs in the restricted section of passages so that pellets
50
of dry ice will be drawn therein and begin to sublime into carbon dioxide gas. This mixture of CO
2
gas and remaining CO
2
pellets plus air is forced in high pressure streams S from the discharge nozzles
68
′,
70
′,
72
′ and
74
′ for sweeping and cleaning the foreign matter here identified as accumulated lubricant
32
from the forming surfaces
31
of the die
14
.
FIG. 2
illustrates the end effector
40
being picked by the operating arm
53
of the robot
54
using the quick connect coupling
52
and moving the end effector into cleaning positions such as P
1
through P
4
between the forming die and upper tool chamber as maintained by the press such as during a cleaning operation and after a number of parts have been produced. Preferably, the robot is programmed to move the end effector in a sweeping manner such as diagrammatically illustrated. During such motions, the nozzle or discharge end of the cleaning head is maintained six to eight inches above the profiled surface of the forming dies
14
. The same clearance is observed in cleaning the upper chamber if needed or an upper mounted forming die.
When the cleaning head of the end effector is in an initial position such as position P
1
, high-pressure air will then be supplied from the pressure sources and the associated hose into the air tube
46
. Pressure air then feeds into the manifold
64
. Streams of air then pass through the four laterally spaced inlet passages
66
in the base plate
65
of the cleaning head
62
and then into the corresponding four finger-like cleaning agent passages in the head and out of the nozzles. With low pressure areas provided by the venturi sections of these passages, dry ice pellets are forced from the supply unit
82
through hose
83
and into the pellet conducting tube
48
. From the tube
48
, the pellets of dry ice will be fed into the venturi sections where the solid pellets of carbon dioxide begin to sublime into carbon dioxide gas. This gas plus solid parts of pellets that have not yet sublimed mix with the air streams and are projected by the nozzles as pressure streams of cleaning agent onto the surface of the die. This cleaning agent flows across the surface of the die and sweeps away the build up of lubricants from previous forming of parts from the blank as well as any foreign matter falling or otherwise getting into the die.
With a mixture of air and carbon dioxide gas and remaining subliming pellets gas being used, a dry and substantially pollution-free cleaning agent is advantageously employed which cannot abrade or otherwise damage the hot forming surfaces of the dies. The remaining portions of the CO
2
pellets sublime during the cleaning operation. This invention accordingly simplifies production and effectively reduces or eliminates subsequent cleaning up of cleaning agent and attendant disposal problems, particularly since no liquids are involved.
In one preferred embodiment, the air supply pressure is in the range of 60 to 300 psi. The dry ice pellets are originally about ⅛ inch in length, and the distance from the nozzle tips to the die forming surface was in a range of 4 inches minimum to 8 inches maximum.
While some preferred methods and mechanisms have been disclosed to illustrate the invention, other methods and mechanisms embracing the invention can now be adapted by those skilled in the art. Accordingly, the scope of the invention is to be considered limited only by the following claims.
Claims
- 1. A method of superplastic and quick plastic forming sheet metal parts which are substantially free of show surface imperfection comprising the steps of heating a profiled metal forming die to a predetermined temperature range, inserting a sheet of lubricated metal stock onto the forming die, forcing the metal sheet onto the profile of the forming die to form a part, removing the formed part from the forming die, serially repeating the forming of parts until a number of parts have been produced, moving a die cleaning head in a predetermined pattern across the forming surface of the hot die, discharging mixed streams of carbon dioxide gas and solids and air onto the forming surface of the die while the head is moved in said pattern to physically force any build up of foreign matter including dry lubricant from the hot die surface while allowing the solid carbon dioxide gas to fully sublime, repeating the insertion sheet metal stock onto the cleaned forming die and forming additional parts free of deformation from lubricant build up on the forming surface thereof.
- 2. A method of cleaning heated superplastic and quick plastic forming dies after forming a plurality of sheet of metal stock each having a coating of dry lubricant thereon into substantially identical components having a show surface comprising the steps of: moving the cleaning head across the forming surface of an operationally hot forming die, discharging streams of carbon dioxide solid and gas mixed with streams of pressurized air onto the surface of said die to force the collected lubricant and other foreign matter from the forming surface of the forming die to thereby clean the die for subsequent continued operations to make additional parts without resulting surface flaws.
- 3. An end effector for cleaning the heated forming surfaces of a heated forming die set while operatively mounted in a press and moveable between opened and closed positions comprising an elongated support having a connector on one end thereof for operative connection with an actuator for moving the support relative to the dies in the press, an elongated air conducting tube secured to the support and co-extending therewith, an elongated tube extending alongside of said air conducting tube for conducting dry ice pellets therethrough, a head member operatively fixed to the end portions of said air and pellet conducting tubes to receive respective flows of air, said air tube and pellets from said pellet conducting tube, said head having a plurality of channels therein for direction sublimed pellets into a plurality of stream of gas and solid pellets directly onto the surface of said die that act on quantities of lubricant collected thereon and displacing said lubricant therefrom to thereby clean excess lubricants from said forming surfaces of said die set so that said die set can produce parts without lubricant accumulation defects.
- 4. An end effector for cleaning the heated forming surfaces of forming dies sets while operatively mounted in a press and moveable between opened and closed positions comprising an elongated support having a connector on one end thereof for operative connection with an actuator for moving the support relative to the dies in the press; and elongated dry ice pellet conducting tube extending alongside of said air conducting tube, a head member operatively fixed to the end portions of said air and pellet conducting tubes to receive respective flows of air, said air tube and dry ice pellets from said pellet conducting tube, said head having a plurality of channels therein for directing sublimed pellets into a plurality of stream of gas directly onto the surface of said die that act on quantities of lubricant collected thereon and displacing said lubricant therefrom to thereby clean excess lubricants from said forming surfaces of said die set so that said die set can produce parts without lubricant accumulation defects.
US Referenced Citations (10)