Transcript Laser Deposited and Pre-Hardened Steel Rapid Tooling

Laser Deposited and Pre-Hardened
Steel Rapid Tooling
Case Western Reserve University / NADCA
David Schwam
Die Cast Aluminum Heat
Sinks for Tank Tracks
Material: A380
Size:4.5”x2.5”x1.15”
Weight: 1.1 pounds
ABSORBS HEAT FROM THE RUBBER, EXTEND
TRACK LIFE, PREVENT STRIP-OFF FAILURE
Die Cast Aluminum Heat
Sinks for Tank Tracks
Industrial Partner:
St. Clair Die Casting,
St. Clair. MO
Die Material:
Pre-hardened 42
HRC Dievar
Leadtime:
Three weeks
Key Advantage: Short lead time. 49,000 parts (x4) were die
cast with this pre-hardened tool.
Shovel Nut
DLA part.
Industrial Partner: Empire Die Casting-Twinsburg, OH
Die Material: Pre-hardened 42 HRC Dievar
Leadtime: Three weeks (instead of 14 weeks)
Key Advantage: Two hundred prototype parts were
initially required. Production run is expected to exceed
100,000. So far at 49,000. The projects is running production
with the prototyping tool, thus saving the entire cost of tooling.
Display Control
Module
DRS’s Driver’s Vision Enhancer (DVE) Display Control Module
(DCM) is a 10.4" liquid-crystal display (LCD) providing a rugged
display technology to the warfighter on today’s digital battlefield.
Warfighter Relevance
Objectives
Problem
• Current tool building practices are costly and time
consuming
• require sequential rough machining
• heat treating
• machining to final size
• use steel that does not allow fast heat removal and
optimal control of the thermal profile
Objective
• Demonstrate rapid tooling methods
• Use of pre-hardened steels to shorten lead times and
extend die life
• Use of high thermal conductivity materials including
Toolox 44, Anviloy and laser deposited rapid and bimetallic tooling to improve rate of production
Benefits
• Accelerate fabrication of parts made by metal
mold technologies
• Rapid tooling for die and permanent mold
casting
– More adaptive to frequent changes in design than
traditional tool making methods
– Can quickly provide small, prototype batches yet, if
needed, make production quantities
• Demonstrate increased productivity and better
mechanical properties of the castings by use
of high thermal conductivity die materials
Technical Approach
Utilization of pre-hardened
advanced steels to shorten
lead-time and lower tooling
cost
Use of high thermal
conductivity materials
(laser deposited H13 on
copper, Toolox 44 and
Anviloy cores)
Utilization of Pre-Hardened
Superior Steels to Shorten
Lead-Time and Lower Tooling
Cost
Display Control Module
Implementation at Twin
Cities Die Casting
• Anticipated production was 40,000 parts
• Using Pre-hardened tool steels of various
types. Heat treat was 40 – 42 RC.
• Machining method was primarily High
Speed but some Electro-Discharge
Machining also.
Project Volume Increased
• Original plan was to cast no more than
40,000 parts.
• Tooling started to show some washout
and heat checking around 20,000 shots.
• Notified by customer that there would be a
second order coming after completing the
first 40,000 parts.
Heat Check and Washout
Inside after 24,000 shots
Heat Checking Outside after
24,000 Shots
Steel Repair Method
• Steel checked for hardness. Steel had
softened through usage to 39–40 HRC
down from 40-42 HRC.
• Cavity steel was ultrasonically cleaned,
machined, welded and re-cut, polished
and then nitrocarburized after 28,000
shots.
• Repair lasted balance of first order.
After Repair at 38,000
Shots
After Repair at 38,000
Shots
Tool Steel after First 40,000
Shots
Next Order is Being
Processed for 20,000 Parts
• Steel has been polished and then Shot
Peened.
• Nitride re-applied after last maintenance.
• Steel checks 39–40 HRC; no change
from 20,000 shots.
• Estimated life to replacement is another
40,000 shots.
• Cost and time metrics needed
Use of High Thermal
Conductivity Materials:
Laser Deposited H13 on
Copper, Toolox 44 and Anviloy cores
Rapid Tooling Method 1
Direct Metal Deposition of H13 on Copper - the POM Method
*-Courtesy POM
Die Cast Part for Evaluation of Improved Cores
The core is surrounded by molten aluminum therefore overheats
and solders. Extracting heat more efficiently from the core can
lower temperature, prevent soldering and allow shorter cycle times.
H13 Deposited on Cu – ready for machining
H13/ Copper Core after
250 cycles
The core creeps due to insufficient stiffness and
strength at high temperature.
Remedial Approaches
Caves in
Bulges out
The distortion of the
core seems to originate
from insufficient strength
and stiffness at the
operating temperature.
Anviloy and H13 cores
do not suffer from this
problem.
Priority 1 - Increase strength: use core as deposited
w/o tempering (downside-lower toughness).
Priority 2 - Increase thickness of H13 layer(downsideslows down heat transfer). Use computer
simulation
Technical Progress
• The life of the laser deposited core has
been extended to 5,000+ shots.
• A computer modeling effort is underway
to optimize the thickness of the laser
deposited H13 layer.
• Other high thermal conductivity die
materials (Toolox 44, Anviloy) are being
tested.
• A current NADCA/NEMAK/GM project is
leveraging this effort.
Finite Element Model
Steel
H13
solidification
cavity
fill
1 cycle
Copper
Alloy
300oF constant
Axi-symmetric analysis model
Temperature variation along
outer surface
Temperature and stress field at the end of
cavity fill (deformation is enlarged by 100)
Temperature (oF)
σVon Mises (Psi)
Project Plans
• High cooling rates the mechanical properties.
Shown is the improvement in Dendrite Arm
Spacing (DAS) and respective tensile strength
caused by a water cooled core.
Average DAS (microns)
40
35
30
25
20
15
10
5
0
-10
10
30
50
Distance from cooling core (mm)
70
Improving Mechanical Properties
with High Thermal Conductivity Cores
High thermal conductivity, cooled
cores in die cast aluminum blocks
Effect of Thermal Conductivity of the Shot Block
o
Material on Cooling Time of Biscuit at 950 F
35
H13
30
Toolox 44
Anviloy
Cooling Time(s)
25
20
3C CuBe
15
10
5
0
0
20
40
60
80
100
120
Thermal Conductivity(Btu/ft.h.F)
32
140
Project Plans
• Continue Utilization of Pre-Hardened
Superior Steels to Shorten Lead-Time and
Lower Tooling Cost for Control Display
Module
• A computer modeling effort is underway to
optimize the thickness of the laser deposited
H13 layer.
Implementation
Conclusions
• Use of high conductivity alloys in die components can
shorten cycle time significantly.
• In the present case, the cycle time dropped from 55 sec.
for H13 to 40 sec.(13% )
• The life of a tempered, 40HRC H13/ Copper laser
deposited core was 250 cycles. By using the core in the
as-deposited condition at 51HRC, life was extended to
5,000+ cycles and going.
• The balance between strength and toughness is critical to
ensure durability of the core. High strength is required to
prevent distortion while high toughness avoids cracking.
Project Metrics
Description
Baseline
Goal
Target Date
(Month/Year)
Progress
% Accomp.
Toughness
•Spray
formed
6 ft-lb
8 ft-lb
Dec 2008
7.75 ft-lb
No. Shots
•PreHardened
10,000
shots(P20)
30,000
July 2009
20,000 in progress
50%
Enhanced
cooling
•Spray
formed – Die
Temperature
Die Surface
800oF
Die
Surface
700oF
July 2010
720oF
80%
Improved
Elongation
•Cooled core-
0.5%
2%
July 2010
New task for
2009/2010
87.5%
JDMTP Criteria - Summary
Jointness
B – Benefit to more than one service, but not jointly funded
Needs and Benefits
• Needs : Short lead times for rapid prototyping and legacy parts.
• Benefits: Up to 75% shorter lead time, depending on the part.
• Benefits: 20% shorter cycle time
Transition
• Parts under evaluation at Empire Die Casting-2007
• Parts under evaluation at St. Clair Die Casting-2007
• Production of new part at Twin City Die Casting
• Composite cores in production at General Die Casters
• Results disseminated through NADCA committee meetings,
NADCA publications for industry, and the Metalcasting Congress
Leveraging
• Building on previous AMC and NADCA/DOE work
• Leveraged by current NADCA/NEMAK/GM project
Relevance to Sustainment of
Weapons Systems
• Strengthen supply chain by increasing number of metal mold
suppliers able to meet DLA requirements.
• Shorten lead time for procurement of components for legacy
systems.
• Improved mechanical properties of components.
MRL
6 - Manufacturing capability to produce in a production
representative environment
Laser Deposited and Pre-Hardened
Steel Rapid Tooling
DLA - POC: Dean Hutchins ([email protected], 804-279-5033)
Partners:
– Case Western Reserve, Twin City Die
Casting, POM, DCD, NADCA, St. Clair
Die Casting, Genral Die Casting, Empire
Die Casting
Problems:
• Standard tooling for metal mold processes requires
long lead times
• High cycle times in the production of metal mold
castings
Objective:
• Evaluate advanced cooling techniques and rapid
tooling techniques to reduce lead times
Benefits:
• Demonstrate increased productivity by utilizing rapid
tooling techniques and improve properties by
incorporating high thermal conductivity die materials
Milestones / Deliverables
• Evaluation of toughness and thermal fatigue of dies
with deposited materials
• Optimization of laser deposited H13 layer
Transition Plan
• The optimized laser deposited cores will be
evaluated in production