Laser Deposited and Pre-Hardened Steel Rapid Tooling

Case Western Reserve University / NADCADavid Schwam

Die Cast Aluminum Heat Sinks for Tank Tracks

ABSORBS HEAT FROM THE RUBBER, EXTEND TRACK LIFE, PREVENT STRIP-OFF FAILURE

Material: A380Size:4.5”x2.5”x1.15”Weight: 1.1 pounds

Key Advantage: Short lead time. 49,000 parts (x4) were die cast with this pre-hardened tool.

Industrial Partner: St. Clair Die Casting, St. Clair. MODie Material: Pre-hardened 42 HRC DievarLeadtime: Three weeks

Die Cast Aluminum Heat Sinks for Tank Tracks

Shovel Nut

DLA part.

Industrial Partner: Empire Die Casting-Twinsburg, OHDie Material: Pre-hardened 42 HRC DievarLeadtime: 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 productionwith the prototyping tool, thus saving the entire cost of tooling.

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.

Display Control Module

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 profileObjective• 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 bi-metallic 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

Use of high thermalconductivity materials(laser deposited H13 oncopper, Toolox 44 and Anviloy cores)

Utilization of pre-hardenedadvanced steels to shorten lead-time and lower tooling cost

Utilization of Pre-HardenedSuperior 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 ThermalConductivity Materials:Laser Deposited H13 on

Copper, Toolox 44 and Anviloy cores

Rapid Tooling Method 1

*-Courtesy POM

Direct Metal Deposition of H13 on Copper - the POM Method

Die Cast Part for Evaluation of Improved Cores

The core is surrounded by molten aluminum therefore overheatsand 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 ApproachesCaves 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(downside- slows 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

Axi-symmetric analysis model

Temperature variation along outer surface

300oF constant

1 cycle

cavity fill

solidification

Steel H13

Copper Alloy

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.

Improving Mechanical Propertieswith High Thermal Conductivity Cores

High thermal conductivity, cooledcores in die cast aluminum blocks

32

Effect of Thermal Conductivity of the Shot Block

Material on Cooling Time of Biscuit at 950oF

0

5

10

15

20

25

30

35

0 20 40 60 80 100 120 140

Thermal Conductivity(Btu/ft.h.F)

Coo

ling

Tim

e(s)

H13

Anviloy

3C CuBe

Toolox 44

• 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.

Project Plans

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.

Description Baseline Goal Target Date (Month/Year)

Progress % Accomp.

Toughness•Spray formed

6 ft-lb 8 ft-lb Dec 2008 7.75 ft-lb 87.5%

No. Shots•Pre-Hardened

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

Project Metrics

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

DLA - POC: Dean Hutchins (dean.hutchins@dla.mil, 804-279-5033)

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

Partners:– Case Western Reserve, Twin City Die

Casting, POM, DCD, NADCA, St. Clair Die Casting, Genral Die Casting, Empire Die Casting

Laser Deposited and Pre-Hardened Steel Rapid Tooling