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Metal Foam Injection System
Project 98.5
Design Team Members:
Dina E. Berlingieri
Harminder Parmar
Shawn P. Riley
Stephanie C. Simpson
Project Customer:
Dr. Chin-Jye Yu
Fraunhofer Resource Center – Delaware
Project Advisor:
Dr. Azar Parvizi-Majidi
University of Delaware Department of Mechanical Engineering
Team 98.5
I. Metal Foam Injection System
Team Members: Dina Berlingieri, Harminder Parmar, Shawn Riley, Stephanie Simpson
Customer: Dr. Chin-Jye Yu, Fraunhofer Resource Center – DE
Advisor: Dr. Azar Parvizi-Majidi
Mission: To design, assemble, and test a system that will inject molten metal foam using a control system to maintain a desired temperature.
Project Status:
Over the past few weeks, we have been testing the critical components of our system. To accomplish this, we divided the system in two major parts: the preheating section and the heating section. Our reasoning behind this was because there is a separate heating unit and controller for each part that had to be calibrated for temperature and tested for time.
The preheating section is composed of a ceramic radiant heater, type J thermocouple, high-temperature steel tube with a machined cut-out, solid state relay, finned heat sink, and a user-interface control box. The ceramic radiant heater caused some delay in our schedule because of its 60 V requirement. After some checking around, our advisor, Dr. Parvizi-Majidi, was able to obtain a Variac for us to use in order to step down the voltage. Once we were able to run the heater, we needed a way to control it. The control box consists of a lighted switch, thermocouple junction, and a microprocessor. The microprocessor, with digital display, had to be programmed to correctly disclose the temperature reading taken by the thermocouple. The preheating section was intended to attain a temperature of 425ºC and we were able to do so in approximately 30 minutes. Once that temperature is reached, a billet inserted at room temperature will take approximately 3 minutes to heat.
The microprocessor has also been programmed to control the temperature of the heater; that is, if the temperature should rise above our desired 425ºC, the heater will shut itself off. Likewise, if the temperature should drop, the heater will kick itself back on to keep itself set at 425ºC by way of the solid state relay.
We inserted the steel tube in the heater as we would in our actual system and heated it up to simulate testing. All was going well until we inserted the piston, which would have to sweep through the inside of the pipe – it got stuck! We had accounted for thermal expansion of the two pieces, but not for bending, which is exactly what the clamped tube did about the piston. We were able to successfully separate the tube and the piston without damaging them. We have made allowances so that this does not happen again.
The heating section is composed an induction heating system and an alumina tube. Initially, the induction heating system required most of our attention, since we were unfamiliar with how would operate. We were impressed with how quickly the induction coils heated up and how they cooled down to room temperature at the instant they were turned off. We need to reach a temperature of approximately of 200ºC with the coils. This was no problem during our testing; we reached that temperature in two minutes. Once a workpiece is placed at the center of the coils, the flux increases and the power increases to the maximum of 5 kW, which heats the workpiece in about 30 seconds. We have not foamed any material as of yet simply because of the potential hazard from the exposed system.
Now that we have tested each part of the system, we are ready to assemble the two together and begin inserting the pre-foamed metal billets in and passing them through to commence the foaming process. There is just some minor machining that needs to be done to secure the system in place. All our major tasks other than the actual testing have been completed. We plan to begin the testing procedure on Thursday, April 16.
Schedule:
º Week of April 13:
Complete assembly of system and begin testing with pre-foamed billets.
Make adjustments if necessary.
Show test results to customer.
º Week of April 20:
Wrap up testing procedures.
Film and record experimental data.
Compose an operator’s manual to inform other users how to operate the system.
Visit advisor and invite her to lab for a demonstration.
Present completed working system to customer.
April 24:
Status report due to professors.
º Week of April 27:
Start writing technical reports for customer and professors.
Presentations to NCDA board.
º Week of May 4:
Complete the technical reports.
º Week of May 11:
May 12:
Technical report due to professors.
Submit copy to customer.
Team Members’ Tasks:
All members will be actively engaged in the testing of the system. Individual duties herein are assigned as follows:
A. Dina Berlingieri
Electrical wiring, carpentry, part assembly, report writing, presentation preparation.
Dina’s deadlines: Additional electrical wiring and carpentry as needed. Technical report due May 12, but should be completed by May 8 to be edited by fellow teammates. User manual needs to be completed in time for presentations (week of April 27) so it may be submitted with the system.
B. Harminder Parmar
Update assembly drawing, part assembly.
Harminder’s deadlines: Drawing is to be completed before presentations (week of April 27).
C. Shawn Riley
Part assembly, machining, report writing, presentation preparation.
Shawn’s deadlines: Machining is to be completed by April 15. Report is to be completed by May 8.
D. Stephanie Simpson
Part assembly, machining, report writing, presentation preparation, update assembly drawing.
Steph’s deadlines: Machining is to be completed by April 15. Report is to be completed by May 8. Drawing is to be completed before presentations (week of April 27).
Relevant Figures
Figure 1. Foamed aluminum samples (actual size).
Figure 2. Current Metal Foam Production Schematic.
Figure 3. Hot Melt City, model PSPRAY.
Figure 4. Hwang Sun, model HS1A RP1100.
Figure 5. Gusmer Corporation, model GX-7.
Figure 6. Injection System with Radiant Heater Controls.
Figure 7. Injection System with Induction Heater Controls.
Operating the Metal Foam Injection System
Please use good sense when installing, operating, maintaining, or servicing this injection system by following standard operational safety practices.
Eletrical shock can kill.
• Do not touch live electrical parts.
• Disconnect input power before servicing.
• Keep all panels and covers securely in place.
• Do not overheat parts.
• Watch for fire; keep extinguisher nearby.
• Do not locate unit over combustible surfaces.
• Do not coil or drape cables around the body.
Induction heating can cause injury or burns.
• Do not touch or handle induction head during operation.
• Remove all metal jewelry during operation.
• Allow cooling period before handling heated parts.
Fumes and gases can be hazardous to your health.
• Properly ventilate work area.
• Read Material Safety Data Sheets and manufacturer’s instructions for material used.
Safety Equipment:
Wear dry insulating gloves and safety glasses with side shields.
Disposal:
Recycle or dispose of used coolant in an environmentally safe way.
Preparing System for Use:
Preheating section:
1. Flip switch on control box to turn on radiant heater. Set the variac to 120 V and turn dial to 50%. Heater will start running and will heat until the temperature programmed into the microprocessor is reached. This will take approximately 15 minutes.
Foaming section:
1. Pull down the handle on the breaker box to achieve 480 V at the source. Flip switch on the Versapower unit and set the switch to Remote 14.
2. Turn on the coolant unit.
3. Set remote display box to desired power input. (3 kW)
4. Wait for green light to appear on the remote display box to signal that the induction unit is ready for use.
5. Press yellow button to engage heating action.
Using the Injection System:
1. Insert billet into recessed area of the piston.
2. Place piston into preheating section and align marked line on piston with the end of tube.
3. Allow the billet to remain in the preheating section for ten minutes.
4. Push piston into the foaming section and align the second marked line on piston with the end of the tube.
5. Allow the billet to remain in the foaming section for ten seconds and then gradually sweep the piston through the section. Material may spark during the process; this is completely normal and signifies the release of hydrogen gas from the material.
6. Completely empty the tube by pushing foamed material through and dispense it into desired cavity.
Shut-down Procedure:
1. Depress yellow button on remote panel to halt heating by induction.
2. Turn off the Versapower unit.
3. Flip the switch on the control box to shut off heater.
4. Turn the variac dial down to 0% and flip the switch to “off.”
5. Allow the cooling unit to run for several minutes to cool down the unit.
Do not touch the system, any wires, or the foamed material until they have been allotted enough time for complete
II. Induction Heating Materials Selection
Ceramic Material PropertiesMaterial / Characteristics / Recommended Temperature Resistance
I-COR 995 / Impervious 99.7% fine grained alumina, highly refractory - most stable in reducing temperatures / 1843° C
I-MUL 900 / Impervious mullite porcelain, highly resistant to corrosive atmospheres, devitrification and deformation / 1593° C
Executive Summary
Metal foams are a new class of open cell, low-density materials which the Fraunhofer Institute for Applied Materials Research has developed to produce lightweight structures for a variety of aerospace and industrial applications including thermal insulation and impact absorption. These cellular materials can be simultaneously optimized for stiffness, strength, overall weight, thermal conductivity, and active surface area. They are thermally stable, low in weight and density, chemically pure, and resistant to thermal stress and shock. However, these materials currently cannot be furnished in various sizes and configurations. The present method of production dictates that the foamed material be constructed into flat sheets of various thicknesses, thus limiting the material’s use.
Fraunhofer Resource Center – Delaware is interested in developing an innovative technology for metal foam processing using a heated injection system outside of the traditional closed furnace. This would enable the foamed metals to be installed into various sized cavities, thus removing the major limitations of the current production method.
After considerable analysis, it became apparent that the major drivers in the prototype were the constraints of temperature and time. According to existing knowledge regarding the behavior of metal foams, the aluminum billet would expand to 300% of its original volume during a brief window of time at 600°C. As we examined the heating practices, we came up with the idea to adapt the principles of a simple hot glue gun to our purposes.
We designed an injection system heated by two separate devices: a ceramic radiant heater to preheat the pre-foamed metal and an induction heater to achieve foaming temperature in the metal. Billets ½” X ½” X 6” of Al7Si12 were foamed in the system to completion. Our system solution fell within the acceptable ranges of measurements as specified by our metrics derived from our customer’s wants and constraints.
Consequently, on the material side, our recommendation for FRC-DE is to continue experimentation on materials selection. We had employed alumina and mullite ceramics for our high-temperature, non-conductive conditions, both of which failed during operation. Our suggestion is to use silicon carbide, graphite, or a composite material for the shaft of the system.
The design practices and procedures were optimized for the lowest cost. The total cost of the project, including machined parts, was $28,346.71. This came in at $21,653.29 under budget.
Results from the foaming trials are promising, and have developed insights in how to direct the next generation of our system.
III. Introduction:
A. Background
The Fraunhofer Institute for Applied Materials Research has developed a powder metallurgical process for preparing foam metals. In this process, commercial powders are mixed with small quantities of a powdered foaming agent. As a result, a semi-finished product is obtained in which the foaming agent is homogeneously distributed within a dense, virtually non- porous metallic matrix. This foamable material can be processed into pieces of the desired size and shape by rolling and cutting. Foamed metal parts can be obtained by heating the material to temperatures above the melting point of the matrix metal. The metal melts and the foaming agent releases gas in a controlled way, so that the metal can transform into a semi-solid, foamy mass that expands slowly. The foaming also can take place inside simple closed molds, which then become completely filled by the foam. After the mold has been filled, the process is stopped by simply allowing the mold to cool down to a temperature below the melting point of the metal. Adjusting the content of foaming agent and varying the heating conditions controls the density of the metal foams. The resulting foamed body has a closed outer skin. If the body is cut apart, the highly porous structure becomes evident, as depicted in Figure 1 of Appendix C. Materials such as aluminum and its alloys, zinc, and lead can be formed using this method.
Metal foaming produces materials with unique properties. The density of aluminum foams ranges from 0.5 to 1 g/cm3, and even lower densities can be achieved; thus aluminum foam has the ability to float on water. Because of their porous structures, foams have a high specific stiffness. Electrical and thermal conductivities of metal foams are considerably reduced but still in the typical range of metallic materials. Aluminum foams possess good mechanical damping and sound insulation properties. Metal foams provide excellent energy absorption features at a higher strength level as compared to foamed polymers. Additional properties are the wide range of service temperatures and the inflammability of the material. Finally, the recycling ability of the foamed metals makes the material environmentally friendly, whereas other engineered materials such as composites can pose the threat of becoming landfill waste or later used as aggregate.