1. Introduction
1.1Client Profile
1.2Problem Statement
1.2.1 Sub-Problems
2. Project Definition
2.1 Mission Statement
2.2 Constraints
2.2.1 Equipment
2.2.2 Cost
2.2.3 Time
3. Project Organization
Introduction
3.1 Project Management Plan
3.1.1 Work Breakdown Structure
3.1.2 Meeting Schedule
3.1.3 Rules
3.1.4 Task Assignment
3.2 Documentation
3.2.1Standards
3.3 Communication
4.Design Concepts
4.1Plumbing and Piping Hardware
4.1.1Plumbing and Piping Hardware on Hand
4.1.2Additional Plumbing Equipment Needed
4.1.3High Temperature Vacuum Chamber
4.2High Temperature Vacuum/Pressure Chamber Design
4.2.1Material Selection and Design Concepts
4.2.2Sealing Vacuum Chamber
4.2.3Testing
4.2.4Connection into the Powder Metallurgy System
4.3Self-Sealing Container
4.3.1Solder material
4.3.2Testing
4.4Fixture Design
4.4.1Material
4.4.2Fixture Features
4.5Nitrogen System
4.5.1Flow meter
4.5.2Pressure Relief Valve
4.6Temperature and pressure monitoring
4.6.1Thermocouple
4.6.2Pressure/Vacuum transducer
4.7Vacuum and Filtration System
4.7.1Vacuum pump
4.7.2Inline Filter
4.8Cooling considerations
5.Appendix
6.Bibliography
Executive Summary
This report discusses the current state of the powder metallurgy (P/M) project and gives recommendations for further actions. The powder metallurgy project includes the design of many sub-systems. There are several options for each sub-system and it is important that the advantages and disadvantages of each option are analyzed. Choosing the best option will require continued research and testing. The Powder Metal Militia has analyzed the existing problem and has come up with a number of practical solutions. The two main areas of design are the vacuum chamber and the self-sealing container.
Vacuum Chamber
The original vacuum chamber had a seal which would not meet our temperature requirement for the sintering process. Buying a vacuum chamber that would meet the temperature requirements was investigated. Many different vacuum supply companies were contacted, but the vacuum chamber’s that they offered were very expensive and still did not meet our high temperature sealing requirements. The Powder Metal Militia recommends designing a custom vacuum chamber to meet the projects design requirements. As a team, we have met with Darrell Andersen and have preliminary CAD drawings for the vacuum chamber. Currently, the vacuum chamber will be sealed by a , however, many other sealing options are being researched. Upon finishing the seal design, Darrell can begin fabricating the vacuum chamber.
Self-Sealing Container
The design of the self-sealing container has been extensively researched. The self-sealing container will be made using the available aluminum tubing as required by our client. However, the method of sealing the container is still unresolved. Our team has been in contact with multiple solder and adhesive companies. Also a method of testing the self-sealing container is being developed. At this point we are waiting on getting some solder samples so we can begin testing their sealing capabilities.
Further Actions
There is a lot of work to be done on this project. Many parts of the powder metallurgy system still need to be ordered, designed, or finalized. The Powder Metal Militia plans on continuing to research and test alternatives in order to arrive at the best powder metallurgy system possible within our budget, time, and design constraints.
1. Introduction
Powder metallurgy is the process of producing a metal part by pressing a metal powder into a die and sintering the powder until it forms a solid with nearly the same dimensions as the original pressed metal. The three basic steps to make aluminum P/M parts are:
1.)Precisely mixing aluminum powder with other alloys to a desired ratio.
2.)Degassing the aluminum powder mixture in a heated vacuum chamber.
3.)Pressing the degassed aluminum and sintering it in a controlled atmosphere until the mixture reaches the desired properties.
Aluminum P/M parts are desirable because they are lightweight, corrosion resistant, and high in strength.
1.1Client Profile
Powder Metal Militia is developing an aluminum P/M system under the direction of Dr. Bill Pedersen. Dr. Pedersen is a professor at the University of Minnesota Duluth and would like to incorporate the P/M system into the engineering department’s lab courses. Students enrolled in the lab would be able to learn hands on about powder metallurgy and produce their very own P/M specimens. The students could test the P/M and develop ways to improve the existing process.
1.2Problem Statement
Design a controlled atmospheric system for powder metallurgy applications. The final product will be a complete powder metallurgy system with the ability to produce a degassed powder metal specimen.
1.2.1 Sub-Problems
1.)Designing the plumbing and acquiring hardware for the vacuum system.
- Additional pipe sections
- Heat transfer calculations for vacuum pump inlet
- Welding pipe
- Monitoring temperature and pressure of system
- Filtering system before vacuum
- Nitrogen system
2.)Designing the system to be safe under all conditions.
- Safely dispensing metal powder
- Fire and electrical hazards
- Vacuum and pressure safety considerations
- Researching industry standards
3.)Designing a self-sealing degassing can.
- Researching and testing different types of solder
- Research lid designs
- Experiment with sealing lid designs
- Research the use of a localized heating element
4.) Designing or purchasing a vacuum chamber
- Research vacuum chambers available in industry
- Design a custom vacuum chamber
- Pick best alternative based on cost, time, and performance requirements
2. Project Definition
2.1Mission Statement
2.2 Constraints
2.2.1 Equipment
Some of the equipment needed to complete this project has been supplied by our client. We are expected to use this available equipment to keep the overall project cost down. For example, there may be a better vacuum pump for the degassing application, but we will have to make the vacuum pump we have work.
The extreme temperature conditions during the sintering and degassing phases also limit the possible materials used for the design of the vacuum chamber as well as the connections within the plumbing.
2.2.2 Cost
Although a budget has not been set, the cost of equipment will come into play when the final design decisions are made. It is important that the equipment purchased is high-quality in order to ensure the operation of the system for years to come.
2.2.3 Time
The Powder Metal Militia has approximately eight weeks to complete our remaining goals. Many hours of work outside the class will be necessary to meet our objectives. Design decisions will have to be made based on the information available at the given time.
3. Project Organization
Introduction
3.1 Project Management Plan
Our team’s project management plan is divided into three distinct phases. Phase 1, or the Project definition phase, consists of initially meeting with other teammates, receiving the scope of the project, dividing the project into different sub assemblies, assigning those sub categories to team members, and brainstorming possible solutions to each sub category. Our team completed phase one Friday February 9, 2007. Phase 2, or the Research and Design phase, consists of each team member doing research relevant to their assigned sub category, building CAD models of the proposed designs, writing and presenting our baseline report, and ordering parts for the various sub categories once the proposed designs have been approved. By following our current timeline, phase two should be completed no later than Tuesday March 27, 2007. Phase 3, or the tying it all together phase, consists of building the sub assemblies, testing the systems, combining all of the systems into a working prototype,producing a powder metal specimen, writing the final report, and giving the final presentation. Phase three should be completed no later than Friday May 11, 2007.
Figure 1: Proposed Timeline
Figure 2: Timeline of Project
3.1.1 Work Breakdown Structure
The work breakdown structure details all of the sub assemblies that make up the entire project. The sub systems are the steps that need to be performed in order to successfully complete the system.Currently our team is at step 4 in the self sealing container sub category, step 3 in the nitrogen system sub category, step 4 in the vacuum and filtration system sub category, step 3 in the general design sub category, step 3 in the fixture design sub category, and step 3 in the cooling system category.
Figure 3: Work Breakdown Structure
3.1.2 Meeting Schedule
Team meetings are scheduled for every Monday and Thursday to report project updates and discuss project development. Meeting times and locations are scheduled in advance during the previous meeting. Meetings with our client are generally held after our team meetings.
3.1.3 Rules
Our team has a couple general rules to ensure that each team member is performing the work they are assigned. During meetings each team member must give a project update and inform the team what areas of the project the member is pursuing. If a team member misses or needs to be excused from a meeting, they must notify in advance the rest of the team and explain why they can’t make the meeting. Unexcused absences from team meetings or failing to perform their portion of the work will affect the team member’s performance evaluation at the end of the term.
3.1.4 Task Assignment
Our team decided to break up the work for the project as evenly as possible with each team member assigned to different sub projects so our team can piece them all together to complete the project. The chart below is a breakdown of the work assigned to each team member.
Task List / Andy / Jeff / John / Sean / Due DateCad Drawings / X / 2/12/2007
Shop for possible Vacuum Containers / X / X
Research Cooling Canister Capabilities / X
Plumbing and Collars / X / X
High-temp O-ring Research / X
Poster for Engineering Week / X / X / X / X / 2/12/2007
Gauges and Thermocouples / X / X / X
Pressure Transducer / X
Self-Sealing Degassing Can Research / X / X / X / X / 3/5/2007
Baseline Report and Presentation / X / X / X / X / 2/12/2007
Work-Order for Heater Rewiring / X / 2/192007
Particle Sizing and Filter Research / X
Fixture For Degassing Can / X
3.2 Documentation
The process being used for document control includes a filing bin located in the senior design lab. Each team member is responsible for filing all relevant documentation used for research and design of the project. This provides each team member with complete access to all related documentation, regardless the presence of other team members. Team members are also required to keep electronic copies of all filed documents. Furthermore, each team member is responsible for recording all sources of information.
3.2.1Standards
The standard used to this point in the design is the B243 ASTM standard. This standard is a glossary of powder metallurgy terms. Future standards that could be used to produce test specimens for gathering material properties are:
- B925-03, Standard Practices for Production and Preparation of Powder Metallurgy test specimen.
- B331-95, Standard Test Method for Compressibility of Metal Powders in Uniaxial Compaction. This standard explains methods for measuring the density of green powder specimens.
3.3 Communication
The preferred method of communication within the group is e-mail. All e-mails sent must be carbon copied to each team member.
- Design Concepts
4.1Plumbing and Piping Hardware
The plumbing and piping hardware was supplied primarily from donated sources. The donated equipment came without any specification sheets; this required researching the capabilities and compatibilities of the existing equipment. All of the plumbing and piping (with the exception of two manual valves) are MDC vacuum products. We were able to obtain technical specification sheets from the manufacture and it was determined that the rubber o-ring seals were only rated for use below 200 ºF, which would not meet the temperature requirementof 1200 ºF for the sintering process. The equipment provided included o-ring seals for all joints.High temperature seals were investigated, but none were found that were compatible with the flanges of the existing plumbing. These temperature constraints lead us to the consideration of other options.
4.1.1Plumbing and Piping Hardware on Hand
The equipment listing for the existing MDC hardware is listed below. The total estimated value of equipment donated is $2642.90. Table 1 lists the hardware on hand.
Table 1: Plumbing and Piping Hardware on Hand
Equipment on HandDescription / MDC pg # / Reference Number / Part Number / Price / Qty. on hand
Clamps / 87 / K075-C / 701000 / $5.50 / 13
Flexible Coupling / 117 / K150-XT-10 / 722022 / $97.00 / 1
Centering Ring / 87 / Not Sure on O-Ring Material / $1.60 / 9
Dual Element Filter / 253 / DFT-4F-AC / 433059 / $52.00 / 1
Foreline Trap (filter housing) / 251 / KDFT-4150-2 / 433015 / $215.00 / 1
Water Cooled Trap / N/A / KDFT-6150-2WC / N/A / $800.00 / 1
Valve (Nor-Cal) / N/A / ILV 1502 NW / N/A / $400.00 / 2
90 deg. With tangent (wide bend) / 123 / K150-2LL / 723020 / $80.00 / 3
90 deg. (tight bend) / 122 / K150-2L / 723002 / $58.00 / 1
KF to Clamp Style (nipple) / 114 / K101-1 / 720002 / $12.00 / 1
KF to Female NPT (1/4") / 158 / K150x1/4 FPT / 731008 / $28.00 / 2
KF to Female NPT (1/2") / 158 / K150x1/2 FPT / 731009 / $28.00 / 1
KF to Female NPT (3/4") / 158 / K150x3/4 FPT / 731010 / $28.00 / 2
KF to PVC Hose / 160 / K150-HPV / 736003 / $17.00 / 1
1/2" Quick Disconnect to KF / 157 / K150xDS-50 / 734025 / $63.00 / 2
Total Value / $2,642.90
4.1.2Additional Plumbing Equipment Needed
The additional equipment needed can be purchased through MDC. The total cost of additional equipment will be $195.00 plus shipping.
Table 2: Plumbing and Piping Hardware Needed
Plumbing and Piping Hardware NeededDescription / MDC Catalog pg # / Reference Number / Part Number / Price / Qty. needed / Availability
Four-Way cross / 126 / K150-4 / 725002 / $135.00 / 1 / In stock/shipping
Vacuum Hose / 262 / PVC-150 / 728037 / $10.00 / 6 / 10 days plus shipping
Total / $195.00 / + shipping
4.1.3High Temperature Vacuum Chamber
4.1.3.1Purchase High Temperature Chamber
The first option explored was to purchase a vacuum chamber that could accommodate the high temperature levels, but also have the dimensions to fit inside the furnace provided. The Snap-Tite company makes a pressure vessel that seems to meet all or our design criteria. We are currently waiting to hear back from them with a price quote. Many other companies were contacted, but none of them had products that met our high temperature requirement.
Figure 4: Snap-Tite Pressure Chamber
4.1.3.2Design and Build High Temperature Chamber
The second option explored was to design and build a custom chamber that could withstand the temperature levels needed and have the correct dimensions to fit the furnace. This would also give us the flexibility to incorporate other design considerations into the system that wouldn’t have been easily done with a pre-manufactured chamber (ex. Thermocouple).
This option was presented to Darrel Anderson for review, and he quoted the fabrication costs at $500. This cost would not include materials, as they would be donated from the MIE department and local scrap metal facilities. Further details of the custom vacuum chamber are discussed in a later section.
4.2High Temperature Vacuum/Pressure Chamber Design
In order to degas and sinter the aluminum carbide specimen, the self-sealing container must be heated in an inert atmosphere, free of oxygen, such that aluminum oxide does not form. This system design requires a vacuum chamber capable of holding both a vacuum of approximately 1 atmosphere for degassing as well as a nitrogen blanket of a pressure around 3 psi for the sintering phase. The proposed chamber will be fabricated from 304 stainless steel and will have a high temperature seal which could withstand both the applied vacuum and pressure. The two flanges will be tightened over the seal using stainless steel bolts. The top flange will then be welded to a portion of the plumbing, which will lead to a quick disconnect from the system.
Figure 4: Vacuum Chamber
4.2.1Material Selection and Design Concepts
(annotate about austenizing temp and melting temps, price of titanium and viability as material)
The material chosen for the chamber is 304 series stainless steel. This material was chosen because of its high melting temperature as well as its non-corrosive properties. Aluminum was ruled out given its melting temperature (1220°F) is so close to the sintering temperature (1100-1200°F). Titanium could also be a viable option for a material subjected to the given conditions, but is very expensive and would have to be fabricated by an outside source. 304 stainless steel is the industry standard for companies developing high temperature vacuum systems, considering donated plumbing from MDC to be used in our system is all fabricated from this material. The MIE department also has the ability to weld stainless steel, such that the canister can be fabricated in-house.
The main body of the vacuum chamber will be constructed of 3 ½ inch 304 stainless steel with ¼ inch wall thickness, giving it a 3 inch inside diameter. This size was chosen because it is available through the UMD MIE department and because of the high price associated with ordering one single section of stainless steel. (PRICE QUOTE) This inside diameter for the vacuum chamber allows specimens up to 2.75” to be produced; however Dr. Pedersen advises that the school would not be capable to press anything larger than 2.5 inch diameter. The main body extends approximately 10 inches below the bottom flange, which is about ½” short of the maximum furnace depth.
The bottom is capped with a piece of 3 inch diameter round stock cut to a thickness of ½ inch, which will be press fit into the bottom, welded around the chamfered bottom ridges, then machined cleanly off.
The top and bottom flanges were designed to be 6 inch in diameter, which will provide enough room for a sealing material as well as a 6 count bolt circle on a 5 inch diameter to seal the chamber. The thickness of each flange is ¾”, which is purposely over-sized given the uncertainty in the sealing method. This way, the flanges could be machined more than once if necessary to fit the chosen seal application. The top flange will also have holes machined into the center portion for an opening to the plumbing and a thermocouple.