1. Introduction....................................................................................................................21.1 Client Profile......................................................................................................21.2 Problem Statement............................................................................................2

1.2.1 Sub-Problems....................................................................................................22. Project Definition...........................................................................................................3

2.1 Mission Statement....................................................................................................32.2 Constraints...............................................................................................................3

2.2.1 Equipment.........................................................................................................32.2.2 Cost.....................................................................................................................42.2.3 Time...................................................................................................................4

3. Project Organization.....................................................................................................4Introduction....................................................................................................................43.1 Project Management Plan.......................................................................................43.1.1 Work Breakdown Structure................................................................................6

3.1.2 Meeting Schedule..............................................................................................73.1.3 Rules...................................................................................................................73.1.4 Task Assignment...............................................................................................7

3.2 Documentation.........................................................................................................83.2.1 Standards....................................................................................................8

3.3 Communication........................................................................................................84. Design Concepts.........................................................................................................9

4.1 Plumbing and Piping Hardware.......................................................................94.1.1 Plumbing and Piping Hardware on Hand...............................................94.1.2 Additional Plumbing Equipment Needed.............................................104.1.3 High Temperature Vacuum Chamber...................................................11

4.2 High Temperature Vacuum/Pressure Chamber Design..............................124.2.1 Material Selection and Design Concepts...............................................134.2.2 Sealing Vacuum Chamber......................................................................144.2.3 Testing.......................................................................................................154.2.4 Connection into the Powder Metallurgy System..................................15

4.3 Self-Sealing Container.....................................................................................164.3.1 Solder material.........................................................................................184.3.2 Testing.......................................................................................................18

4.4 Fixture Design..................................................................................................184.4.1 Material........................................................................................................184.4.2 Fixture Features...........................................................................................194.5 Nitrogen System...............................................................................................20

4.5.1 Flow meter................................................................................................204.5.2 Pressure Relief Valve...............................................................................20

4.6 Temperature and pressure monitoring.........................................................204.6.1 Thermocouple..........................................................................................204.6.2 Pressure/Vacuum transducer.................................................................21

4.7 Vacuum and Filtration System.......................................................................214.7.1 Vacuum pump..........................................................................................224.7.2 Inline Filter...............................................................................................22

4.8 Cooling considerations....................................................................................225. Appendix...................................................................................................................236. Bibliography.............................................................................................................23

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Executive SummaryThis 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

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.

1.1 Client 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.

1.2 Problem 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

2

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

2.1 Mission 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.

3

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

4

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

5

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.

6

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

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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 Date

Cad 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

8

documents. Furthermore, each team member is responsible for recording all sources of

information.

3.2.1 Standards

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.

4. Design Concepts

9

4.1 Plumbing 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 requirement of 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.

4.1.1 Plumbing 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.

10

Table 1: Plumbing and Piping Hardware on Hand

Equipment on Hand

DescriptionMDC pg

#

Reference

Number

Part

NumberPrice

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

4.1.2 Additional 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 Needed

Description

MDC

Catalog

pg #

Reference

Number

Part

NumberPrice

Qty.

neededAvailability

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

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4.1.3 High Temperature Vacuum Chamber

4.1.3.1 Purchase 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

4.1.3.2 Design 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

12

from the MIE department and local scrap metal facilities. Further details of the custom

vacuum chamber are discussed in a later section.

4.2 High 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

4.2.1 Material Selection and Design Concepts

13

(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.

14

4.2.2 Sealing Vacuum Chamber

Given such extreme conditions, the sealing issue becomes very complex as

normal seals such as o-rings and rubber gaskets would break down under these high

temperatures. Many representatives for high temperature seal companies have responded

back stating that the sintering phase would still be too high for their products to work in

our application. After much research, and while waiting for responses from a select few

companies stating they may have a viable solution for us, we have narrowed our seal

design to the following possibilities:

Cutting gasket rings from a material offered by Slade Inc. called MRG

Gasket Sheet, which is a sheet of stainless steel mechanically bonded

between two foil sheets. This option seems the most viable, especially

considering the working temperatures this product is specified to

withstand. See Appendix for product specifications.

Machining a cup and cone set of rings on the upper and lower flanges,

then compressing a sheet of brass or copper foil between the two flanges

by tightening the bolts. This design requires more research as well as

finite element analysis into the effect on the mechanical properties of

either metal under such extreme conditions if this option is chosen.

Implementation of a ceramic, high temperature gasket. This idea is

relatively new prior to this report and requires much research to ensure its

viability for our project.

The reusability of the seal would be highly beneficial. However, the seals being

researched would be plastically deformed when the flanges are fastened together and may

not provide an effective seal after multiple uses. Therefore, the seals will most likely

have to be replaced every time the vacuum chamber is used, based upon their

performance after one run. The chosen seal application will be tested to determine its

useful life for this application.

Currently the vacuum chamber flanges will be fastened using 6 stainless steel

bolts, which will be positioned equal distance around on a 5 inch bolt circle. The bolts

will then screw into a stainless steel fabricated bolt flange, which is comprised of a 3/8

inch by 6 inch diameter slice of stainless steel round stock with 6 stainless steel nuts

15

welded concentric to machined holes matching the flange bolt holes. See Figure 5. This

will eliminate the need to hold an additional wrench on a nut while tightening each bolt

down. A torque wrench will be required to administer a uniform torque on each bolt of a

magnitude yet to be determined based upon the type of seal chosen for the application.

Figure 5: Bolt Flange

4.2.3 Testing

The vacuum canister will be tested to ensure the seal will hold up under the

vacuum and pressure states under the elevated temperatures. This testing will occur once

the entire system is assembled and is run through a couple of dry runs. The effectiveness

of the seals will be monitored using the pressure transducer, which will provide feedback

on whether the system is maintaining a constant vacuum or a constant pressure.

The reusability of the seal will also be tested in this fashion, performing multiple

runs using the same seal, which would prove highly beneficial if the same seal could be

reused over and over. However, the seals being researched would be plastically

deformed when the flanges are fastened together and may not provide an effective seal

after multiple uses. Therefore, the seals will most likely have to be replaced every time

the vacuum chamber is used, based upon their performance after one run. The chosen

seal application will be tested similarly to determine its useful life for this application.

4.2.4 Connection into the Powder Metallurgy System

The machined opening on the top flange of the canister will be welded to a 90°

elbow, which will be welded to the finned pipe used for heat dissipation. The other end

of the finned pipe will use an MDC Kwik-Flange o-ring and collar connection which we

have in stock and will serve as a quick disconnect from the system. The reasoning

behind welding these components together is to limit the number of high temperature

seals in the system to just vacuum chamber seal, especially considering the chosen seal

16

will have to be experimentally tested. This will simplify the system and reduce the

number of locations a seal failure could occur.

4.3 Self-Sealing Container

The self sealing container is comprised of a 40 mil thick thin walled 2024

aluminum tube, with a 1.5 inch inner diameter, that has been cut to a length of 6 inches.

A disk was cut and welded to the bottom of the tube to seal the bottom. Sealing the top of

the aluminum container is more complex because the container must be sealed in an inert

environment after the aluminum powder mixture has been degassed. Our team

immediately thought of a hands free application that could be used immediately after the

degassing stage inside of the pressure vessel itself. There were originally four alternatives

being researched for the lid of the aluminum container.

The first alternative is to completely encase the aluminum cylinder in a ballistics

gel that would seal the aluminum powder from the outside atmosphere after the degassing

was completed. This alternative was later determined unfeasible because the aluminum

cylinder would then have to be taken to the die and crushed for the green compact. If it

was encased in ballistics gel the exact dimensions of the outer diameter of the container

wouldn’t match the die and there would be a high risk of leaking if any of the ballistics

gel was carved away. This method was also discredited due to the fact that there is no

research available to conclude how the dispersing of ballistics gel reacts to a vacuum

environment.

The second alternative is to attach 2mm by 2mm chunks of solder around the top

lip of the aluminum cylinder and place an aluminum disk on top of the chunks to form a

type of gravity seal with the aluminum container once the solder melts. This was

determined to be extremely complex because of the 40 mil wall thickness on the

aluminum container. Also after talking with Larry Lepervow from Johnson’s

Manufacturing Company, a solder and flux manufacturer, he expressed concern that the

solder wouldn’t travel completely around the top lip of the aluminum container but would

have a tendency to flow down the side of the walls.

The third alternative is to buy a lid that already had solder dispersed around the

outer edges from Williams Advanced Materials. This was a company that was found by

doing internet research into self sealing lids. The lid that was found to be applicable was

17

a 1.60 inch diameter lid made of Kovar material. The solder on the lid is comprised of

81% aluminum, 19% Indium with a melting temperature of 909 deg. Fahrenheit. The

main drawback in this approach is there wouldn’t be any way of degassing the aluminum

container because the lid would create a cap even before it sealed. Below is a picture of

some of the lids Williams Advanced Materials manufactures with the solder dispersed

around the outside edges.

Photo Courtesy of www.williams-adv.com

The fourth alternative is to create an aluminum plug that would be press fitted into

the aluminum container. The plug was designed to be inserted with the punch of the die

and distribute uniform pressure as the powder is being compacted. The plug has 45

degree chamfers on the edges to reduce wobble when being inserted into the aluminum

cylinder and to create a space for the soldering ring to seal the aluminum plug to the

container wall. The center of the plug will have holes drilled in it to allow the moisture

and oxygen to escape during the degassing process. To seal the holes after degassing is

complete, an aluminum alloy solder will be dispersed around the holes. The solder used

to seal the holes and to seal between the plug and the container wall is comprised of 80%

aluminum, 20% zinc with a melting temperature of 890 degrees Fahrenheit. The pictures

below are the preliminary drawings of the aluminum plug.

Figure 5: Aluminum Plug

The fourth alternative was chosen to be the most feasible because it will not only

allow for degassing of the aluminum powder to occur, but it also provides a larger cross

18

sectional area of solder between the aluminum plug and container wall forming a more

secure seal.

4.3.1 Solder material

The solder and flux being used for the sealing of the aluminum container is

supplied by Johnson Manufacturing Company out of Princeton, Iowa. The name of the

flux is Zinc Tech-A, it is a paste flux with a melting temperature between 950 and 1000

degrees Fahrenheit. The cost of the Zinc Tech-A flux is 20$ per ounce.

The solder is a “hard solder” that is a super plastic material comprised of 80%

aluminum, 20% zinc with a melting temperature of 890 degrees Fahrenheit. Multiple test

strips of wire solder with different diameters will be donated by Johnson Manufacturing

Company.

4.3.2 Testing

Before making a sample, the self sealing container needs to be tested to make sure

the solder seals are airtight. The method of testing is to seal the aluminum container as

described in alternative four in section 4.3 and then submerge the aluminum container in

tinted water for 48 hours. The water will be tinted with a red color to make it easier to see

if there are any leaks. After 48 hours the sample will be collected, dried off, and cut open

to inspect for any visible red water. This process will be repeated 3 times to ensure no

variability. Additional research is currently being performed into alternative testing

methods.

4.4 Fixture Design

This project will also require the design of a fixture to support the system as a whole.

4.4.1 Material

The proposed frame material for the fixture will be aluminum extrusion T-slotted

framing. The reason for this choice is modularity, such that the frame design can be

easily adjusted for any future modifications to the system as a whole. A welded steel

frame would not allow this type of simple modification.

19

The aluminum extrusion material, commonly referred to as 80/20, is also

lightweight, which will reduce the overall weight of the system greatly compared to a

welded steel frame.

Many companies offering this type of framing offer a large variety of cross

sections in their extrusions. This can be utilized when determining the structural

requirements of the frame, based upon the stresses put on structure from the weight of

system and its associated components.

4.4.2 Fixture Features

The primary purpose of the fixture is to hold the powder metallurgy plumbing and

canister. However, there are various other features that will be built into the design to

make it ergonomically friendly and to make the specimen production much easier.

The fixture will be designed with a set of wheels at the base, such that the

operator can maneuver the entire system around with ease. This allows the

system to be stored when not in use, freeing up valuable lab space. To ensure

stability and limit movement during degassing and sintering, the wheels will have

the ability to be disengaged and the fixture will then sit on the floor on its base.

While the fixture will be designed to hold the plumbing, it will also have

mechanical lift equipment incorporated into its design. This will allow the

operator to mechanically lower the canister and plumbing into the furnace for

sintering and degassing. The operator will then be able to lift the entire apparatus

out of the furnace when the process is complete, which is much safer than

removing the hot components by hand.

The fixture will also have sections dedicated to housing the vacuum pump and a

laptop. All necessary equipment will be integrated into one user-friendly fixture.

4.5 Nitrogen System

Nitrogen was chosen to blanket the part during the controlled atmosphere

sintering operation because it is relatively inexpensive and produces a part with desired

20

mechanical properties. The vacuum canister will be pressurized to approximately 3 PSI

while the part is being sintered in order to keep aluminum oxide from forming.

4.5.1 Flow meter

The team has met John Petrovic, who works at Airgas in Duluth, and discussed

equipment needed to ensure safe operation of the nitrogen system. A single stage

regulator and flow meter combination for use with nitrogen was quoted at nearly $300.

More research needs to be done in this area before final decisions are made.

4.5.2 Pressure Relief Valve

A pressure relief valve may be used in the system in order to provide protection

from over-pressurization. The pressure relief valve would be self-operating and would

let gas escape the system when safe pressures exceeded. Many companies supply these

valves. To order a valve the gas (nitrogen), set pressure, and size of thread piping must

be specified.

4.6 Temperature and pressure monitoring

4.6.1 Thermocouple

The monitoring of temperature for the degassing and sintering phases is a crucial

element. The temperature for the degassing process must be maintained at 400°F and the

temperature of the sintering process must be maintained at a minimum of 1000°F. The

temperature will be monitored by mounting a thermocouple directly into the top of the

vacuum chamber. The thermocouple provided has a male threaded end and can be

directly threaded into the top flange of the canister. By threading the thermocouple into

the system, it will minimize the possibility of a vacuum leak in the system. This will also

provide a fixed location for temperature measurements, minimizing the variation in

measurements. Another option for the placement of the thermocouple is to have the end

dangling in the middle of the canister. This would require a compression fitting where the

wire goes through the top flange. The compression fitting could pose a higher risk for

vacuum leaks and the end placement of the thermocouple would not be in a fixed

location. This option would not be recommended.

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Further research will be done into monitoring and recording the temperature using

software such as Labview or similar products. This will provide a method of recording

temperatures that could be of value for further research purposes.

4.6.2 Pressure/Vacuum transducer

The system will require a pressure and vacuum monitoring device to ensure

proper conditions during the sintering and degassing phases. The degassing phase will

require the system to be at .1 Tor. During the sintering process the system will be

required to be under a nitrogen blanket of 2 to 3 psi. The purposed transducer is a

compound unit which measures both pressure and vacuum. The range selected for this

application is -14.7 psi to 15 psi. It can be supplied by Omega for $195. The transducer is

in stock and has immediate availability. The part number is PX209-30V15G5V. The

pressure port can be threaded directly into an adapter that goes from a Kwik Flange to a

¼” Female NPT. The adapter is listed in the table of equipment we have on hand. The

transducer can also be integrated into the lab view software for monitoring and data

recording.

4.7 Vacuum and Filtration System

The vacuum system consists of a Savant vacuum pump and a MDC inline filter.

The vacuum pump was also a donated piece of equipment and came with no

documentation. The user and maintenance manuals were eventually acquired from the

pump manufacture BOC Edwards. Complete user and maintenance manuals are available

electronically.

An option to control the vacuum pump through a vacuum control switch is

available through Omega. This would start and stop the vacuum pump at preset

conditions, eliminating the task of manually monitoring and controlling the vacuum

pressure. The model number is PSW-626. The price is $85.00.

4.7.1 Vacuum pump

The vacuum pump is a BOC Edwards Model RV12 rotary vane pump. The RV12

is a two stage, oil seal, sliding-vane vacuum pump. The pump is driven by a single phase

electric motor. Some additional specifications are listed below:

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Maximum displacement is 17 Calculate time required to

evacuate the system

Maximum inlet temperature of 180ºF

Equipped with a thermal overload device

4.7.2 Inline Filter

The inline filter was provided with the other donated equipment. It is a 4” dual

element filter that has activated carbon and fiberglass as its filtering agents. This filter is

primarily a vapor filter, but it will also trap some particulates that may reach this point in

the system. Because of the low velocity of gases in the system (4.55 ), particle

movement is expected to be minimal. The model reference from MDC is: DFT-6F-DE, it

is also listed in the table for equipment on hand.

4.8 Cooling considerations

The cooling of the gases before they reach the vacuum pump is a concern. The

maximum temperature of the inlet gases must be below 180ºF. Therefore we must take

into account a method for cooling the gases. Two pieces of equipment that were on hand

can be utilized to accomplish this. They are discussed in the next sections.

Finned Pipe

The finned pipe is actually designed to be a flexible coupling from MDC, but for

our purposes will provide an excellent finned surface to dissipate heat. The purposed

design will have welded piping from the vacuum chamber up to the finned pipe. At the

vacuum pump side of the finned pipe is where the Kwik Flanges will begin. We

anticipate that the finned pipe will reduce the temperature at this point to a value less than

the o-ring limits (200ºF). Calculations and an experiment to test the heat transfer are still

to be done. Below is a picture of an MDC flexible coupling.

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.

Cooling Canister

The cooling canister is another piece of equipment that was donated. The canister has

stainless steel coil that lines the inside of the canister. We would run cool water through

the coil to provide additional cooling to the gases before entering the vacuum pump. The

cooling canister is yet to be determined if it is needed. If the finned pipe provides

adequate heat transfer, the cooling canister will not be used.

5. Appendix

6. Bibliography

http://www.snap-tite.com/index.asp?loc=/Autoclave_Engineers/High_Temperature_

Vessels/index.html&title=High%20Temperature%20Vessels

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