About Resources Education Directory Meetings Technical Foundation News

Investment Casting Product Group

At the first meeting of the Investment Casting Product Group there was great interest in developing training programs for front line supervision. A small task group identified and ranked the following as the topics of greatest interest, #1 being of greatest and so on down the list;

  1. Wax Room
  2. Shell Room
  3. Engineering
  4. Melting/Pouring
  5. Tooling
  6. QC
  7. Metallurgy
  8. De-waxing
  9. Investment casting finish
  10. Finishing

We are planning to go ahead and run a course on "Shell Room". To make this course of greater value we will be running the course at a member foundry, Eagle Precision. The course will include a tour of their investment foundry, plus Cannon Muskegon (ingot producer) and Argueso (wax producer) all of these plants are in Muskegon. Eagle Precision have generously offered to host this first training module.

Targeted participants: Operator, shell room supervisor, production manager, engineer/engineering manager, QC, support (purchasing, maintenance).

Participants should bring examples or pictures of examples of issues you would like to discuss. Anything you specifically want to learn?

The schedule is as follows;


8:00 am - Continental breakfast and tour at Eagle Precision, 5142 Evanston, Muskegon, MI 49442.

Tours of Eagle Precision, Argueso (wax producer), and Cannon Muskegon (ingot producer)

12:00 noon - Lunch at Eagle Precision

12:30 pm - Shell training course

Introductions - Malcolm Blair, SFSA

Overview of the course - Instructor: Victor Okhuysen*, Cal Poly, Pomona, CA

7:00 pm Group Dinner (Dutch treat)


8:00 am - Continental Breakfast at Eagle Precision, 5142 Evanston, Muskegon, MI 49442.

12:00 noon - Adjourn.

*The course is detailed as follows and the instructor will be Victor Okhuysen, California Polytechnic University, Pomona, CA. Victor obtained his PhD from Penn State and was in intimately involved in the casting dimensional study. Victor's area of study was investment casting tolerances and he has had extensive experience in this field. Victor continues to work in castings and is responsible for the foundry program at Pomona.

There will be a small fee for this course of $100. This fee will include a copy of the book on shell defects.

Registration form and meeting notice.

The course will take place in the meeting room at;

Eagle Precision, 5142 Evanston Ave, Muskegon, MI 49442-4800

There are a number of hotels in Muskegon that you can use, Eagle has a corporate rate at;

Shoreline Inn & Conference Center 750 Terrance Point Blvd. Muskegon, MI 49440 Ph Toll Free 866-727-8483. You need to request the Eagle Alloy corporate rate of $79.00 plus tax.

Hotel reservations should be made as soon as possible.

If you need any additional information please contact Malcolm Blair, 815 455 8240 ext. 202 or blairm@sfsa.org

From participants: Bring examples or pictures of examples of issues you would like to discuss. Anything you specifically want to learn?

Targeted participants: Operator, shell room supervisor, production manager, engineer/engineering manager, QC, support (purchasing, maintenance).






Brief instructor tour to see what the attendees will see to tailor remarks and also to collect relevant samples for show and tell.


Pre-seminar survey



(Time TBD throughout the day)




Identify specific goals for each individual in the seminar. Recommended way to take notes.


How does the shell building fit into the overall Process?

Part Design/Dimensional



Wax Assembly (Bridging, structural strength of assembly, orientation of parts, drying)



Dewax (how it works, bleeders, types of wax)



Burnout (sintering)



Pouring (Handling damage, patching)



Finishing (knockout ease, kolene, blasting, contaminated revert, cutting into ceramic, reclamation)


Overall shell

Is concrete, with a precipitation cement



Overall composition and function



Overall characteristics and function


Colloidal silica

What is it? Particle and colloid characteristics


Colloidal silica binding mechanism

What happens when CS dries?


Colloidal silica maintenance

Concentration control, electrolyte control


Carrier (solvent)

Why add deionized water



Characteristics: mineralogy and size


Size distribution

What it means, characteristics


Properties by materials

Thermal expansion, top temperatures, fused silica, mullite (types), zircon



Minor components: Wetting agents, antifoam, biocides, latex, fibers


Wetting agents

Function (wax, ceramics), Matching chemistry to slurry (electrolytes), Primary vs back up















Analogy to concrete


Mixing objectives

Mixing objectives (wetting)


Mixing procedures

Sequence: Liquids, solids (sifting), temperature control, done when viscosity does not change 1 second in 1 hour.


Mixing Methods

High shear, very high shear, vacuum



Total solids, "good" rheology, strength development



Too concentrated: unstable (or wasted). Too diluted: weak. Carrier (water) to control level.


Composition Flour

Flour: Too much, unstable. Too little, very thin coats, perhaps insufficient stucco adhesion.


Flour Size Distribution

Wide distribution for improved rheology (thicker with uniform coating)





Maintenance composition

Maintain composition (proper ratios)


Maintenance chemical

maintain chemical characteristics (electrolitical)


Maintenance turnover

Effects of turnover



Analogy to concrete, add bulk


Mineralogy and size distribution

As with flour but coarser



Very possible.


Dipping cycle into and out of slurry and stucco

Entry angles, forces, submerged time, draining. Slurry and stucco pockets.


Manual coating

Weight limitations (size of tree, draining positions slurry and stucco)


Robotic coating

Issues: robotic payload (weight and distance combination), accuracy, tank levels, gripping, shaking of tree, safety of robots (cages), programming, broken parts in slurry tank/fluid bed.


Stucco coating

Rainfall sanders vs. fluid beds. Clean fluid beds of agglomerates.

Coating sequence


To remove parting agents from injection and to create changes in the surface of wax.


Primary coat

Fine for superior surface finish. Primary coats will have high viscosity slurry (better initial coverage) and finer stucco. Often also more thermally resistant ceramics (zircon). Slow drying (higher humidity/no air) to minimize uneven drying and danger of crazing. Slurry tank free of stucco.


Secondary coats

1-3 coats, similar to primary but lower viscosity slurry.


Back up coats

Lower viscosity slurry, coarser stuccos to build bulk fast. Lower grade ceramics.


Seal coat

Last coat, slurry only, prevents stucco from falling off through handling.


Post dewax coat

Only some places to cover cracks post dewaxing. Note dipping difficulty due to buoyancy.



No significant advantage.



Between parts. When, why, impact on drying. On ends of holes.



What happens, really.


Heat transfer process

Explain that heat has to go in.



How it works. Boundary layer.


Air velocity

Graph of effect: None vs. little vs. much. Note local effects (no wind reaching surface, blind holes). Note impact of boundary layer disruption and heat going in.


Air temperature

Effect of heating air: more heat into mold, more moisture carrying capacity.


Primary and backup coat drying difference

Temperature differentials vs. speed of heat removal. Temperature drop of shell.


Reverse wicking

Moisture is attracted to cool surface of shell. Free surface drying, but limited to exposed pores.



Relationship of relative humidity vs. moisture amount in air vs. temperature.

QC Controls

Vendor certification

First line of defense. Compare certs historically.


Raw material testing

Once in a while to keep honest


Slurry tests

Most important



Flow cups/rheometer/plate weight/film thickness (rheology test).


Specific gravity of slurry/density



Binder solids

How much "glue" is in slurry


Total solids

Flour and colloidal silica particles and latex


Gel test

Remaining life of slurry



Slurry stability


Slurry temperature



Finished product tests




4 point modified test



Green is most important, fired is much, much higher.


Build thickness

Consistency (with MOR, actual load carrying capacity).

Defects and Troubleshooting

Per questions from the attendees





Dewaxing Autoclave

Autoclave, components

Pressure vessel, boiler, accumulator, big valve.


Saturated steam pressure/temperature correlation



Need for speed

Prevent mass wax expansion


Initial heat transfer mechanisms

Condensation on surface


Wax film into primary coats

Green permeability of shell is key (determined by primary coats).


Wax draining, sequential melting points for wax types.

Theoretically, lower melting temperature wax first.


Mold placement

Interfere with steam? Form a "cold sink"?


Mold repair

All molds are cracked. Are they cracked enough? Probably overrepair and underrepair. Mud is magical.

Post seminar survey



Registration form and meeting notice.

Malcolm Blair
VP Technology, SFSA
Chairman/Secretary ISO TC17/SC11
Steel Founders' Society of America
780 McArdle Drive - Unit G
Crystal Lake
IL 60014

Ph +1 (1)815 455 8240 ext 202
Fax +1 (1)815 455 8241
Cell +1 (1)815 245 4213