3D Printed Inserts and Mold Cavities That Can Be Used for

Producing Wax PatternsJacob Lehman, CMfgE

Associate Professor

Pittsburg State University

Fall 2019

Introduction – Using 3D Printing in the Foundry

Current Uses for 3D Printed tooling at the PSU foundry-

• Printed patterns for sand castings– Quick way to produce tooling for student projects without the need for machining a pattern or match plate

• Printed patterns for investment castings• Printed patterns used to make Silicon-Rubber molds that may be filled with

wax• Investment/Lost PLA – Printed patterns are assembled onto sprue, coated,

then “burned out” during the shell firing

• What about printing dies/tooling that can be reused for producing wax patterns?

Project Scope - Summer 2019

• Utilize inexpensive 3D printing technology – widely available, easy to use, and reasonably reliable

• Explore the possibility of using of 3D printed inserts in existing wax injection dies

• Explore the possibility of using of printed mold cavities for injection dies as an alternative to machined dies

• Demonstrate a Proof of Concept – Printed inserts and die cavities for wax injection tooling

Printer – Equipment Used for this Project

• Ender-3 3D Printer

• Single Nozzle, FDM printer

• Print Bed: 8.7” x 8.7” x 9.8" (220x220x250mm)

• PLA Filament

• Purchased online ~$200

Printed Tooling Inserts

Results

• Attempted to used same process parameters (temperatures, shot time, die closed time, etc.)

• Parts cooled slower on side with PLA insert

• Frequent defects

• Stuck/Difficult to eject parts due to “rough” printed surface finishes

Common defects

Summary of Printed Inserts

• Produced lower quality parts than the machined inserts

• Printing did not save a significant amount of time vs. machining the simple aluminum inserts

• Slower cooling rates for the printed PLA inserts

• Less detail/resolution due to the layer thickness/nozzle size

• May work for prototype tooling with very simple geometries

• Further research to try methods of smoothing the insert surfaces

Printed Die Cavities

• Produce a very simple “Test” cavity

• Rectangular cavity that is 2 1/2” by 1 1/8” and is 3/8” deep

• 5 degrees of draft added for easy part removal

Printed Test Cavity in Aluminum Base

• Machined a simple “Universal” mold base to hold the printed cavity insert

• Able to withstand the camping force of the wax press without crushing the printed cavity

• A through hole (under the insert) allows for removal of the printed cavity

First Trial Run – Setup wax press

Summary of first Printed Cavity

• Part worked well – Very simple Geometry with plenty of draft angle

• Somewhat slow cooling time – insert tended to insulate / retain heat

• Reasonably fine detail – reproduced the printed surface finish with the layer/tool marks

• Considerably faster/easier than machining the cavity from Aluminum

Small Production Run w/ Printed CavitiesDouble 6 Domino Set

• A single cavity with 28 interchangeable domino inserts

Printing the Domino Cavity and Insert

• Used PLA filament

• Used a 0.2mm layer thickness

• Print time = approx. 4 hrs.

Installing the Printed Cavity – Compressed Air Removal

Mold base with different domino inserts

First Wax Domino from Printed cavity

Additional Cavities

• The PLA required longer cycle times due to slower cooling rates

• Additional cavities were printed to speed up cycle times

• 2 cavities were cooling while one was being injected

Wax Dominos

First production Run

Economics – Cost breakdown

• Ender-3 3D Printer – purchase price (online, included shipping) = $193.49

• PLA build material - $21.49 per 1 kg spool of filament

• Breakdown for the Domino Project:• Each cavity used approximately 52 grams of PLA build material, thus a material cost

of $1.12 per cavity. Since there were 3 cavities produced, a total of $3.36 for the build material for the prints.

• Each domino insert used approximately 6.2 grams of PLA build material, thus a material cost of $0.14 per insert. Since there were 28 inserts needed to produce a full set, a total build material cost of $3.92 for the printed inserts.

• Total expenditures - $193.49 (printer) + $3.36 (PLA for cavities) + $3.92 (PLA for inserts) = $200.77

* Not included – Labor, Aluminum Mold Base (reclaimed), Wax/Injection Press

Conclusion

• Proof of Concept – Possible to produce inexpensive printed wax tooling for simple geometries

• May not be ideal for large scale commercial production parts, but may be useful for small production runs or prototype tooling

• Educational potential - allows students to experiment with die designs without large costs or significant die manufacturing time

• Future research into • accuracy/sizing of the parts• methods for “smoothing” the printed surfaces• other printing technologies/materials• a more detailed economic analysis and comparison for a production part

Questions?

Jacob Lehman, CMfgEAssociate Professor

Pittsburg State University

1701 S. Broadway

Pittsburg, KS 66762