3d printed inserts and mold cavities that can be used for
TRANSCRIPT
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