3D Printed - V6 Internal Combustion Engine

Greetings and welcome to our V6 Internal Combustion Engine project! Our team consists of Aseesh Paul Bandaru and Vaishnavi Dabhade. We are graduate students from San Jose State University and members of SJSU’s American Society of Mechanical Engineers. Understanding the working of an internal combustion engine is a key aspect of Mechanical Engineering that every student should know. We sought to design a 6-cylinder engine using Autodesk Fusion 360 and fabricate the prototype using 3D printing as our form of digital fabrication. The inspiration behind this project is to help students studying the IC engines visualize and understand better through our almost transparent V6 model.

• Creality CR-10 Printer
• Creality Ender 3 Printer
• Cura Slicing Software
• Autodesk Fusion 360
• Hatchbox PLA Filament (Red, Gold, Blue, Black, Mint Green)
•  Bearings
• Acrylic Sheets
• DC Motors
• Motor Controller
• Batteries
• Electric Wiring

The design of components was kept as realistic as possible. Hence, the piston head is a cylindrical section with two fork-like teeth at the bottom to hold the connecting rod between them. The piston head was then locked with the connecting rod using rivets, this ensured the pistons to reciprocate within the cylinders smoothly as one combined unit. Furthermore, as one end of the connecting rod was locked to the piston, the other end was to be attached to the crankshaft. The connecting rods and the crankshaft were printed separately. To mesh them together the connecting rods were designed to be divided in two parts at the crankshaft such that one end had protrusions and the other had holes to serve as a lock and key mechanism.

The crankshaft had to abide by the firing order of the cylinders, hence it was designed in a way that the cylinders undergo combustion in the order ‘142536’. Hence crankshaft design was the most complex of all the parts. Also maintaining the cylinder and piston dimensions such that the rotation was perfectly performed and the mechanical system continued to run, was the most challenging part of all. The balance between these dimensions was bridged by the crankshaft, even at extreme ends the pistons had to adhere with the cylinders.Generally, the length of the connecting rod is at least thrice the length of the crank arm, in order to compensate for the unwanted acceleration of the piston. So, for this project the connecting rod is four times longer than the crank arm. First one piston was prototyped and tested over a cylinder after which the crankshaft and pistons were modified and built.

In order to print the casing using 3D printers it was divided into 3 parts. The bottom was separated from the top and the top was split into two sections, each one holding 3 pistons. For assembling all the 3 parts together we used the lock and key mechanism similar to the one used for the connecting rod by making cylindrical indents and teeth on parts. We also added the Autodesk logo as well as some text to indicate it was a V6 engine. 

Initially, the casing design when modeled in Fusion 360, had to undergo several precision changes like tolerance adjustments for cylinders on the casing, and axial length of cylinders, etc. Then centering of the system was done, that is the main axis which passes through the centers of crankshaft, bearings, flywheel, and handle, needed adjustment for the pistons to operate in the TDC and BDC. The center of the casing was designed to hold the two bearings that yielded the crankshaft. 

Fun Fact! The model comes with creative thinking and has ‘V6’ embossed over its surface such that the ‘V’ is almost inline with the cylinders, signifying why it’s called a V6 engine!

A compartment for holding all the electronics and supporting the motor in place was designed. Same lock and key mechanism was used to attach the pocket to the casing. The pocket was essential for the aesthetics of our model. This allowed the motor controller, wiring and battery to perfectly sit within the model. Also some ventilation holes were provided for cooling away the circuitry.

All the parts were digitally assembled using appropriate joints, like slider joints between pistons and cylinders, revolute joints between crankshaft and casing, rigid joints between teeth and slots of casing, flywheel, etc., in Fusion 360.

The pistons, rivets and connecting rods were printed by utilizing Cura’s slicing software. In order to import the file into Cura, the components were exported out as an STL. In order to save print costs all 6 pistons were printed at once in Hatchbox’s Transparent Black PLA; also 6 connecting rods were printed together in Hatchbox’s Red PLA . Pistons were printed with a 20% infill and a 45 degree support angle. The print took roughly 9 hours and 70 grams of filament to produce.

The crankshaft was a pretty tough part to print because no matter the positioning it would require a lot of support. Additionally, the nature of the crankshaft’s use demanded a sturdy part. Hence, the part needed to be printed at 100% infill to ensure it wouldn’t break during use or during the removal of supports. The part took over 13 hours to complete and cost roughly 80 grams of filament. This part was printed in our University’s blue color via Hatchbox’s Blue PLA filament. The flywheel was printed in the same color as the crankshaft, which took roughly 3 hours to print and cost about 30 grams of filament. The handle needed to be printed at 100% infill as well to prevent breaking. The handle took 25 grams of Gold filament to make and roughly 4 hours to print. 

Each piece of the casing was printed on our club’s Creality CR-10 3D printer. The brim was used as an adhesion method and kept the traditional 45 degree support angle applied. For the filament of this print Hatchbox’s Silk Gold PLA was utilized. These prints took over 72 hours to print and cost an entire one kilogram roll of filament.

The pocket was printed using the same gold filament as used in the casing. It also had the same print settings as the casing prints. This part took over 10 hours to print and cost 62 grams of filament.

Once all the parts were printed, the connecting rods were attached to each piston head using the rivets that were 3d printed as well. Then the connecting rods were assembled with the crankshaft. Bearings were then inserted on either side of the crankshaft. The crankshaft assembly was seated into the lower part of the casing. A DC motor was attached to the crankshaft on one side and the flywheel with the handle on the other side.

Superglue was used to lock parts together for added adhesion, where there are rigid connections.

Here are the final videos!

Here are all the part files and assembly files