Movable 3D-Printed Engine!
Introduction: Movable 3D-Printed Engine!
Hi I’m <PERSON>
And in this Instructables I’ll be showing how I designed a Movable Print in place engine model (Print in place meaning it does not require any assembly after printing).
While you might not be interested to know how to design a engine model, the tricks an techniques in this Instructable will be applicable to other projects and will enable you to create things that move and have more versatile functions way past the typical 3D printed bracket or figurine.
This is the 3rd Instructables I’m writing on the subject on designing mechanisms for 3D-Printing, and with these three you will have a lot of different techniques to face your upcoming projects!
The previous two Instructables can be found HERE and HERE, but this one can be read completely by itself. I already made a video on the subject showing of an in-line 3-cylinder engine and giving a rough explanation on how I made it, in this Instructables I’ll be designing a V twin engine. :
The STL Files of the engine models will be linked at the end.
(I included a picture of the components of an internal combustion engine with the names of the parts, I will be using these names during this Instructables.)
Supplies
Fusion 360
3D-Printer
Step 1: Finding the Manufacturing Challenges
Identifying the challenges of a potential mechanism is something that should come as early as possible in the design process. Knowing the limitations of your manufacturing process is key. In my case I’m planning on using an FDM 3D-printer, and the limitation of this type of printer is vastly different from say a DLP or SLS 3D printer.
In my case, one of the major challenges will be to print parts of the engine that will have to be able to move relative to each other (conrods + pistons), but manufacture these without them touching the build plate.
Other challenges of my project will be to find clearances that will allow parts to move and interact relative to each other without too much play but at the same time not sticking together during printing.
(The picture shows the parts of an internal combustion engine and their names)
Step 2: Solution Concepts and Design
A mayor component of this model is the Crankshaft. We were able to design it for it to be able to touch the build plate during the print operation. On the V-Twin the crankshaft only needs to touch the build plate in “one orientation”, but on the inline-3 we had to be smart about the crankshaft design to enable it to touch the build plate even though the crank pins are in 3 different orientations.
The crank “segments” were designed to be able to print in different orientations with flat surfaces at 0, 120, 180 and 240 degrees that are designed for build plate adhesion. 737
This allowed for the same crank design on the V-twin as well as the inline 3 engine (see pictures)
Most people familiar with FDM 3D-printing will be able to tell you that you are not able to print into thin air, and if you want to, you will have to use some sort of supports. This is exactly what we are going to do, but unlike most designs, we will not have physical access to the supports to remove them post printing, so a different approach is needed.
My proposal for this issue was to design supports in a way that would allow us to break them away after the print is finished by simply spinning the crankshaft.
The supports for the pistons and conrods need to be designed as small as possible to make the break away as easy as possible. But making supports too thin can result in difficulties on printing onto them. So usually finding a happy medium is the optimal solution.
However, in our case, we have a very fortunate geometry around the "floating parts" (there are supporting walls near by), and in additionally we have a mostly symmetrical and light weight parts that need to be supported. So in our case we will try to produce the thinnest possible supports. Since we have parts in close proximity to the “floating” parts, just bridging across a single strain of filament seems to be a good option that we will test in the next step. (see picture for design, the support is highlighted in red)
Step 3: Testing
Now its time to put it to the test
As always, its more time efficient to test design features separately rather then everything at once and then trying to figure out what part of it failed. 933