Task: Large Modular Structural Interfaces
Description: We need your insight to help us create a better support for the flexible design methodology of DDM vehicles. The construction should be modular even at a large scale. For our first prototypes, we have a front steering module, a center occupant module and a rear power module. We need a fastening methodology to connect these very large modules together so that they will perform under heavy driving as well as crash situations.
Challenges to Overcome:
1. Fastening points will see forces from many directions so the overall solution will have to handle all the potential force vectors that would occur between modules.
2. As always, assembly should be minimal, precise and repeatable. This means that the use of both chemical and mechanical fasteners should be implemented using a method that is not labor intensive, and either minimizes variability of the execution or ensure performance is not impacted by the variability.
3. Our current printing capability is still only 3 axis for the moment, so fastening methodologies should be conscious of the impact of the printing vector of the parts that will have mechanical connections.
Please provide your suggested general process approaches to join large printed bodies. We don’t need all the models and assets created; we simply need your suggested approach. Please include the following:
o A general description of the mechanism and approach
o A short description of hurdles addressed
o Links to any supporting info
o Essential links or leads to any specialized materials, hardware or equipment for the solution
o Simple diagrams to illustrate the connection method
Will you help with this task?
If divide the car into three parts. I would have connected them approximately so :
More simple solution.
Adhesive bonding using large overlap shear joints on three planes
Design the large chassis sections to have large overlap shear joints in all three directions, X, Y, and Z. The amount of overlap or shear area for bonding may be larger for the Z and Y directions than the X. In order to achieve this the parts will need to slide together like a puzzle.
I am currently working on coming up with some options for your fastening methods and I wanted to run a couple calcs as for as stresses go. Could you please tell me per your original design how thick at the base connecting the T-bird frame to that of the ABS how thick the ABS is?
Thanks, Erika Adams
Are you just looking to connect the three modules? Or are you planning to cantilever structure in between. Since I am conservative, I would use typical aluminum extrusions on the center module embedded in the print if cantilevered structure is required. The extrusion would fit into rectangular recepticles on the front and rear modules allowing some flexibility of positioning side to side. Bolt connectors could be used to lock them in.
Then I would use something like the 2nd or 3rd image as a "nut plate" between modules, probably 4-5 nut plate interfaces module to module. The nut plate would distribute the clamping force. If more distribution is needed, then your embedded expanded metal could be used to distribute pressure internal to your 3D printed structure. You could buy a preexisting plates ($10-$20) like I show below or fab your own.
Just use something like 3d-pen (termo-head of 3d printer, driven by hand) as weilding machine. To allow this you are to create large surface area (e.g. dovetail-like or just spikes, with gaps for filler when connected, sure it is easy to make on printer) on connected surfaces (ensure it is not contaminated during transportation - duct tape protection should work), place it close to each other and fill the gap with same filament as car is made of. It is strongest way to connect parts because you will get one solid part but not 3 connected if you do ir right. We can make some illustrations on demand.
The connection method the modules of the car . Through external metal bandage and (V) figurative internal bolts - pins connections
You should consider coating all components of the exoskeleton in carbon fiber, with reinforcements where it counts (pillars, doorframes, etc).
All fiber layup could be engineered to combat stresses, and then cut accordingly in prepreg carbon to be laid, vacuum bagged, and autoclaved. Of course, you would have to use a prepreg that can be cured at temps that won't significantly or detrimentally affect your plastic substrate (like Gurit SE70). All parts could be bagged easily by someone experienced in clever bagging tactics.
You could easily and simply prove the concept by laying and doing vacuum infusion for probably $2-3,000 bucks on a larger part.