3D Printing for Speed
The GoEngineer Technical Support team gained access to a Stratasys Fortus 250mc 3D printer. Naturally, we were all excited and started getting in line to use. I decided to make a bike light holder for my road bike without really understanding the potential and caveats of FDM prints and layer orientation. The general idea for the design was a handlebar clamp to hold a bike light with a sliding lock that would allow gradual positioning.
Below you can see the CAD model on the left. On the upper right, the sliding lock that keeps the light in place and on the lower right, the end result after one rough ride. Looks good on the outside but the inner features failed their design intent miserably. Clearly, I did not know what to expect out of a 3D printer.
Design-wise, the top sliding lock worked pretty well. The printing orientation did a great job at handling flexure to allow the light to slide in and lock into place. The main clamp worked well too, the print orientation also provided the needed flexure to stay mounted on the handlebar without adding a thin piece of rubber to add friction.
Now, what I consider to be the massive flaw: the positioning teeth. Initially, I thought that bigger teeth would give me more adhesion between layers. I didn’t think about how far the teeth were sticking out and how the further they are – the higher the bending moments would be. This was the results after a single rough ride:
Gone! Nearly a clean detachment, you can see that only the first layer stayed behind (Left). On the other hand the opposite part proved to be VERY robust (Right). Even with the teeth gone the assembly was still able to stay in position while riding my bike relying on friction alone but every bump would bring the light down.
FAIL!! Now what?
Since SOLIDWORKS PDM Professional 2018 (Not available in SOLIDWORKS PDM Standard 2018) now allows you to venture into different designs by Branching/Merging versions. I decided to use this new feature to further develop my epic fail.
The Branch/Merge command is found in the Tools drop-down button while browsing the vault by default or you can add it to any other menu via the SOLIDWORKS PDM Admin Tool. Below I show how to add the Branch command to the Action button in explorer:
To start the development Branch I select the assembly with the components I want to redesign, go to Action > Branch.
This opens the Branch dialog window shown below. Here we add a name to identify the Branch we will create (1). Since my vault is set to not allow duplicate file names I added a suffix (2) to the new files (3). Check the name change under the “Branch File Name” column, check in the file (4) and create the Branch (5).
After SOLIDWORKS PDM is done the new files are created and checked in the workflow initial state as version 1 with the suffix “-SOLID”. You can see the Branch title in the version tab as shown below:
What is so convenient about this? When I am done with the two design ideas and I decide which is the better option I can Merge both projects and keep the final design without the clutter of the discarded design. This provides a documented trail showing the design development while keeping unnecessary files under check to avoid confusing other users to review the project in the future.
The Brainstorm – My 2 Ideas
- Low profile triangular teeth to avoid high-stress moments.
- Keep the ability to change head angle.
- Three piece assembly.
- Remove the joint and combine top and middle to a single piece.
- No head position control.
- Two piece assembly.
Printing orientation: All three parts will be printed in the same orientation as the original since I don’t want to sacrifice the current sliding lock. I considered the positioning teeth should be printed as triangular teeth with 0.007 in layer but both prototypes will be printed with 0.01 in layers. Layer adhesion will be strong enough to function this time and I was confident Design B would be impervious to menial details.
Here are the parts after the print:
Which Design Works Best?
The triangular teeth in Design A still turned out pretty terrible. It could be expected due to the layer thickness and the overall size of the features. What I need is more resolution. The teeth incline is 60 degrees which created an acceptable finish for the top piece but the pocket in the bottom left much to be desired. Using a layer of 0.01 in. made those inner teeth look more like bumps. The assembly wiggled slightly even when fully tightened, forcing the teeth to mesh. I decided to not even bother with the 0.007 in layer print. This design is out.
The winner: Design B!!! The single piece turned out great. It’ll take shock consecutively and it does not slide up or down. The clamp is strong enough to prevent the light from looking down with each bump.
Now for the finishing touch, I will Merge the two design concepts to completely forget about the failure those triangular teeth created. The best part is there will be a revision controlled record of this attempt and it will show where those files came from and what the root of the branching was, just in case anyone runs into them years from now and wonders if the model is worth looking at.
I select the assembly I want to Merge into my branched project go to Tools > Merge
In the following prompt, I get the same options as the Branch command. I select Check-in on Merge, add a comment and Merge.
Once PDM is done, the original branching Assembly “Mount Assy.SLDASM” gets a new version containing the design from the Merged assembly. If someone on my team REALLY wants to rub the bad design in my face they can always retrieve it by looking at the history of the file and use “Get” on the version prior to the Merge. Below you can see Design A (left) as version 11 and Design B (right) as version 12.
The bottom line is that I don’t have to worry about someone printing the failed design idea when they “Get latest version”!