Our first observation from trying to set up the cervix holder was that it was really tedious to screw the screws and confusing on which direction to place the wooden boards, and you simply needed too many hands than we had. Our first ideas of how to simplify the design was to use “tooth and hole” joints to press fit the wooden pieces together and eliminate most of the screws that needed to be put together by hand. Also, the cervix holder seemed much too complicated than needed to be when all I needed to do was hold the cervix in place. 

To fabricate the pelvis frame, we used laser cutting and MDF wood boards. We used the dimensions from the LUCIA model to design and cut out the parts. We ran into a lot of issues with picking the right speed and power in order to cut through the wood without burning it, even with using tape. We also had issues with getting the perfect fit with the tooth hole hinges, and had to cut a few times in order to get the right dimensions and kerf to keep the boards in place without being too wobbly. We didn’t think that the teeth and holes alone would be secure enough to hold the cervical holder in place and we also were worried about breaking them potentially so we 3-D printed joints in order to hold the two panels in place and support the corners. This took many iterations (thanks Nico) but eventually we got the perfect fit and we added lettering to help simplify which side each corner joint went onto. We added numbers and an arrow to the cervical holder in order to make it very clear how to set up the frame.

 

Symone mocked up the cervical holder, which, after much discussion over design, we decided the hook method would be the simplest way to hold the cervix in place. Designing and printing the cervix holder took a few tries as we had a few failed prints and tolerance adjustments to make, and there was some fragility along the hook due to a 3-D method of layer printing, but after increasing the density of the print, we were able to get a sturdy final model.

We had to do a little bit of post processing to remove extra ash from the edges of the laser cut pieces and sand any splinters or supports away from the cervical holder and frame. Although we wanted to eliminate screws from our design, we still used a few screws in the panels in order to hold the fabric in later iterations.

After getting our laser cut pieces press fit into each other, we still had an issue with a bit of wiggling which made the structure unsteady. In true engineering fashion, we used an elastic band across the edge of the platform in order to give it some grip and prevent wiggling, and this made the whole contraption more stable. 

To make 50 of these models, we could continue using laser printing fabrication with quality control to post-process the wood parts and should fabricate the 3D printed parts using injection molding. If we were to scale up production to make 100 or 1000, it may be better to use injection molding to make the 3D printed parts and then replace the wood panels with injected molded pieces. 

Overall, this was a great way to practice our iterative design skills and apply laser cutting and 3D printing to solve tangible user issues. It was interesting to see how other groups approached the same problem and how different some designs were to each other. 

Cost analysis:

Cost Type	Cost	Price	Source	Quantity	Total
Materials	¼” MDF Laser Cutting Wood	$64/16 pieces	link	1	$64
	Screws	$7.97/100 pieces	link	1	$7.97
	Washers	$12.76/25 pieces	link	1	$12.76
	ABS material	$19.99/1kg	link	49g	$0.98
	Sand Paper	$7.09	link	1	$7.09
Labor	Laser cutting operator	$19/hr	link	6	$114
	Prototyping Engineer (You!)	$18/hr	link	6	$108
Overhead	Facility Cost (Machine Time)	$25/hr	link	3	$75
Design	Engineering and Development	$32/hr	link	4	$128

Total: $517.80

Clean workspace:

Thanks for an awesome semester BIOE 555 and OEDK!!! <3