design portfolio- kyle woodard
DESCRIPTION
A summary of engineering projects I have completed throughout my careerTRANSCRIPT
Background: Sacro-‐iliac (SI) joint fusion is a rapidly growing market in spinal orthopedics. The procedure is becoming more commonplace as clinicians realize that they have been misdiagnosing SI joint pain as emanaAng from the lumbar spine.
Design Problem: There are two types of implants that surgeons use for SI Joint Fusion: Screws and Fusion Rods. Screws and used to fixate and compress the joint, whereas fusion rods are used to fuse bone to the implant to help increase fixaAon of the joint. Surgeons requested Screws that allow the user to pack bone graJ into the implant to allow for fixaAon and bone fusion, and Fusion Rod implants that had more surface area for greater bony fixaAon.
Screw Design Highlights:
The SIJFuse Screws were designed with a large enough cannulaAon to allow the surgeon to pack bone graJ through the implant. Fusion holes allow bone graJ to contact surrounding bone for fusion. Fusion holes are paKerned along a helix for greater strength in bending.
SIJFuse® Implant Designs
Fusion Rod Design Highlights:
The fusion rods were designed uAlizing a 6-‐point star shape so that the implant has 50% more surface area than compeAtor implants of the same “diameter” and length. Two versions of the implants are available: a fusion rod with a solid core and porous surface to allow for fusion onto the surface, and an implant with a laScework core to allow for bony ingrowth into and through the implant, made uAlizing DMLS addiAve manufacturing.
Implant Expulsion Resistance
Design Problem: Surgeons reported few instances of 1st generaAon T-‐LIFT implants backing out of the vertebral disc space aJer implantaAon. Root cause analysis lead to the conclusion that the tooth design of the implant did not allow for proper fixaAon in the disc space.
The direcAon of the teeth allowed the implant to resist moAon in the anterior-‐posterior direcAon, but the implant did not adequately resist pushout forces along the posterior-‐oblique window through which it was inserted.
Dorado T-‐LIFT® Implant Redesign
The first iteraAon of the new T-‐LIFT featured teeth designed to resist movement in the direcAon of inserAon. The teeth were designed conservaAvely so that they did not break in faAgue tesAng per ASTM F2077. However, the pushout resistance of the implant was only marginally improved. A more aggressive design was needed to beKer resist the pushout, while balancing performance in faAgue tesAng.
1st Itera4on
InserAon DirecAo
n
Implant Teeth
2nd Itera4on
Dorado T-‐LIFT® Implant Redesign
The 2nd iteraAon of the T-‐LIFT design featured teeth that are far more aggressive than the 1st iteraAon.
The teeth were designed to allow for ease of inserAon while sAll resisAng pushout. Movement of the implant toward the paAent’s anterior was not deemed a risk, as surgeons leave the anterior annulus fibrosis in-‐tact.
Many iteraAons of this design were created, working to achieve balance between pushout strength and compressive faAgue life. Tooth geometry such as the tooth point (flat tooth vs. sharp tooth), tooth angle, and tooth spacing were the parameters modified to opAmize the implant design.
A combinaAon of FEA simulaAng ASTM tesAng and prototype bench tesAng were used to evaluate the strength of the design.
The pictured design was the implant that best balanced pushout strength and faAgue life. This design was ulAmately submiKed to the FDA for 510(k) clearance, and has been used in clinical pracAce since January 2012.
Compression Test FEA
Design Task: Design a product that demonstrates the ability of the Connex line of 3D printers to print mulAple materials simultaneously.
For this task, I chose to design a flashlight, as consumer flashlights contain mulAple materials, ranging from hard plasAcs to silicone overmolds of differing durometers.
Design Concepts: The main area of focus for this project was the feel of the flashlight in-‐hand. My research of available products revealed many soJ-‐touch, paKerned silicone overmolds which give the flashlight a secure and comfortable grip.
I developed several grip concepts, but ulAmately chose a studded grip paKern as opposed to a ribbed or diamond knurl paKern. The studs, I felt, gave the grip a beKer feel in-‐hand.
Preliminary Design
Concept Drawings
Challenges: The problem with the first design iteraAon was the grip feel. The grip did not have the desired “squishiness”, due to the thickness of the overmold and the differing material properAes between silicone and the Objet rubber material. The funcAon of the grip design also proved troublesome, as the studs on the overmold were easily scraped off during use and transport. Since the product was intended to be displayed at a tradeshow and handled by many people, this design was inadequate.
Final Design For the final iteraAon, I addressed the deficiencies with the grip design. By making the grip studs larger, the grip had a springier feel and felt more akin to silicone. In addiAon, the larger studs beKer resisted stripping as compared to the first iteraAon. This provided beKer longevity for the show piece.
The new design was tested for durability by other employees of Objet. Employees carried the flashlights to and from work in their briefcases and work bags, and handled the flashlights periodically throughout the work day. With this new design, the flashlight grips lasted for several weeks on average, which is a long life-‐cycle considering the deficient material properAes of Objet resin. The markeAng team was pleased with the product and sent fully funcAonal flashlights out to the sales team for use in meeAngs.
Personal Projects
Background: Sedentary lifestyles lead to a host of health problems, including cardiovascular disease and obesity. These problems are exacerbated by the fact that our society spends a majority of their day siSng while at work. Sit-‐stand desks have been gaining popularity as they allow employees to stand at their desk and sit when a rest is needed.
While these desks offer great health benefits, there are many problems with current desk designs. Inexpensive desks are staAcally in the standing posiAon, necessitaAng use of an uncomfortable high chair to sit at the desk. Desks that allow the user to move between a siSng and standing posiAon are very expensive, upwards of $1500 per desk. In addiAon, these require the user to manually move the desk from one posiAon to the other, which is cumbersome and annoying for the user.
Design: The desk I designed uses linear actuators to move the desk surface from a siSng posiAon to a standing posiAon. The actuators are controlled by a program on the user’s computer that moves the desktop surface from a low siSng posiAon to a desired standing posiAon (up to 12 inches of movement). The frame of the desk is created from stock 80/20 Aluminum extrusion, anodized black. The desktop is a stock table surface from IKEA.
This design addressed all of the shortcomings of commercially available desks: allow the user to quickly and easily go from a siSng posiAon to a standing posiAon, and have a reasonable price point of $500.
Automated Sit-‐Stand Desk Desk Posi4ons
“The High Voltage Fish” Custom Bass Guitar
The High Voltage Fish is a collaboraAve effort between myself and Dave Cohen, personal friend and owner of Equilibrium Guitars. Equilibrium Guitars is a start-‐up company that hand-‐builds custom guitars for musicians who seek unique designs and cuSng-‐edge sounds.
The High Voltage Fish aims to shake the bones of its listeners. It is a neck-‐thru style bass, which increases the sustain of the instrument. The neck is made from a laminate of Bloodwood and Black Walnut. This wood combinaAon captures a sharp aKack and adds a full midrange frequency spectrum to the instrument sound for that “growliness” of 70’s rock and metal. The body wings are made from Padauk, which adds warmth and further punch to the sound.
For the body and headstock design, I wanted a modern streamlined look that also captured the aggressive nature of the guitar sound and was consistent with the design vision Dave has for his instruments. This is the look that I tried to capture in my iniAal concept sketches, which I am sAll in the process of finalizing with Dave.
Concepts & Inspira4on Gluing the Neck Blank Finished Blank
8-‐String Guitar Bridge
The bridge of a guitar is an integral piece of the instrument. It anchors the strings to the body of the guitar and transmits the vibraAons of the strings to the wooden body of the instrument. The 8-‐String fanned fret guitars that Dave Cohen of Equilibrium Guitars creates are problemaAc to manufacture as no bridge parts exist for these exoAc instruments. Fanned fret guitars require an angled bridge to account for the highly varied string length on the guitars and ensure proper intonaAon of the instrument.
I met with Dave to create his specificaAons for the bridge components, which I turned into CAD models and drawings. He decided that he wanted the bridge to be made from brass, which was ideal for sustaining string vibraAon (and for machining!). Before creaAng the bridge plates, I created the plan to fabricate the parts: cut the stock material on a band saw, mill the holes and slots by placing the stock in a vise with parallels, and then put the part in a fixture to mill the final profile. The holes of the parts were then hand-‐tapped to allow the bridge saddles to be aKached. AJer tapping, the plates were powder coated black to match the instrument aestheAcs and laser-‐marked with a white EQ Guitars logo.
Plate AMer 1st Milling Opera4on Final Profiling Finished Plate
Spec Sketches