EME150A - Well Pressure Relief Valve

It's been a long while since I've posted anything on here. Figuring since finals just ended for school I would add something. I have been working on a lot of projects at work machining things on the 5 axis machines. I could have easily picked from a handful of cool projects I have been working on but none of them were completely my own. Sure I machined a blisk impeller that is pushing the limits of the CAM software developed by Esprit, but I didnt completely make the entire project from start to finish. So I thought I would document one of my projects I have been working on in one of my mechanical engineering classes.

In my Mechanical Design class EME150A, we continue to learn about static failure but dive into fatigue failure of mechanical structures. Who knew that steel can have an infinite fatigue life but aluminum parts have a finite life no matter how minimal the loading is? The class was very interesting and I learned a lot of information that can be applied to real world situations. Over the past quarter, we had two design projects. The first was to design an adjustable indoor bike rack. This project was fun and was the first time I was able to design a product now having a good basis of engineering fundamentals. The second design project was to design a well pressure relief valve and have an infinite fatigue life. After looking at what products were out there and researching the common materials, dimensions, pipe threads and designs, I came up with my own creation. After I generated the solid model and the manufacturing drawings, I was to analyze how strong the product was and to make sure that it had an infinite fatigue life. The picture below shows a cross section view of all the inner parts. The parts include: the body, top bonnet, spring, stopped disc, o-ring seal, and set screw.

The project had about ten design requirements, some of which included: must use standard pipe fittings, withstand outdoor environment, be made with standard machine tools, have a max flow of 25 gpm, withstand infinite pressure fluctuations from zero to 100 psi, have an adjustable pressure relief preset from 50-100 psi, and the adjustment must be locked once set. After doing all the calculations for the critical areas, it was found that the threads, body and disc would not fail as well as the spring would not fail under fatigue loading.

This project was fun to work on and it was nice to be given some freedom to exercise all of the theory that is taught in the classes. This class was my third upper division engineering class and more specifically it was my first mechanical engineering upper division that is specific to my major. I look forward to taking more of these classes.

Die Sinker EDM Electrode

At my internship, this week I have been working on machining two identical copper electrodes for one of the lab members to do some testing on the Electron Beam Melting machine. This machine is used to smooth the surface of mold parts created on EDM machines. Its works in vacuum by using a wide beam of electrons to sweep across the part melting the surface on a microscopic level producing a mirror finish. Here are a few shots of the three processes to complete the electrode including roughing, semi-finishing, and finishing. The finishing is done with an R1.5mm ball end mill (3mm diameter) with a 2% step-over (0.06mm step-over) which produced nearly a mirror finish. I accidentally put scratches on the surface by using a rag to wipe off the coolant. Total machining time was a little under 2 hours.

UC Davis Seal Project

Top secret lab internships are really interesting, especially ones with expensive CNC machine tools that you get to learn how to operate. I've been working hard on a test project to turn the UC Davis seal 2D image into a 3D solid model and machine out of aluminum. This is just step one of the project. Well more so steps 1 through 3 with probably 5 or so more steps to go. I first created the solid model in SolidWorks which was then imported into Esprit 2010 CAM software to generate the tool paths to machine in aluminum stock. Once the NC code was generated I ran on one of the small 3 axis linear motor CNC machines.

The next step in the project is to scale it down to smaller sizes. Right now it is about the size of a coffee mug (~70mm) and the goal is to get it down to the size of a cufflink between 10-15mm. And there's more. The next goal is to create the negative form of this so that it can be used on a die sinker EDM machine to die sink into titanium cufflinks. Im not sure how well this is going to go; I'm imagining a lot of frustration. Anyway, enjoy the pictures.

General Update

Finally those uprights that I wrote a post about got finished today.. completely finished. After many hours the final finishing pass to bore out the center for the bearing was completed. The bearings snugly tap in and the snap ring pops right into place in the groove. The setup looks quite impressive with the brake caliper and bottom lugs bolted into place. I'll have to shoot some pictures of everything together.

Also the rear subframe is coming together nicely as well. There's still a lot of small (annoying) things that need to be finished on it, mainly drilling and tapping holes for things. But at the moment the assembly is mounted to the engine with the shocks and springs mounted (and functional!).

Subframe Assembly

The rear subframe is starting to take shape. I drilled the 66 holes, counterbored some and reamed others to the proper sizes, then pressed dowel pins in an "every other" pattern. The side plates are both bolted and dowel pinned together. The idea is that the dowel pins are hardened to around 60 Rockwell and one hole side is reamed to .249" and the other hole is reamed over to .251" (dowel pins being .250" ideally) giving a secure fit between the pieces. The fit is so close that I have to tap the pieces together with a rubber mallet and also to get them apart. Once the pieces are together, 1/4-20 bolts are tightened down so the pieces dont come apart. The dowel pins provide much more rigidity and shear strength when compared to only bolts holding the subframe together. I have worked on the bellcrank mount and made spacers for the shocks and bolts those in place as well. The springs are on order, hopefully they will be in soon. There is a lot more work on this thing, updates to come.

Subframe Back Plate

Spending lots of time in the student shop working on the formula SAE car, today was my first official part that I designed, generated tool paths, then drilled/tapped and CNC milled on the Bridgeports in the shop. It was all of my creation. This piece is a crucial part of the rear subframe that is being designed for the new race car. All of the rear suspension, drive shafts, and differential all mount in the box-ish aluminum subframe that bolts to the back of the engine. By removing 6 bolts, the whole rear portion of the car comes off, away from the engine. I wish I had a picture of the design, its pretty trippy, and its still up in the air if its going to work. Fingers crossed! This part took a lot of setup and different operations. I wont go into details but there was a lot of drilling and tapping, then some CNC work. In the end, the part turned out flawlessly and should work very well. Enjoy the pictures. The first two show CAM tool path simulations.

Formula SAE Rear Uprights

After learning Esprit 2010 CAM software, we have been using this to create rear uprights for the Formula SAE team. It has been a huge learning experience, including multiple failures and problems along the way. A huge problem arose when trying to post process the code from Esprit to the Acu-rite controller for the Bridgeports in the shop. After re-writing and editing a generic 3-axis post processor for Esprit (again including many trial and error failures) we now have a working post processor for our setup. These uprights are milled out from a 4 x 8 x 1.8" block of aluminum. Much of the material is removed using 4 tools including roughing, ball and flat end mills. Posted below are pictures that document the process from solid model, to CAM tool paths, to final part (well almost final, final pictures will be updated soon).

Control Parts for Second Build

So I decided that I should invest in some new bearings, shaft collars and couplers for my second machine. Purchased some pretty basic stuff, Lovejoy couplers one side 1/2" the other 1/4", 1/2" shaft collars for the lead screws and some 1/2" ID bearings for the 3 axes. Bearings were from Ebay while the collars and couplers were from McMaster Carr; in all I think I spent around $35 for everything.

Control Box Update

The box is now completed with everything installed. Fans, power supply and control board are all crammed inside and everything is wired up and working. I ended up using DB25 connectors (radioshack) to make the connection between the control box and the wires that go to the CNC machine. If you look closely you can see the connector on the right hand side of the box.