Follow up on Literature Reviews

In thinking about my own experience with writing literature reviews and re-reading my earlier post Those old papers are worth something…, I’ve realized I have more to say about this topic. I forgot an important detail about how to actually do the writing of literature reviews. It’s probably worth a deep dive so let me give a little history on this and then walk you thought how to use the modern tools.

I completed my graduate degrees between 2003 to 2008. I’m confident to say that I was probably the last group of graduate students who needed to physically go to the library to find the older books and scan in articles. After that time internet search engines improved, and libraries offered services to scan articles. In recent history, I’ve only gone to the library to retrieve some books that have too many pages to offer a digital copy or old enough that the digital copies that exist online are poor quality such that I need the figures in real life.

Ok, so here we are in the present with a need to do a good literature review and great tools to accomplish it but relatively underdeveloped skills in using these tools. Maybe this is not a problem for you, so please offer your tips but here are my own. First, use internet search tools or library database tools to find your favorite reference using a keyword search. I teach in a metallurgical engineering field so I’m going to pick out something interesting to me. In fact, I’m going to give you a pickup line to use, “Are you made of copper and tellurium? Because you are CuTe.” Corny I know, but what temperature does this alloy melt at? I want to know how hot CuTe really is.

Step 1 go ahead and do a keyword search for “CuTe phase diagrams.” Realize the first 10 articles are generic resources on phase diagrams because those are way more popular than copper tellurium alloys. If you scroll down far enough or revise your search for “copper tellurium phase diagrams” you will find articles related to what you were looking for.

Step 2 after the keyword search, we have everything we need right? Why would anyone really need to know this info besides the pickup line requirement? Cu₂Te has semiconductor properties in a liquid state so maybe that’s cool for you. This is about literature reviews so let’s work through this. Maybe you are interested in liquid semiconductors, so we could do one or two more searches using these new keywords. However, in our case I’m going to recommend a different plan. Who wrote the article? The search engines for searching papers are much better at finding authors than looking for every combination of keywords. Typically, a graduate student or advisor develops a theme on certain topics. Therefore, you can see the evolution of the research area if you follow a certain research group or set of people. Also, you can track the topic in time both backwards and forward from the article that you start with. If the individual only wrote one paper, then you are complete. If there are more, you can collect all the articles that author has written. Then you can also look at co-authors as well as the references for that work.

Step 3 I need to emphasize this again, using keyword searches on internet search engines will never reveal all the reference articles. You must find the papers the same way that they are written, by authors! Eventually authors will write other papers or wander off into other areas. So, what we end up with are small groupings of papers that are relevant to your research topic. I also generally advise to add papers until the reference set is “complete” for me complete is that there are no other authors or groups that have anything else to say on the topic. If you have too many papers then you don’t have enough specifics and if you don’t have enough, then you need to widen the search. I use a rule of thumb that about 100 papers is usually enough to define the edges of my research topic.

Step 4 don’t stop looking for papers. Eventually using keywords, author searching, and references gathering you will find a complete set of papers. Then you may have reviewers that reveal complete new sets of literature related to your topic.

Metal Casting Scholarship Aggregation

One of the greatest challenges to my program is the difficulty of connecting the right information to the right person at the right time. Sometimes the info is too late, or the person is overwhelmed, or the instructions are unclear. The right mix requires a new perspective, or attitude change to “eat a frog” and move on to new opportunities.

Ramblings aside, I’m launching a google sheets tracker for scholarship activities so that future students of our program can see what has come up before. Maybe that will help connect students with the right info at the right time. I recommend that you put a reminder in your calendar at least one month earlier that the previous years scholarship deadline to remind yourself to look for these ahead of time.

Here’s the google sheet link. I hope that is helps a few people.

Also, couple more comments about being competitive… Work experience, internships, co-op, work study all help make you more competitive for these scholarships. I advise all my students to get experience even if it adds one or more semesters to graduation. It’s better to know you have a job immediately graduating in 5 years rather than graduating in 4 and being without a job.

Cast Knife results

Finally, the moment of truth has arrived. Did the mold lock design work? Are the two halves of the mold aligned, are the molds resting in place or held apart enough to generate significant flash? In this case, these molds were not even glued. Instead we weighted them with a steel block and attached a pouring cup after using a 3/4″ drill to make a hole to the parting line. The pouring is captured on video below for your review.

The pour went well, the material you see is a eutectic iron which is not the material of choice for making knives. However, this material is very fluid and can fill many details. If our mold halves are misaligned or likely to have significant gaps, we should see it with this pour. Shakeout was very satisfying and pictured below. The metal took exactly the shape we hoped for.

I wanted to use these to demonstrate how the final steel knife could look so I made a handle using parachute cord and wrapping the handle. There were a few areas were the mold left more roughness than desired. Therefore, we will play around with a mold coating before pouring the steel version. Anyway, I’m content with the process documented here and I’ll debating the next pattern for us to make in the lab. Please let me know you comments and thoughts about this process.

Knife molds

After 2 coats of lacquer, it is time to try to make the mold. Our chemically bonded sand is a phenolic urethane coldbox system. In the picture below the Tinker Omega system is shown which has a supersack capacity of sand. The sand is fed by gravity to an auger where the sand is mixed with the 2 part binder contained in the drums pictured in the lower right of the image.

The mixed sand with binder is roughly about 2% binder by weight and hardens in about 10-15 minutes after mixing. Therefore, we run the sand through the system, pack it into the mold box, scrape the top surface to make it level, and set it aside until we are ready to extract the hardened sand mixture.

At the end of this time we can extract the sand by setting the mold box on some 2×4 to support the edges and rap the back of the pattern with a hammer. If everything lines up well then the sand will fall out in one piece. If there are undercuts or if the sand twists then the mold can get locked up and can be difficult to extract.

After both sand mold sides are extracted, the mold lock can finally be put to the test in the assembly. Pictured below is the two mold halves before putting them together.

Finally the mold is assembled and I’m going to let them rest because the sand is not quite set up until about 24 hours or so. By setting them on top of each other, and relaxing and dimensional changes will help them match the other side. Before we melt metal and pour, it is required to cut the spruce and gating system which I’m still considering the best size and direction to add them. We are planning to try to pour these with cast iron because of some testing we are doing on Friday this week.

Hopefully the alignment and parting line works as well as the mold assembly went today.

Knife pattern boxes

Using some 2×4 pieces, I completed the pattern boxes for the knife patterns that we made on the desktop cnc. This is good because it gives me a chance to mention wood sealers and my experience so far trying various paints. First, let me direct you to a common source for these supplies (at some point I hope to have a longer list of suppliers) at Freeman Supply. They have a nice catalog that you can search and find all sorts of supplies which also indicate the commonly used products in making metal castings. So, the top choices that are possible are Lacquers, Epoxies, Urethane, and Shellac. If you are finishing a floor or furniture there are some nice articles that discuss the differences between these products. The coatings have different amounts of protection, shelf life, ease to sandpaper, tolerance to heat, etc. However, we have one additional twist to the average need to protect the wood surface. In our lab, we use a phenolic urethane coldbox binder system. So, we can use any of the coatings but particularly the urethane tends be more difficult to protect and return to the original finish. For now, we are using a clear Lacquer to coat the patterns and we’ve seen pretty good results on other patterns.  The picture of the boxes that I made and how they look after the first coat of Lacquer is below.

Our next step is to pull a couple molds from these pattern boxes to see if the geometry fits the way we expect. If everything goes well, we will try to cut a temporary gating system and pour the next time we are melting down (likely friday, cast iron). Making these knives of cast iron is not the correct final material but we pour cast iron often and it’s a good material for checking out the geometry.

Knife pattern update

So, the entire week was filled with failures of getting the other side of the knife mold cut on the desktop cnc. I ended up adding 1mm of stock to the machining surface to prepare it because I couldn’t quite get this wood piece flat. Also, I made some improvements to the control system. Specifically, I upgraded the raspberry pi controller to an Intel Compute Stick which was nice because now it has an easy headless interface that is more stable on the WiFi than the raspberry pi. If this machine stayed on a personal wifi network, the raspberry pi would probably be fine. The other update was to add a webcam to check in on the machine progress, added a connection for the vacuum, and connect everything to an uninterruptable power supply. Unfortunately, even with all the updates I was having the machine stop arbitrarily in the middle of the job.

In my frustration, I ran across a blog post about the same problem. It was an excellent thread with some nice brainstorming about troubleshooting this system. My personal takeaway was to disconnect and disable the hardware limit switches to see if they were accidentally causing the machine to shutdown. After making that change I started my job yesterday about 3pm and left it to finish over night. My result is pictured below. Note, I already dissembled the hold downs for the pattern wood.

The two pictures below show the cope and drag sides of this pattern. The top down shot looked like an optical illusion to me so I also took a picture from the profile with a pencil lying on it to show what goes down and what sticks up. 

Next step is to create the box for these patterns and see if I actually hit the dimensions of the mold lock I was aiming for. Everything looks nice right now, but I have some feeling that I may need to back the lock edges from each other to make sure they sit deep enough. I certainly don’t want these to rest on the lock edges and not on the parting surface. Anyway, a small victory to start the week after frustration…

Jobs

There are some strange parallels between searching for a mate and searching for a job. For example, it feels always like the best one is taken. Or, it should be easier to find one that recognizes my value, skills, and interests. Also, when someone finds a job/mate, it’s in an unexpected and unique circumstances that everyone can’t repeat. Often, I find myself thinking about this again for my students looking for jobs.

Let me post a couple of suggestions and links for those of you searching. First, please update a LinkedIn account. What are the important features? Basically things you think and employer would want to know. Accomplishments, things completed, etc. I’m not sure we emphasize completed tasks enough in our resumes. Not listed on my LinkedIn account is my first job, airport detailer. Basically, I washed airplanes at the local Lake in the Hills (LITH) airport. It was a pretty simple job, planes take off and hit a whole bunch of insects… Then they land and hit more insects. When the planes would finally taxi and park they were covered with bug guts. Why am I telling you this? Because I learned a lot about finishing tasks while I was cleaning planes. I may have started to clean every plane on the jet way but the only ones that counted to my supervisor were the ones that were totally clean. Really you want to be able to tell stories about finishing tasks from your classes, work, hobbies. No one really cares that you started to learn to play the piano… But if you’ve performed for as many people as Victor Borge then you’ve probably got something to say.

Anyway, you may have gotten my point. It’s easier to sell yourself if you have some interesting material to work with, so do something interesting. And, it’s hard to find all these positions so you need to treat your job search with more importance too. Look for a job like it’s your job! I have a number of different pages that I keep tabs on because I’m interested in manufacturing engineering jobs so here you go. I actually have them send me the jobs too so I can circulate them to all students.

https://afsinc-jobs.careerwebsite.com

https://www.fefinc.org/job-listings.html

https://www.aeroindustryjobs.com

http://spe.4careersolutions.org/jobs

I’m adding one more paragraph to comment about salary research. Desland Robinson sent me a link to an awesome site to research position, titles, salaries of similar positions in the state and way more. The site is maintained by the US department of labor and is called O*NET Online. I think if you are looking for a position this is a great place to do some background expectation setting. At some point, I’m going to post about estimating costs and expenses that I think will be interesting for anyone reading this blog.

One more thought to leave you with. The best way to get connected is to know someone, so use LinkedIn, and email, and your work to get to know everyone. That way you aren’t the only one saying you are capable to do the job.

Forge day at UAB

We went to the pull apart and retrieved 3 sets of leaf springs given the availability and condition of the springs. Fortunately, there were two pickup trucks that looked prepared just for us because their beds had been removed. The picture below shows Zeb Dahlke unbolting the axle from the leaf springs. It was raining, so if you do this bring the right equipment. For us, this included rain coats, set of large ratchets (1/2″ torque were choice to provide the most leverage), sockets (13/16″ was the needed size for our project), hacksaw, and PB blaster. 

The leaf spring cost about $25 apiece with the core charge which is not free but still less than about $1 per pound for the steel so I consider it a pretty decent spend. We checked out and brought these back to the lab to start the disassembly. After some attempts to unbolt the remaining fasteners we switched to the angle grinder to remove the hardware.

Afterward, we laid these separated spring sections out to survey. The section at the bottom of the picture, I cut to length for my first sword. This section is about 20″ approximately.

We worked on these pieces and some rebar sections to continue form double sided hooks. Overall a good day, thanks to everyone who came…

Swords from Leaf Springs

There’s a lot of discussion boards and blog posts about using leaf spring steel to make swords. I’m going to collect some information I find about this topic here so that it’s easier to get started with and I’ll probably post some info about our project (since I’m headed to the pull apart tomorrow to see if we can get a few leaf springs to start with).

All leaf springs are made of spring steel which is commonly assumed to be AISI 5160. Removing leaf springs is straightforward but if the bolts are rusted then you want to make sure to bring some lubricant and big wrenches! I’d also inspect the springs because old springs may have fatigue cracks initiating along the edge which may be difficult to remove and finish the sword. Also, leaf springs come in various sizes so starting with an idea of the size of the sword may narrow the choice of the vehicle you are choosing to remove the springs from. I found this video about removing a Jeep Axle to be helpful with getting access to the leaf spring and beginning to remove it.

Once you have the springs in hand then you could take a look at an instructable for swordmaking or various videos of making swords like below. I’ll be posting how we do with our own efforts soon.

 

Image analysis casting manufacturing

We’ve found that image analysis techniques are interesting for developing manufacturing routes for castings. William Warriner is developing all of the routines shown below to be used in his PhD work. For example, watershed segmentation of the solidification profile of a casting geometry is quite illustrative. Below, at left is a component, shown transparent, and at right are the watershed segments of the component’s solidification profile overlaid on the component. Essentially the segments tell us what regions of the casting can be fed by the same feeder or group of feeders. Feeding will occur from segment boundaries where solidification begins and proceeds the thickest section.

Using attributes of each segment and the solidification profile, we can apply known feeder design guidelines to generate feeder geometries. Below are the feeders generated from the segments. In practice, feeders that interfere with geometry can be replaced by side-attachment feeders, or by gating directly to the location of the feeder. In the meantime, it is still worth visually reporting that a feeder is required.

Several of the sections are close and it is believed that number of feeders is correlated with increased cost and with decreased ease of manufacturing. One goal could be to decrease the number of feeders. One way to do so is to provide connections, or feed pads, between segments. Creating feed pads can be accomplished by drawing a solid tube between the feeder locations of neighboring segments. Below at left are the connecting tubes overlaid on the component. At right is the same image with greater visibility of the tubes.

One strategy for reducing the number of feeders is to cluster their segments by proximity. From the perspective of connector tubes, that would mean removing longer tubes and retaining shorter ones. Below at left are the original set of tubes, and at right are the reduced set. Note that currently there isn’t an obvious quantitative metric for doing this without human intervention. The tube removal process here is based purely on human intuition and is intended to illustrate the usefulness of the tubes.

Now that the connector tubes have been pared down to several clusters, it should be possible to reduce the number of feeders so that each cluster is fed by only one feeder. An example, purely for illustration purposes, is shown below. The number of feeders has decreased from 16 to 6. Note that the connector tubes are quite crude, and would almost certainly not be able to be implemented as they appear here.

A casting designer would have to work closely with a product designer to rework the original geometry. They would likely incorporate the connector tubes as wall thickness changes in appropriate locations. Any changes would have to avoid altering features that must remain as-cast. There is also the consideration of avoiding more net-shape machining by adding material in locations where machining is not required.