Added Links

I use primarily SolidWorks for CAD. I occasionally use AutoCad. I have added links to bloggers on the two CAD programs I use. These links have useful tips and tricks.

True safety versus reviews

Safety of the systems you design is your responsibility. You cannot rely on others to ensure that your systems are safe.

When I designed my first large hydraulic system I asked our division safety officer for some assistance in reviewing the system. At that time hydraulics were in the spotlight. A few months earlier a fitting blew off an accumalator missing a technician's head by a few inches. The fitting embedded itself into a control cabinet. A true near miss. The root cause was improper selection of the crimp die by the pipefitter. The safety officer replied she knew nothing about hydraulics and her job responsibility was limited to ensuring I filed the correct paperwork and had the proper reviews. So much for assistance there.

I went to an outside hydraulic consultant to review my system for safety.

After the system was built there was a preoperational review with the high pressure committee. The item they were most interested in was that the accumulator was ASME stamped. This generated the most questions before the review.

For the preoperational review they wanted to see the actual system. It had been sent out to an outside hydraulic assembler. It returned the evening before the review. I had specified 4500 PSI rated hoses. This was in excess of the 3000 PSI operating pressure. I did this to have some margin due to the possibility of severe impact loads.

The morning of the preoperational review we met in the conference room. I reviewed with the committee the system design, the FMEA of the system, and the outside consultant's review. We then went out to look over the system. There was the high pressure committee, the controls engineer, the manufacturing engineer, and myself. The pressure committee looked over the system, asked a few questions, reminded me of the need to get the ASME paperwork in order and then left.

When the pressure committee left, the controls engineer called me over and whispered, "look at the hoses."

Hydraulic hoses typically have their maximum working pressure stamped on them. All the hoses were labelled 1500 PSI! I rechecked the drawings to make sure I had specified the correct hoses. I had. The assembler had goofed and put on something other than what I had specified.
Here was a glaring mistake. It was literally in front of the eyes of the pressure committee. A mistake that could have led to a serious failure. And they did not see it. Had they seen it they could have declared themselves heroes. Why look at the gross incompetence we just discovered! Putting 1500 PSI rated hoses on a system with an operating pressure of 3000 PSI and having serious impact loads!

We quietly shipped the system back the assembler. As the error was theirs the hoses were replaced for free.

I have discussed this incident with other engineers and they have similar stories of reviewers failing to catch obvious flaws or reviewers being concerned about minor issues while ignoring other significant issues. I have concluded that despite the best of intentions of having safety officers and review committees no one cares the way you do.

Lindsay Books

I firmly believe that goal of an engineer is the design of, oversight of manufacturing, or oversight of operation of physical items. All else computer modeling, mathematical analysis, CAD modeling is in support of that first goal.

The design of and oversight of manufacturing is greatly aided by knowledge of the physical processes used to make the part. I have taken some night classes in welding and machining to better appreciate the physical fabrication of equipment.
While books do not fully capture the knowledge to build something they are a good start. If you want to learn about casting, machining, machine tool design and how to do it yourself I would suggest Lindsay Books. Lindsay Books has a wide variety of books on engines, motors, machining, casting, metalworking, blacksmithing, and archaic industrial processes. Don’t look down your nose on knowledge of archaic industrial processes. Some of those processes served as the foundation of more modern processes. Knowledge of archaic processes will also serve to make you appreciate modern processes.

Go to Lindsay Books.

I am currently reading two books from them. These two books are of historical interest as opposed to practical how-to. The first, "English and American Machine Builders" is a history of the early days of machine tool design and manufacture. The second, "Instruments and Accurate Mechanisms" is from 1934. It covers techniques for the design and analysis of precision machinery.

Origami and airbags

An interesting article on the application of origami to automotive air bag folding is here. Robert J. Lang, the gentleman in the article, has a personal web page on origami here. Lang developed software to find the creases to flatten a shape.

His personal web page shows origami that he has designed. His origami creations include insects, people, dinosaurs, fish and more. Amazingly, most of the creations are made from a single uncut sheet of origami paper. His creations show incredible creativity and craftsmanship.

When I was I child I played some at making origami. Lang's creation's are beyond anything I could have conceived of when I was making origami.