Ceramic molds and cast parts

Ceramic molds and cast parts - click to enlarge

Old school machinists, listen up, a newly developed technique for creating ceramic molds to a foundry-ready state for investment casting of intricate metal parts may disrupt the current process in a big way.

We're confident that our approach can lower costs by at least 25 percent and reduce the number of unusable waste parts by more than 90 percent, while eliminating 100 percent of the tooling. (emphasis added)

Molds for relatively simple pieces can be produced without a problem using methods developed over, literally, thousands of years, but today's precision parts have pushed the boundaries of the old processes to such a degree that the time necessary to create production ready molds along with a high scrap rate can make some kinds of parts extremely expensive.

The new process, developed at Georgia Tech, called Large Area Maskless Photopolymerization or (LAMP), is a form of 3D printing.

Direct Digital Manufacturing using the LAMP process

The technique places one 100-micron layer on top of another until the structure is complete. After the mold is formed, the cured resin is removed through binder burnout and the remaining ceramic is sintered in a furnace. The result is a fully ceramic structure into which molten metal – such as nickel-based superalloys or titanium-based alloys – are poured, producing a highly accurate casting.

The LAMP process lowers the time required to turn a CAD design into a test-worthy part from a year to about a week,” Das said. “We eliminate the scrap and the tooling, and each digitally manufactured mold is identical to the others.”

Although the current work focuses on turbine-engine airfoils, Das believes the LAMP technique will be effective in the production of many types of intricate metal parts. He envisions a scenario in which companies could send out part designs to digital foundries and receive test castings within a short time, much as integrated-circuit designers send CAD plans to chip foundries today.

As demands continue to grow for pieces like these along with ever more complex parts for any number of uses, the old methods which have served so well for so long, may find it difficult to keep pace.

Digital foundries, ... cool!

Link: Georgia Tech via PhysOrg

Related: Production ready rapid prototyping

Suman Das - developer of the LAMP process

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The Hossack Engine – a Square Piston Two Stroke

by Paul Crowe - "The Kneeslider" on 5/15/2012

in Engines

Hossack engine - square piston 2 stroke

Ever hear of Norman Hossack? Of course you have. He designed the Hossack suspension, often confused with the far more basic girder front suspension and adapted by BMW under the name Duolever, but the Hossack engine? What's that? Well, it's just your average square piston two stroke, that's all.

When I received an email from Norman, I read through his description of the engine and couldn't ever recall hearing about this. He included a number of images and videos and it looked pretty interesting and I thought all of you engine buffs might like to hear more.

It seems Norman Hossack started thinking about this idea, way back in 1969 while still living in Rhodesia. He moved to the UK and spent several years working for McLaren as a mechanic and was part of their 1974 Indy 500 team, but kept thinking about his engine, so he worked out the design and found some assistance getting the patterns made and the engine cast. After putting it all together, the engine ran, but no one was showing much interest, so he shelved the project and moved on, he had some ideas about motorcycle suspension he wanted to develop. Last year, he dusted off the old engine and carefully rebuilt it, installing a new carburetor while paying special attention to the seals, but keeping everything else as it was. The engine runs, quite well, actually, and is currently installed in a pocket bike.

You have to watch the video, but the piston has no wrist pin, it rocks side to side as the rod travels around the crankshaft, giving this engine its unique character. Very interesting.

Hossack engine - square piston 2 stroke

It's probably better if I just let Norman explain the details himself:

Abstract
The HOSSACK engine is an internal combustion engine that employs a novel set of internal components and works on the 2-stroke principal. The 2-stroke type of engine has fallen out of popularity in recent years for several reasons. Prime amongst these is low specific output due to the fact that these designs waste up to 30 percent of their fuel charge unburned through the exhaust. The HOSSACK engine design seeks to correct these losses and gain from some of the advantages that the 2-stroke design offers, namely low weight, low part count and more power strokes per cycle.

Design
The HOSSACK engine crank and the lower end of the connecting rod are the same as any conventional 2-stroke engine. However from there on up to the combustion chamber things are very different. The working chamber that would normally be considered the cylinder is now rectangular in cross-section and the connecting rod and lobe (piston) becomes one fixed item. There is no wrist pin. The crown of the lobe rocks within the working chamber. This means that to maintain a shape that fills the chamber, it has 2 radii opposing each other and these radii provide the running faces. The center point of these 2 radii provide a focal point for the strip seal that seal against the chamber wall opposite the loaded running face.

Objective
There are several gains to be had from this format.

Prime among these is the ability to make the port timing asymmetric. Conventionally piston ported 2-stroke engines open the exhaust port first followed by the transfer ports. This is an acceptable sequence but as the cycle continues the transfer ports close before the exhaust and because of this up to 30 percent, by some studies of the fresh unburned charge is lost down the exhaust port. The HOSSACK design seeks to avoid this loss by varying this sequence. This is achieved by positioning the ports on different sides of the lobe. In this way the transfer ports can open later and close later and the exhaust can open sooner and close sooner. By this it is claimed the losses normally associated with 2-strokes can be limited.

Secondly the HOSSACK engine having dispensed with the wrist pin and its associated structures can be built much lighter. The normal wrist pin requires a strong support structure at the proximal end of the connecting rod as well as a beefy structure in the piston. Add to this the retaining circlips and a bearing and the weight of the rod itself. The HOSSACK engine provides a lighter structure allowing for higher engine RPM or lighter construction.

Thirdly in a conventional engine all these just mentioned masses stop and start 2 times every cycle. At TDC and at BDC these masses decelerate to and accelerate from a complete stop. The HOSSACK design changes this by virtue of its shape. The lobe never stops. It rocks. There is no instant in which the lobe is stationary.

It takes up to 30 degrees of crank rotation for the total mass of the lobe to change direction over TDC and up to 40 degrees of crank rotation over BDC. By this change in the reciprocating pattern the end loads generated are reduced which could lead again to a lighter component or higher RPM.

Norman thinks the engine has a lot of potential and would like to see some academic involvement to analyze its operation. He believes the first engine has run well enough to justify further research. His thought is the engine would be ideal if developed for small engine applications like drone aircraft or lightweight military power packs.

I think it's very interesting and innovative. Square pistons! Don't forget, this was all pre-CAD and pre-CNC, just drawings and machining the old school way. I like it.

Videos below: [read the full article…]

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Autodesk Inventor Fusion screenshot

The explosion of new computer tools for anyone with a desire to work in mechanical design and manufacturing is impressive, and here is an opportunity to try out a real heavyweight from Autodesk. You can download Autodesk Inventor Fusion, which is offered as a technical preview, and use it free of charge until it expires, but that's quite a long time down the road, January 1st, 2013 on the Mac and April 1st, 2013 for the Windows version.

Inventor Fusion derives its name from the fact that it is the first 3-D modeling package that allows users to switch between solid and surface modeling. This app enables robust mechanical engineering and spontaneous artistic expression with the same tools. It can natively export .STL files, the key file type needed to 3-D print or mill objects. It can import DWG files, making it easy to design things in Adobe Illustrator or similar vector-based programs and turn them into three-dimensional objects. There are very few things a hobbyist will need to do that this software can’t support.

Learn it, use it, put it through its paces and see if it's right for you. If you've never used CAD software like this before, here's your chance to see if you can master it, certainly no small task, but there are plenty of tutorials and online help to guide you through the process.

Autodesk Inventor Fusion

Opportunities like this to learn skills that are substantial and valuable are all around us, it continually amazes me and the only thing stopping anyone is desire and hard work. Nice!

Link: Autodesk via Wired

Video below: [read the full article…]

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About That On Board Electric Generator Idea

by Paul Crowe - "The Kneeslider" on 5/14/2012

in Alternative Fuels, Electric motorcycles

Butane fuel cell from Lilliputian

Remember when I was wondering recently about a fuel powered electric motorcycle? I thought, why not build a motorcycle using an electric motor but then generate the electricity on board with some kind of fuel powered generator instead of a battery so you had electricity as long as you had fuel and you could refill quickly instead of recharge slowly. I just saw this little butane fuel cell soon to be sold by Brookstone that can recharge your smartphone 10 to 14 times or any other electronic device multiple times before needing to be recharged itself with a new butane cartridge. Swap cartridges and you're good to go. Right idea, if only it would scale.

Of course, fuel cells are the next step beyond what we were talking about in the other article, there we suggested a more basic setup using gasoline with some type of ICE powered generator, here we're using butane in a fuel cell, no actual generator involved, but the focus is on making electricity rather than simply trying to store it.

Storing electricity for mobile applications like motor vehicles is a very rough road where everyone stumbles. It's notoriously hard to store it in the amounts required to do serious work. For stationary applications, electricity is unbeatable.

Link: Lilliputian Systems via Business Insider

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