proposal for Solids Works training and 3D printer/ CNC training, whistle/piston motor

[Mike Bushroe]

       I was excited about the thought of a mouth blown, plastic piston motor that I decided to rough out some design details and see how hard it would be for a beginner's class in Solid Works, as well as result in data files that could be converted into CNC or 3D printer command files. I think I have something that should be possible in both plastic and aluminum, a bit of work to define all the parts, but possible to make on either machine, and hopefully fun to play with and show off as a gee-whizz, look what WE can do here at HSL!

   The basic idea is a pair of double acting pistons, with the crank offset by 90 degrees so that no matter what position it is left in, there should be enough torque to start it pumping the next time someone blows into it. Although I have sketched in places for rings to improve the seals, efficiency will not be a big part of this design. And I just drew in propellers for output, but anything else simple can be put there instead.

In the overall drawing we have a top view. The mouth piece is at the top, and then the 'cylinder block' section', with a central air intake runs down the middle, two slide valves on either side of the intake, then the double acting pistons. Below that is the 'crank case' section, with the piston rods coming straight out and going to an external piston rod pivot (necessary for double acting pistons) then the pivoting part of the piston rod, then a two part crank bearing. The straight to pivot joint has long projections out each side, one to slide in the frame and help keep the straight part straight, and the other side sliding in a slot in the slide valve to push it into reverse flow at each extreme of motion. Sorry, no overhead cam on this one. I tried to come up with the simplest design to make it better for a first or second project. The frame of the crankcase is U shaped to stiffen the crank shaft area.
 

   In the second drawing I have tried to detail most if the individual pieces. Sorry, but until I take the SolidWorks class, it will hard to make a better, more detailed set of drawings. But this way, there is still a little fine tuning engineering for the class to do as the design is entered. There is a side view of one piston, with the slide valve behind it.The piston rod passes through the back of the cylinder (probably a good place for an o-ring slot) then reaches the pivot. The slide valve with its slot is visible behind that part, and a section of the crankshaft is shown at the right. Above is the piston themselves, will piston rings sketched in. The pivot arm joint should be two-sided so that the pivot is under double shear. The other end needs to be big enough to bolt on the bottom half of the crank bearing because I don't see how to assemble even the plastic pieces without it. The Slide Valve has a tapper cut at the front end to vent the top of the piston when the slide is pulled back , and then plug the exhaust and position a slot over the piston port to let air in from the intake manifold. The opposite is done at the other end so that when one side is venting through a cross hole, the other is passing compressed air, then slide it in the direction of the piston motion at the extreme end of travel to switch it to go the other way.

  I have sketched it out to make the cylinder in a constant cross section cylinder head. On the 3D printer, the air plenum can be square, when milled from aluminum round is going to be easier. The two valve slides channels will be the hardest part to mill, but the top and bottoms can be left rounded if the valve slides themselves have rounded edges. The heads at each end contain the notches the will vent air in and out of the cylinder. The remaining pieces should be easier to cut without complex internal channels. In aluminum, I have sketched 4 long thin bolts to hold the heads, cylinder block, and crankcase together. In plastic, this can either be bolts or just glued together.

   Well, what do people think about this as a project for learning Solid Works, then learning how to take the files from Solid Works and run them through CAM software to generate g-code to run the mill or printer?


Mike

[Mike Bushroe]

Forgot to point out that this would also be fun to use the animation feature of SolidWorks, and would also be a good way to check the slot width for the pivoting part of the piston rods to make sure they clear through the entire range of motion.

Jasper, sorry, no surface following on this one :(.

Mike

[Ben Humpherys]

.........surfaces........*shudder*

Anyway, were it me teaching the class, I would go for a model with fewer moving parts. One single-acting cylinder and flywheel would do nicely I think. Like this one. Actually, SolidWorks has rather good tutorials, those are a good place to begin. Though they don't tell you much about what a chamfer, fillet, extruded boss/base, etc. actually ARE, just how to do them. Which is really quite a bad way to go about it in my opinion. But ill spare you that rant.

To my knowledge, its actually easier to use a solidworks model for a 3D print than machining. The reason is, you can directly export to an STL file, which is what the 3D printer uses to generate its code. But CamBam is only 2.5D, so you would have to start from a 2D sketch. Which means the additional step of creating a drawing of the part, then exporting that into a .dxf or similar, and cleaning it up before loading it into CamBam. Experimentation will tell whether that process can be streamlined.

[Mike Bushroe]

Ben,

  yes, that is a nice, simple looking steam engine. However, it doesn't look quite as comfy as a piston pumping mouth harp. I am assuming that the 'steam' or compressed air comes in the little nipple one the side. I am still a little unclear about how the piston mounts and does the porting, but I think it would work out when doing the detailed drawings.

  If we intend to do CNC work, we are going to need some form of full 3D CAM software. If CamBam is only 2.5D then it is going to be tough to get the more complex shapes out of the CNC. I seem to remember so talk earlier about other CAM software. Jasper, do we have something else on hand? Or was it someone else that was talking about converting drawings to CNC files?

Mike

[Mike Bushroe]

On the CamBam website, they list 3D import from STL files, so maybe that issue has been resolved in more recent releases.

Mike

[Corey Renner]

I'm not sure why people think that CamBam doesn't do 3D.  This 747 model doesn't look 2.5D to me:

http://blog.cnccookbook.com/2011/01/04/amazing-projects-with-cambam/

I think that one of the Solidworks built-in tutorials is a steam engine.  I don't know if it's worth re-inventing another steam engine rather than just modeling the one that the tutorial already takes you through.

cheers,

c

[Ben Humpherys]

Mike, I think you should absolutely make the dual piston engine! I just think its slightly more complex than necessary to teach everyone else :)

Cambam can do complex surfaces, so exporting an stl file from solidworks probably would work. The thought simply hadnt occoured to me before lol. Anything more complex would require more axis on the machine anyway, so cambam shouldn't pose a limitation.

That said, I'm stumped how they pulled off that 747. Yea, the wings are separate pieces, but how they clamped it to machine the round shape of the body is beyond me. I'm looking forward to learning how you go about machining both sides of a part for things like that.

[Mike Bushroe]

Great! I was thinking how fun it would be to have a 3D printer demo that was sort of like a plastic whistle, but was also a piston engine. I think it would impress newcomers more than some of the complex hollow shapes because it actually moves and 'does something'. If it doesn't too much time, we might even make some to give away. And maybe if it gets done in time, it can become one of the 10 instructables we want to make. At the very least put the files and instructions on our project wiki to get more outside interest in the projects.

Mike

[Mike Bushroe]

 

Hey, I just activated Solid Works Student on my laptop. I installed it as part of my mentoring a FIRST robotics team. We took a couple of weekend classes in Solidworks from Gateway Community College, but I was always falling behind the kids. Now I will see if I can find the steam engine tutorial, then maybe work on my double piston.

Mike

[Ben Humpherys]

Sweet! You know, I bet that might be a good candidate for being made via plastic injection molding. You could probably get a finer finish than you can just printing the parts. And more plastic molding in general would be lots of fun. I wonder if any of the casting people have done anything with plastic?

Two tips for solidworks: always fully define your sketches, so there is no blue colored geometry. And aim to use no more features than necessary when constructing a part.

[Ben Humpherys]

[afmanufacturing]

I have a few cnc mills we can use, as well as visual mill 6 for cam software(full 3d). I wouldnt mind trying solidworks i use rhino4 or alibra for cad.  

[Mike Bushroe]

I am really looking forward to the toy, plastic piece. But once I get the files done, I would be happy to email them to you to try on a CNC. I am trying to keep the design simple enough to do on a 3 axis machine. Which means it should also be possible to do casting molds and injection molded plastic parts as well. We will just have to see how many things we can get out of on whistle/piston motor!

Mike

[Will Bradley]

Where are your CNC mills? We're in the process of buying one ourselves (which needs more donations, I believe!)

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[Artform]

I'm at 5614 n 51st ave see the post about a west side location

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[Amelia]

I love your idea Mike, but I agree, it may be a bit much for the first class to tackle.  Let's stick with the simpler steam engine to begin with.  No one is saying we can't get crazy later on.

[Mike Bushroe]

Yes, I have gotten that idea. I will try to work on it at home, and then share it with the class, and the rest of the group, too, so that we can try converting it to 3D printing and have people make their own. I have not seen the drawings for the steam engine, but I bet it will be easier to do on the CNC than my toy, so we might have that transfer process for a later class. We may want to have the actual CNC work done by someone more experience, but I think everyone will still feel personally involved when the files they have generated are offloaded from their own flash drive into the CNC machine, and then later the steam engine parts come out.

Mike