New member seeks advice on Solidworks

[Ryan]

I am interested in designing steam engines particularly beam and mill engines. I have quite a bit of experience with 3d modelling applications for artistic uses, but at the moment I am learning Solidworks. I cannot actually build/machine parts as I have a disability. However I have someone who owns a lathe and has made some basic parts for various things. I am not familiar with CNC, is it at all practical and not overly expensive to send solidworks files to a small workshop and have them machine most of the parts. Is it just a matter of them outputting the files to their machinery, or does it require someone to manually program the codes ( I imagine this would be expensive) Then I could get the person with the lathe to make simple parts.

does anyone have some solidworks assemblies as examples they could send me, so that I can look at how the engines function? can you assume that if you get the engine to work properly in the software it will work if manufactured? I've noticed that you can apply a virtual motor to machines in SW, or is there a way to actually apply pressurised "steam" to the assembly?

as far as plans are concerned that are designed in imperial measurements, is there a degree of rounding up/down. For example is one inch chosen for a starting point and not something like 1.246 as it is a nice round number. Whereas I work in metric, 1 inch = 25.4. I suppose I am wondering how 'scaleable' steam engines are as I have heard combustion engines do not scale down too well.

I Appreciate any advice people could offer, if I have not flooded my message with too many questions

 

[rickharris]

First Hi & welcome. Although I am not familiar with solid works I am sure that it will export the final drawings as DXF files. This is a common transfer format that any CAM/CNC system should be able to import and convert into G code for the machine to use.

In short your drawings should be manufacturable from a CAD/CAM point of view. Under normal circumstances they will use the orthographic (2D" output from your solid works although all engineers like to see the 3D over all view so they know what they are making!

"If you draw it right will it work" - Mmm well lots of things I draw have to be fiddled with before they work to my stisfaction - Part of the prototyping process. Although a good animation of a 3D model will let you avoid all the obvious errors you might otherwise make.

Wont solid works allow you to draw in decimal inches and then convert automatically to metric?

As for rounding scaling - Ill let others with much more practical building experience give their opinion.

 

[Ryan]

I have seen software for solid works, that allows you to output G-code. But I suppose that is something that a specialist machinist would have to set up? given I don't know what tooling they would have. I am wondering if there is any business catering to small/single run jobs, a quick search on google revealed mostly industrial/ high precision work.

 

[Kermit]

I KNOW there is a website for this.

A Machine shop that has their own version of CAD that you download onto your computer and create parts with. The parts are then made by the machine shop and sent to you.

???

 

[Kermit]

http://www.emachineshop.com/machine-shop/Download-Free-CAD-Software/page17.html


Here is the "how it works" page,
Kermit

 

[joeby]

There are many shops, probably more now than ever, that will make your parts; but the file format that they would want depends on the software that they are using.

CAM software, that actually creates the G-code, is an intermediate step between design software and the machine tool. Depending on the shop, machinists, and machine tool; some of the parts may be programmed right at the machine on it's control. The shop doing the work will tell you what format they can work with.

Solidworks will export in several different formats, iges, step, stl, prt, etc.. I used to get many files in .iges; but had some troubles with bad surfaces, so I changed to .step format and that helped. A shop that has SolidWorks may ask that you send along the sldprt file and they will export to their CAM software as needed. The 2D files (.dwg, .dxf) probably won't be needed for the actual machining, but are nice to have.

To answer your question about model to machine, yes, someone will have to do the programming for the machine using your model, and the cost is related to the complexity of the part and how good a job you did constructing the model. If you leave gaps and holes in the model that the shop has to fix, the cost goes up. If you design very small details, sharp inside corners, small inside radii, deep pockets, and the like, that will be hard to machine the cost will go up.

Your dimensions for the various parts are going to be determined by the design, of course; but I try to make as much as I can to nominal sizes. In inches, for example, I wouldn't design a shaft to be .192" +/- .002" diameter unless forced to. If you would do that, it would require making the part from larger stock and paying for machine time and wasted material. If you make that same part .1875" (3/16") +/- .002" perhaps off the shelf material could be used, saving time and cost.

Just a few thoughts.

Kevin

 

[fdew]

What you are asking is what I do for a living. I design in SolidWorks, the designs are sent to shops and prototypes are made. Depending on the shop, I send step files, DXF, or drawings.

The only problem you will run into is cost. It takes a lot of time and skill to setup and run a machine and therefor costs a lot of money.

As a example, I just finished a very simple little optical gadget. We took a chance and had 5 sets of parts made to drive the cost per part down. Even so the mechanical parts cost $300 each from a good CNC shop that I have a good relationship with.

Here is the assembly. http://lbpinc.com/Filter Wheel.jpg

 

[Ryan]

thanks heaps for all the helpful comments. It does sound rather too expensive to have things machined. Might stick to building virtual machines for now. I suppose casting sets could be a place to start. A family member actually has a lathe, are castings easier to work with than building from scratch?

 

[fdew]

Well, Yes and no. Castings are near the final shape so you make less chips, and they have a nice cast look.

BUT You spend a lot of time thinking about how to hold them and how to start. With stock you pop it in the vice or the chuck and go. with a casting you need to think about what machined surfaces are important and them what surfaces you need to create to be able to set up for the important machining. It is fun and challenging, but it takes time.

I just machined a casting for the end cap of a cylinder. It took a while to figure out how to hold it to machine the OD. (Think how you would machine the OD of a silver dollar.

Perhaps you could work out some sort of a team build with a family members or? You design, Do final assembly, painting, whatever your disability allows. the other person machines two of each part.

This forum has a group build section. I don't know anything about it.

Frank

Frank

 

[fdew]

BTW There are a few of us who like to design and do it in Solid Works.

If you would like to kick around some ideas, I would like to join in. Example You mentioned Beam engines. I want to build one and I would like to build a slow runner. I wonder what brainstorming we could do to design a slow runner.

Carfull crank shaft balance,
Ball bearings at least in the main pillow blocks,
low friction seal for the piston.
valving designed for metering the exhaust?

Just thoughts.

Frank

 

[Tin Falcon]

as far as plans are concerned that are designed in imperial measurements, is there a degree of rounding up/down. For example is one inch chosen for a starting point and not something like 1.246 as it is a nice round number. Whereas I work in metric, 1 inch = 25.4.

The imperial system is based on fractions of an inch or 1/ 2^x. X being equal to 1 through 6. Most imperial stock usually being in 1/16 increments sometimes 1/32 increments for small sizes. So if yo are designing you should round to the nearest 1/16 for sizes over 1/8 inch to the nearest 32nd or 64th for small sizes. Familiarize yourself with standard stock sizes to reduce excess machining. Browsing McMaster Carr web site will give lots of information about available materials the suitability of a particular alloy for various applications and standard sizes.

I suppose I am wondering how 'scaleable' steam engines are as I have heard combustion engines do not scale down too well.

Remember the rules when scaling down. linear measurements are proportional area is proportional to the square and volume is proportion to the cube.
In other words a 1/2 scale engine is half the length of the original the surface areas are 1/4 that of the original and the volume of the piston displacement is 1/8 of the original. So a 1/2 scale engine produces 1/8 the power of the full sized version .A 1/8 scale model engine will only produce 1/512 the power of the original.
That being said I have seen some very fine running small versions of various types of engines including v-8 automobile engines.
Tin

 

[kvom]

the piston displacement is 1/16 of the original

I think you meant to say 1/8

 

[Tin Falcon]

I think you meant to say 1/8

Yep I did thanks!
Tin