I'm rather in the middle of a long-term project at the moment, so I thought it would be interesting to discuss a process for planning projects.
Step 1: Direction and Key Features
If you're thinking through how to go about making a project, you probably have some idea of the basic function, but this is the time to think through what features are integral to your project and which features are ancillary. You may want to go through a few concept drawings to develop a sense of direction for the later steps.
Do as much research as possible in this step. You can research how other people have solved your particular problem in the past, or you can break your idea down into smaller parts and research the mechanics behind each of those parts.
When designing my lathe, I searched through twenty plans to develop a vision for a machine that would have my desired functionality and that I could fabricate without issue. This research and later planning paid off in greatly easing the building process.
This article focuses primarily on developing mechanical projects and reflects what experience I've had in designing such things.
Step 2: Begin Designing Components
This is where things start taking shape.
armed with a sense of direction, you can start designing components and assemblies. As you design parts, check how they interact with the rest of your project.
A quick drawing to a rough scale can really solidify design concepts. It can expose interferences and after a few iterations can really help you find a strong design. I always enjoy having a vernier caliper on hand for this step as it gives me a quick reference for how big things are.
Next up is either the detailed drawing or moving into computer-aided design (CAD) to work out the final dimensions, locations, and tolerances.
Useful articles on tolerances.
As you spec out components, two questions you should keep in mind are "how will I fabricate this" and "should I buy this". For instance, you can punch out a set of washers out of a bit of sheet metal, but why would you when the hardware store sells a pack of them for a few bucks? Then also, springs, bearings, tapers, and wheels are generally best purchased.
In designing my rosette compass, I employed CAD to make the 3d printed components but just used a few sketches for the remaining parts.
The lathe was nearly entirely modelled in Solidworks, with models of the bearings downloaded and inserted from McMaster. The box-treadle and the tool rest wereonly partially modeled, and I used sketches to lay out the dimensions after the base framework of the lathe was built. This let me work with a few materials I happened to have on hand, as well as work to the finished dimensions and scale of my lathe.
In working through the design for a recent project with a set of pulleys, I spent a considerable amount of time figuring out the sizes for a set of stepped pulleys to make sure that they would deliver the desired mechanical advantage, maintain a constant belt length, and not interfere with each other.
Step 3: Costing
There's an old adage that "Things always cost more than they do".
This derives from the saying that things always take longer than they do, which basically works out that you are going to be working on your project a lot longer than you think, and paying a lot more for it than you think
Not to discourage you from your endeavor, but if fabrication time or money are potential issues, you'll want to take some extra time cycling between the part design and the costing step to really dial in your estimates.
Finding the right supplier for each part that you'll need can mean the difference between moving into the fabrication process with no issues and having to revise the vision or your project due to cost concerns.
McMaster-Carr is an industry standard supplier providing everything from raw materials to warning signs, bearings to end mills. I've used them a number of times to get bearings for school projects and a lathe a while back. For the CAD user, they provide free models and drawings of their components to inspect or insert in an assembly.
Hardware stores are good sources for things like threaded rod and nuts/bolts.
For general steel or wood, it is almost always cheapest to find a dedicated supplier for each material.
When building my lathe, I could figure out exactly how much lumber it would require and calculate the cost accordingly. Then add in the cost of steel for the shafts/threaded rod and bearings, and I had a good estimate of the cost of the build.
Step 4: Cycle Back Through
You may find that the best design for an assembly or component precludes the best design for another assembly or component. Frequently, these conflicts can be resolved by slightly modifying your design.
In building my lathe, I had designed this lovely flywheel which would store a specific amount of energy between 1100 and 1200 RPM. Unfortunately, it would be exceedingly difficult to make and balance, so I simplified the design and changed the constraints to successfully build the flywheel.
Step 5: Takeaway
So where to from here?
I'd be willing to guess that you do something akin to this process on a regular basis.
Say you want to make a healthy breakfast in the morning. you know that the parts for this project are a protein, a fruit, and a calcium source, so you envision a spinach and cheese omelet with two clementines and a glass of milk. You get to the kitchen and discover that you have no eggs. An omelet being out of the question, you rummage through the larder and settle on a sack of pop tarts and a can of grape soda. Breakfast of champions :)
What went on here?
Problem ID, "What's for breakfast?"
Setting a vision: Healthy breakfast
designing parts: selecting components
Cost: 2 eggs and sundries
cycle through: didn't have eggs so changed vision
Perhaps the example is a little bit trite, but that is just to expose that this whole article is just trying to put a proverbial finger on a process that in truth is fairly nebulous. Some of the projects I've done have had parts live in my head all the way to fabrication, while others have been meticulously researched/designed/analyzed for over a month before setting blade to stock. Every project or part will have its own demands and you'll probably have some level of intuition about what each will take.
Thanks for indulging my little ramble. I enjoyed working through the process and hope you found it useful.
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