Ask An Engineer #2: Should I Use an Online Machine Shop or a Local Machine Shop?

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Welcome to our new ‘Ask An Engineer’ series, where Dan Slaski addresses questions that have you losing sleep or staring off into space during important meetings. Have a question for Dan? Send it in.

Question: I’m thinking about using an online machine shop. Am I betraying my local machine shop?

Dear Loyal Luddite,
Respect. In an ideal world we would only use our local machine shop, shop at the farmer’s market, and ride bikes everywhere. Boosting our local economy, sense of community, and hipster ideals.

I use my local shops whenever possible. If for no other reason than they let me hang around sometimes and check out the machines while enjoying that sweet, sweet coolant smell. However, there are times when my project isn’t a good fit for my local shop due to size or schedule.

You have likely heard of the project management triangle. The three points of the triangle are good, fast, and cheap. Pick any two, the thought goes. When applying this principle to machine shops, online shops are going to be good and fast (not cheap). Local shops are going to be good and cheap (not fast). This is like a real life game of rock, paper, scissors. Pro tip, rock gets chosen most frequently. But life is more complicated, so this is more like a game of monkey, ninja, pirate, robot, zombie. Our real life variables being good, fast, low volume, options, and cheap. Got it? Good. Let’s look at the options.

You

Fast, low volume, cheap

Just wear safety glasses.”

In your garage with a dremel. Wait. When did this turn into a game of Clue? In practice this is you, the designer, using the tools and proficiency you have access to, patiently and iteratively hacking away at a solution. The goal is to find a functional proof of concept without concern for repeatability or scalability. This is a totally valid prototyping method. A surprising, and perhaps scary, amount has been accomplished using this crude approach. Just wear safety glasses.

Small Machine Shop

Low volume, good, options

Generally, a one-person local enterprise with varying reasons for operation. This could be a person moonlighting or just starting up. Perhaps a skilled machinist with a home shop or a hobbyist with some prosumer CNC equipment. The consistent thread is that the owner/operators tend to be entrepreneurial and not setup to handle volume. Consequently, they are willing to take on your small projects. These shops can be harder to find (try word of mouth) and may operate more informally than you are accustomed to. All that aside, the service they provide may be that perfect sweet spot niche for certain projects or design phases.

Traditional Machine Shop

Good, options, cheap

From turbine blades to robot pincers, traditional machine shops make parts. They are able to take 2D drawings and use skill, machinery, and tools to create precision physical objects. They have a lot of overhead and need to maximize operational efficiency to stay competitive. It is typically more profitable to run continuous jobs for longer, as during the setup time between jobs they aren’t making parts and parts = money. They prioritize their queue and where your project falls in that queue depends on a lot of factors; so be smart about scheduling and be a valued customer that they want to keep at the top of the list.

Online Machine Shop (Limited)

Fast, good, low volume

The parameter of speed often outweighs all others and allows for the rapid design iterations and the inevitable project emergencies/crisis.”

These vendors selectively limit the scope of what they can do. By using automation, standardizing machines, and stock materials, they slash lead time maintain reasonable cost. The result is machined parts within a specified range of options like size, materials, secondary operations, threads, machining axis, etc. They don’t even accept drawings. When it comes to design, more options mean more potential for creative synthesis and fusion of sed options. Consequently, it would seem anything that limits options hinders design. In this case, you can still rely on other vendors and all the options you had before; you are just adding a rapid machining option. Get creative and play within their rules by turning larger parts into multiple smaller parts or sending it to the “you: shop” afterwards. The parameter of speed often outweighs all others and allows for the rapid design iterations and the inevitable project emergencies/crisis.

Online machine shop (Full)

Good, low volume, options

These operations offer all the services of a traditional shop. They are typically larger and have streamlined business practices which gives them the bandwidth and willingness to take on your smaller jobs (for a cost). I consider this a backup option if your local shop is busy.

I worked with a local shop once on an unusual project. They helped me to blind broach a spline into 316 stainless steel shafts and grind the exterior to a specific roughness. The part had a deep blind hole down the center, one side had a tapered cube and the other side was a circular shaft. No easy task, and a fair amount of patience and trial and error were required. Ultimately, we worked together and they figured it out for me. No other vendor would even talk to me about it. The result was an essential component in an assembly that was granted a patent with my name on it.

Whenever practical, use your local machine shop. Selectively using different kinds of shops to accelerate the design process while getting to the best possible production design and then giving the production work to your local shop can be a win-win. Remember you are building a relationship, which is key in business and life. Your local shop is a hub for local businesses that make things — businesses that you could cross paths with down the road. One, two, three, shoot!

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