Monday, June 24, 2013

3D Printing or Laser Cutting?

I am a big fan of 3D printing and we use it in our lab all the time. But I am beginning to realize that many new users often don’t fully understand limitations of 3D printers and try to use them while they would have been much better served by using a laser cutter. 

3D printing is inherently a slow process. This becomes obvious if you try to print a big part. If you are trying to make a large part and you want it quickly, then you might want to consider exploring laser (or waterjet) cutting instead. Let me try compare laser cutting with 3D printing with the example of a support bracket shown in Figure 1. 
Figure 1: Concept of a bracket

Figure 2 shows a 3D model of this bracket that you can make on a 3D printer. It will take several hours of printing time on a fused deposition modeling machine. You will also need to wait for many more hours for the support material to dissolve. Therefore, you will have to wait for an entire working day before you can get your bracket and start using it. 

Figure 2: Bracket design that can be made on 3D printer
Laser cutting is a fast process that requires no setup time. Unfortunately, fast speeds in laser cutting are only available if you are cutting two dimensional profiles. You can cut pockets using raster cuts, but then the laser cutting process tends to be slow. For the bracket shown in Figure 1, you can simply design it to be a four piece assembly (shown in Figure 3). Each of the four individual parts can be simply cut as a 2D profile on a laser cutter in a few minutes. 
Figure 3: Bracket design as a four part assembly; each part can be cut on a laser cutter.
If you can design the desired shape such that it can be assembled from parts produced by laser cutting two dimensional profiles, then you can realize your parts at a low cost and get them in a matter of minutes. You will be surprised by what can be realized by this simple process. For example, we have made several versions of legged robots using this process. 

If you really need to make integrated 3D parts and it is not possible for you to convert your 3D model into an assembly of 2D parts, then you should go for 3D printing. For example, to build a robotic bird we decided to use 3D printing to make structural parts. Assembling a structural frame from small laser cut parts would have been simply impossible in this case, so 3D printing was the right choice in this case. 

3D Printing or Laser Cutting? The answer to this question depends upon the part. 3D printing is a great process and the right answer in many cases. Laser cutting is process with remarkable capabilities, and you should think about it as an alternative to 3D printing. Laser cutting tends to be a lot faster and cheaper than 3D printing, but making it work requires creativity during design.

Wednesday, June 5, 2013

Buying Custom Mechanical Parts on the Internet

Prior to the widespread use of the Internet in mid 90s, getting a custom mechanical part manufactured was a time consuming task. For example, if you were an inventor with a brilliant idea living in a small town, you had to travel to the nearest city that had the appropriate manufacturing facility. Once you got there, it might take you days to meet the manufacturing expert and find out how many and what kind of changes were needed to make your concept work from the manufacturing point of view.

Today, if you have an Internet connection, you have access to companies who will be happy to make your custom part. Once your CAD model is ready, you can order the part with a few clicks of your mouse. The Internet has enabled new e-commerce models in the manufacturing space and you have many options. You can directly order parts from manufacturers, let a broker find you a manufacturer, or work with a manufacturing service provider. Basically, you don’t need to leave your home to get your parts manufactured. 
So a natural question is – what option should you choose? Let us quickly review what you might need to think about before answering that question. Here are the four basic issues that you need to consider: 
  • Can the process under consideration make your part? Every manufacturing process imposes restrictions on shape, material, and achievable accuracy. So it is important to ensure that the process can produce the part.
  • How much will it cost? For some people, cost is the main driver. Other issues are less important. In many situations, other considerations are more important and hence cost minimization is not the right approach.
  • How long will it take before the part is delivered to you after you place the order? Sometimes, people are under tremendous time pressure and getting the part as soon as possible is the most important criterion. Some customers are willing to pay a premium price to get the part shipped quickly.
  • What is the probability that the part that is delivered to you actually conforms to your specifications? Unfortunately, many things can go wrong when placing a part order on the Internet. Moreover, an outfit with a good looking website and a promise of the lowest possible price may not actually have the right capability or expertise. If you receive a defective part, then it may cause a major problem for your project schedule.
Depending upon your requirements and situation, you may need to consider the following four other issues:
  • There might be a few different ways to make a given part. For example, a part can be laser cut or can be made using a water-jet cutter. So it might be useful if the manufacturer can provide multiple process options to you.
  • If you are new to designing mechanical parts, then you might need help in performing manufacturability analysis and improving your part design. Different companies offer different levels of help in this area.
  • If you are working on a sensitive project, then you may worry about protecting your intellectual property. How do you know that the manufacturer will not inadvertently share your CAD models with others? If this is your concern, then you may need to carefully review the data protection policy of the manufacturer. You may need to sign a non-disclosure agreement (NDA) with the manufacturer. Please keep in mind that enforcing NDA with an international company might be quite hard.
  • Different manufactures require different CAD model formats. So you will need to find someone who can accept files produced by your CAD system.
There are three different types of models to buy custom mechanical parts. I will use representative companies in each model to explain the basic idea:
  • Direct Purchase from Manufacturers: There are many job shops with websites. You can upload your CAD model and they will make it and ship it to you. A well-known example is Protomold ( for ordering injection molded parts. Usually, directly working with a well-known manufacturer gets you a good price and the fastest delivery. However, the process options might be limited. This appears to be the best option when you have experience with the process under consideration and do not need significant help in ensuring manufacturability.
  • Purchasing from Manufacturing Service Providers: Quickparts ( uses a number of manufacturers to fulfill its orders. They take care of all the backend details of working with the manufacturer after you order the part. This appears to be the model of choice if you want process flexibility and do not want to directly deal with the manufacturer yourself. This model also provides good support to new designers. However, you might not necessarily get the lowest possible price or the fastest delivery time.
  • Finding a Supplier Using a Brokering Service: There are brokering services that will allow you to find a manufacturer to make your part. For example, MFG.COM ( can help you get quotes from different suppliers. You can then select the supplier who meets your needs. This appears to be a good model if you have experience in dealing with job shops and want to minimize the cost.
In summary, this post gives you a list of questions to ask as you attempt to buy custom mechanical parts on the Internet. I look forward to hearing your experiences. Did I miss anything important?