Making the build-versus-buy decision

Now, some of you may be wondering whether to buy or build your own CNC machine. There are pros and cons to both options. I chose to build my machine because I primarily wanted to use spare parts I had from other builds that I knew might require some customization. I also wanted some freedom to add functionality that might be limited by an off-the-shelf kit.

However, based on what you want to do with your machine and how much time and money you have to spend, you can also choose to buy a complete machine.

To make the buy-or-make decision easier for you, in this section, I will highlight all the considerations that you may need to take into account, based on my personal experience.

Before we begin, I want you to ask yourself the following questions:

• What is the overall budget for the machine? Consider the cost of building as well, and factor in the amount of time you will spend in assembly.
• Which materials will be milled/machined?
• How thick will any given workpiece be?
• How large will the workpieces be? Is a typical 3018 work area enough? Is a desktop-sized unit sufficient, or would a workshop-sized unit be more suitable?
• Will a laser be added afterward? Or is a laser what is primarily desired? Will there be a need to work on curved surfaces?
• What size/power motors are available for the proposed budget? Are they sufficient for the workload anticipated?
• What kind of controller is desired? Is a commonly available purpose-made CNC controller such as the one in Figure 2.3 sufficient, or is more sophistication wanted, such as an MKS DLC board, mentioned under the How CNC works and when to use it section of Chapter 1, The What and Why of CNC? Is a touchscreen controller desired?
• What sort of features are desired/required? Are endstops important? What about a dust vacuum attachment? Can features such as that be added later? Are the added features widely available off the shelf or will you have to fabricate them yourself (for example, for my 3018, I will have to make my own mounts for the endstop switches)?
• Will it be possible to move the workpiece around, or is it more practical for all the axes to move around the workpiece?

The last question asked can dictate what sort of machine you choose. For example, BumbleBee (Figure 1.2 in Chapter 1, The What and Why of CNC) was designed to operate on workpieces that are too large to be moved by NEMA 17 motors, and my design criterion was to minimize the use of heavy-duty motors. Consequently, BumbleBee

sits on top of a workpiece, and the toolhead moves in all axes around it. This allows for the positioning of the whole machine over a specific piece of material that can be as large as I want it to be and then cut from it directly. On the 3018, you would have to cut your raw stock to fit on the machine first.

When you select a machine, consider carefully what your use cases are before you invest time and money into a specific unit. Still, even though we are focusing on the 3018 here, all the concepts apply to most other CNC and laser machines.