Steps that help you get the cost for DIY CNC milling machine

The first question you ask yourself as soon as you set your mind on building a CNC machine: How much will it cost me? And sometimes it feels you don’t know where to start, with so many options that our out there that get you overwhelmed. Although there is no definite answer to this question, this post is here to help you get clear on what you want (and need), so you can get closer to the final price.

cnc-machine-cost

Decide the basics: what

To even get started on calculating your costs, you need to be clear about this part. There are so many things a CNC machine can do, but you need to settle for the ones you need the most. You don’t want to build something that would cost you too much but end up not being used. So, first determine:

What type of work do you want to do on your machine? Is it carving, cutting, engraving, or all of those?

Now combine that with the type of materials you will be working on. Raw wood, plywood, MDF, metal (aluminium), foam, plastics… all have different levels of resistance and thus require different machine structure. For example, materials that are soft like foam don’t require high power motors, but for a machine that plans any type of aluminium work more powerful motors are recommended.

Next, define the working area for the machine. Think about the biggest part you would want to work on. How big is it? If it’s too big, can you somehow split the work in pieces and save some space in machine size with that? Also ask yourself how thick the materials will be, as this will determine the Z axis travel.

Work out the details: how

Axis

Now that you know the what part, you can start thinking about the how. Do the products you will be making require more advanced approach, like adding an extra axis, or not? Hobby CNC machines can generally have from 2 to 5 axis, depending on the requirements. 3 axis machines are most common DIY milling machines that you can find online. 4th and 5th axis are added for rotary movement and add more possibilities to your machine.

Linear motion

Linear motion system is an important part of the machine which needs to be done precisely as it supports the entire machine so it needs to be able to hold the weight and guide it precisely. A poorly done linear motion system results in bad machine performance, keep this in mind.

It consists of 2 parts: some type of linear bearing + linear bearing guides. There are options to have either fully supported or partially (end) supported systems. The most common choices (and one of the best in my opinion) are pictured below:

linear-shaft-bearing-blocks

Linear shaft + linear bearing blocks

linear-shaft-supported-open-bearing-blocks

Linear shaft with support + open linear bearing blocks

 

 

Miniature linear guide + carriage

 

You can also find various uses of inexpensive systems like drawers and wheels and other DIY systems, but as a perfectionist I must say that I’m not a fan of these because I think they aren’t good for any type of  accurate machine work.

Linear drives

This part is in charge of driving the machine along the axis, by converting the rotary motion from the motor to controlled linear motion of chosen component. There are different technologies for these components and it is up to you to choose the appropriate one for your machine:

Lead screw

Ball screw

Ball screw

Rack and pinion

Rack and pinion (gear)

 

Timing belt and pulley

Timing belt and pulley

Each of the systems mentioned has it’s pro’s and con’s and are more suitable for different machine types and sizes.

Electronics

Electronics are essential part of any CNC machine. They cover everything from motors, drivers and breakout board to switches, connectors, cables and other electrical components.

For motors you have 2 options – stepper or servo motors. Each of them have their own (dis)advantages and to discuss them all now would take a whole new post. I suggest  you do a further research on this subject if you would like to know the details. In my opinion, stepper motors are more adequate for DIY machines and people that are just starting to get into building them, as they are cheaper than servos and are almost easy as ‘plug and play’. Regardless of the motor type you choose, each motor will have one driver to control it.

Spindle

There are 2 paths to take here – choosing either industrial spindle or going with a regular router that can be bought at any hardware store. Wood routers are very noisy and sometimes even more expensive than industrial spindle motors. It all comes down to money and types of work you will be doing on your machine.

Small parts

Things like stop buttons, connectors, switches, cables, cable chains, cases for electronics, screws, grease and similar are all small parts that you initially don’t count in your price but when it comes to buying these, it can easily pile up and increase the price. So, count them all in and find prices so you don’t get surprised later.

Design it: machine frame

After you’ve done your research on the things above and narrowed your choice, you can start designing your machine. I wrote about the software I use for this part, as it helps me visualize my idea and discover possible errors or bad calculations. The way I like to work is to first order my linear motion system for X and Y axis, measure them to the finest detail and then go sketching from there.

As one of our European proverbs say: measure thrice, cut once. So, make sure you think and plan  ahead as many things possible, even if it means adjusting your design few times.

Conclusion

This post really just scratched the surface of the whole design and planning process for your machine, but it’s a starting point. There will be more posts explaining in more detail each of these sections, but if you have any questions to the above let me know in the comments, I would love to hear from you.