Cheap CNC Motion Control

After you have your motors and motor drivers ready to go, you’ll need to have a way to actually control the motion of your motors. CNC motion controller may seem like a simple problem, but the fact that your motors will need to run in a highly coordinated fashion along with the fact that that your motors will likely require some sort of ramp acceleration curve, greatly complicates this problem.

Best hobby CNC control software

You can have a CNC controller be as simple as a parallel port from your computer, or as complicated as a dedicated synchronized multi-axis board. But no matter what you choose, you’ll need some sort of software to control it. This article will show you the more popular options to actually control your CNC machine from a computer.

Vectric’s Cut3D Reviewed in Detail

Before using a CNC machine to mill out a piece of artwork or a machine part, you’ll need to have a valid set of G-code instructions to feed your CNC machine. Many people use CNC machines to mill pieces of art that are generated with CAD packages such as Autodesk 3ds Max, or Maya. Unfortunately, these designs are usually so intricate that there is no possible way of manually writing G-code so a CNC machine can make the part. That’s where Cut3D comes in.

Spindle vs. Router

Hobby CNC machines typically use either a spindle or a router. While these two devices appear similar, they each have distinctly different characteristics.

The difference between a mill and a router

Three axis CNC machines generally fall into two separate categories. Some CNC machines are routers while others are mills. These two types of CNC machines are for very different purposes, and as a result of that, are designed and built differently. For this article, the term ‘router’ is referring to the type of CNC machine, not the device used to rotate the cutting tool at high speeds.

Selecting the material for your CNC machine

CNC machines can be built out of a variety of materials. If you’re going to build a CNC machine, it’s up to you to choose the best material to do it with. One of the main things that will determine the best type of material to build your CNC machine with is what you’re going to be cutting with your CNC machine.

How to cut line art with CNC machines

Generating G-Code for line art is a simple process that can be perfected with a little practice and the appropriate software. CNC machines are spectacular for cutting line art, whether you are doing a one-off piece or mass production. Line art can mean anything from actual line art, to simple mechanical components that can be easily drawn with a line, such as a gear or wheel. CNC machines can replace machines like a scroll saw, and make part to precision. This article will discuss exactly how to create G-code from line art.

Step 1: Get a good digital image of what you need to create

If you have line art on physical paper, such as a scroll saw pattern you purchased, you need to first digitize the image. A digital camera won’t do, since even the slightest tilt will result in a stretched image. What you really need is an orthographic view of the page, and a digital camera can’t do that for you. You will need a scanner with at least 600 DPI scan resolution. To my knowledge, this is about as high as most scanners go, and is a common number. Scanners are cheap if you’d like to purchase one, just make sure if has this scan resolution. Otherwise, you can use a FedEx Express if you only have a few pages that need scanning.

Step 2: Cleaning up the digital image

Scanning in the image is not enough. You must clean it up before you can use it to create G-Code. Your goal is to produce a nearly black and white image with very crisp lines. To the left is an example of the clean up process before and after. Note, the image is fairly large, but you can see all the details if you click on the image.

There are a couple things you should notice. First, the image is very large, especially for a gear that is about 3 inches across. This is because many CNC machines are accurate to a few microns, so you need to keep everything in the original resolution of 600 DPI. This will produce good, accurate G-code later on. In the original image, notice that you can see the other side of the page leak through, as well as one of my hairs that apparently got on the paper before scanning. These can both be easily removed.

 

To perform the image cleanup, you’ll need a copy of Photoshop. If you don’t own a copy since it’s expensive, Adobe recently started a model where you can rent Photoshop for a month for thirty dollars or so. That puts it well within reach for many CNC hobbyists. To clean up an the edges of all the lines as well as eliminate the bleed through from the back of the page, go to Image->Adjustments->Levels, and play around with the arrows under the histogram until you have nice, crisp lines that are very well defined. Don’t go too far, however, since you don’t want any breaks in any of the lines. To get rid of other defects such as hair or text, you can use the small eraser in Photoshop and zoom in very far. This will let you remove any defects with ease.

Up Cut vs. Down Cut Router bits

upcut_vs_downcutWhether you have a normal router, or a cnc router, you’ll still need to choose which bits to use in order to cut your material. There are many types of router bits, but most of them can be put into one of two categories. Up cut bits and down cut bits.