Ivo's CNC Corner

Motor Types

Mon, 01 Jan 0001 00:00:00 +0000

Motor Types#

CNC machines use stepper motors for precise movement of each axis. The stepper motors are able to turn a fraction of a degree at the instruction of the CPU.

Here you can see side by side an open-loop motor and a closed-loop motor.

Stepper motors contain 2 electromagnetic coils. The coils are energized in sequence, which in turn rotates the shaft one step at a time.

Grbl Variants

Mon, 01 Jan 0001 00:00:00 +0000

Grbl Variants#

There are 3 major families of the Grbl firmware.

Grbl#

Project website: https://github.com/gnea/grbl

The original Grbl firmware targets the 8-bit microcontroller Atmega 328p, the same one found in Arduino Uno boards. It has a few major limitations:

Only 3 axes are supported - X, Y and Z
Because of the limited ROM size, not all features can be used at the same time. Each firmware has to choose which subset of the available features to include
Because of the limited RAM size, the command buffer is quite short, meaning it can slow down for complex toolpaths

Still, despite its limitations, it has enough capabilities to power most hobbyist CNCs and remains one of the most popular choices to this day.

Parser State

Mon, 01 Jan 0001 00:00:00 +0000

Parser State#

Before you can understand and use G-code commands you have to understand the concept of parser state.

The parser state is a table that remembers the last used command parameters so future commands can use them by default. These parameters are the unit of measurement (millimeters or inches), relative or absolute positions, movement speed (AKA “feed rate”), and more.

Deep Dive: Parser state and movement commands

Every movement command contains coordinate values like X, Y or Z. These values can be interpreted differently depending on the current parser state. It stores things like:

Pin Testing

Mon, 01 Jan 0001 00:00:00 +0000

Pin Testing#

The motion controller has multiple electrical inputs for receiving external signals. They are called “pins”.

The most common pins are used for limit switches and probing. Others can be hooked to physical buttons, like for initiating homing, or pausing a job.

It is important to ensure that they are working properly.

Testing limit switches#

First, you need to find the limit switches. There are usually two for each axis. They could be stationary on each side of the axis. Or they could be mounted on the carriage and move with it.

Tramming a CNC Router

Mon, 01 Jan 0001 00:00:00 +0000

Tramming a CNC Router#

Introduction#

To get the best performance out of your CNC machine, you need to “tram” it - this is the process that ensures that all axes are square. It includes:

The X and Y movements are perpendicular
The Z movement is perpendicular to the XY plane
The spindle shaft is parallel to the Z axis

Most online tutorials describe an overly simplified process that almost exclusively focuses on checking if the spindle shaft is perpendicular to the XY plane. And worse, the prescribed method for correcting the alignment almost certainly gets the spindle out of parallel.

Spindle Types

Mon, 01 Jan 0001 00:00:00 +0000

Spindle Types#

We’ll do a quick overview of the different spindle options and how they can be controlled.

Here you can see side by side a 400W DC spindle, a 1.25HP trim router, and an 800W water-cooled VFD spindle.

DC motor#

Most hobby-level machines come out of the box with a simple DC spindle. Such DC motor spindles are often underpowered and have low-quality bearings.

Basic Movement Commands

Mon, 01 Jan 0001 00:00:00 +0000

Basic Movement Commands#

Before reading about the movement commands, make sure you are familiar with the parser state. It is critical to understanding how the command parameters are interpreted.
Read about it here: Parser state

Another important concept to understand is that a movement command will only move along the specified axes. If your command only contains a Z coordinate, then it will only move up or down. If it contains only X and Y, it will only move horizontally. (G28 and G30 are exceptions, as they will move on all axes if none are listed).

Electromagnetic Interference

Mon, 01 Jan 0001 00:00:00 +0000

Electromagnetic Interference (EMI)#

Disclaimer: I am not an electrical engineer. Everything you read on this page is bits and pieces I’ve collected over the years that seem sensible. They could be incomplete, totally wrong, or simply a case of cargo cult (magic ferrite beans, really?).

Consult with other more reputable sources before making drastic changes to your equipment.

Electromagnetic interference is the bane of all electronics.

CNC machines are especially susceptible to it for three reasons.

Sender Software

Mon, 01 Jan 0001 00:00:00 +0000

Sender Software#

There are 3 main options for interfacing with your CNC machine. A dedicated sender software, a design package, or an offline controller.

Dedicated sender software#

A dedicated sender software has only one purpose - to operate the CNC machine. It will provide the best experience if you only need to execute your existing G-code files.

Such software will show the current machine state, tool position, and other information.

Wiring a VFD for a Spindle

Mon, 01 Jan 0001 00:00:00 +0000

Wiring a VFD for a Spindle#

How I connected a Huanyang VFD to a FoxAlien Vasto CNC

Introduction#

The 400W spindle that comes with the FoxAlien CNC machines is adequate for a beginner, but for more serious work you need an upgrade. I chose to go with an 800W water-cooled VFD spindle. You get multiple benefits:

The extra power allows you to cut faster and deeper
Improved accuracy and stability reduces tool chatter
You can control the RPMs directly from the G-code
The spindle is significantly quieter, especially if you choose a water-cooled variant

Here I’ll describe in detail how I achieved this upgrade. My experience is with the Vasto V1 model, however it should work for any other CNC that has a PWM output for a laser module.

Controlinator 3000

Mon, 01 Jan 0001 00:00:00 +0000

Controlinator 3000#

CNC handheld pendant for OpenBuilds CONTROL

Introduction#

I started my CNC journey on a pretty advanced Roland MDX-540 machine. It had a nifty pendant with a lot of useful features. It displayed the current machine state and coordinates, had controls for jogging and zeroing, and could control the running jobs.

Other Useful Commands

Mon, 01 Jan 0001 00:00:00 +0000

Other Useful Commands#

Pause (G4)#

G4 inserts a pause in the G-code. It is also called “dwell”.

G4 P3 - a 3-second pause
G4 P0.5 - a half-second pause

This is useful for example when you want to insert a pause in the G-code to allow the spindle to get up to speed. Make sure you don’t pause during actual cutting. If the tool spins in one place for long, it could burn the material and start a fire.