Motion Control in 3D Printing

3D printing used to be an abstract concept. It was something out of science fiction. Or it was what a child thought would happen when they put their favorite toy under the lid of their parent's copier and expected another one to come out...no? Just me?

Today, 3D printing is very much a real thing. What was once rare and exclusive technology is now widely available. Not only is it becoming well-known, it's also becoming an increasingly important part of the design and manufacturing process. Creating prototypes and conceptual pieces has never been easier. But none of it would be possible without precise motion control technology.

What is 3D printing used for?

Creating design concepts and prototypes is a critical part of the engineering process. In many cases, engineers would have to use considerable time and resources completely manufacturing parts that would later be thrown out after one use. Engineers can now forgo making expensive molds for prototype castings and instead design their part on a computer and print it out with a 3D printer.  This process is now commonly known as rapid prototyping.

While rapid prototyping is one of the main uses of 3D printers, 3D printing can also be used for production. Some parts are hard to make by other methods. Traditional casting does not allow for the creation of hollow structures. And with the improvements made over the years, 3D printers can print parts with a variety of different materials, including various plastics, waxes, and metals. They can even switch materials mid-print. Especially for custom pieces, 3D printing is becoming an increasingly important manufacturing tool.

In even more recent years, 3D printing has become something for hobbyists and other individuals outside of the business world. There are dozens of manufacturers for desktop 3D printers. Recent editions of Windows include 3D model building, viewing, and printing programs by default. Toys, crafts, and tools can easily be made with 3D printers in a matter of hours or even minutes.  In fact, many of our demos at AMC have 3D printed parts from the desktop printer in our lab.

How does it work?

There are a few variations of 3D printing methods. Most 3D prints, however, are done by adding layer by layer of print filament dispensed from a nozzle. The series of layers is defined by a G-code file, usually generated by a slicing program on a computer based on a 3D CAD model.

The filament is melted before it leaves the nozzle as print material, but it cools and hardens quickly after exiting. The first layer of the print is printed onto the printer's build plate, which is sometimes heated so that the filament at the bottom stays stuck to it. The nozzle is moved along a dual-axis gantry system to draw out each layer. After each layer is completed, the build plate is lowered, and nozzle starts printing the next layer on top of the previous one. Gradually, the print is built layer by layer. In the cases where one layer overhangs over previous layers, the printer can generate support material, a thin layer of filament that supports the overhanging layers as they cool but can be easily broken off for the final product.

Motion Controlled Components

Both the horizontal movement of the nozzle gantry and the vertical movement of the build plate need to move and be positioned precisely. The material comes out in small increments, but overlapping or diverging too much within the same layer can make the print very messy. The printer nozzle needs to move very carefully in order to draw out the shape of each layer, which can consist of completely separate parts for some layers of certain shapes. There is very little room for error. And if the nozzle is too close or too far away from the build plate, the filament will not stick correctly.

All of the movement and positioning of the build plate are usually accomplished with some form of linear actuator. The nozzle gantry, on the other hand, usually uses linear motors of stepper motors with belts to achieve the necessary positioning and movement. And where there is a stepper motor or linear motor, there must be some sort of drive, often a servo drive.

Since DriveWare update 7.4.2, ADVANCED Motion Controls' digital servo drives can provide closed-loop control for both two phase and three phase stepper motors. In addition, our drives can control linear motors just like any other dc motor. For 3D printers using multiple motors to drive the same axis of motion, our drives can communicate with each other via a network for perfect synchronicity.

Another critical motion control component is in the extruder, the feeding mechanism that pushes and pulls filament through the nozzle. material isn't always flowing through the nozzle. It needs to stop when the nozzle is moving over a gap in the layer and while the build plate is lowering. The nozzle flow also needs to be regulated when the nozzle moves through different geometries. For example, if the nozzle keeps extruding material at a continuous speed when it makes a sharp turn, you can end up with corner swell. The material flow rate needs to be lowered during the corner to get an even thickness with no swell.

Motion Controlled System

So we have a lot of different moving parts in a 3D printer, each controlled by servo drives, but how does it all come together into a coordinated system? That is where you need something like AMC's Click&Move motion control system. ADVANCED Motion Controls has developed Click&Move solutions to run several different 3D printers. Click&Move is able to coordinate all the different axis with different motor types and use the g-code to smoothly generate a perfect 3D print. AMC even developed a custom function block for Click&Move that eliminates the previously mentioned problem with corner swell.

Click&Move can also be used to easily coordinate systems with multiple print nozzles, used for making single parts with different materials or colors. Since Click&Move isn't specifically limited to motion control, it can regulate things such as the nozzle and build plate temperatures, so developers don't have to create a separate system for those.

The Click&Move can easily be integrated into a 3D printer with one of our motion automation control cards (MACCs). The Click&Move program is stored on the MACC and connected to the servo drives. Click&Move can also be run from a PC. Plus, Click&Move is modular and scalable, so it's very easy for a 3D printer manufacturer to keep using it for future 3D printer models as their product line evolves.

If you are developing a 3D printer, contact us for help designing the motion control to make it run. We'll see if ADVANCED Motion Controls' servo drives or Click&Move can be the solution for you.

by Jackson McKay, Marketing Engineer