The newest printer build is coming along nicely. We decided to explore the CoreXY motion system. There’s still much work to be done along with some design decisions/changes to make.
The whole idea is to build a printer that has:
- BOM utilizes standard and available printer parts people already have so they can convert their printer into a SolidCore
- All Metal or Printable
- Independent Z-Axis Motors (even though often frowned upon compared to a shared belt setup)
There’s a lot of wasted space at the moment when you compare print area to the actual size of the build. The extra length and width gives me room to make more adjustments as the design process moves forward. It’s easier to cut extrusions and material then re buy or remake parts.
We’ll probably make some changes such as reorienting the the y-axis linear rail into a vertical position similar to the RailCore, redesigning the carriages and motor/belt mounting plates where the z-axis motors are placed on the bottom of the machine. When I first designed the plates I thought it would look cool with the motors on top but after I machined everything I realized that moving the bed up and down could cause deflection in the main plates. I’m also considering making the carriage components and rail support one piece similar to the latest update on E3D’s Tool Changing printer.
We’re working on a small budget lol which “recycling” parts from previous builds. For example the bed is made from 3/8 inch thick aluminum that we robbed from an old printer. We’ll change that to 1/4 inch thick once we get more money.
The left motor plates are going to be re-machined to give room for a tool changer setup.
The overall footprint of the machine relative to print volume is somewhat excessive. In order to have a solid enclosure design I had to move the motors inside the frame boundary. This sacrificed the overall printer size to print volume ratio.
This design was inspired by the RailCore, HEVO, D-Bot, Mike Fisher’s QuadRod and Maarten van Lier’s corexy build.
I’ll publish the files open source on Thingiverse when finished but there’s still a lot of work to be done.
The CoreXY 3d printer design is very different than most common 3d printer motion systems that have dedicated stepper motor for each axis. The core-xy motion system is designed to minimize torque while moving the gantry and carriage.
The Advantages of the corexy system is the increased print speeds that can be achieved due to the light weight carriage. While 3d printing is a very slow process any kind of reduction in print time is much needed. In addition to faster print speeds the smooth motion that the core xy uses is also known to reduce artifacts commonly found in 3d printed objects.
The corexy kinematics mechanical arrangement includes a unique motor movement where
X or Y motor move together or opposite of each other to move the carriage from left to right or towards or away . If you were to move just one motor you would see the print head move diagonal.. If the two motors move opposite of each other the print head will move along the X-axis, If the two motors move in the same direction the carriage will move along the Y-axis.
CoreXY vs Cartesian
Most printers utilize Cartesian or plotter style motion where one or two motors will move the carriage from left to right or towards and away. This is the simplest approach in 3d printer motion. While the core xy setup is more complicated but a more efficient approach.
CoreXY Belt Path
The corexy 3d printer belt path has been explored in many mechanical arrangements. The main two corexy belt routing methods are belts crossed or not crossed. The main focus should be to keep the belt routing path parallel to the X and Y guide rails. There’s an excellent blog about corexy belt path by Mark Rehorst here.
CoreXY vs Hbot
Source: Shaqour, Bahaa. (2016). Developing an Additive Manufacturing Machine. 10.13140/RG.2.2.10190.77128.
A similar mechanical arrangement of the core-xy is the H-bot. The Hbot uses the same concept of carriage motion as the corexy but is much more simple and requires less math. In addition the hbot is harder to “get wrong.” The corexy belt path has it’s pros and cons. The corexy’s disadvantage is that it requires two belts on two separate planes. The coreXY balances the forces while moving the gantry or carriage to minimize “racking’ where the mechanical system is pulled out of square.