The new corexy design is slowly materializing. For now we decided to focus on a simple design that can later be adapted and reconfigured for additional tools and configurations. After moving the z-axis motors to the bottom of the printer we explored a simple setup that would allow the machine to either use three independent driven z-axis motors or a single driven motor with the belt path connecting to three z-axis lead screws.
- All Metal Parts (or 3d printed)
- Linear Rails
- Balanced Carriage Pull
- BOM utilizes most available parts
- Z-Axis: Independent Driven or Shared Belt Routing
The SolidCore design is a work in progress but our long term goal is to is to build a modular platform, not just a printer. Think of it as an ecosystem of parts that can be arranged in different configurations and adapted for unique applications.
- Customized Parts
If you noticed the motor and idler mounts to be placed in the corners of the frame. This eleminates any design constraints of overall length and width. So if you need a printer to be a specific size or you already have a frame and rather not cut it down you’ll be able to use it. Eventually we would like to have a spreadsheet or configuration tool that will allow you to input the current frame or linear rails that already own and output length and rail options. Or if you’re aiming for a specific print volume, you can input the data and it will output the frame and rail length options.
All Metal Parts
The SolidCore is designed to be a highspeed workhorse for repeated use. All-metal-parts and components will give us the durability and repeatablility needed. But we want people to have the option to use 3d printed parts so they can upgrade later on. Solid all metal parts are durable and less likely to deflect at high printing speeds. The aluminum components are also less likely to breakdown over time when introduced to the forces and heat from repeated use. Buy All Metal Parts
- High Speed
Carriage / Gantry
The carriage and gantry are designed to be light weight and strong. We currently use c-shaped aluminum stock because it reduces machining time. The reduced machining time and minimized waste helps but it’s a compromise. Thats going to change soon. We’ll probably make some changes such as reorienting the the y-axis linear rail into a vertical position similar to the RailCore but the current horizontal version will be easier to adapt an E3D Toolchanger. The top plates or motor/belt mounting plates that mount the idler pulleys have recently changed as well. The motor/belt mounting plates shown position the z-axis motors on top vs 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.
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.
We’re aiming to balance the pull to the center of carriage instead above it or below. It seems to be more rigid and minimize deflection. The belts are somewhat within the same plane of the three linear rails to avoid rocking cantilever loads that other designs may have with the belts up high or down low.
At the moment the current build volume is about 350mm x 350mm x 350mm. After we make next set adjustments and assemble the next updates we’ll be looking at 400mm and a 500mm build plate.
This design was inspired by the RailCore, HEVO, D-Bot, Mike Fisher’s QuadRod and Maarten van Lier’s corexy build.
The SolidCore has two different z-axis designs. The SolidCore picture shown on this page has the z-axis motors at the top of frame.
- Independent Driven Z-Axis Motors (On Top)
- Single Z-Axis Motor (Bottom)
Both z axis designs use 3-point bed leveling (3-lead screws). The image below is of the prototype build which uses 12mm ball screw. The new design (yet to be shown) uses lead screw.
All Metal Kit
The design is still a work in progress but we’re looking to find some experienced beta testers. If you’re interested in being a beta tester for the SolidCore project fill out the form below. This is not a finished product and only includes the machined XY hardware, hotend mount, bed brackets for $75.
or Email: firstname.lastname@example.org
Crossed Belts vs Offset Steppers
At the moment crossing the belts instead of offsetting the stepper motors giving the belt path a clean run.
Simpily offsetting the motors may give a much better alignment path
The belts don’t have to cross if the pulleys are at different z-levels, I always thought that was bv the difference between the hbot corexy was the corexy belts crossed at the m segment. But the difference between hbot and corexy is that hbot has a single belt on a single plane, corexy can have either 2 “non-intersecting planes” or a single plane + idlers on different levels to keep the belts from touching.
Hypercube for example doesn’t have that “x” because the belts are on different planes. The Railcore has the crossing belts but the belts are on different planes.
Motors at differing planes = straight belt paths
Motors at same plane = Crossing belts
What is a CoreXY Printer?
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 corexy parallel kinematics mean’s that the motors are the largest source of inertia within the system, are stationary. This means rapid acceleration because the two stepper motors provide a means of moving both axes independently or simultaneously. The major benefit of the design is that the motors remain in a static position.
The corexy kinematics is a complex motion system 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.
Is CoreXY Better?
Over the last few years the popularity of the CoreXY kinematics has became a community favorite. New designs, developments and opens source contrubutions have led many to claim it’s the best motion system for 3d printing but that really depends on the user and application.
- Higher Print Speeds: The stationary X and Y motors reduce mechanical weight and momentum giving the motion system a mechanical advantage compared to other motor placement configurations.
- Quality: With the reduced weight and momentum the setup also results in reduced vibrations and increased repeatability at higher speeds.
- Mechanicaly Optimized: With the x and y motors out of the way the machine size compared to actual build volume ratio gives you more printing space with a smaller footprint. Unlike the hbot the corexy carriage isn’t problematic to twisting or buckling when x and y motors rotate in the same direction.
- Maintenance: The longer x and y belts introduce belt tensioning issues(belt stretch). The increased number of belt idlers increase maintance.
- Scalabilty: The belt stretch and tensioning issues introduces a design constraint as the machine size increases.
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 the 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.
Two Motors (X and Y)
- Both Motors Move Clockwise >> Carriage Moves Left
- Both Motors Move Counter Clockwise>> Carriage Moves Right
- Both Motors Move Opposite of Each Other>> Carriage Moves Toward & Away
- One Motor Moves>> Carriage Moves Diagonal
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. The difference between corexy and the cartesian motion system is the corexy reduces inertia from the static motor positions while the cartesian setup uses at least one motor to drive along each axis. The weight of the motor increases inertia making it more difficult to change direction. Which results in the corexy theoretically being faster in and more accurate than the cartesian.
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.
What You Need to Know Before Buying a 3D Printer
Every user is different and has different needs. There isn’t one printer for everybody. You have to consider:
Experience: What is your experince with 3d printers or mechanical components and electroncs that may require technical maintance or steep learning curves.
Application: What kind of parts are you going to print? What size? What materials? How many?
Expectations: What kind of quality or user experience do you expect? What kind of maintance can apply?
Budget: How much can you spend or how much are you willing to spend? You get what you pay for but you may not need much.