CoreXY vs. H-Bot: Which System is Better for a 3D Printer?

Author
Recent Posts

Martin has a M.Sc. in physics and has gained many years of experience in industry as a lab manager and quality assurance manager. He has now tested dozens of 3D printers and is happy to share the collected experience with each new article.

CoreXY

The best way to understand how both systems work is to see them in action. The very descriptive videos of thang010146 on Youtube are perfect for that.

Here is the video for the CoreXY system:

It is important that both timing belts are firmly attached to the violet object at both ends.

The linear movements of the violet object along the X and Y axes are controlled by the red and orange driving pulleys. The black timing belt connects the red drive pulley with the pink pulleys. The red timing belt connects the orange drive pulley with the yellow pulleys.

When the red and orange pulleys rotate at the same speed in opposite directions, the object moves along the X-axis.
When red and orange pulleys rotate at the same speed in the same direction, the object moves along the Y-axis.
If only one drive pulley is rotating, the violet object moves diagonally.

The green line is the trajectory of a point on the object.

H-Bot

There is also a video about the H-Bot system:

The orange object moves linearly along the X and Y axes. The direction is controlled by the pink and green driving pulleys.

Very important is that one part of the black timing belt is attached to the orange block and the other part runs through it.

If only one pulley rotates, the object moves diagonally.
When the pink and green pulleys rotate at the same speed in opposite directions, the object moves along the X-axis.
If the pink and green pulleys rotate at the same speed in the same direction, the object moves along the Y-axis.

The green line is the trajectory of a point on the object.

Which System to Choose When Building a 3D Printer?

CoreXY vs. H-Bot; what is the best mechanical system to build a 3D printer? When you look at the H-Bot’s construction, it seems much more effective and smoother than the CoreXY at first glance.

This may be due to the fact that the Core-XY has considerably more belts and pulleys, which are also distributed on several levels. However, the movements of the Core-XY are not only very precise and compact but also repeatable and linear. Therefore CoreXY systems are becoming more and more popular.

Both systems use the Cartesian coordinate system.

Instead of one stepper motor for each of the three axes, two motors are coupled to move the X and Y axes.

The stationary motors of the parallel kinematics are not only convincing due to their higher acceleration and the resulting very low inertia, but also due to their positioning accuracy. No accumulated guide errors occur.

H-Bot systems are very similar to the CoreXY systems in the area of the drive. However, the H-Bot systems work with one very long belt and not with two short belts as it is the case with the CoreXY system.

This not only increases the source of error but also possibly reduces the print quality. The longevity of the H-Bot system is also at risk if the axes and belts are not perfectly matched and aligned.

The differences between the CoreXY system and the H-Bot system are explained in the following.

Differences CoreXY vs. H-Bot

The CoreXY convinces by its square design with a Cartesian coordinate system. It differs from a Prusa, for example, in that its printing bed only moves on the vertical Z-axis. The print head of the CoreXY, however, moves on the horizontal X and Y-axis.

The CoreXY differs from the H-Bot by its much longer belt. The pulley system is also much larger. This mechanism prevents excessive torque and thus reduces wear and tear on belts and the printer in general. Optically, the H-Bot was also designed in the Cartesian style.

Printers based on the CoreXY mechanism are usually square-shaped. High-end models are also convincing due to the design of their housing. The print head itself is driven by two relatively long timing belts that are connected to a stepper motor.

According to the direction in which the motor rotates, the print head moves in different directions. If only one stepper motor is running, the print head moves diagonally. If the print head is to move in either X or Y direction only, the motors must move in opposite directions or together.

Because of the frame design and the way the axes move relative to each other, CoreXY systems have a number of advantages over comparable 3D printers. Like other systems, the CoreXY system has weaknesses and disadvantages compared to the H-Bot system. The advantages and disadvantages of both systems are discussed below.

CoreXY – Pros & Cons

Unlike other Cartesian designs, the CoreXY system is based on a change in the X and Y-axis. Two coupled stepper motors control the axes. This coupling is based on a special arrangement of the belts. This type of design has been proven in many 3D printers.

Advantages of the CoreXY system:

High precision
High printing speed
In direct comparison to the H-Bot system: prevention of unwanted torque in the area of the frame.

One of the biggest advantages of the CoreXY system is that the system is able to print very fast. Incomparable printer designs, a movable portal is often attached to the respective stepper motors or even to the printing bed. During the actual printing process, these are flung back and forth. This not only leads to excessive vibration but also to wear and tear on the respective workpiece.

The CoreXY system convinces with its firmly fixed stepper motors. The fact that you can move the printing bed vertically is also positive. The tool head is the only part of the printer that moves mass at a significant speed. The amount of vibrations is significantly reduced by this mechanical aspect.

Printers that work with the CoreXY system therefore not only enable much higher print speeds but also enormously high print quality.

Another advantage of printers manufactured in the CoreXY design is the print bed, as it moves in the Z-axis. CoreXY printers can therefore produce the same construction volume with smaller overall dimensions. The CoreXY system has this function in common with the H-Bot.

Since the tool head of a CoreXY printer moves horizontally in both the X and Y direction, it can access the entire building board.

For beginners, the straps or the belt system often pose a problem. While the straps are essential for the functionality of the CoreXY printer, they can of course also cause problems. This is the case, for example, if they are not properly aligned or if they are too tight or too loose.

If the belts are not properly aligned and do not run parallel, other major problems can occur.

Excessive belt tension can possibly lead to increased wear. Also, the accuracy of the printer can be significantly affected by too much tension. In a few cases, excessive belt tension can lead to further malfunction of the printer components.

In the CoreXY design, the tension of the belts plays a major role. For example, if the belts are selected from inferior material, they can stretch more quickly and therefore wear out more quickly. This often causes the 3D printer to lose accuracy after a short time.

Disadvantages of the CoreXY system:

Generally more complex to operate than a normal Cartesian design
Makes many deflection rollers necessary
Long belts are required

However, the CoreXY printer with a too high or too low belt tension is not the only one with this problem. Other 3D printers also have recurring problems in this area with various wearing parts. These include, for example, defects in accuracy and overall print quality.

Another disadvantage of the CoreXY system is the design of the frame. While the frame is relatively stable compared to other 3D printers, it can be inaccurate if the frame is not assembled perfectly square. However, this problem can be resolved with a fixed square. Corner brackets can also help keep the CoreXY printer permanently square.

Many printer designers choose the CoreXY system instead of other systems because its core is more compact. Another advantage is the easier setup. If the assembly was carried out correctly, the CoreXY design will convince with its high print quality.

H-Bot – Pros & Cons

The H-Bot design convinces by its straight and elegant construction. Nevertheless, the H-Bot has an inherent design problem. The precision movements – with the exception of the few H-Bot systems that are manufactured with very tight tolerances – can get out of control.

Due to its specificity, the H-Bot system is more suitable for professionals. Similar to the CoreXY principle, the H-Bot system uses two stepper motors that are coupled together. Thus, the H-Bot system generates movements on the X-Y plane. The motors rotate in the same direction (X-axis) or in the opposite direction (Y-axis).

However, there is a serious drawback with this 3D printer variant. If belts and axles are not optimally aligned, additional torque is generated. Perfect alignment is impossible. Additional torques cause the print quality to suffer and the printer may even jam. Although the negative effect can be reduced to a minimum, this requires real know-how and means a great deal of effort in terms of alignment.

Advantages of the H-Bot system:

Only one belt
Purely theoretically a very high precision can be achieved

The H-Bot uses two motors to move the timing belt. This belt is guided by a system of guided pulleys. The belt itself is attached to the carriage and moves on a guide along a single axis.

This is mounted on two further guiding attachments to allow movement in the orthogonal direction.

H-Bots can be designed to provide the same functionality as XY-stage portals but without their disadvantages. The movement of the H-Bot can be planned and can be combined with other components. This functionality enables many different types of applications.

Applications for an H-Bot system can include point-to-point positioning, selection of location, material filling and application, plannable or three-dimensional cutting, and many other functions.

Other factors that speak in favor of the H-Bot is the possibility to reduce the total cost of buying. For example, the H-Bot can use less expensive pulleys or sprockets instead of threaded spindles. Belts cost significantly less than lead screws or linear motors. This reduces initial investment and maintenance costs.

Since the axes are not stacked on top of each other like the CoreXY, the total weight is reduced and the complexity of the system as well. This form of reduction also saves costs. Thanks to the weight reduction, smaller motors can also be dimensioned subsequently. The smooth-running design of the H-Bot has the additional advantage of increased throughput. The system is accelerated with less mass.

Since two motors share the same load, the load distribution within the system is relatively balanced. The use of two identical motors is possible. Replacing the threaded spindles with the belt drive reduces the friction in the system.

The H-Bot can be built modularly. The working area can be enlarged or reduced depending on the size. Changes in the speed or accuracy of the system can be achieved by changing the diameter of the drive pulley.

Instead of expensive linear motors, cheaper rotary motors can also be used.

Disadvantages of the H-Bot system:

The belt is very long
Perfect alignment required
Additional torques can reduce the quality of the printer

The main disadvantage of the H-Bot system is that the movement of an H-Bot requires meaningful XY coordinates. Due to the coupled design, additional safety aspects for limit values have to be considered. To bring the system to a standstill when a limit value is reached, both motors have to be braked in a coordinated way. In this area, the timing belt can cause a load position error due to its flexibility.

Conclusion: CoreXY vs. H-Bot

Both CoreXY systems and the H-Bot have their right to exist. The CoreXY randomly solves the net torque problem inherent in the H-Bot. The CoreXY is a two-axis linear motion implementation. Developed by MIT Media Labs, even the design for this printer is open source.

Overall, the CoreXY printer offers the same functionality as the H-Bot printer but convinces with its easily movable platform, in which both motors are attached to the frame. By crossing the belt, the unwanted torque vectors are eliminated. A great advantage over the H-Bot system. This is exactly where the H-Bot has its biggest weakness.

Compared to other 3D printers, CoreXY and H-Bot designs can be considered a special case. Both printers are an ingenious solution with fixed motors. Thanks to their ingenious timing belt system, the print head can be positioned anywhere in X and Y.

Fast movement and reduced wear are the focus of both printing systems.

Disclosure: This website is the property of Martin Lütkemeyer and is operated by Martin Lütkemeyer. Martin Lütkemeyer is a member of the Amazon Services LLC and other Affiliate Programs. These are affiliate advertising programs designed to enable websites to earn advertising revenue through advertising and linking to Amazon.com and others. Links marked with * are affiliate links.