Hbot and corexy | which system is better for laser engraving machine?

The biggest difference between the CoreXY and H-Bot systems is that the CoreXY system has two timing belts, while the H-Bot system has only one. This means that the CoreXY system has less vibration than the H-Bot system, and can be carved more accurately and faster.

Corexy and Hobt structures are common two-arm parallel structures. No matter the XY motion requires the cooperation of two motors, it is called parallel connection. The principles of the two structures are the same, as follows

 

Motor A moving belt distance△A

Motor B moving belt distance△B

Two motors in clockwise/counterclockwise positive direction

Actual movement of the slider

△X=1/2 (△A+△B)

△Y=1/2 (△A-△B)

There are several ways to understand this law. The movement of the slider will move in a 45-degree tilt direction, and the relationship between the A motor and the slider can be obtained. Similarly, the movement of the other motor is also tilted by 45 degrees, but the direction of the second motor is downward, so the sign of the second expression is slightly different from the sign of the first expression. The actual law of motion can be obtained by combining the upper and lower formulas. No matter which winding method is adopted, the movement principle is the same. There are three main differences between Corexy and Hbot structure:

1. Slider installation is different

The corexy structure slider can be connected to two layers of belts. The reason is that the upper and lower belts move in the same direction; in Hbot, the slider can only be connected to one layer (up/down) because the upper and lower belts will move.

2. The winding method of the belt

The hbot structure is characterized by its simple winding method, and only one belt is needed for the entire loop. It is on the same plane, but it also brings structural problems: the core layer structure requires two belts. Since the belts are crossed, they need to be installed on two different planes. The complex structure also brings structural advantages.

3. The force of the crossbar is different

First, the principle of force analysis needs to be explained. First of all, the belt is a flexible material that can only provide pulling force but not thrust. This principle can be used to analyze the force at each point. When the Hbot moves along the y-axis of the slider, the two pulleys on the lower layer of the beam will not be energized. Because the belt is pushing the pulley at this time, and the belt cannot provide thrust, and the upper two are pulled, so there is power. Therefore, the beam moving along the y-axis is force-balanced. When the slider moves along the x-axis, the results obtained by the same analysis method are as follows:

The force of the beam is not in a straight line, which will produce torque, squeeze the track, and the perpendicularity will be affected. In the corexy structure, the force of the movement along the y axis is the same, so regardless of the xy motion, the force of the beam is balanced. The force transfer is realized by adding 2 more rounds.

Motor installation location guidelines

Theoretically, as long as they are installed on both sides of the beam, in actual use, hbot is usually on the same side (beautiful), and the corexy motor positions are more diverse: there are two common installation methods, the first is The most common installation method, the second installation method has its own name called BLV structure.

Common problems and solutions

1. The size of the machine is too large, and the belt is too long, which will cause a large deformation effect

Use a thicker and wider belt and try to be as tight as possible

2. The force of hbot

Method 1. Reduce the width of the beam and reduce the moment arm

Method 2. Use high-strength sliders and rails on both sides of the beam to reduce deformation

Printer features: The printer with this structure can achieve high-speed and high-precision printing. Its characteristics are similar to the um structure, and the two structures are comparable. Compared with the um structure, this kind of installation will be relatively simple and suitable for DIY. In terms of cost, it is medium, not high.

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