X-Y positioning system is the main index for evaluating the accuracy of surface mount machine, which includes transmission mechanism and servo system.
I. Drive train
The increase of pick and place speed means the increase of X-Y drive mechanism’s running speed, which leads to heat generation. Ball screw is the main heat source, and the change of its heat will affect pick and place accuracy. The newly developed X-Y drive system has a cooling system in the guide rails. By adopting frictionless linear motors and air bearing guideway drives in high-speed surface mount machine, the operating speed is made faster.
II. X-Y Servo System (Positioning Control System)
Driven by AC servo motors and commanded by sensors and control system to realize precise positioning, so the accuracy of sensors plays a key role. Displacement sensors are garden grating encoder, magnetic scale and optical scale.
1. Garden grating encoder
Garden grating encoder installed in the servo motor, it can measure the position of the rotating parts, angle and angular acceleration, it can convert these physical quantities into electrical signals to the control system. The encoder records the number of screw placements and feeds the information back to the comparator until it matches the linearized quantity. The system is highly resistant to interference, and the measurement accuracy depends on the number of gratings on the encoder disk and the accuracy of the ball screw guide.
2. Magnetic scale
It consists of a magnetic scale and a magnetic head detection circuit, which utilizes electromagnetic properties and the principle of magnetic recording to measure the displacement. Magnetic scale is based on the non-conductive scale using chemical coating or plating process in the non-magnetic scale deposited on a layer of magnetic film (generally 10 ~ 20um), in the magnetic film recorded on behalf of a certain year with a certain wavelength of the square wave or sinusoidal magnetic track signal. Magnetic head in the magnetic scale to move and read the magnetic scales, and into electrical signals input to the control circuit, and ultimately control the operation of the AC servo motor. Magnetic scale has the advantages of simple manufacturing, easy installation, high stability, large range, measuring accuracy up to 1 ~ 5um, patch accuracy is generally in 0.02mm.
3. Grating scale
Grating scale using the principle of light interference to measure the position and movement of objects. When the light passes through the grating strip, the wavelength of light compared with the period of the grating strip, will produce interference phenomena. Based on the nature of the interference phenomenon, the position and motion of the object can be measured.
The measurement accuracy of a scale depends on the period of the grating bars and the resolution of the readhead. The smaller the period of the scale bar, the higher the measurement accuracy. The higher the resolution of the readhead, the higher the measurement accuracy.
4. Synchronization of Y-axis operation
The X-axis operation of the mounter adopts the dual AC servo motor drive system with fully synchronized control loop, which minimizes the internal vibration and thus ensures the synchronized operation in the Y-axis direction, with fast speed, low accent, and smooth and easy operation of the mounter head.
5. Speed control of X-Y motion system
The speed of the adjusting machine is up to 150mm/s, and the instantaneous start and stop will generate vibration and shock.
6. Z-axis rotary positioning
The mounter directly installs the micro pulse motor inside the head to realize the high precision control of the rotating direction. the resolution of MSR type is 0.072 degree/pulse, which directly drives the suction nozzle device through the high-precision at-wave driver (the reduction ratio is 30:1), due to the at-wave driver has the advantages of high concentricity between the input axis and the output axis, small gap, low vibration, etc., the resolution of the placing direction is up to 0.0024 degree/pulse. 0.0024 degree/pulse.
Company Profile
Zhejiang NeoDen Technology Co., Ltd. has been manufacturing and exporting various small pick and place machines since 2010. Taking advantage of our own rich experienced R&D, well trained production, NeoDen wins great reputation from the world wide customers.
with global presence in over 130 countries, the excellent performance, high accuracy and reliability of NeoDen PNP machines make them perfect for R&D, professional prototyping and small to medium batch production. We provide professional solution of one stop SMT equipment.
We believe that great people and partners make NeoDen a great company and that our commitment to Innovation, Diversity and Sustainability ensures that SMT automation is accessible to every hobbyist everywhere.
Post time: May-07-2024