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The DMC-III is a next generation professional desktop CNC milling machine. The innovated technologies are as the followings:
1. Advanced Digital Control System
1.1 Motion control
Advanced "Bipolar sine wave" instead of "Bipolar Chopper" micro-step control algorithm is used to provide the optimal control for the step motors with no harmonic noises. This technology allows the stepper to move in micro precision without skipping pulse and remain in cool condition for many hours continuously running. The resolution for the each micro-step is 2 micron.
The most common step motor is 200 steps (mechanical steps) per revolution. In order to have better resolutions for the step motor, it requires micro step controller to further divide each mechanical step. The most common technique using by all other manufacturer is the "Bipolar Chopper" technique. Bipolar chopper is to generate square waves in both directions to achieve half step, quarter step or one eight step resolutions.
This number must be power of 2. Since the derivatives of the square wave are not smooth, it will also generate a lot of harmonic noises in the motor circuitry. These noises not only produce extra heat to the motor but also degrade the accuracy of the micro stepping and cause skipping pulse. However, "Bipolar Sine wave" is our company proprietary technology. We have spent 4 years research and development to finalize it. We divide each step into 10 micro steps which provides 2000 steps per revolution.
This is equivalent to the most of high quality servo resolutions and reaches to the mechanical limits. We use extensive computer power to determine the exact voltage in sine wave and implement the accurate voltage and achieve the micro step motions. Since all the derivatives of the sine wave are smooth, it produces no harmonic noises. Therefore, it produces no extra heat to the step motor and guarantees 0.00008" (2 micron) resolutions. It is much better than the "Bipolar Chopper" technique using by all the other manufactures in the market.
1.2 Spindle control
Light weight, high torque, variable speed, 1,500 to 12,000 rpm, brushless motors are used for the spindle driver. It is a small light weight but powerful motor. The motor has no brush to be worn out and can last long time.
It is controlled by a sophistical digital control board. It senses the zero crossing of the back EMF in the circuit to determine the motor speed and uses PWM (Pulse Width Modulation) to control the timing of the firing sequence and interval to achieve the variable speed. The spindle speed can be controlled directly by the CNC software in the PC. No gears or no pulleys to be changed and no variable frequency driver (VFD) are needed.
1.3 Other features
- Integrated system with power supply, digital control and motor drivers into a single controller box and built-in to the machine.
- There are 5 CPU in each control unit to coordinate and optimize the motions for each axis to achieve the highly accurate motions (or cutting) in truly 3D or 4th axis. All axes are moving simultaneously in high precision.
- Built-in optic sensors in the control and motor drivers boards to protect the system in any overloading conditions.
- Modified Mach 3 CNC software with extensive graphic display and user friendly operation in the PC Window environment.
- All electronic parts are built by quality parts and minimize any possible down time.
- All PC board and the controller are thoroughly tested for vibration and temperature variations for lasting reliability.
2. Optimal Mechanical Design (US Patented, Patent No. 7467449)
- Completed system integrated into a single piece machine weigh about 260 lbs which is movable by 2 persons without using forklift.
- Cast iron frame and T slot table provides rigidity and precision for all metals machining.
- Special designed clamp set to secure the work piece(s) directly on the T slot table for machining. No vises are required.
- Special designed work piece(s) holding devices for thin plate machining such as PC board drilling and electric panel machining.
- All parts are precision manufacture with final calibrations and alignment. The machine repeatability is 0.0001".
- High precision ball screw with zero backlash and the linear guided rails are used for all 3 axes.
- High quality ball bearings and thrust bearings are used for all 3 axes and the spindle.
- Light weight, high torque and variable speed (1,500 to 12,000 rpm) brushless DC motor is used for the spindle driver. No gears and pulleys to be changed. The spindle speed can be changed directly from CNC software in the PC.
- Belt and pulley system is used to isolate any vibration between the motor and the spindle. It provides mirror like machining surface.
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