Router Control - FabRap

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Router Control

Generation Two

After serious investigation into a large number of different control options, we have decided to invest in Planet CNC's Mark 3 control board using the Planet CNC software.  When compared to the various alternate options this appeared to be very compeetitive with only the Chinese hardware able to improve on the price.  The Chinese solution appears to rely on the use of the Mach software and after a lengthy investigation on the Internet, I came to the conclusion that support for Mach software has deteriated to the state that there are many very unhappy customers out there.  Furthermore support for the Chinese alternate is strictly limitted and is further complicated by the language barrier.

From the experience gained by using the CNC USB software as a simulator for g-code over the past 3 years, the choice of the solution came easy.  Subsequent dealings with Planet CNC has proved to be constructive and positive.  E-mail are answered the same day and confidence is quickly built with them.

Basic feature of the hardware are as follows:   

   9 axes controller for stepper and servo motors
   USB and Ethernet connection
   110 kHz maximum step frequency
   25 us pulse width, 50% duty cycle
   8 digital outputs on board
   3 PWM capable outputs with selectable frequency    

Allocation of the 9 Axis will be as follows:

Axis 1 to 4                 X Axis Motor,  Left Y Axis motor,   Right Y Axis Motor and Z Axis Motors.
Axis 5 to 7                 A Axis Motor,   B Axis Motor,  and C Axis Motor.  Possible future Implimentation.
Axis 8 & 9                 X Axis and Y Axis motors for the Lathe conversation.

Once again we have chosen to use the same DQ542MA Stepper Mptpr controller and typical Chinese switching power supply.  After 5 years without a problem, we have total confidence in this combination.  Furthermore, Dabula Kahle has the motors running at below their maximum power and we have never had the requirement to increase the current to reach maximum power.  This has resulted on the motors and power supplies running slightly cooler.

Once the CNC USB controller was received, it became apparent that connecting it to the stepper motor controllers would be problematic as the ribbon cable is hard to split and is of a small guage.  Furthermore to order the standard IO cards from Planet CNC would be expensive due to the airfreight to South Africa.  The decision to make our own PCB's was taken.  The router will have dual motors on the Y axis and these will be supplied by different power supplies.  The stepper motors have a high inductance and when the power is switched off, large electro magnetic fields are created.  This results in high power being induced back into the power supplies. Having the motors fed from different power supplies lowers these forces that would be generated using only one power supply.  Making our own IO cards has allowed us to place a Zener diode circuit onto the card so we can monitor the alternate supply on the error input of the Planet USB control card.  When using these cards for other inputs and outputs, we will fit zero value resistors into the circuit.  Please do not connect a 36 Volt signal into the controller if you are using the Standard Planet CNC IO cards.  The circuit for our IO cards follows:

We will also be making our own IO cards for the 16 pin connectors used on the Planet USB controllers.  These circuits will be as per the following drawing.

The wiring for all the motors will ba as per the following diagram.

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