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  1. #1
    Join Date
    Feb 2009
    Posts
    14

    automating a mobile sawmill.

    not quite cnc but i didn't know where to ask.

    so iv gt a mobile Lucas sawmill that is operated manually. ie i walk back and forth all day pushing the frigin thing. [nomedia="http://www.youtube.com/watch?v=bYnpVAHi0oE&feature=fvw"]YouTube- Portable Sawmill[/nomedia]

    i want to automate it. so it works like this one [nomedia="http://www.youtube.com/watch?v=a_yjXn4o5iU"]YouTube- Portable Sawmill - Automated Swingblade Mill (ASM)[/nomedia]


    3 things need to be automated.

    feed. forwards reverse variable speed. this moves the blade threw the log wile it cuts.
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    horizontal sizing. this moves the powerhead/blade across to adjust teh width of board that is cut.
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    blade swing. only needs to be horizontal or vertical.
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    Feed : i was thinking of running a chain down each track and running a drive shaft with a cog on each end along the front of the carriage and putting in a variable speed electric motor.

    Blade Swing: i was planning on using a 2 way air ram/actuator to swing the blade over and back. but after researching on servos/steppers i have found electric actuators that could do the job and would eliminate the need for an air compressor. but i cant find any that are strong enough.

    horasontal sizing: now this is the bit that has me stumped.

    the mill has a chain running across the front and is moved by turning a handle (not fitted in pic)

    i need to be able to move the power head accurately (withing bout 1mm or so).

    it needs to be able to move from where it is (any point on rail) a set amount in either direction.
    if im cutting a log into boards i need to be able to make movements of different amounts.

    eg: make cut, move right 100mm, make cut, move right 50mm, make cut, move right 200mm, make cut, move right 38mm, make cut, move right 12mm, make cut, move left 12mm.

    now that would be very hard if everything is indexed from one side.

    i would really like to have a key pad that i can just key in the movement i need and it dose it.

    i was thinking a stepper motor setup with a cog running on the chain. so that each step is 1mm or something. when 25mm is keyed in the motor dose 25 steps.

    but then i was told that steppers are not accurate an i should use servos but i dont know how they work.

    any ideas boys or am i dreaming.
    carl http://brisbaneportablesawmilling.googlepages.com
    Boards, Blanks, Slabs, Logs, International postage.

  2. #2
    Join Date
    Jun 2006
    Posts
    95
    Money is the big question. Electronics and vibration/outside/wood do not mix.

    If it were me I would go hydraulic for everything.

    -I would drive the feed with a hydraulic motor and limit switches.
    -I would drive the swing with hydraulic cylinder and limit switches.
    - I would drive the horizontal sizing with a hydraulic motor and some kind of screw with a fine pitch. I would put an encoder on the screw and shut the valve off when it got to the number I wanted (or just before to acount for overshoot).

    Run the hydraulic pump from the motor or some other power source.

    I would use a small PLC to drive the thing using whatever power I have available (120V) or 24V DC (2 car batteries together). I would use a digital display (serial best or some kind of BCD number switch) to tell the PLC what size I want the boards to be.

    To do it this way and using Ebay for as much as possible it will cost you a few grand. The money is in the motors and pump.

  3. #3
    Join Date
    Feb 2009
    Posts
    14
    i was trying to stay clear of hydrolics, they give me the ****s. and i woul have to put in another motor to run the pump. as i there is not enough power in the existing motor to run a hydrolic pump as well.

    we saw will be set up in a fixed location inside a shed. 99% of the time.
    carl http://brisbaneportablesawmilling.googlepages.com
    Boards, Blanks, Slabs, Logs, International postage.

  4. #4
    Join Date
    May 2010
    Posts
    0
    The setup you are describing sounds like it would be best suited for a PLC, as Flash319 stated. You can use a few DC motors with gear reducers driving a Belt or Chain set up to run the feed and swing parts of the machine. This way you can control the speed of both units. For the sizing, you could use a stepper and an encoder, or a servo to ensure proper height. You can add a small screen to adjust the height with ease. A NEMA 4 or NEMA 4X box will protect the electronics. And a TENV motor should hold up to the dirt and dust. Limit switches on the feed and swing rails will make for easy plc programming. I don’t know if you can get these parts in Australia, but you can check out the website to get an idea of what you want and how much it will cost. http://www.automationdirect.com/adc/Home/Home they sell everything you would need except for the DC drives. You could go for a VFD setup as well. Provided the voltages will work. Check out the GS2 vfd drive.

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