Let's Make Robots!

DIY CNC Part II

26/05/09

2 more draw slides to use for the Y axis purchased from here. High quality slides with ball bearing inserts. Still have to work out how I want to mount them. They were only $15 each.. money well spent now that I can see them close up.

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Construction has started! Original blog post with ideas and parts is here.

The first motor driver board is almost finished. Its based on TinHeads design of making each board communicate through I2C to a master, but uses the SLA7026M driver chip instead of the L298. Behind the chip are the sense resistors. I couldn`t get any single resistors with high enough wattage that weren`t wirewound so I ganged up a bunch of 1ohm 1/2W. Theres also a 5v regulator and trimpot to adjust the coil current. It can be set from 0.6A to 2.8A.

The 2 chip sockets are for the optoisolator and attiny. Still have to work all that stuff out but theres a video at the bottom using an arduino to pulse it in full step mode.

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I ended up completely changing the design again to a moving table on 1 axis to keep the machines footprint down. It will stick out from the side of the machine when it has to reach the other end of the table but the cutting area will always be supported by the frame. And a big plus, when stored it will be smaller than before at 300x420mm.

I also decided to make it completely out of 20mm aluminium square tube. It was cheaper than I expected at $6/m and it will be easier to work with than MDF.

I may have to add some angled struts on the gantry later to stop it twisting.

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I cut down 3m of the tubing to make this..

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This is the base plus 1 side of the gantry. I still need 2m more aluminium to finish the other side of the gantry and the Z axis assembly.

Because I don`t have a printer I drew up a label as accurately as I could with all the holes marked on. I will photocopy it several times and tape it to the aluminium to mark the holes. I hope that the time and effort making it pays off and my drilling is spot on.

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My square.. it works.. but its pretty dodgy.

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Lots of stuff to do yet, need some more tubing for the rest of the gantry, and I have to take the pieces to my local classroom after hours to do the drilling. I think it will be too noisy in the apartment.

I have some tiny2313s but I have to work out how the hell I can program them without a serial or parallel port.

I wonder if I should put this on a robot page?