Printed Circuit Board

Milling Machines

An automated machine tool that cuts away the copper and leaves traces. They can go from gerber files to 2 sided board(3"x5") in a couple of hours ready to solder.

http://freeandeasy.sourceforge.net/ A very inexpensive design for a computer controlled milling table. Not X-Y but has the same effect. A rotating base with an offset rotating table.

Main Arc Rotation= theta = 2*arcsin(sqrt(x^2+y^2)/2/R)
Table Rotation= phi =arctan2(y,x)+(theta+pi)/2
where R is the radius of the Main Arc

The second solution is found by changing the sign on theta, and the sign on the pi in the second formula. (In practice that sign may need changing anyway - it depends which direction is considered "positive" for the relevant rotations...)

When x==y==0 the second formula breaks down completely - you can spin the table to any angle you like, it just isn`t going to make anydifference.

As for how you generate a set of stepped angles for the machine, I think it works as follows...

• a) Break the path you want to traverse into Bezier curves (they are easy to subdivide)
• b) The two end-points will have two values for theta and two values for phi, which presumably you will step between in the same period of time. What you need to know is: are any of the points on this curve too far away for comfort from the original Bezier? (You may be very lucky and have a circle centred on the centre of the table!)
• c) Doing b) properly seems pretty difficult to me. So it`s a darn site easier to do a subdivision if theta or phi differ by more than 1. Eventually they will differ by either 0 or 1, in which case you step the motors to the correct place (with the drill-head up, if further awaythan 1).

As an algorithm you get:

  DrawBezier(Bezier B)
 (theta1,phi1)=Angles(B.start)
 (theta2,phi2)=Angles(B.end)
 If abs(theta1-theta2)>1 or abs(phi1-phi2)>1 then
  (BLeft,BRight)=SplitBezier(B)
  DrawBezier(BLeft)
  DrawBezier(BRight)
 else
  if abs(currenttheta-theta1)>1 or abs(currentphi-phi1)>1
   lift the drill
   endif
  move drill to (theta1,phi1)
  drop the drill if lifted
  move drill to (theta2,phi2)
  endif

It`s important that the point called B.start is part of BLeft (and consequently that B.end is part of BRight)

http://www.tinaja.com/flut01.html "Flutterwumpers are low cost machines that spit or chomp. Such as printed circuit drills, sign routers, animation stands, CAD/CAM mills, plotters, Santa Claus machines, etc. A new approach to designing these machines involves both the PIC microprocessor and the PostScript computer language. This library shelf holds tutorials, resources, and application notes you can use to build yourself a flutterwumper. Such as a $100 printed circuit drill or a $200 Santa Claus machine.

PCBFab@, PCBCAD@

See also:

• http://www.cncdudez.com/ Very nice aluminium table from England. The controller and spindles are all for U.K. power.
• http://www.lpkf.de/home_us.htm Laser Cutters
• http://www.t-tech.com/
• http://hometown.aol.com/drigotti/HobbyCNC.htm
• http://www.geocities.com/siliconvalley/lab/3685/plotter/plotter.htm General info
• http://www.thinktink.com/stack/volumes/volvi/etching.htm Mechanical Etching
• http://www.sherline.com In particular, take a look at the Sherline vertical mill: #5000-CNC (inch version): Standard vertical mill w/ 10" base plus 3 stepper motor mounts (Metric P/N 5100-CNC) $750.00
• http://www.linuxcnc.org/links.html
• http://www.majosoft.com Homebuilt Engraving Machines (even a wooden one with drawer slides)
• http://www.isd.cme.nist.gov/projects/emc/emc.html The Enhanced Machine Controller (EMC) program is a NIST effort to develop and validate a specification for interfaces to open architecture controllers

Metals and Metal Working / Machineing +

Questions:

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