5. How to set up the CNC Mill?

This is almost like the chicken and the egg as some setup may have to occur in the Design System in addition to setting specific machine parameters. If you use Carbide Create then there are many setup paramters that must be included in the design. That is not so much the case with G Simple. Once you have the Machine code then it is also necessary to set up the CNC Mill.

 

Design System Set Up.

  1. Carbide Create (CC) asks are you doing inches or mm. Sorry guys I simply cannot think in mm. I do know that 6.35 mm = 0.25 inches but if you tell me you need a 3 mm nut -- no clue but f you say a 4-40 or a 6-32 -- instant understanding. BTW if you see a G20 in the G Code listing = inches and if you see a G21 = mm.
  2. Next CC wants to know the size of the work area -- kind of important you keep the work area less than the size of the mill bed working area. Since I purchase singel sided copper PC Board in 6x4 inch sheets I enter 6X4 in CC and the graph paper sheet displayed on the screen is 6X4.
  3. CC also wants to know the size of the squares spacing -- typically 0.25 inches square (6.35 mm square). But you might want to adjust the square spacing to 0.20 inches because a single dip pad should be 0.1 inch by 0.3 inches. So it is easy to make the pads if the squares spacing is 1/2 or 1.5 times the base square
  4. Next is how thick is the material stock and typically it is 1/16 inch (0.06 )
  5. Now comes how much you want the z axis to travel upwards as it is moving from cut to cut. Too uch of a movemnet causes additional machining time. Too little and you are liable to bump into a tool hold down mechanism.
  6. It also needs to know where the top of the stock material is and this is set to "0.0". It also wants to know how deep to cut. Think about the 0.06 inch material and if you put the cut depth to 0.1 -- you have cut through the board and ruined your bed. I set the max cut depth to no more than 1/2 of the material thickness or 0.03 MAX --better to be safe than sorry so best use 0.025.
  7. While we are at it we haven't mentioned the width of the cut as it may affect what is your result. Suppose you want a panel cutout for a color TFT display that is 2X3 inches -- if you use that net size the hole will be too big. So what you enter into the design has to be less than 2X3 to account for the cutter width. You would not use an engravig bit for cutouts. So if you use a 1/16 inch end mill the dimentions have to accout for the radius of the cutter so 1/32 inch less. I would even make it the 1/16 inch and hand file the final hole. Likely with the less expensive CNC Machines there is "wobble" in the cutter motor so 1/16 inch less may actually be PERFECT and spot on!
  8. The ROOKIE problem is Cutting through the material stock and ruining the bed. Trust me it will happen the very 1st time you use the mill. That is why they have JOANN Fabrics that sells hobby plywood that is 1/8 inch thick. Get a chunk the size of your bed and then this plywood is placed between the piece being milled and the top of the bed. This is a must and often is called "a sacrifice board". You will also need hold down tooling which typically does not come with the machine although one of the machine on the CNC Mill page does come with such tooling.