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Home Switches for the IH CNC Mill
I've had a set of optical limits from IH for quite a while. It's time to get them connected!
Home Switch Wiring
I spent an hour and a half tracking this down on CNCZone. Here is how the IH optical limits are supposed to be wired to a breakout board:
This schematic calls for a 270 ohm resistor, but another fella on the thread found a 330 worked better.
I will connect my home switches to Port 1, pins 11, 12, and 13 (X, Y, and Z, respectively):
I need to wire up a little PC board to will house the diodes and resistors.
CNC Enclosure Rear Panel Layout and CAD Work
Since I have a working CNC now, I wanted to make a nice rear panel for the Home Switch connections. While I was at it, I decided to make the panel ready for future connections including my probe and coolant. In addition, I put a connector for the power cord, which currently snakes its way crudely through a rough hewn hole in the panel.
Here is the Rhino3D rendering I did of the 11" x 4" panel:
The circular cutouts are for microphone connectors I purchase from Action Electronics.
To CNC this panel requires the following operations:
1. Cut the panel free of a larger 12 x 12" plate by milling 2 of the 4 edges.
2. Engrave the text. To engrave I plan to use a simple spot drill with very shallow depth of cut. Since I will have the spot drill loaded in the mill, I will also spot the 4 corner mounting holes. I'll run the spot drill at 1600 rpm with a feedrate of 7 IPM, and I will cut to a depth of 0.040. According to G-Wizard's chamfer calculator, that will give me an engraving width of 0.080. Note that by engraving everything, I also leave a nice little chamfer for all the edges.
3. Drill 4 x 1/4" corner mounting holes with a twist drill. This calls for 1600 rpm with a feed of 9 IPM. Should be no need to peck, or at least so says G-Wizard!
4. Interpolate 7 x round holes for microphone connectors and the odd shaped hole for the power plug. Given the radii on the connector's shape, I plan to use a 1/8" endmill to do the finish pass. At my mill's maximum spindle speed of 1600 rpm, we need to take it real slow and easy on this little endmill, so I will feed at 1.6 IPM only, which will make things very slow, but it will be less likely I break the endmill and I will cut full depth of hole. To do the roughing, I plan to use a 3/8" 3 flute endmill, run at 1600 rpm and 19 IPM, with each pass taking 0.040" depth of cut.
5. Surface the back side. This is 1/4" 6061 plate, and some of the connectors won't reach all the way through. So I plan to take off 80 thousandths with a face mill. I will do this with my Glacern 45 degree 3" facemill, at 1600 rpm and a feedrate of 38 IPM. I'll make two passes of 40 thousandths each.
All feeds and speeds are courtesy of G-Wizard. I like to figure them ahead of time and have them handy since G-Wizard gives better numbers than my OneCNC CAM program.
Making Chips via G-Code
I did the panel cutout just by hand typing g-codes into Mach3's MDI interface.
Here is a screenshot from OneCNC of the engraving and spot drilling toolpath:
And the G-Code for that operation is here.
G-Code to drill 4 holes is simple, and here.
G-Code to go through the 8 larger connector holes is fairly complex, and here.