Im planning a build of the MPCNC using the Dewalt DW660 (I already have one). Just wrapping my head around the function of the machine, what does homing look like? What about workoffsets, or tool offsets? Im planning on doing the Rambo board with the LCD screen.
Also im guessing it spins too fast to use an edge finder, so are we just touching off the part with paper?
(PS I am a newish cnc machinist for my job, this is a hobby I thought that would be an interesting crossover.)
Kris,
Welcome to the forum!
First question: Homing is used to "square the machine. If you’re using switches to do it, when you select “Home” from the menu, the system will move the gantry to the Y stops and then the core (router) to the X stop. When each of the axis stops are reached, the steppers will stop, then back up and move more slowly to the stop to set the ) point. But, you don’t need to do that with switches. Just move the gantry to the hard stops, plus the router to the x=0 point and turn on the power. The system will just that point as the origin for X,Y.
Offsets are done by driving the machine to the point you want to start the CNC machining, and selecting the menu item to zero the values. The Z height is done (with the router off) by the paper method you mention, or by using the Z-plate the Ryan sells. The latter method is supported in the firmware.
I hope that is close to how it works with the LR3, I’m still in the process of building mine.
I’m sure that if I’m really off with my explanation, someone will show up shortly to correct me.
Mike B.
Compared to your work environment, you will find that most people handle their MPCNC in a very primitive way. Homing X and Y, as Mike indicates, is almost exclusively for squaring the machine. Jobs are done by resetting the machine origin relative to the stock. Edge and corner finding are not used. Typically, things are cut out of wood stock, so accurately finding an edge is not an issue. Z height is often done using a touch plate either on the top of the stock or at the top of the spoil board.
What that said, there is the ability to take a more sophisticated approach. Marlin has probing g-codes, so you could use it to find an edge. There is the concept of workspaces, so you can maintain both a machine and a job workspace. Few people use these features (at least people who contribute to the forum), so you will need to create your own process on how to use them for your jobs.
Also, the Rambo board will run GRBL (though without display support). I believe GRBL has support for corner finding and other CNC-specific tasks that are not supported by Marlin.
I don’t use one myself, but generally the edge finders I’ve seen used in the hobby CNC space are either simple conductive touch plates (basically a switch where the bit is one pole and the touch plate is the other), or the electronic digitizing probe type, where a non-rotating piece is chucked in the tool holder and driven to find the faces of the work piece.
I have not seen the spinning spring-loaded mechanical style of edge finder used here on the forums. I think you are correct in assuming the spindles we use are too fast for them.
I use aluminum tape on the corners to edges find. 
so not very advanced but it woks f[r my needs. I use the same electronics as tom on my MPCNC that use GRBL and universal gcode sender or cncjs
I made a touchplate to find Z and the rotation with Estlcam. It works pretty well.
