Tool change during a job: How are you doing it?

Hi Guys,

I’m pretty new to the world of CNC since the MPCNC is my very first machine. For now, I’ve experimented the very basics, but I would like to go further and doing more complicated stuff.

I’m wondering how you people are dealing with tool changes.

Here is my “problems”:

My CNC is very close to the table, for maximum rigidity. So I cannot remove the bit everywhere I want, it has to be in a specific spot where I have a particular hole that allows me to remove it easily.

So I need the CNC to go there whenever a tool change is needed. But how?

Second issue: Changing the bit and securing it tightly may involve using quite a bit of force. So it is likely that at some point the CNC may lose a few steps. In which case, how to fix this?

I have a lot of other questions on this topic but lets just start with these two ones for now. :slight_smile:

I used Estlcam, if this information is relevant.

The gcode below begins right after the last line of gcode in a program before a tool change. My tool change code below is inserted automatically because I put it in the “Tool Change” text section of Estlcam. This can be run from Repetier, but you must have an LCD controller. The click wheel is the only way I have found to restart after an M00

Your machine must have limit switches and end stops to home/square like in the video above. Z must have a max limit switch. Changes to configuration.h in firmware and Repetier must match your machine’s limit switch setup and your machine’s limits must be defined.

You must insert the workpiece’s coordinates any time it changes

So here we go, A program, started with Repetier is running. Z has just been sent to the 2mm “clearance plane” as defined in Estlcam…

G01 X0 Y0 F9600 ;returns x and y to the workpiece origin
G92 X257.99 Y146.29 Z17 ;redefines xyz to their positions relative to the machine’s xyz home
G01 Z40 F480 ; Z to a good height to change a bit
G01 X100 Y100 F9600 ; x and y to a good position to wrench the collet nut
M17 ; locks xyz position with steppers-helps when changing bit
M300 S300 P2000 ; sounds the beep alarm
M00 ; machine paused till you press the click wheel on LCD
Change tool: End Mill 1/8"f ; Insert bit, holding it in place, but don’t tighten…press click wheel to continue
G01 Z4 ; Z drops to set tool length (mine will be 4mm)
M17 ; steppers locked while you tighten the collet nut
M00 ; machine paused while you tighten…press click wheel to continue once tight
G01 Z83 F480 ; rapid z to almost max
G01 X1 Y1 F9600 ; rapid xy to almost min
G28 ; Home All (mine sets x0 y0 z84 upon home all)
G90 ; Just to make sure all moves are relative to machine home
G01 X257.99 Y146.29 F9600 ; Rapid x,y to workpiece origin
G01 Z19 F480 rapid z to workpiece origin PLUS clearance plane amount
G92 x0 y0 z2 ; redefine xyz to “0” workpiece origin (plus 2 on z) program restarts with new bit

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