New to CNC - Retaining Workpiece Zero?

Hiya folks!

First the ultimate question I have, followed by more details below: How do you retain work piece zero over multiple days?

So my MPCNC (22"X, 11"Y, 3"Z working area) is my first CNC router ever. Dual endstop firmware (but switches are not installed yet), ramps 1.4, fusion 360 CAM.

I’m starting to get the hang of work locating, CAM tool paths in fusion and the endless rabbit hole that is feeds/speeds/chip load/and MRR. My plan is to make some coaster sets for christmas for friends and family. The coaster design has rounded top and bottom edges with an inset pocket on the bottom for a cork insert.

So far working in pine I have had satisfactory results milling both sides, using locating pins and getting the design to come out how I want it. The issue comes in that I set workpiece zero at the start of the first cut and then mill for 6 hours straight without shutting off the machine to retain it’s zero reference.

The coasters are going to be milled out of hard wood which is likely to require longer milling times due to lower speeds/feeds required to maintain appropriate chip load on 1/8" mills. So the question becomes, how do I keep the workpiece reference zero so that I can mill one operation, leave the workpiece in place and come back the next day and start the next operation?

I’m sure I’m just being dumb and missing something here. Thank you!

Homing with dual endstops, or hardstops. This means zero is always zero and you have to account for the materials location in CAM instead of just hitting go.

You will learn much faster starting with estlcam. Everything you need is there and when you fully understand it and it seems simple to you, fusion lets you make very specific changes. No reason to learn on fusion, nothing is wasted time in this transition the simple concepts are the exact same. Where I strongly feel you can waste countless hours trying to trouble shoot the most simple of jobs in fusion.

 

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Except for Z, you always have to measure Z again. You can generally, use a piece of paper under the bit to find a good Z height after a poweroff or after changing the bit. You can also use a touchplate.

If your first operation destroys the original Z, you can use a fixture on the side to set the Z. So, for example, if you are going to surface the top of the coaster, or generally cut around X=0, Y=0, you can find a place on the workpiece where you won’t mill and do your Z measurement there for the first and second operations. You can do G92 Z0 to set the Z independently of the other axis.

I just want to second this advice. I think that’s often overlooked when people want everything in fusion, but you might even learn fusion faster if you learn estlcam first. That hasn’t been proven, but it makes sense to me.

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