I have a Shapeoko 3
It’s killin’ me.
I want to face mill 19.8 mm mdf down to 18 mm.
I’m using Fusion 360 to create my model and Gcode.
my model is 18mm thick and I add .17mm to compensate for 2x-side tape, so 18.17 mm.
when I mill the piece using Motion I keep getting wood that’s around 17.3 mm.
How does an 18.17mm model end up at 17 and change? Seems like F360 sees 18mm differently than Motion
I bought this machine for precision and control. I get niether.
If you’re certain the table is flat & parallel to the XY axes, and your stock is a consistent 19.8 mm everywhere, why not just zero off the top of stock & remove 1.8mm?
If you’re uncertain, remove 1.5mm, measure, then adjust your Z to get the remaining 0.3mm
Are you measuring the stock in the same location where you set your Z0? Have you checked multiple locations on the stock after setting your initial Z0?
GCode is GCode. Attach your GCode and we’ll look at it. PS For simple facing operation like this, I recommend Carbide Create. You could create this GCode in about 2-3 minutes. PPS Painter’s Tape and Super Glue is far superior to Tape.
Well, I think Create is kinda out of the question. I have $$ invested in F360. I can create Gcode in a couple minutes using F360.
CA and Blue tape is an option but I’d still have to compenasate.
I’ll attach the Gcode for you. this has an additional .5 mm added.
2x2x18_test1.nc (1.3 KB)
How are you setting zero?
How are you measuring the stock?
You are removing 0.581 thickness with your first pass, and 0.75 more w/ the second to remove 1.331mm of material.
Agree that if you want to remove material from the surface, it would be far simpler to set the origin there and just remove one layer at the depth per pass, then measure, and then move zero down by the thickness of material remove and repeat or adjust as needed.
Carbide Create (CC) is Free…Just saying. (I also pay for a F360 license), but sometimes CC just is a better way to go…Your choice.
Z0 should be from the top of your material. (right?)
EVERYTHING Tod said.
Back to your program: 19.8 -18 = 1.8mm but your program is lowering the Z to 1.331mm in two cuts. (Um, why the difference (1.8 - 1.331) (?)
Your Program is only removing 1.33mm, not 1.8mm
Sounds like you have a non-flat setup.and your Z0 is off…
OK the bed is level - at least as far as I can tell. A single pass look to be of consistent depth.
For the sake of discussion let’s stipulate a level bed.
The stock is 19.8 mm
The target is 18mm
The tape is .17mm
XYZ zero is espablished with BitZero (1?) So, on top stock surface. Zero is 2x checked manually (eyeball)
after milling
With Tape I’m at 17.5mm milled
I don’t understand why you’re including the tape thickness if you’re setting the origin at the top of the stock — if you’re setting origin there, it doesn’t matter if there’s zero layers of tape or 100 — it doesn’t affect the G-code.
Mount a piece of scrap — set a rough zero relative to it and make a bunch of pencil marks across it — run a surfacing operation which removes a sufficient thickness of material to remove all the pencil marks.
Jog down to the bottom of the surfacing operation — set zero there.
Cut a series of stepped pockets, each of which is a set distance high — measure the steps — are the steps of an even, regular thickness? How does that compare to the height which they should be?
For this, in Fusion 360, I set the WCS to the top of the stock for milling. Your model should be 18mm and your stock (tab 2 of the set up) should be the 19.8. Then create your code. Set your start point in top of stock.
If you want to do it the other way, you use choose the bottom of the stock as WCS. Model it the same way plus the tape height. Set your Z on the spoilboard.
You can’t really mix the two versions, which seems to be why your cuts are not working out right.
Charles,
This may be a bit easier if you mill to Z zero. Never mind BitZero for a moment. Take you cutting tool down to the top of your tape that’s on the table and touch off. Now move up 18mm and set Z zero. Now adjust your Z values in your code. The first pass will be a positive value and the final pass will be zero (0).
Hey Joe and All.
I created a new model, setup and face based on what I’m reading. I generated the Gcode based on an 18mm model, 19.8 stock and 2, .9mm passes.
It worked.
I get 17.9 mm +/- which is close enough for today.
It may be that my bed is not evel. I’ve been thinking about a new wasteboard. Might be time.
Thanx to all
Heck 0.1mm is about .004”. For a CNC…that’s pretty damn good.
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