Fusion 360 - negative coordinates in x and y

Mostly Printed CNC - MPCNC Troubleshooting
#1

Using the post-processor found through these forums (rep to martin-db, I think), I have the origin set to the lower left top surface. I didn’t review the gcode the first run and quickly realized that X and Y are moving to negative values (Z is fine).

I tried searching on autodesk for an answer but only came up with answers for troubles with Z. I am sure there is something simple I am missing.

Here are the snippets of code with negative values:

G1 X607.681 Y-0.101 F800
G1 X607.217 Y-0.185 F800
G1 X606.752 Y-0.257 F800
G1 X606.284 Y-0.316 F800
G1 X605.816 Y-0.362 F800
G1 X605.346 Y-0.396 F800
G1 X604.875 Y-0.416 F800
G1 X604.404 Y-0.424 F800
G1 X602.962 Y-0.453 F800
G1 X601.519 Y-0.471 F800
G1 X600.076 Y-0.478 F800
G1 X598.634 Y-0.474 F800
G1 X593.687 Y-0.478 F800
G1 X554.116 F800
G1 X1.766 Y-0.486 F800
G1 X1.375 Y-0.358 F800
G1 X1.039 Y-0.119 F800

G1 X-0.118 Y2.015 F800
G1 X-0.199 Y2.479 F800
G1 X-0.268 Y2.945 F800
G1 X-0.324 Y3.413 F800
G1 X-0.368 Y3.882 F800
G1 X-0.4 Y4.352 F800
G1 X-0.42 Y4.822 F800
G1 X-0.427 Y5.293 F800
G1 X-0.461 Y7.354 F800
G1 X-0.48 Y9.415 F800
G1 X-0.486 Y11.476 F800
G1 X-0.479 Y13.537 F800
G1 X-0.48 Y49.811 F800
G1 X-0.498 Y607.725 F800
G1 X-0.457 Y607.927 F800
G1 X-0.297 Y608.306 F800
G1 X-0.04 Y608.629 F800

I am not sure what I fudged around with after the first run but this time around there are very few lines directing the machine into the negative (my work area is 609.6x609.6 and it was printing 300 to -300 last time).

This is not that big of a deal at this point (my machine can actually move 26 inches in x and y).

I was thinking that this might be a problem with my roughing operation, I have 0.50mm set for material to leave… thoughts?

#2

Negative is fine. This usually means that your part is at the zero point and to cut it out it has to move a little beyond it. Usually at least the cutter width. Another reason we don’t usually use end stops.

What is the actual problem you are having?

1 Like
#3

I had this problem too. What I did was change my material size so that the stock was larger than the item I was cutting. I then centered the part in the stock and set the 0,0,0 of the CNC to be the corner of the stock with the bit just touching the top of it.

Doing this also allowed me to locate hold down screws in the stock so that the mill would make sure and miss them during rapid movements across the board.

1 Like
#4

initially it was generating the gcode from -300 to 300. Now there is that bit of negative movement, so no problem with the part currently, just wanted to make sure there wasn’t a setting I was missing as I move on in the things I create with Fusion360.

am I wrong in thinking that when I do this roughing operation that Fusion360 will not allow my tool to go anywhere that it cannot fit/safely remove material without messing up the design? Right now I have it set up so I use adaptive clearing with 3/16" flat mill, then 1/8" ball spiral cut, then finish off with some cheapo HF diamond rotary bits (1.9mm and 0.7mm). The simulation appears to preserve the model and avoid collisions… didn’t allow my rough cut the other night to run long enough to see if it would avoid more intricate details when using the larger tool.

#5

If you attach the gcode file I/we can see if there are any abnormalities. It’s a little tough to diagnose by description.

#6

nothing to diagnose now, your initial explanation fits the results I get out of my gcode…

I was also wondering if, by default, fusion360 prevents the selected tool from taking off too much material. For example, if I am doing relief work for intricate shapes like calligraphy, will a 10mm flat mill violate a space that will only accommodate a 2mm mill?

My current project is a sign for one of the doctors I recently rotated with. It is set up as 3/16" flat mill and then 3.23mm ball with adaptive clearing for the roughing, followed by the cheap HF diamond carbide rotary bits (1.9mm and 0.7mm) using parallel for the finishing passes.

#7

Yes it does. The CAM will only remove whatever material the end mill can do without touching the actual part.

I do my roughing in with a 1/8" bit and then if I need finer detail, I’ll go back with a 1/16".

1 Like
#8

Thanks.

Do we have a repository of known tools assembled somewhere? If not, I’d be willing to share my toolset, although it is rather limited… I was waiting for a 3D print to finish one day and took my micrometer to all of the mills, lollipops, and spiral cut bits I had… Fusion360 is so awesome, I am surprised there is not a space in the cloud for tools and setups.

What feed rates do you use? I stick with 800mm/min and 300mm/min plunge rate. Have not really pushed the speed limits of my machine except when using the laser or plotting pen.

#9

I don’t know of a place to share tools. My collection is very limited too. Basically the two end mills I mentioned and a chip breaker that I haven’t used yet.

I will be adding a thread mill to my collection and some ball mills soon. Possibly even a 60* engraving mill.

I haven’t messed with feed rates either. I’ve tried a few different DOC, but I’ve left the feed rate whatever HSM’s CAM defaulted to. I think it’s running at 40 in/min, but I’ve also only cut 1/4" plywood and particle board. At 40 in/min I can cut a .1" DOC. I’ve tried .15" once or twice. It cut fine, but had just the slightest chatter occasionally.

This is all with the Dewalt DW660 spindle.

#10

Turns out tools can be exported from Fusion360. Here is my list so far:

0.7 to 6.4mm tapered mill (2, different angles and LOC)

1.9mm, 2.6mm, 3mm, 3.5mm, 4mm flat, 4mm lollipop mill, (HF diamond rotary bits 1/8" shank)

3/16" Bosch flat mill with center cut

3.23mm ball spiral cut bit from HF.

if you think it worthwhile, maybe I should start a new thread and we can share toolsets.