Newbie looking at 6040 (China CNC) for polypropylene 15mm sheet

[JOGARA]

Having some trouble with Fusion and I have no idea what is going wrong.

For some reason my heights are all over the place and is taking away too much stock on the Z.

Here is part of my case, in RED is what it is meant to be, and in BLUE is what I am getting (using my cheap caliper but it is pretty close to accurate).



I am using 3D adaptive clearing for the inside of the case, I set the bottom of the operation on the face of my part at the bottom. This is 2.5mm above the bottom of the stock (I have just switched to +2.5mm bottom stock instead of face selection). I then have another 3D adaptive to clear out the holes at the bottom of the case (I do this because I leave stock and then clean it up using a 3mm carbide).




Both operations are the same, just different heights and stock to leave.

(All my heights are .0mm or .5mm I don't have any heights that are .1mm other than telling it to go 0.2mm lower than the stock bottom for clearance reasons later in the setup)

Any ideas?

[Snapper]

There are so many things that could be causing this.

Are all those top surfaces cut by the same tool in the same set up? I can't see how you're cutting 1.7mm too deep from the side wall to the pocket surface, but then the pocket surface is only 1mm deeper than it should be compared to the bottom surface so I think this is a set up error. If you're sure you're setting your Z height accurately, its probably an error in the heights or stock to leave.

[JOGARA]

There are so many things that could be causing this.

Are all those top surfaces cut by the same tool in the same set up? I can't see how you're cutting 1.7mm too deep from the side wall to the pocket surface, but then the pocket surface is only 1mm deeper than it should be compared to the bottom surface so I think this is a set up error. If you're sure you're setting your Z height accurately, its probably an error in the heights or stock to leave.

There is no stock to leave. Z height is all the same for all the operations.
I am using the 6mm roughing bit for most of the milling on this part. It does all the surfaces too.

I just ran the operation again but specificity all the heights manually from stock bottom and now it is just 0.3mm out.

The towers are all the correct height which is okay. But the bottom being so far down means my PCBs don't sit and the part that sits in the curved section is not being clamped down, it is just lose as there is 0.6mm too much Z.

This is definitely something in my Fusion operation.


I do have the minimum Z DOC at 0.5, so why it is cutting down at something not divisible to that, idk..

[m_c]

Is your Z axis calibrated correctly, and not gaining/loosing steps?
I'd double check the calibration, then mark the z-shaft, create a program that runs the Z up/down a hundred or so times, and check it's returning to the same mark.

If that reveals nothing, try modelling and machining a simple stepped block, to see if it's a fusion or machine problem.
While machining pay attention to where the mark on the shaft is at a known position, then return to that position at the end to see if anything has moved.

[JOGARA]

Is your Z axis calibrated correctly, and not gaining/loosing steps?
I'd double check the calibration, then mark the z-shaft, create a program that runs the Z up/down a hundred or so times, and check it's returning to the same mark.

If that reveals nothing, try modelling and machining a simple stepped block, to see if it's a fusion or machine problem.
While machining pay attention to where the mark on the shaft is at a known position, then return to that position at the end to see if anything has moved.

This has only been a problem with the last 2 setups I have ran.
All the ones before executed as expected.

[m_c]

This has only been a problem with the last 2 setups I have ran.
All the ones before executed as expected.

I wouldn't make assumptions!
Are your previous setups still working as expected?

[JOGARA]

My stock in Fusion is the same size as my actual stock. My part is the same height as the stock so no offsets.

I am manually moving the bit down till it touches the surface. It has been more than accurate for what I am doing. Not 0.3mm out though..

I am pretty sure this is a thing in CAD though not the machine or my physical setup of it.

I wouldn't make assumptions!
Are your previous setups still working as expected?

I can test tomorrow.

[Snapper]

If you have your heights set up accurately, where do you have your part located in the actual set up? Fusion automatically sets the part in the centre of the stock and you have to change it manually. If correct...

How are you setting your Z height? If using the Z setter I tested that quite a bit one day and got errors anywhere up to 0.3mm even using a slowed down double probing routine, its just not consistent for some reason, or at least mine isn't anyway. I don't use it anymore and touch off with a feeler gauge which takes a little longer but is far more accurate and repeatable.

Also the original hollow panel OMIO bed is a block of turd to put it lightly, putting a sheet of A4 paper on it will probably cause it to deflect. Getting smooth top surfaces and accurate heights is nigh on impossible, so expect to see a bit of error. I got a big slab of aluminium tooling plate to replace it and the improvement is massive. The last part I made was meant to be 12.55mm high and came out at 12.54mm with both surfaces flat to within 0.00mm and smooth to the touch. An impossible task on the original bed, its an addition worth its weight in gold imo, well worth looking in to.