topic Re: Problem with wobbling in Fusion Manufacture Forum

Problem with wobbling

samihofert — Thu, 26 Sep 2024 12:09:41 GMT

Hi,

I have a cnc milling machine and wanted to mill out a jewelry box. I'm not that familiar with fusion 360 yet. I have now taken a drop from canva and then exported it as SVG and imported it into fusion. But if I now try to mill the shell, the machine moves back and forth the whole drawing as if it wobbles. Why is that? Unfortunately, I don't know my way around very well.
Thanks for all the answers

Re: Problem with wobbling

FrodoLoggins — Thu, 26 Sep 2024 12:48:24 GMT

It would be helpful to post a video of it running but it's probably wobbling when it's helically ramping and rapidly changing direction at that sharp point. I'd slow the feedrate down or put your machine on a sturdier table. Maybe model in a fillet at that sharp corner preferably larger than your tool.

Maybe specify a minimum cutting radius and then finish that portion up with another toolpath that has a much slower feed:

Then on the slower follow up toolpath enable rest machining:

Or use feed optimization to slow the tool down in that corner:

It's also possible your machine just can't handle a tool that large. An 8mm tool cutting 5000mm/min 3mm in deptch might be too much for your machine to handle. Does the spindle sound like it gets bogged down at all?

You also might need to hold your part down better or use a downcutting end mill.

Betreff: Problem with wobbling

samihofert — Thu, 26 Sep 2024 13:38:58 GMT

ok, i´ll try now
i got an evo mekanika evo s by the way.
if it dosen´t work i send you a video.
Greetings

Re: Problem with wobbling

samihofert — Thu, 26 Sep 2024 14:09:34 GMT

Hey, I've tried it now, but it's still wobbling in the outer areas. As you can see at the beginning of the video, everything works fine, but then with the last lines it's always like it gets stuck or something, I have no idea why I hope you can see it on the video

(Don't be surprised, I've tried to mill something out of the part, that's just a test part)

Re: Problem with wobbling

samihofert — Thu, 26 Sep 2024 14:11:14 GMT

here the updatet code by the way:

Re: Problem with wobbling

HughesTooling — Thu, 26 Sep 2024 15:01:34 GMT

I f you enable points in the view setting on the toolbar bottom of the screen you can see you have a lot of short moves.

I've disabled multiple step downs to make it easier to see. With the standard smoothing set to 10% of the tolerance you don't get much arc fitting. Total tolerance 0.11

If you set the tolerance to 0.05 and smoothing to 0.05 it's a lot better and a lot less points. Total tolerance is only 0.1. Try these tolerance and see if you get a smoother cut.

Re: Problem with wobbling

samihofert — Thu, 26 Sep 2024 16:40:57 GMT

Hi, I've tried it now but it's still partly there, especially at the contour and still on the outermost line, I'm sending 2 more videos where you can see it, do you know what could be the reason?
Greetings

Re: Problem with wobbling

samihofert — Thu, 26 Sep 2024 16:49:39 GMT

here the file

Re: Problem with wobbling

HughesTooling — Thu, 26 Sep 2024 17:26:38 GMT

You can get even better arc fitting if you tighten up the tolerances even more, try a tolerance of 0.002mm and smoothing of 0.01mm. Also the feed optimisation is adding points so might not be helping.

With the tolerances above and feed optimisation.

Without feed optimisation.

Unfortunately smoothing is not going to work with a ramp toolpath. The ramp will be calculated using the tolerance, so 0.002mm will create a lot of points but if you increase this the smoothing will not work as well on the profile when it reaches depth.

Here I've played around with tolerances to get good arc fitting on the flat profiles but the ramp does not fit at all so you get thousands of moves on the corners!

Part of this problem goes back to the way Fusion offsets splines. Unfortunately when Fusion offset a convex spline it creates a corner rounding fillet between each move and this kills the arc fitting in smoothing. You can workaround this if you use a very tight tolerance around 10 times smaller than the smoothing tolerance. This works well in the pocket but not on the ramp.

Maybe you need to look at the controler on your machine and see if it has any inbuilt constant contorting settings. What control are you using?

Re: Problem with wobbling

samihofert — Thu, 26 Sep 2024 17:26:51 GMT

Im using an raspery pi if u mean that

Re: Problem with wobbling

samihofert — Thu, 26 Sep 2024 17:29:57 GMT

Maybe the link to my machine helps: https://www.mekanika.io/shop/evo-3545#attr=

Re: Problem with wobbling

HughesTooling — Thu, 26 Sep 2024 17:56:30 GMT

Sorry don't know anything about that control. Might be worth asking the manufacturer if there's any settings for this sort of toolpath.

Just to show the difference between splines and arcs I redid your model. It doesn't quite match but shows how simple the toolpath is using simple lines and arcs. File's attached.

Re: Problem with wobbling

HughesTooling — Thu, 26 Sep 2024 18:04:27 GMT

@samihofert wrote:

Maybe the link to my machine helps: https://www.mekanika.io/shop/evo-3545#attr=

I had a bit of a look around on their website but couldn't find any info on programing the control, is there a g code reference anywhere?

Re: Problem with wobbling

samihofert — Thu, 26 Sep 2024 18:16:32 GMT

hey, i don´t know if there is any sorry.

Re: Problem with wobbling

samihofert — Thu, 26 Sep 2024 18:17:41 GMT

thank you for the model! i think i´ll try to draw the next models by myself instead of importing files. I don´t reaaly get how to shot the points could u describe real quick for me?

Re: Problem with wobbling

HughesTooling — Thu, 26 Sep 2024 18:22:13 GMT

You can show points from the toolbar bottom of the screen.

Betreff: Problem with wobbling

samihofert — Thu, 26 Sep 2024 18:22:57 GMT

*i meant how to show the points

Betreff: Problem with wobbling

samihofert — Thu, 26 Sep 2024 18:23:43 GMT

also do you know any website where you can get files for cnc miling? or maybe some good ,,sellers,, ?

Re: Problem with wobbling

samihofert — Thu, 26 Sep 2024 18:28:39 GMT

thanks!

Betreff: Problem with wobbling

samihofert — Thu, 26 Sep 2024 18:30:04 GMT

also THANK YOU so much for all your effort! i hope i find out how to import files so there are not that much points and that i will be as good as you sometimes... Thank you!!!!