help with 3D file/cutting

[denmanmarine]

Hi all,
I just cut a 3D file in part works 3d and used the cut out tool path for the first time after cutting the 3D. I found that the cut out tool path wasn't nice and straight/fair as expected but was very jagged, following the small scallops left by the 1/2" bullnose cutter. see images below;

http://i63.photobucket.com/albums/h131/bloggs1968/foilpic2.jpg (http://s63.photobucket.com/user/bloggs1968/media/foilpic2.jpg.html)

http://i63.photobucket.com/albums/h131/bloggs1968/foilpic1.jpg (http://s63.photobucket.com/user/bloggs1968/media/foilpic1.jpg.html)

The hole in the piece in the lower pic is meant to be perfectly round 7/8" hole.

I have gone back over settings but can't find where I have caused this problem(although I know I have!) Any ideas from those more experienced?

[kubotaman]

It may be that there are too many nodes which will cause the problem that you have. In other words. the tool path will follow the nodes when created so you will have to go back and smooth them out.

[adrianm]

If that was the finish cut rather than the cutout I would say that the stepover was too high.

How rough is the vertical edge of the model when zooming right in on the preview?

[tlempicke]

1/2 inch bullnose seems kind of big for 3D carving. It takes a lot longer but produces beautiful work if you use a 1/8 inch bulllnose and keep the stepover down to 6 or 8 percens.

[tlempicke]

Oh by the way - because the machine must always break a circle down into x and y moves it will never produce a true hole. Gets close, but never truly going to be round. There are two ways to go - make the hole just a bit larger than needed or better yet make the hole a bit smaller and ream to size. Notice that a drill will always produce a hole bigger than it self.

For the purposes of our forum the only way to get a true round hole is to make it undersize and ream it.

[bob_reda]

firstly, I wouldn't use a ball nose for a cutout toolpath, I would use an endmill. It looks likes the settings on the machine are off. Even if the bot doesn't make a true circle, I have never had one that looks like that one. You may be using too big a bit for the circle, but if the circle and the cutout look like that for everything your unit values may be off.

Bob

[adrianm]

From what Andrew had said I thought the ballnose had only been used for the 3D cutting not the actual cutout itself? :confused:

[scottp55]

I had a cut that looked like that last week, only to find out I'd accidentally left it on raster so what I saw was actually the 30% stepover. My marks were more regular, so suspect nodes.

[Brady Watson]

My guess would be that the 3D file that you brought in has a low polygon count & appears somewhat faceted or jagged around the perimeter of the part. If you cannot find or generate a higher count polygon model, then you will need first generate your toolpaths (all except profile pass) in PW3D (run thru all steps until simulation) - then save the PW3D file via File->Save As.

Open up VCP SB Edition and IMPORT the PW3D file. Manually trace a clean outline using the polyline & vector edit tools. Use this vector as a profile vector for a regular 2D profile toolpath. Tweak the vector shape until you are happy with the edge quality. Use a square end tool (end mill, or straight router bit) to do the cutting.

You may want to consider upgrading to Aspire if you intend on doing a lot of this type of work. The tools and toolpaths are more advanced and you can work faster and more precisely than the entry level PW3D software. It is available at a discount via ShopBot.

-B

[denmanmarine]

Thanks for the replies guys.

I went back and recalculated the finishing toolpath to the smallest stepover reasonably possible and then re-calculated the cutout toolpath - still looks very jagged along the edges. The model out of rhino 4 was exported on the highest settings we could use and certainly in both rhino and PW3D, the model edges look clean and crisp. I'm going to export the profile out of rhino and just do a v-carve profile toolpath which should fix the issue but I still would like to find out why PW3D cut out tool path is so jagged. Sent a message off to Vectric to see what they think.

Just for info the actual job size is roughly 8' x 4'.

[paul_z]

I've used 1" ball mills with good results. It just depends on the job.

As others have mentioned, use a profile toolpath for the cutout and the edges of any other interior voids.

Paul Z