Could someone please check my simple file for suitability for cnc cut?


#1

Hi All,

I am a bit of a newbie but i have prepared a model which I believe is ready to send to a cnc cutter. It is a very, very simple part consisting of a flat sheet of stainless steel, cut out to resemble a leaf.

I think my main query is whether it will cut smoothly given that I have elected to have 48 segments in the curved part of the model. It really has to come out smoothly as it needs to butt up against another face and be welded into position. (there are four copies in the file but they are all the same).4 leaves for forum opinion.dxf (107.4 KB)

As I said, I am new to this and just want to ensure that it cuts smoothly. I had something else cnc cut recently and there were some faces that showed how segmented it was…oops!

Would some kind person who has experience in this area give me an opinion please?

Thanks so much,
Simon.


#2

Can you post the SKP file too? That could be useful.


#3

Where the leaf shape butts up against another part and will be welded, will the weld bead span the gap or butt joint between the two parts? If so, the fit between the two raw parts probably does not need to be super small, because the weld bead would fill and cover it. (I have not looked at the DXF file, so sorry if the answer would be obvious from the model!)


#4

I took a look, and the 48 segments/arc should get the edges close enough to the adjoining piece that, as @TDahl indicates, the weld bead should fill the gap –

Except!! Your .dwg file came into Sketchup without units! As I normally model in meters, that’s how it came in - over 11 meters across the width of each leaf! If this is indeed the size you intended, then the weld bead likely won’t fill the gap.

However, if your target size is smaller, say 1 Meter or less in the width of each leaf, then you’ve got enough segments that the weld bead should fill things in.


#5

Thanks Ian. Here is the skp file…4 leaves for forum opinion.skp (110.4 KB)


#6

Thanks a lot for looking and replying. I am such a newbie at this that I assumed the file would have dimensions embedded in it.

The leaves are 700mm long and 400 mm wide. The need for the accuracy is this:
the edge of the leaf is welded right up along its edge to 8mm round bar. I initially cut the stainless leaf by hand but it is actually very hard to get a perfect cut with an angle grinder, hence the laser cutting. I have attached a picture of one I did earlier.

It looks alright but it took AGES to smooth out for welding…leaf-example
I am going to have a jig machined for future builds of this and the jig will need to be perfect.


#7

I’m not home to take another look now that you’ve given me the overall dimensions, but with an overall width of only 400mm, I’m virtually certain that the use of “only” 48 segments for the arcs will result in a gap small enough that the best welder in the world couldn’t run a bead so small that it couldn’t fill any gaps!

But what’s the harm of using more segments? Usually, we here on the forum encourage the use of the smallest segment count you can get away with, but that’s because arcs and circles are later parts of a push/pull or follow-me operation, so can cause face and edge counts in a model to get out of hand fast.

That’s not the case here! Increasing the edge count in your arcs will only marginally effect the size of your model, and likely won’t effect anything once it’s translated to G-Code for your laser cutter! Yes, the G-Code file will be larger but, no matter how many segments you have, the laser will be moving slowly to cut through the stainless, Who will care if the laser head changes direction 48 or 200 times while going around your arcs?


#8

If the Arcs you use are kept as SU Arcs, meaning they show in entity info as Arc not Curve you can export them as True arcs. Set up your model with top view, assuming the arcs are on the z plane, and parallel projection and export as 3d model to .dxf. Tis should be seen by the cnc as a true arc with no segments.


#9

The reason I asked for the file were that I thought you could get true arcs from the output as noted by @box in the last reply. However, there have been limitations found using this as shown in this thread…

I would suggest you orient your pieces flat on the red/green plane as shown like so…

Your arcs do report as “arcs” in Entity Info and do translate out to DXF as such. However, my prediction is that the arc on the right hand side using “3d export” will disappear into no mans land once into the machine software. The way to avoid this is to draw the arcs in an anti clockwise direction as outlined in the mentioned thread above. There has been talk of an extension being made to avoid the issue you could cast your vote for it there if you wish.

Although it may import into your machine software ok, so it could be worth a shot as is.


#10

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