How to make a blade edge


#1

Hello,
I am designing a model with a custom shape, where a surface needs to be shaped like a blade. In other words, I need a custom shaped knife - a model for cutting things in shape. How can I do that? I am pasting my work so far. Can anyone help me, how to make an upper surface “sanded” in blade.
Thank you
rozica.zip (587.4 KB)


#2

Do you want to make the top flat face on your model into a sharp cutting edge? Bevel on inside, outside or both?

BTW, you zipped your backup copy (.skb) not the latest model (.skp). And is there any reason the model isn’t centred on the origin?

The starting point is the FollowMe tool.

You would have made life much easier for yourself if you had made the model with subcomponents, and kept the arcs as arcs. At the moment, it is difficult to select the inner top edge to act as the path for FollowMe since it is all individual edges.

Does it have to have such small segments? I’ll have to scale it up by x10 or x100 to make sure FollowMe doesn’t run into SU’s small edges problem.


#3

@bmandl

Assuming I read your question correctly, you could select the 6 inside surfaces, then use the scale tool and drag the center of those surfaces up, this will give a sharp edge on the top.
You will need to tidy up some of the resulting faces however.


#4

I’ve had a go at redrawing your model from scratch, making just one segment as a component. Then I managed to use FollowMe on a top inside edge, and copied it round to get six of them. Had to use Intersect Faces to clean up at the ‘point ends’, extending the flat end face of the single segment upwards to intersect the sharp edge.

Looks like this, and the SKP file is attached.


rozica.skp (1.6 MB)

That left bits over, which I haven’t completely cleaned up. And the points inside are quite right either - there’s a small discrepancy between start and end points in a segment.

This is a good deal trickier than I thought it would be, and the result is not a SketchUp solid.

But the result might just be good enough to use.

Explode the components and tidy up the slightly overlapping edges, and it might be 3D printable.

Someone else may be able to do better than I did, and/or provide details of the process, but I haven’t time to take it any further.


#5

Just a thought, but would simply selecting the inner edge and moving it upwards give a decent result?

Could be worth a try for someone, or completely wrong.


#6

That’s a very clever idea, and might well work!

Try it. If you can select the edge!

But if you redraw it as I did, it should work. I can’t undo back to that shape, and haven’t time to redraw now, but IF you can preserve the edge as a series of arcs, it should work.


#7

Scale it up first, THE DAVE METHOD.


#8

Did that. The problem was that the original model had somehow exploded all the arc edges.

By the way, @Thorleyian, you started from the 3D Printing template. Don’t. Purge the model, and it will come down to a fraction of its original size.


#9

Tig weld?


#10

Helpful, if you have the patience to select all the edges one at a time before applying the weld. I haven’t. Even if you do it in stages, it’s very tedious.

You’d find it quicker to start over.


#11

I didn’t start from any template, I haven’t touched the file!


#12

Well, it’s got the 3D Printer Build Volume component in it - a complex DC which has (I think) details of the build volumes of a wide range of 3D printers in it. It adds over 1MB to the file and you can get just the same result by drawing yourself a wireframe box the size of your maximum build volume, if you need that as a check on your size.

It’s a waste of space.

SOMEONE started from there, if you didn’t.

Purging the file I just uploaded brings the file size down to 71KB vs 1.6MB. Virtually all of that difference is bloat from the template.


#13

The person posting the topic, must be that someone.


#14

I’m so sorry, I wasn’t thinking - you weren’t the OP.


#15

Had another look at this, my move method just didn’t “cut” it. Had a go with follow me instead, the cutter face has to be perpendicular to the arc as always.


#16

Why doesn’t it work? It looks as if it should. If you can select the inner edge, will it not move up on blue axis?


#17

It does but on some of the arcs it kind of distorts and pulls the outer arc inwards, that’s on my effort I did. Tried a few times but it kept distorting. I could be doing it wrong but I’m sure the geometry is clean.

That’s why I did the follow me.


#18

I’ve just tried it too, and get the same result. Doing just a 30° half segment limited the distortion, and it is then possible to restitch the last few distorted joins between inner and outer arc, but I don’t know why it does the distortion in the first place - I had matching numbers of arc segments in inner and outer arcs.

Wonder if it would work with a whole circle? … Just trying.

That works fine. Why won’t a part circle work?


#19

No idea, I tried at 10x and 100x scale, glad it’s not just me. I figured it’s probably quicker (less steps) the follow me route anyhow, without cleanup too.

I know it works in circles, that’s where the idea came from. I sometimes make a hole, offset it and move the edge down to create a bevel.


#20

Did you redraw the cutter, to get a selectable inner edge composed of arcs, not just loose edges?