DWG to Model - how to approach?

[Rhodan]

I'm waiting for my K2CNC package to arrive (Late January most likely) and in the meantime I'm playing with the Rhino demo to try and get familiar with it.

My first (real) project after the machine arrives will be to do cutouts in a plastic enclosure for an LCD and buttons. Truth be told, Its simple in that I'm only really dealing with a 2.5D flat object (the front of the enclosure) but I thought I'd try to model the entire enclosure in 3D.

I have 2d drawings of the enclosure in both DXF and DWG format and I'd like to use that as the basis for the 3D object. The drawings are downloadable from http://www.hammondmfg.com/dwg6.htm and I'm using the 1599EBKBAT version.

Whats a good way to appoach this? I was thinking I could use the top view and extrude the entire thing, then use boolean operations to cut away the insides etc. The radiused edges should be creatable afterward once I look up and figure out how to use fillets (I think).

Not looking for step by step instructions, just a general idea of how to go about it.

[turmite]

Rhodan if you are just beginning to use Rhino I would suggest you try several different ways of modeling the part. I have found in my limited experience with Rhino there are sooooo many different ways to get to the same place.

For instance the thicker part, which I am assuming is the base, has a depth of .91" and a fillet that surrounds the part. There are at least three different ways to get that fillet that comes to mind. Fillet edge, filletsrf and then one I have never used is to build a curve where the center of the radius would be and pipe a tube around the edge then use either split or trim to get your fillet.

Like I said....there's lots of ways to get there. Try them all while you have some time.

Mike

[Rhodan]

Oh I plan on trying many different ways - once I figure out what they are!

Yesterday I was just experimenting with filleting around a box, trying to get both rounded edges and rounded corners to match using filletedge. I succeeded but now I'm trying to get the edges filleted with one radius and using a different radius on the corners. It sort of works but the transition between edges and corners is not smooth. That's today's task - figure out how to smooth those out.

It'll likely be a lot easier once I receive my package from K2 and get all the manuals etc on disk. The demo tuts are exceedingly simple and don't cover a lot of ground.

Back to it!

[chmillman]

Yesterday I was just experimenting with filleting around a box, trying to get both rounded edges and rounded corners to match using filletedge. I succeeded but now I'm trying to get the edges filleted with one radius and using a different radius on the corners. It sort of works but the transition between edges and corners is not smooth. That's today's task - figure out how to smooth those out.

This is relatively easy. The general rule is if all the rads are the same, fillet all edges at the same time and the program will put in the small sphere segments at the corners automatically. If you are filleting different radii, always start with the large fillets first, then proceed to the smaller ones ("wrapping" the smaller fillets around the larger ones). The other way won't work. Do not try to fillet around an existing corner with a same-size or larger fillet - always smaller.

Filleting prismatic forms is not too bad in Rhino, but many solid modelers can do better. For free-form objects where fillets get very complex, you can generally get through in Rhino (with some "manual" labor) where many solid modelers will just refuse. In either case, some experience is required for filleting to be successful. --ch

[Rhodan]

Ah yes, that worked perfectly. First the large fillet radius in the corners, then the small fillet radius on all the bottom edges (including the bottom edge of the corners) at once. Thanks for the tip!

Now on to trying to extrude the 2D drawing into a 3D model!

[Rhodan]

Ok, got the first part of then model almost done using extrusions - I just have to fillet the bottom edge, which I cannot seem to figure out.

The model is basically made up of three seperate objects - outer wall, inner wall, and bottom. The outer wall is .32 high, the inner wall is .44 high, and the bottom is .11 high.

The fillet needs to be 0.19R but the outer wall is only about .1 thick, so the fillet fails (of course). What I need to do (I think) is join the three objects into a single object, which is where I'm stuck.

I tried the join button with the three objects selected, it appears to have no effect. I also tried the boolean union command but that gives a failure message. I've been searching the help files etc, but cannot see anything that would appear to be helpful.

Am I just approaching this wrong using the extrusions? Is there a better way?

It appears I cannot attach a model file so I can't submit the model for inspection but I've attached a jpg showing the model with one wall selected so you can see what I'm talking about.

[chmillman]

Sorry, I haven't been watching this thread. Not seeing the model, I suspect that you are trying to BooleanUnion a bunch of concurrent surfaces, in general something that is a hit and miss affair in Rhino. Your alternative is generally some manual trimmming and joining. It shouldn't be too hard.

I'm not sure if I would build your part from 3 different extrusions and try to union them, rather, I might build it more like a solid modeler and have a base part to which I added or cut away parts, punch holes, etc. Modeling in Rhino often has, like most other programs, an "optimum" way to build the part, although many other methods will also get you there.

You should be able to post the model, you just need to zip it. I think if the zip file is under 8.5 megs, it will go (your file once zipped should be pretty small). --ch

[Rhodan]

Thats what I was working on this morning - starting the model as a single large box (sorta).

The top of the enclosure is a bit smaller than the bottom, making all the sides sloped. I couldn't find anything do do this automagically so I created two rectangles at the proper locations then riased the smaller one to its proper height. Using end snap, I attached the four corners with curves to create an elongated and truncated pyramid.

After fumbling around a bit, I discovered I could create a surface using points so with end snap on I created six surfaces using the curves as a guide. I then hid all the curves (different layer) and used join on the surfaces which appears to work fine. Then I filletted all the edges and got exactly what I was after (though I undid the fillet in anticipation of other operations later)

I was thinking doing this like a solid modeller would be a good approach as well. I'll build another box to the inner dimensions and use that to cut out the inside of the enclosure, lay a set of boxes around the inside for the interlocking lip then cut that out of the top part (preserving the boxes as the bottom lip).

Once all that is done, then I can fillet the inner and outer edges of the enclosure and interlocking lips, cut out the inset on the top, and add the bosses to the interior.

The battery door was pretty easy and I'll just use the same method again.

That should do it I think, unless anyone has any suggestions?