[Beansdiesel]

I have always had issues with making something using surfacing to create a solid then working with that solid later on. Seems like if I try and do any Boolean subtracts or extrusions to it they just dont work or dont work right and most of the time if it does cut anything away it leaves the part with a hollow center like it was never a solid to begin with.

Here is an example I have been working on for a couple days. The first file I first drew a cross section of it then revolved the cross section to create the base part. Then stitched it into a solid. The larger holes I used Extrude Cut and they seemed to work ok. But I then need to create a ball mill effect that runs next to the hole. In the end it will look similar to the picture of the truck wheel I attached.

What I have been doing to try and achieve that ball mill cut is to create a swept cylinder, capping the ends and stitching it. Then doing a Boolean and subtracting it for the main wheel. On the wheel that I used the Revolve tool to make it winds up leaving areas that are open to a hollow inside of the wheel.

So I then tried to do it all over again and create an extruded solid to start with and work it all off of that.(second file attached called solids) But when I tried to use the swept cylinders again it left weird surfaces that just stuck out into nowhere. Those little protrusions wont go away either with any kind of Extrude Cut.

My guess is its a problem with the geometry I am trying to use to create the little cylinders or something. I am not sure. Just know its been super aggravating. I know I could just draw lines and cut everything without having a solid drawn, but I want to draw it. I like to see what it will look like before I go to doing the cuts.Just has always seemed like I cant cut away anything that has been made using surfacing, just never cuts away correctly like its a real solid.

[jrmach]

you can always simulate it and save it as a .stl
but that is not the point ?

[Beansdiesel]

you can always simulate it and save it as a .stl
but that is not the point ?

Not sure what ya mean. Can a simulated piece be saved as an stl? If so I did not know that.

[jrmach]

Here's is an example in V26,,,,,I saved this from op1 and used it as stock in op2
or
there is a picture of your part

.stl are limited what you can do with them though

I am sorry,,but not enough hours today to look at your files

Red circle is the magic button

[Beansdiesel]

Well, at least I learned something today. Day not wasted.

[Beansdiesel]

Did the .stl file save after cutting it but like you said only so much I can do with it. For some reason it slows down BCC to a crawl plus I cant extract edges off of it or anything.

[The Engine Guy]

Did the .stl file save after cutting it but like you said only so much I can do with it. For some reason it slows down BCC to a crawl plus I cant extract edges off of it or anything.

The .stl files from the simulation are usually quite large megabyte wise so your BobCAD file can end up at 100Mb or even 200Mb and become very very slow to work with unless you have a PC like the ones used to make Toy Story etc

Basically only to be used as a shaped stock when it is too much trouble to create one in solids, personally I try to make things like that in Onshape, their solids are quite small files and easy to work with plus it`s free

Regards
Rob
:rainfro: :rainfro: :rainfro:

[aldepoalo]

Here is a video I did with some work flow...

https://youtu.be/F1mBzskO8Fk

[Beansdiesel]

Thanks Al, that helps some.

Why is it though that if I start with surfacing then stitch it all together, then start subtracting other shapes away from it say with an extrude cut it will either fail and do nothing or after cutting away it leaves openings to a hollow center or the part? I have run into that a lot.

[aldepoalo]

If you stitch surfaces together and there have overlaps and intersections that are not cleaned up you can run into the problem you are having. Instead you may need to add the surfaces together, then un stitch delete the intersection parts that need to be removed then stitch the surfaces back together. Let me see if I can get a video for you on this.

[jrmach]

Everything works on almost the "Atom: level,,,lol

Means everything must be done in a perfect,concise order

I feel your pains

Luckily in most of the World I do "Real" parts that I make $$ from,,,,,Fancy Solids are not necessary to machine with

Hence my statement,,,simulate and save as a .stl,, and there is your picture for your customer

So depends if what you need vs. what you want,,,,,,,,,,,,,,,,,,,,,,,$$$$$$ vs. I just wanna learn and do it because I can

[Beansdiesel]

Everything works on almost the "Atom: level,,,lol

Means everything must be done in a perfect,concise order

I feel your pains

Luckily in most of the World I do "Real" parts that I make $$ from,,,,,Fancy Solids are not necessary to machine with

Hence my statement,,,simulate and save as a .stl,, and there is your picture for your customer

So depends if what you need vs. what you want,,,,,,,,,,,,,,,,,,,,,,,$$$$$$ vs. I just wanna learn and do it because I can

I dont have to model stuff but I prefer to for two reasons, I want to learn how to do it better and also I like to see what my final product is going to look like. I could do it with the simulator like you learned me on, which I will use some in the future but, I still would like to learn more about what I am doing wrong in modeling. I could model something like this in a couple hours if it were not for running into these issues down the line then spend 6 hours trying to make one thing on the model work.

[BurrMan]

I dont have to model stuff but I prefer to for two reasons, I want to learn how to do it better and also I like to see what my final product is going to look like. I could do it with the simulator like you learned me on, which I will use some in the future but, I still would like to learn more about what I am doing wrong in modeling. I could model something like this in a couple hours if it were not for running into these issues down the line then spend 6 hours trying to make one thing on the model work.

I saw your model last night. I think your issue is going to be with "stitching and unstitching and stitching" and what you are expecting from that. You will want to stick with using solids and boolean adds and subtracts. Surface modeling is more advanced and not needed for this model. BobCad has a "split" command which might be used here also. I'll look at making a video of your model later maybe. What version of bobcad are you using?

[aldepoalo]

This video you give you more insight on how to use surfaces to create a solid.

https://youtu.be/xAMSBXPaSvI

[Beansdiesel]

V27

I have found the quickest and easiest way to make a wheel like this or round objects is to make a profile of it then use surface revolve which is how I went about doing this one. Once I revolve it then I have been stitching it together, but it must not be air tight for some reason thus the hollow center in some areas. With just revolving it and stitching it the center part will extrude cut just fine, its when I start trying to use the Boolean subtract that things start going south.

This is the geometry I start with.

[BurrMan]

V27

I have found the quickest and easiest way to make a wheel like this or round objects is to make a profile of it then use surface revolve which is how I went about doing this one. .

YES! That's perfect and a good profile. The revolve is a solid and ready for more work. However:

Once I revolve it then I have been stitching it together, but it must not be air tight for some reason thus the hollow center in some areas.

This is the part I was referring to. Stitching WHAT together? The revolve you have made in this file is a perfect solid. Your next operations would be to make more solids and do more Booleans with those.

BobCads "stitching command is very raw and will allow you to create "malformed solids" (There is a lot of this in your previous files.)

From this revolve you have posted most recently, what is the next operation you want to do to it? Cut the spoke holes then cut the "tubes" like in the other files?

[Beansdiesel]

YES! That's perfect and a good profile. The revolve is a solid and ready for more work. However:



This is the part I was referring to. Stitching WHAT together? The revolve you have made in this file is a perfect solid. Your next operations would be to make more solids and do more Booleans with those.

BobCads "stitching command is very raw and will allow you to create "malformed solids" (There is a lot of this in your previous files.)

From this revolve you have posted most recently, what is the next operation you want to do to it? Cut the spoke holes then cut the "tubes" like in the other files?

You taught me a few things. I didnt realize that once I did a full 360 Revolve it would already be a solid! I thought that since it was done with a surface tool that it would still be separate surfaces.

I figured there was something wrong with the splines on those cylinders. I am starting to use splines more and figure out how to make them work right. I have trouble getting them to be smooth geometry.

Thanks Burr, you helped me a lot!

[jrmach]

Listen to Burr,and watch his video he makes,,,he knows how to model

[BurrMan]

I have also found that the "tubes" you posted earlier are malformed. This will screw up the Booleans later. I can remake those and it works fine (Rebuild them into a cleaner spline)... Your tubes stop kindof short of half way in the middle of that outer fillet. kindof makes a little funny end. I would extend the tubes out further, then do a Boolean split with a proper circle to cut them even with existing edges. I'll make a video of that.

[BurrMan]

Here's a video I made doing your wheel with what I thought you were after:

https://youtu.be/EVoUox82ISE

In the video I point out the tubes as "bad" (weird intersecting surface) from the original sweep. I rebuilt the path with spline approximate to get a good sweep. I also extended it out more to get a good cut at a better intersection point with the wheel solid.

I'll make a quick video that talks about BobCads stitching and how you can get into trouble with it.

As an added note here. I have found that if your CAD tree gets to LONG with dilly dallying, it can start to affect operation in general. Every now and again when I get to a successful point, I clean the tree by saving out the file and merging in geometry with no tree (Or copying and pasting into a new file to start fresh)