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Black Forest
08-18-2010, 12:46 AM
I have realized one of the advantages of using a CAD program to help in making parts. One can build the part in the CAD program and print it out. Go to the shop and machine the part. If when you machine the part you make a mistake and remove too much material and have the machined part off size all you have to do is go back into your CAD program and change the dimensions! Now you have a part exactly machined. If you draw with pencil and paper it is a lot more work to get your parts exactly!!!!!!!

One of the big advantages of a parametric CAD program!

RB211
08-18-2010, 12:55 AM
Just use larger tolerances, that way you don't even have to change the cad drawing!
For me, modeling in 3d parametric cad allows me to "build stuff" when I am forced away from my work shop due to "life".

Black Forest
08-18-2010, 04:58 AM
For my farm work my tolerances are not often very critical on the parts I make!

Yesterday I made a CAD part in Alibre Design. It was a trunion plate for a air cylinder for my sheep shearing machine. In CAD my design seemed like it would work. In reality I didn't leave enough room for the nut on the end of the rod on the cylinder. So in the shop I changed my design and built the plate. Then I went back and changed the CAD drawing.

Of course I was making a half joke about changing the CAD to match my mistakes but......only half a joke. For you real machinists of course that is not an option I know. And as I get better I hope it happens less often.

digger_doug
08-18-2010, 08:07 AM
Yesterday I made a CAD part in Alibre Design. It was a trunion plate for a air cylinder for my sheep shearing machine. In CAD my design seemed like it would work. In reality I didn't leave enough room for the nut on the end of the rod on the cylinder. So in the shop I changed my design and built the plate. Then I went back and changed the CAD drawing.



If you took the time to build your model completely, the nut would have been
in there, you would have fixed that interference problem on the screen.
Even in 2-d autocad, you could lay out the complete working range of
the machine in question, showing the complete range of motion
of that offending air cylinder.

Fixing the CAD model to match what you made is bass ackward.

One of the bigger reasons for CAD is the ability to export the surfaces
(electronically) directly to a cnc plasma cutter, a cnc mill, a cnc lathe.
Thereby programming the machine using the CAD file *granted there is a
CAM program step in there, along with post processing to talk to
the machine.

Black Forest
08-18-2010, 08:14 AM
Digger Doug, are you being serious? I was being sarcastic or whatever you call it.....

Of course all that you said is true and I knew that already. OK, I'll say it again, It was a joke!!!! Sorry for taking up your time with a joke....

digger_doug
08-18-2010, 08:20 AM
No I was being serious, I have to assume your a new-to-cad operator,
and do not re-alize all the advantages and techniques to making
a complete layout.

10 more minutes in front of the screen to draw all of the elements,
saves several hours (or days) in the shop of fix-ups.

Evan
08-18-2010, 08:33 AM
Facetious is the word you were looking for. I also like using cad to design parts that I may never build. It is a lot like making things in the shop. 3D Cad is much like a machine shop simulator which is what it is supposed to be.

Black Forest
08-18-2010, 08:40 AM
Yes Evan, that was the word, Facetious!

What is interesting to me is as I build a part in CAD I try to build it how I would build it in the shop.

Now if I could render my pictures in POV from Alibre I would have much better pictures to hang in my shop.........deflector to keep the whosh from being lost!

Don't worry I have not been drinking...that last comment actually will make sense to one particular member here......

Black Forest
08-18-2010, 08:42 AM
Machine shop simulator and we have an endless supply of raw materials to boot.

Evan
08-18-2010, 08:47 AM
I think my version of Alibre may be broken. I will have to try reinstalling. I sure do not like that program. It is very non-intuitive to me.

Black Forest
08-18-2010, 08:52 AM
I have version 12.1 and I think you might have a problem opening 12.1 files in a earlier version. Next month they release a new version.

I acutually really like the program. I find it pretty straight forward. But I don't have a lot to compare it to so my opinion is not so valuable.

loose nut
08-18-2010, 10:01 AM
It was a trunion plate for a air cylinder for my sheep shearing machine. In CAD my design seemed like it would work. In reality I didn't leave enough room for the nut on the end of the rod on the cylinder. So in the shop I changed my design and built the plate. Then I went back and changed the CAD drawing.



Design is the work that you do before the parts are made, engineering is the work that you do to fix the design after the parts are made.

Black Forest
08-18-2010, 10:55 AM
I like that Loose Nut! We always called it "jury rigging" I have no idea of the origin.

S_J_H
08-18-2010, 11:12 AM
Black Forest, lol, I got it and I'm sure most others did as well.

Steve

beanbag
08-19-2010, 02:04 AM
I used to do this kind of "revisionist" CAD work all the time back in grad skool. I would go to the shop with a drawing and come back with a crooked part and revised drawing. One of my co-workers claimed that it was very "1984", in reference to the book.

Black Forest
08-19-2010, 07:13 AM
Hey may parts aren't crooked! They are size optimized!

Evan
08-19-2010, 07:33 AM
I have it working. The script does an ok job of creating a Pov-Ray script but it doesn't do it all. It isn't one stop shopping. He makes the assumption that you know how to use PovRay and can make the necessary adjustments.

That isn't a put down of the program. The part it does is the really tedious part which is converting the geometry to PovRay Scene Description Language (SDL). SDL is a real programming language and it has a steep learning curve like any other programming language. SDL is steeper than most because the functions are oriented to the creation of graphics and the handling of the physics of light. The language syntax is pretty similar to C but that is where it ends.

I can show you how to make simple changes to things like the camera positions and the lighting but if you want to do things like changing the background scenery then you will have to start reading the tutorials and help files. They are excellent, probably the best documentation of any software out there. It is filled with small code scraps that you can cut and paste into the editor and try right away. PovRay has been in development for over 20 years as it first came out for the Amiga which is when I first used it.

Circlip
08-19-2010, 07:59 AM
The biggest advantage of using CAD for designing

It allows you to design it wronger - Faster.

Regards Ian.

Black Forest
08-19-2010, 08:49 AM
Evan I appreciate your time and effort. I would like to try/use POV. But right now it is not important for me and you need to maybe devote your efforts to your home situation. But when you have time I would appreciate your help. I have started reading the tutorials for POV. As you say very good.

The exact steps to follow as to getting the right file into POV would be a good start for me. But only if it is convenient for you.

tmc_31
08-19-2010, 10:06 AM
Of course I was making a half joke about changing the CAD to match my mistakes but......only half a joke. For you real machinists of course that is not an option I know. And as I get better I hope it happens less often.

It's called an "As built" drawing

Tim