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Senior Member

Joined: 27.Nov.2009
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Points: 220

Posted: 07.Apr.2010 at 04:58

If we're talking 'bout tolerance, exact drawings, this would help keep the accumulative tolerance low (or within limits).

One item might be .250"±.002", BIG stuff might be ±1.0" or more. Like some of the BIG storage tanks I might be designing at the time. I might dimension a BIG item, 15'-0" ± 1.5". A small gear might be dimensioned 1.000"Ř ± .002".

I've worked on machinery that had literally hundreds of gears and rollers.

Imagine if each and every part went to the max tolerance?

The accuracy required depends on what you're designing.

In the steel industry the saying was, "Get to work, we're not building watches!"

Edited by Tankman - 07.Apr.2010 at 05:02

Tankman

"When the well's dry, we'll all know the value of water."

tulip3D

Senior Member

Joined: 23.Jul.2009
Location: United States
Using: AutoCAD2011, Inventor2011
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Points: 427

Posted: 25.Mar.2010 at 21:34

As in theres no machine that can hold a tolerance beyond @4 decimal places. And if you have interworking parts, like...a car...that tolerance increases or grows larger to account for material expansion caused by friction...; literally hundreds of varibles account for a tolerance being increased or decreased. Simply put, you cant hold a tolerance much beyond 1mil or 0.001". So all those other decimals are just there to make us designers feel good inside. And so when mirroring and mating parts in virtual space things match or line up. Keyword being 'virtual', not 'actual' or physically fabricated.

JoDCad2

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Joined: 20.Mar.2010
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Points: 3

Posted: 25.Mar.2010 at 19:45

Thanks ya all for the replies.

bcbenton wrote:

One issue with CAD, when compared to drawing on the board, is its precision. We can draw more precisely than we can build. So CAD is limited to real life application because it is so powerful. I have run into this in several industries and it is always an issue. If the CAD drafter doesn't take into account real world conditions, the drawing may not work.

Very interesting point, but I don't know I fully grasp it, do you think when you feel like it you can elaborate on this a bit? Would that be in issue say in building construction, what do you mean that we draw more precisely than we built?

bcbenton

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Joined: 11.Mar.2008
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Posted: 23.Mar.2010 at 13:45

One issue with CAD, when compared to drawing on the board, is its precision. We can draw more precisely than we can build. So CAD is limited to real life application because it is so powerful. I have run into this in several industries and it is always an issue. If the CAD drafter doesn't take into account real world conditions, the drawing may not work.

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Tankman

Senior Member

Joined: 27.Nov.2009
Location: United States
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Points: 220

Posted: 23.Mar.2010 at 01:35

Tons of work! Back in the 60's I did a lot of board work.

My eraser was 110 volts, hanging off the edge of the board with a cup hook.

My ex neighbor in Perkasie asked me if I wanted his used board.

Nice, big, all the bells 'n whistles. I turned the offer down.

The only artifact I have left is the board brush, just for memories.

If I need full size prints, I email the *.dwg to Richter's in Souderton.

Very inexpensive and the prints are usually same day or the next day ready for me to pickup.

Tankman

"When the well's dry, we'll all know the value of water."

tulip3D