Remove scale? 6

[ctopher]

I have been looking into updating our drawing templates.
I was thinking about the Scale block, and scale listed under views.
What do you think about not using scale anymore?
There isn't really any use for it anymore. Drawings are never printed full size, and they are saved as PDF's.
Who cares what the scale is anymore? After printing, the drawings are not to scale.
Thoughts?

Chris, CSWA
SolidWorks 14
SolidWorks Legion

 

[ewh]

I know from experience. ;-)

That, and the velum swelling overnight when it's taped to the board made me realize why exact dimensions weren't to be had from drum-copied prints, and the DO NOT SCALE DRAWING statement started making more sense.
Ink on mylar - that's a different animal.

"Know the rules well, so you can break them effectively."
-Dalai Lama XIV

 

[weavedreamer]

Enamel paint on aluminum sheet. Lines roughed in with aluminum, fine-lined with gold.

Sent a print out for what they called a wash-off at the time. By the time I discovered it was out of scale, I had put half a day trying to figure out why I couldn't get two of the views to project correctly.

 

[CheckerHater]

I've posted this story long ago, but is seems appropriate to repeat it.

AutoCAD drawing is sent to fabricator.

Fabricator is having hard time printing.

Instead of changing print settings, they decide to scale drawing (together with dimensions).

Fabricator ships piece 2X the required size.

Instead of "DO NOT SCALE" drawing should say "DO NOT PRINT".

(True story)

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[drawoh]

We bought a product line from another company. All the drawings were in AutoMAD. They liked to use unusual scales for detail views like 7:1. Now you can easily scale up from 1:1 to 7:1 because it's an integer multiplication but to make dimensions in the scaled views you have to set "dimlfac"...

Back in my AutoCAD days, I drew everything 1:1. If you want to print at some other scale, you can mess with the scales at which the dimensions, notes and titleblocks are printed. I wrote AutoLisp scripts to make this easy.

CAD should be drawn/modeled at 1:1 scale, only.

--
JHG

 

[ctopher]

<CAD should be drawn/modeled at 1:1 scale, only>
I agree!

Someone making a part based on the scale, and not the dimensions, should not be making parts.

Chris, CSWA
SolidWorks 14
SolidWorks Legion

 

[KENAT]

Going MBD is no guaranteed fix - occasionally parts may come in a factor of 25.4 off.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[CheckerHater]

Tru dat!

"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future

 

[weavedreamer]

This makes me wonder if there isn't a simple elegant fix, such as adding a snippet of geometry that would stand out to someone trying to work with the file. A scale geometry, if you will, consisting of 2 lines, one of 1mm, the other of 25.4mm.

If the lines came in at 25.4 and 645.16, or the reverse of 0.3937mm and 1mm, it might raise a flag.

 

[JNieman]

Or you could just script files to close with all layers/objects hidden other than a "General Notes" layer, zoom-extents / zoom-fit on a block of text giving you the general "Ok, before you get started, here's what you're looking at..." block of info.

_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5

 

[dgallup]

Drawoh - I was referring to detailed views, obviously they can not be drawn at the same scale as the rest of the drawing. Real CAD systems can create scaled views from the model. AutoMAD has to scale a collection of lines and circles and then inversely scale the dimensions. Scales whose reciprocal is a repeating decimal cause a problem if you have to go out quite a few decimal places.

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[drawoh]

dgallup,

Can you type in fractions when you scale stuff? It has been a while since I have used AutoCAD. Definitely, I can do this in LibreCAD, which is way less capable.

--
JHG

 

[dgallup]

I have not used AutoMAD for several years, but if I recall correctly, you had to type in an Autolisp function to get it to use a fraction to it's full internal accuracy. Something like ( / 1 7 ) return. There was no problem if you typed in 10 or so decimal places for the repeating fraction. The problem in the drawing I'm talking about was that the original drafter had only put in 3 or 4 decimal places for 1/7 and when I tried to check the accuracy of the geometry I was getting round off errors. This was a drawing of a very fine grinding operation with tolerances in the .0001" range so I was trying to make sure the geometry was exactly correct. Later I completely modeled these products in a solid modeling system and made new drawings but I didn't include any 7:1 detail views even though it would not have been a problem in the new system. Some things are just not right.

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[ctopher]

If 7:1 is used, it should indicate "NONE". The scale 7:1 (or 7/1) should not be used.
BTW, I have always been taught that scales with a colon (7:1) are for metric dwgs.

Chris, CSWA
SolidWorks 14
SolidWorks Legion

 

[dgallup]

I just went looking for those awful drawings, I haven't actually worked on them for over a decade. Found one with 2 detail views, the first is 21:1, the second is 52.5:1. I also found 3:1 & 9:1. Amazing. These same geniuses managed to mis-draw the cross section of an uncompressed o-ring so CAD was not one of their strong points. (Hint: It's a circle)

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[drawoh]

dgallup,

I do not know how common drafting scales are. I still find mine useful, as long as I select appropriate drawing scales. I do like to hang E[&nbsp;]sized drawings (A0[&nbsp;]approx) on my walls.

--
JHG

 

[ctopher]

<21:1, the second is 52.5:1>
This brings me back to my original post, what's the point of having scale, especially if it's a scale that can't be 'easily' measured?

Chris, CSWA
SolidWorks 14
SolidWorks Legion

 

[dgallup]

If those scale had not been on the drawings I never would have been able to figure out what had been (poorly) done originally and make accurate new drawings.

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[tbuelna]

Back in the old days, there were drawings made at 1/1 scale that required very high accuracy. These drawings were OML masters or sheet metal flat patterns. The flat pattern drawings were used to project photo images onto the sheet metal of the flat pattern outline, mold/bend lines, and centerline location of features like holes and dimples. While the OML masters were used to construct templates for making various types of tooling. So these drawings had to be very precise.

A while back I worked for Boeing CAG on the 757-300 program doing structures design work. The legacy structure drawings were all done on paper or mylar, but the -300 design was being done with CAD. Boeing developed a CAD software tool that would take a scanned image of a sheet metal master template and allow you to convert it to a solid model of the formed sheet metal part simply by selecting and defining the scanned geometry. It was pretty impressive, and the resulting solid models were amazingly accurate.

 

[looslib]

I used to get frustrated when looking at drawings done in 3:100 scale. Pro/Engineer just puts the scale of the base view as the default scale so whatever the designer drags the size to, that is it. I have seen a whole bunch of odd scales with CAD drawings.
English ddrawings should be scaled in even units: 1:1, 1:2, 1:4, 1:8, 1:16, etc.
Metric drawings should be scaled in 10ths: 1:1, 1:2, 1:5, 1:10, 1:20, etc.

I even put that in the company CAD standrads at one time, but the designers still violated it. The Pro/E designers were worse than the Unigraphics designers, though.



"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

 

[dgallup]

I do find the metric 2, 5, 10 scales a little confining. I've been know to use 8:1 on a metric drawing because 5:1 was too small and 10:1 would not fit. I know it's against the rules. Sometimes you just have to bend the rules.

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