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howitzer

Survey: How important is linework accuracy?

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howitzer

I'm interested in what others do and/or think, wondering if I'm on track, or whacked out.

 

How important is it that linework be accurate? By accurate I mean, lines that are supposed to be parallel are indeed parallel, not a couple seconds off... two lines that are supposed to meet at their endpoints, do indeed meet at their endpoints, not overlap... things like that.

 

My position is, or has evolved to be, that you save yourself so much time and trouble and heartache in the long run if you're accurate from the very beginning. It's easier to do it right from the start than it is to do it wrong then make it look right, especially where dynamic labeling is concerned. Even if it ostensibly 'doesn't matter because it won't be built that close anyway'. If I'm laying out a sidewalk, for example, I expect the sides of the sidewalk to be parallel. I expect lines/arcs to be tangent (excepting the rare scenario where you have no choice for whatever reason).

 

Others in my firm do not believe I should be so dogmatic about it, that there are times where it's just wasting time for something that will never matter. Yet, in my experience, my rear end has been saved from blame because my linework was accurate. If nothing else, there's potential liability reasons.

 

Your thoughts?

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rkent

To me it is actually easier and quicker to do things accurately, and it looks so much nicer. From the stand point of getting something like a sidewalk built it probably doesn't matter, but I can't bring myself to "sketch" with CAD.

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BIGAL

Your listed as CIVIL so with GPS setouts, 3d machine control accuracy is becoming more important. Its so easy to do it correct using snap and ortho to say it does not matter is not the sign of a good designer.

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steven-g

I probably spend half my time making other peoples drawings accurate, I have to take off quantities from drawings supplied by others, and it is so much easier to do that if polylines are closed and not made up of overlapping objects, it's a fairly simple formula to find the length and width of a wall given perimeter and area, but only if that information is accurate. For a 160 apartment tower block, it can take me nearly a week to clean up the drawings and get things on sensible layers. It is then just a question of days to take off the quantities and create the schedules, doing all that normally is 3 to 4 weeks.

And by far the best drawings, in general, come from the structural engineers, that's just a question of checking for odd errors. Drawings from Architects, that's just hoping that you can find a few that are straight. I think many of the errors are due to how "other" programs are converted to dwg.

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SLW210

It's too easy to draw it accurate and correct to accept anything less. Like rkent, I see no reason to sketch with AutoCAD.

 

I fix any and all drawings I get or come across with inaccurate CAD work, if I am to work in them, if someone just wants something printed, I rarely bother to check it over for such things unless it just doesn't look right. Like steven-g, I find some programs convert poorly to dwg.

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CyberAngel

It's been my experience that, once an error creeps in, it will get carried through everything that connects with it. An architect will use fractional units and believe that getting within 1/4" is close enough. In other words, he'd never see a difference as large as .12. After a few more near misses, each one amplifying the ones before, he'd wonder why his stuff wasn't lining up properly.

 

As SLW210 says, there's no excuse for doing it wrong when you have the tools to do it right. The people who will use your drawings are expected to work within certain tolerances. You owe it to them, and everyone else, to do the same.

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ReMark

Accuracy is paramount in the world of design. Anyone who tells you otherwise should be doing something else.

 

A defect in a measuring device used to polish the mirror for the $1.5 billion Hubbell telescope made it virtually useless. It took a second mission (and additional monies) to fix the problem.

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dtkell

I thought the ease of drawing accurately was one of the benefits of using a computer aided drafting program. If you don't want accuracy, use a pencil.

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howitzer

Thank you all for your replies. It sounds like we're all pretty much on the same page... no pun intended.

 

I like the word 'sketch' for what I am describing. I think that's highly descriptive. The way I portrayed it is that, if accuracy isn't important, then we can buy some lesser program than AutoCAD and save a lot of money... but we don't, because accuracy IS important.

 

Turns out that I am not the only one who fixes things that aren't right when I get a drawing from someone else. Even if it's someone within my own company. If I get a drawing from an architect my mind is already conditioned to know that I will be reconstructing the majority of their drawing. I once had to trash literally an entire site layout once because not a single thing was accurate. Even the arcs for curb returns was just a series of short lines, all wildly inconsistent in length, that looked fine in a plot on paper, but served no useful purpose whatsoever.

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Ski_Me

My drawings are not accurate at all I even tell people don't use my drawings to confirm the distance or the size of some feature that may be on the drawing. Most of the time the drawings I get are vectored PDFs that I convert to DWG. Then I have to scale them up. Of course doing fire alarm drawings accuracy of the drawing is not the most important part it's showing where the devices are going and how many. I know it sounds strange but my drawings are only for a relationship between devices installed and to where they are going. Any thing that requires any accuracy I show in a typical or a detail with dimensions. Rule of thumb is not to have your thumb where the hammer is going to hit. Translated leave the hammer alone and don't hold nails.

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Jman

In my line of work, line work and Layer Management are crucial as we design and build here. We fab most of our own parts. I work for a modular building manufacturing

company. Our modules have to fit together both horizontal and vertical as we do a lot of 2 story schools. If parts don't line up and fit it costs the company both time and

money. It's always better to do it right the first time. Speaking for myself, My pet peeve is lines on top of lines.

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jagwinn

Building Automation. We used the Architectural CAD given us by builder to xref for walls and existing HVAC. So it is embarassing to have the field installers call to say there is a swimming pool where I told them to put AHU-1.

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ammobake

Pretty much everything you will ever draw is only meant to be conceptual and tentative anyway.  As a drafter, this means you can relax (in a way) and get the drawing "close".  My old boss told me when he hired me on that as long as I could maintain 60% accuracy on the asbuilts I was fine.  But, obviously, for military/government work you need a little better than that for most applications.  I think some of us stress quite a bit about accuracy early on, including me.

 

Later on you realize it's less about the dimensions being accurate and more about the drawings reflecting the design intent.  Percentage of accuracy should be an afterthought and only really applies to the asbuilts and even then it's not going to be 100%.

 

What plays into this is your understanding of what a project manager or designer wants to do on the project.

So coordination is pretty important and understanding the scope of work/narrative.

 

In some instances more accurate and dimensioned drawings can be required like for doing framing or re-routing conduit in a plenum.  But those don't usually even make it into the set and more for subcontractor use to do the install.

 

ChriS

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Jman

Most drafters set their units at 1/16th or 1/8". Here that is not acceptable, our units are set @ 1/256. our buildings are modular. Steel frame with wood infill. our modules

have to bolt together and are welded so every building has to line up and when you are spanning over 100'-0" design is Critical. Our main product is schools so we have to 

submit our drawings to the Dept. of state state architects office (D.S.A) for approval . I know that most built on site jobs allow for some wiggle room.

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RobDraw
On 5/15/2019 at 1:30 PM, ammobake said:

60% accuracy on the asbuilts I was fine.

 

That is ridiculous! I'm sorry but that opens up a big ol' can o' worms. As built drawings that can be way less accurate than the design drawings?

 

In what world is this acceptable? I want to stay away, very far away.

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CyberAngel
40 minutes ago, RobDraw said:

 

That is ridiculous! I'm sorry but that opens up a big ol' can o' worms. As built drawings that can be way less accurate than the design drawings?

 

In what world is this acceptable? I want to stay away, very far away.

 

As we used to say, "close enough for government work." Maybe it's different in mechanical, where the contractor may have to route a conduit around obstacles.

 

In civil, where I've done most of my work, a 40% error would be totally unacceptable. Try to imagine finding a property corner buried in weeds when you have the location within 3" (after a 400 foot trek along a property line). Now try finding if you have a 160' circle.

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tzframpton

We produce fabrication-level shop drawings, so our initial drawings are the as-builts. If anything changes during construction, it gets reported back to us immediately and we issue a clouded revision so our client can get some change order cha-ching. 

 

I guess this topic is very relative depending on the nature of the work involved and the outline of the scope. 

 

-TZ

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ammobake
4 hours ago, RobDraw said:

 

That is ridiculous! I'm sorry but that opens up a big ol' can o' worms. As built drawings that can be way less accurate than the design drawings?

 

In what world is this acceptable? I want to stay away, very far away.

 

Yeah when that company hired me on in 2008 I heard the site manager tell me that and that's when I realized I would kind of be on my own for drafting stuff.

Also, asbuilts for military bases are even more important in many ways because the moment something breaks or goes wrong the asbuilts is the first place they look.  Plus, on military bases you're commonly building around 60 year old utilities and the projects were regularly historic buildings.

 

But I was usually able to get 90-100% accuracy on the asbuilts because for me it was a matter of pride.

The base I worked on maintained a vault with permanent mylar prints and a few hundred sets were ones that I prepared personally.  And it's kind of neat because I know they'll stay there. 

 

For one building they had a structure from 1940 and I went off the asbuilts to design a LEED renovation project in CAD.  So I felt a kinship with that old drafter from 80 years ago.

 

And then I wondered if my drawings would still be there in 80 years with some drafter in the future wondering who I was.

 

-ChriS

 

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RobDraw

Thanks for clearing up that situation for me, Ammo. My jaw still hurts from hitting the floor earlier today.

 

As-builts should be more accurate than the design drawings and, coming from the design side, 60% accuracy means we would be taking a shot in the dark with our eyes closed or doing presentation drawings for intent of concept or maybe drawing on napkins.

 

I've done several LEED projects on historical buildings. At the residential/small commercial level they have passive house which is extremely hard to do without completely gutting existing buildings. One of my favorites was a co-gen project at the Empire State building. It might not have been a LEED project but it is still related. I was given tiff files of the entire set of the original architectural drawings so I could create CAD backgrounds for our stuff. I only needed a few plans. The rest was eye candy. Only 60 or so sheets total, including details. I also had a smattering of drawings from subsequent projects that pretty much verified that the dimensions from original design drawings were met.

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