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What is your blueprint checking method?

ttrager

Cast Iron
Joined
Jul 23, 2015
Location
East Side / Detroit
Number of people, who does it, and are they dedicated blue printers or people doing this as one of several duties?

Environment:

We don't do design work and we do not produce original blueprints. We receive customer prints dimensioned and toleranced as they have it.

We produce a "re-print" for our shop that may have some dimensions re-toleranced for production purposes. For instance: Overall lengths may be stated by the customer at the Low, tolerance -0 / +.0005. Our reprint will have that dimension at the high to -.0005.

In another case you may have a dimension like an OD at .5000 -.0005 / -.001, and the shop foreman may reprint that DIM as .4995 +0 / -.0005.

We have a two-person dynamic in place:

Shop foreman takes prints from customer service, reviews the job and produces a reprint. I get the job packet and run a basic check of the elements using the customer blueprint & sometimes the 3D if necessary.

Mistakes are still slipping through the both of us. Not often, but it happens periodically. Usually simple eyeball errors like what was supposed to be a .4995 +0 / -.0005 actually stated as .4955 +0 / -.0005. I'm sure when I was checking the blueprint I "saw" .4995 on our reprint when what was actually there was .4955. So the reprint from person 1 put the wrong DIM, and person 2 didn't catch that error either.

The first obvious answer is "pay attention, don't be distracted, stay focused". And that's the right advice. Yet, periodic misses are still occurring between two people, one of whom has 35 years machining experience.

So I'm looking to switch up some dynamics if I can figure something out. The two of us deal with the blueprints amidst other duties (not dedicated blueprinters), etc.

My point in coming here with this question was to simply sonar-ping what you do, how many people are involved, and specific notation methods employed in the process.

Thanks in advance.
 
I really hate having to change customer dimensions for the exact reasons you have stated. The customer should be giving decent drawings. The one case that pisses me off is an exmple you gave...they needed a bore 2.8346 -.0002 -.0009....meaning that if you actually hit the number on the drawing, the friggin part is scrapped.

Whoever came up with dimensioning shit like that is a moron because it lends itself to scrapping. If you hit the number called out on a dimension and yet the part is scrap, that is a bad dimension by whoever drew it.

If I were you, I wouldn't be changing any dimensions unless absolutely necessary. WHy risk scrap?
 
That sounds like a lot of unnecessary work. Why not just mark up a copy of the customer's print and use that on the floor?
 
We produce a "re-print" for our shop that may have some dimensions re-toleranced for production purposes. For instance: Overall lengths may be stated by the customer at the Low, tolerance -0 / +.0005. Our reprint will have that dimension at the high to -.0005.

So, when you watch daytime TV, the price is right for you for whomever is closest to the number without guessing below it, eh?


I really hate having to change customer dimensions for the exact reasons you have stated. The customer should be giving decent drawings. The one case that pisses me off is an exmple you gave...they needed a bore 2.8346 -.0002 -.0009....meaning that if you actually hit the number on the drawing, the friggin part is scrapped.

Whoever came up with dimensioning shit like that is a moron because it lends itself to scrapping. If you hit the number called out on a dimension and yet the part is scrap, that is a bad dimension by whoever drew it.

If I were you, I wouldn't be changing any dimensions unless absolutely necessary. WHy risk scrap?

I have done this once in my life and it caused a bunch of confusion, but at least nobody needed to cut steel. It was on an assembled plastic part, one cavity molds for both parts, two features that interfaced with each other ended up coming off the tool out of spec in the compatible direction. On one of the deviation reports that ended up being approved by me as a -x/-y tolerance for that feature, as long as it was within that range it would interface properly with the other part. If it was to the original design, it wouldn't work right.

But for a newly designed machined part? Forget about it. If you really feel the need to tell people it's clearance for a .500" something like the OP's example, add another reference dimension, or make a note, or add the information elsewhere.
 
Whoever came up with dimensioning shit like that is a moron because it lends itself to scrapping.

Its not the Cad Jockey's/Engineers job to make the print easy for the machinist to read. Its to describe a functional part. You may not like the GD&T stuff, or the weird off angle dimensions for seemingly no reason, but it is there for a reason.

And yes.. Sometimes it drives me nuts too. And then I do the assembly and then... And Then... It all makes sense.


To the OP.. WHY??? are you redrawing everything. That's like buying oreo's, then bringing them home, opening the package, not eating a single one, and then putting them in another bag and vacuum sealing them.

You have a copy machine, they are cheap, and so am I, and I have 2 of 'em. Copy the customer print and mark it all up.

Higlighters, Sharpies, Colored pens. Blowing up specific areas if you have to, and occasionally, just a quick sketch with dimensions to check.. I do that a lot.

Re-drawing and re-dimensioning the entire drawing just seems like a huge waste of time, and one more step you can screw up.

I believe in the KISS principal.
 
Do you have anyone in the shop who's OCD? If not, hire someone so "afflicted" (enabled?), and have them check the customer prints and your redo-s.

FWIW, I would never work off a in-house reprint without consultation with the customer as to why it's been redone. If it's a badly made drawing (like excess dimensional callouts that conflict) they should reissue a corrected version and I'll work from that.

Yes, I hate the +/+ and -/- style of dimensioning too, but I've learned to live with it.
 
Colored pencil. Every dim is colored yellow when the checker verifies it. Errors are marked in red.
Drafter to checker to engineer to drafter to checker to engineer for final sign off.
This works best with dedicated checkers who do noting but.
 
Colored pencil. Every dim is colored yellow when the checker verifies it. Errors are marked in red.
Drafter to checker to engineer to drafter to checker to engineer for final sign off.
This works best with dedicated checkers who do noting but.

Coloring every dimension won't fix the 9 written as a 5 error as there are multiple numerals written together and their eyes take them in as a whole.

When your people check your revised blueprint against the customers have them cross check and color each "numeral" in each dimension against its counter part.
 
One good way to check numbers is to first do it left to right as is normally done and then do it right to left.

And say each digit out loud each time. You can use a small piece of cardboard to expose one digit at a time as you speak them.
 
I periodically have to redraw a customer print due to sloppy dimensioning practices. Normally when they have dimensions stacking from different directions and I need to have them all reference a common origin to make programming easier. During setup and production I compare with original drawing and use my re-print as reference if I need to make program edits. Modifying tolerances for readability or convenience seems like a recipe for disaster
 
That sounds like a lot of unnecessary work. Why not just mark up a copy of the customer's print and use that on the floor?

Because the Customer prints aren't always . . . "clean" . . . and the markups are often times a whole lot of chicken-scratch with pen. Cleaning up customer submissions for consumption by our machinists is unavoidable.
 
Its not the Cad Jockey's/Engineers job to make the print easy for the machinist to read. Its to describe a functional part. You may not like the GD&T stuff, or the weird off angle dimensions for seemingly no reason, but it is there for a reason.

And yes.. Sometimes it drives me nuts too. And then I do the assembly and then... And Then... It all makes sense.


To the OP.. WHY??? are you redrawing everything. That's like buying oreo's, then bringing them home, opening the package, not eating a single one, and then putting them in another bag and vacuum sealing them.

You have a copy machine, they are cheap, and so am I, and I have 2 of 'em. Copy the customer print and mark it all up.

Higlighters, Sharpies, Colored pens. Blowing up specific areas if you have to, and occasionally, just a quick sketch with dimensions to check.. I do that a lot.

Re-drawing and re-dimensioning the entire drawing just seems like a huge waste of time, and one more step you can screw up.

I believe in the KISS principal.

I'm not redrawing a thing, the person just upstream from me is. He's taking the customer supplied print and re-tolerancing only certain features, and in selected instances based on his judgement and experience may articulate features and characteristics that might be missing, mis-stated, or unclear on the customer print.
 
Coloring every dimension won't fix the 9 written as a 5 error as there are multiple numerals written together and their eyes take them in as a whole.

When your people check your revised blueprint against the customers have them cross check and color each "numeral" in each dimension against its counter part.

This is a teeth-grinder to consider. But it's actually a straight forward technique that fits right in with what I established in the process already:

I have the customer print. I have our reprint. I look at each DIM and tolerance on our print and match it to what I see on the customer print. Using a green ink pen I green dot the DIM, then the tolerance checked on both Customer and Reprint.

What is slipping past occassionaly are the eyeball errors. The correct reprint dimension was supposed to be .4995, but on our print it was stated as .4955. What I "saw" in that moment was .4995. I'm horrified by the mistake. I take pride in getting it right.

So, your suggestion is mechanically spot on and takes little effort really. It's just an extension of what I'm already doing. The process stays the same.

It seems silly. It seems unnecessary. But it is probably the relevant check-pointing that addresses "eyeball error" scenarios and mitigates that Risk.

We do have the customer print attached to the job packet as well, for reference by machinists if need be, but the burden for this kind of thing isn't really on them. Their job is to take the job spec they've been provided and make the part to that specification.

Take care.
 
One good way to check numbers is to first do it left to right as is normally done and then do it right to left.

And say each digit out loud each time. You can use a small piece of cardboard to expose one digit at a time as you speak them.

Such simple stuff, and because of that a good suggestion.

I will fit this in with the strategy from the other fellow about dotting every numeral, not just the whole number of the DIM checked.

Thanks.
 
on the rare instances that I would draw or re-draw a print for a job I would have the customer look it over and approve of it.

Anything that gets revised will be noted on the print with a revision date and initialed by the person making the revisions.

Always get the customer to sign off on anything that gets changed.
 
What is slipping past occassionaly are the eyeball errors. The correct reprint dimension was supposed to be .4995, but on our print it was stated as .4955. What I "saw" in that moment was .4995.

I ran an entire job like this once. I caught it before it shipped and had to remake them.
It wasn't a print error, it was an eyeball error. And I saw the same error every time I checked a part.
 
Whoever came up with dimensioning shit like that is a moron because it lends itself to scrapping. If you hit the number called out on a dimension and yet the part is scrap, that is a bad dimension by whoever drew it.


You're joking, right? If you machine blindly to a number without considering your tolerance, the dimension isn't bad... But the part you made is.
 
It's probably the ISO system of fits with the limits written out instead of using F or G.
I hated prints like that.
 
Send drawing back with red circles round the mistakes, (yes aspergic and autistic high end are ideal, hard to find one with enough to be a nightmare not enough to be a bloody pain, I know)
If you don’t treat a drawing like goods inward the goods inward will never improve, don’t tolerate sloppy drawings, I have seen things made out of spec that can’t be reworked and cost hundreds,..of thousands
Mark
 








 
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