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In lugnet.lego, Jake McKee wrote:
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I’ve had a number of people ask me about a perceived quality issue lately: If
you take a number of plates and create two or more large stacks, they tend to
be differing heights. For example, Ben has posted some photos here:
http://www.brickshelf.com/cgi-bin/gallery.cgi?i=793687
I mentioned that this is a “perceived” quality issue because on the surface
it seems to be an obvious quality issue, but in reality, there is nothing out
of place. I have checked with our Quality Assurance department for some
details and they have passed along some info.
When you build, the height difference will often be aligned as the elements
typically will vary in element height from one end to another. In order to
get the maximum deviation all the plates have to turn the same way and they
have to be from the same tool. This is not likely.
The height measure on our plates is 3.2 +/-0, 1 mm. With a height difference
up to 0.2 mm per plate it will be approx. 4.0 mm. If you build 20 plates
above each other. On the photo the difference is under 2.0 mm.
Consider that in the official LEGO models, the LEGO designers never use more
than three plates in a stack. As a model is built, the elements will equal
out and create a solid model regardless of these very very minor tolerance
changes (+/- 0.1 mm), creating a very stable model.
The tolerances used today are the same as years past.
Hope this helps clear this up. Please know (and remember) that LEGO has
always been, and will always be about quality. We have a great team in the
Quality group, manufacturing, and Design that works hard to ensure the best
parts are being created.
Sometimes there are mistakes or problems, but as you all know, those times
are rare. And unwelcomed... thus the desire by the entire company to ensure
they never happen.
Jake
---
Jake McKee
Community Liaison
LEGO Community Development
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For storage I stack my 2x3 plates with 3 studs along one edge overlapping.
There is a 3mm difference in height between two stacks of 38 2x3 plates. This
is within the tolerance you quoted of 3.2mm +/-0.1mm, since 3mm/38 = 0.0789mm
per plate. I have not deliberately sought to match thin ones together to create
these stacks - the parts are new 2x3 sand green plates from Yodas (7194) and
Statues of Liberty (3450), stacked as I sorted the parts from the new sets.
However, this is a 2.5% tolerance on the height of the plate. Your maximum
quoted tolerance of one plate being 3.1mm high and another 3.3mm high would be
6.25% of the height, such that over 16 plates height there could be a difference
of one plate.
As an experienced builder, limiting myself to a maximum of 3 plates on top of
one another would be a serious restriction. If I am building a train that has
grilles in the body sides, I use more plates to build around the grilles and
attach them to other things in order to keep the body side as strong as
possible. In some cases the full height of the body is made from plates, being
about 20 plates high. The plate thickness would not bother me as long as it
were consistent. The problem comes if there is a gap anywhere. Yoda’s head is
consructed almost entirely of plates, so even if the Lego designers limit
themselves to 3 plates in a stack, they still build much higher things out of
plates.
I have noticed when building walls out of 2x4s and 2x8s that the bricks don’t
fit together as well as older ones that have been used the same amount.
Also some new 2x8 sand green plates that I bought at LLW the other day have
formed stacks that are not straight but slightly twisted. Since I won’t be
using them as a stack, the effect on the model might be negligible, but the
effect of the warped stack on my confidence in the quality of the product is
significant.
I believe that over the years the tolerance has been widened, with the aim of
reducing production cost. When I first heard what the tolerance was, I remember
thinking “that’s a very tight tolerance, far tighter than industry standards”.
As far as I can remember, the tolerance was a fraction of a thou, which is
0.025mm, I don’t remember whether it was half a thou (0.0125mm) or a tenth of a
thou (0.0025mm). The 0.1mm tolerance you have quoted is pretty much industry
standard for non-critical parts, but insufficient for Lego plates.
I once had a role in dealing with a quality issue on some power switch wafers
that were cracking. They were produced to a particular thickness tolerance.
The problem was that they weren’t quite flat. The manufacturers agreed to add a
surface flatness tolerance tighter than the thickness tolerance, and this cured
the problem.
I have three questions:
1. Would you personally buy two stacks of 16 plates at the extremes of the
tolerance of +/-0.1mm, if one stack was one plate higher than the other? Please
would you ask members of the quality department this question. It would be even
better if they could see the stacks.
2. We are expressing concern about a height difference of 2.5% where the quoted
tolerance is 6.25%. If customers are unhappy about 2.5%, do you really think
6.25% is an acceptable difference between the heights of two Lego pieces?
3. How much would it cost to bring the tolerance in to +/-0.01mm, which is a
common industry standard tolerance for fairly precise applications (well within
moldability tolerance but still nowhere near spacecraft spec)?
I’m glad to hear that quality is still important to the company, even after the
original motto of “det bedste er ikke for godt” (only the best is good enough)
was changed. I really want to see consistent quality, then I will go home
happy.
BTW thanks for your discussion at LLW - we certainly went home happy from there,
knowing that progress is being made.
Mark Bellis
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Message has 2 Replies:
 | | Re: Quality issue - update
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| (...) Hmm. In the realm of tangential anecdotal evidence, I bought the Mini-Robots (4097) set. I noticed that many of the 1x1 elements coming with the set, such as cylinders, 1x1 bricks with technic holes, headlight bricks, etc seemed to be having (...) (20 years ago, 4-Jul-04, to lugnet.lego, lugnet.color, lugnet.general)
| | | Re: Quality issue - update
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| (...) OK so I just went to my box of childhood LEGO (circa 1970-80) to check this out. Discounting the CA bricks which have known deterioration problems, I put together 4 stacks of 10 ABS bricks, 2 red and 2 white. I made sure I picked out the "best (...) (20 years ago, 4-Jul-04, to lugnet.lego, lugnet.color, lugnet.general, FTX)
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Message is in Reply To:
| | Quality issue - update
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| I've had a number of people ask me about a perceived quality issue lately: If you take a number of plates and create two or more large stacks, they tend to be differing heights. For example, Ben has posted some photos here: (URL) I mentioned that (...) (20 years ago, 30-Jun-04, to lugnet.lego, lugnet.color, lugnet.general, FTX) !
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