Tolerances Explained in CNC Machining (Defining for production)
Summary
TLDRThis episode of 'Mastering Manufacturing' delves deeper into tolerance issues in CNC machining. It addresses common challenges like design for assembly, where parts may not fit due to nominal diameters being the same. It also discusses the impracticality of overly tight tolerances like ±0.02mm, which can be a nightmare for machinists and costly for customers. The video highlights the importance of focusing on critical dimensions rather than over-tolerancing, and the potential conflict between tight tolerances and surface finish requirements, suggesting masking as a solution.
Takeaways
- 🔧 The first issue discussed is design for assembly, emphasizing the importance of fitting parts together correctly.
- 📏 A common problem arises when male and female parts have the same nominal diameter, leading to potential fitting issues.
- 🔍 Engineers often face challenges when customers request very tight tolerances, such as plus-minus 0.02 millimeters, which can be difficult and costly to achieve.
- 💡 It's suggested to only tolerance critical dimensions that affect assembly or function, rather than applying tight tolerances to the entire part.
- 🛠️ The script highlights the potential conflict between surface finish requirements and tight tolerances, especially after processes like anodizing.
- 🎨 The example of anodizing type 3 finish shows how tolerances might be affected and advises considering masking off areas with tight tolerances to protect them.
- 🔄 The video script emphasizes the need to balance cosmetic requirements with assembly and tolerance needs.
- 📦 An example of an electronics casing needing to fit a PCB inside an aluminum case illustrates assembly requirements.
- 👥 The script addresses the challenges faced by both machinists and customers when very tight tolerances are specified.
- 📈 The video encourages viewers to subscribe for more content and invites feedback on topics of interest.
Q & A
What is the main topic discussed in the video?
-The main topic discussed in the video is the issues that engineers or designers may encounter when dealing with tolerances in manufacturing.
What was covered in the first episode of the series?
-In the first episode, they went over what tolerances are and what makes a tolerance in CNC machining.
What is one of the first issues mentioned in the industry regarding tolerances?
-One of the first issues mentioned is design for assembly, where parts may not fit together as intended due to tolerances.
Why might two parts with the same nominal diameter not fit together?
-Two parts with the same nominal diameter might not fit together if there is no margin for error in the tolerances, leading to both parts being at the maximum size and thus too large to assemble.
What is the significance of the tolerance example given with a diameter of 25 millimeters?
-The example with a 25-millimeter diameter illustrates that without a margin of error, parts are likely not to fit, emphasizing the importance of considering tolerances in design.
What assembly requirement issue is mentioned in the context of electronics casing?
-The issue mentioned is ensuring that an electronics casing can fit a PCB inside, which requires precise tolerances to be maintained.
Why is it challenging for manufacturers to meet an overall tolerance of plus or minus 0.02 millimeter?
-An overall tolerance of plus or minus 0.02 millimeter is very tight, making it difficult and potentially costly to maintain such precision across all features of a part.
What is the recommendation for tolerancing parts that are critical for assembly?
-The recommendation is to only tolerance the critical dimensions that are necessary for assembly or function, rather than over tolerancing the entire part.
What conflict might arise between surface finish requirements and tight tolerances?
-A conflict might arise because processes like anodizing can affect the tolerances of a part, even if it's assumed that tolerances remain the same before and after the process.
Why might masking off certain areas of a part be a good idea?
-Masking off areas where tight tolerances are required can prevent these tolerances from being impacted by surface finish operations, ensuring that they remain precise.
What does the video suggest doing if you want more information on the topic?
-The video suggests subscribing to the channel for notifications on new videos and providing feedback if you want to hear more on this or other topics discussed in previous videos.
Outlines
🔍 Understanding Tolerances in Manufacturing
This paragraph introduces the topic of the video, which is about tolerances in manufacturing. It mentions that the first episode covered the basics of tolerances in CNC machining, and this episode will delve deeper into issues that engineers and designers face with tolerances. The main issue discussed is 'design for assembly,' where parts may not fit together as intended despite being within standard tolerances. An example is given where a male and female feature have the same nominal diameter, leading to a fitting problem. The importance of considering assembly requirements and avoiding overly tight tolerances that could complicate manufacturing and increase costs is highlighted.
Mindmap
Keywords
💡Tolerances
💡Design for Assembly
💡Nominal Diameter
💡Standard Tolerance
💡Assembly Requirements
💡Surface Finish
💡Anodizing
💡Cosmetic Requirements
💡Masking
💡Machinists
💡Over-Tolerancing
Highlights
Introduction to the second episode of a mini series about tolerances in manufacturing.
Discussion on design for assembly issues and how they relate to tolerances.
Example of a customer wanting two parts to fit together with the same nominal diameter causing assembly problems.
Explanation of how standard tolerances can affect the fit of parts.
The importance of having a margin of error when designing parts to fit together.
Challenges faced by engineers and manufacturers when dealing with very tight tolerances.
The impact of tight tolerances on the cost and manufacturability of parts.
The need to prioritize tolerances based on assembly or functional requirements rather than over-tolerancing.
Example of a nano satellite panel and the importance of tolerancing critical distances.
The conflict between surface finish requirements and tight tolerance requirements.
The potential impact of anodizing on tolerances, especially for type 3 anodizing.
Suggestion to mask off areas with tight tolerances to prevent interference from surface finishing operations.
The importance of balancing cosmetic requirements with assembly and tolerance needs.
Advice on how to handle parts that have both surface finish and tight tolerance requirements.
Encouragement for viewers to subscribe to the channel for notifications on new videos.
Invitation for viewers to request more content on tolerances or other topics covered in previous videos.
Transcripts
hi everyone and welcome back to our
newest episode
of mastering manufacturing in our second
video of the mini series about
tolerances so in the first episode as we
mentioned earlier
we went over tolerances what makes a
tolerance in cnc machining
and in this video we will be going a bit
more in depth into the several
issues that engineers or designers may
encounter
when dealing with tolerances so one of
the first issues we
often encounter in our industry is
design for assembly
and basically i can put this as i want
this part to fit with this one and it's
not fitting or i would like it to fit
how should i tolerance it
so let's say we have a customer who
wants to design two parts that go
together the first part
must assemble with the second one male
feature with the female feature
and then the part is standard tolerance
2768 fine
and then unfortunately the male feature
has exactly the same nominal diameter as
the female feature
what's going to happen in most cases if
the two parts are at 25 millimeters
diameter for instance
they're just not going to fit most times
we can show you actually now on the
paper
that if you see that the first part has
the exact same diameter as the second
one
even with the margin of general
tolerance the two parts probably won't
fit unless you have some margin of error
in that case the diameter of part one
will be
smaller than the diameter of part two
and in that case
you will be sure that they fit the
second one that we sometimes see
is when people have let's say assembly
requirements let's say they make an
electronics casing and they just want to
make sure they will be able
to fit let's say the pcb ins inside of
the aluminum case that they just
manufactured
and sometimes what we see is just the
customer coming to us and say hey can we
just make
the overall part at a tolerance is plus
minus 0.02 millimeter
that is oftentimes an absolute nightmare
for engineers or manufacturers to deal
with
because when you have a part with
overall tolerances of 0.02 millimeter
which is
very tight then all the features on the
part
will have to be maintained and the fact
that the tolerances are so tight will
either
will make it a nightmare most likely for
the machinists who will have to make the
part
but also for the person paying for the
part so let's take again the example of
this nano satellite panel
if what actually matters to you in the
way this part will be assembled or the
way this part will function
if what actually matters to you is the
distance between this plane and that
plane
then you should tolerance that and that
only
over tolerancing and saying the whole
part should be made at plus minus 0.02
will actually not bring you anything
more than just tolerancing what you
actually
need to be at a tight tolerance the
third one that we often see is let's say
someone coming to us and saying oh okay
i would like this part to be cosmetic
but i also have assembly requirements
and i have those tight tolerances that
i'm sure will make my assembly work just
fine
um let's take this part and to show you
a little bit what an example
of conflict may be between a surface
finish requirement and a tolerance
requirement
let's say this part has been made with
an anodizing type 3 finish
and the customer needs a really tight
tolerance on the contour here in order
to be assembled this part with another
part and even though there's an
assumption generally in the industry
that the tolerances will be identical
before the anodizing and after the
anodizing in the case of especially type
3 anodizing
the tolerances may be impacted for very
tight tolerances
and that may be a problem let's see for
this feature if tolerances are really
important to you
more generally speaking if you have on
the same physical part
surface finish requirements and tight
tolerances requirements
it's probably better to think about
masking off the areas where you know you
will have tight tolerances
so that these tight tolerances are not
impacted in any way shape or form
by the surface finish operation and or
just a function
of the work done by the machinist so
that's it for this video i hope you
enjoy the content
subscribe to the channel and you will be
notified of every video that
comes out and of course let us know if
you would like to hear more on the topic
or any other topic that we already
talked about in the previous videos
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