this post was submitted on 26 Aug 2023
852 points (94.1% liked)

Technology

59593 readers
3063 users here now

This is a most excellent place for technology news and articles.


Our Rules


  1. Follow the lemmy.world rules.
  2. Only tech related content.
  3. Be excellent to each another!
  4. Mod approved content bots can post up to 10 articles per day.
  5. Threads asking for personal tech support may be deleted.
  6. Politics threads may be removed.
  7. No memes allowed as posts, OK to post as comments.
  8. Only approved bots from the list below, to ask if your bot can be added please contact us.
  9. Check for duplicates before posting, duplicates may be removed

Approved Bots


founded 1 year ago
MODERATORS
 

Tesla is facing issues with the bare metal construction of the Cybertruck, which Elon Musk warned was as tricky to do as making Lego bricks

you are viewing a single comment's thread
view the rest of the comments
[–] AlDente@sh.itjust.works 1 points 1 year ago (1 children)

I think there is a very important distinction between accuracy and tolerance in engineering. +/- .010" is not a dimension, but a tolerance that can be applied to a dimension. However if your example was changed to a .010" dimension, I would agree with you as I stated in my last comment. There is no need to give any further accuracy to that dimension if you are just adding zeros to the end (unless you are using block tolerances that rely on a specific number of digits to correspond with a standard tolerance). Unfortunately, not everything is designed using the same units and you will inevitably end up with a part designed in mm that uses a bolt-on component using a hole span in inches (for example, a nice round 1-in span). If you want a +/-1 mm tolerance on that part, you wouldn't want to round every dimension to the nearest mm because you may end up with a tolerance of 24-26 mm when you really wanted 24.4 to 26.4 mm. I like to provide true dimensional accuracy (to microns or .0001" if I'm not just adding zeros) and then apply a suitable tolerance independently, using GD&T.

Regarding paperless manufacturing, I agree that many components are made straight from the models these days and imported directly into a CNC machine. However, there should always be a drawing or a digital equivalent a drawing. This is the contract that specifies acceptable tolerances to the manufacturer, and it will be used during QA inspection to determine if an acceptable part has been delivered.

[–] Hazdaz@lemmy.world 0 points 1 year ago (1 children)

I think there is an important distinction between accuracy and precision in engineering. I'm having flashbacks of sitting in class when the professor was going over this stuff. I honestly always found it some of the most boring topics in the curriculum.

[–] eestileib@sh.itjust.works 2 points 1 year ago* (last edited 1 year ago)

One of my physics profs had a story about this. He needed two resistors to be very similar in performance for a circuit he was making, so he asked for a couple of the super-high-quality ones.

His advisor said "fuck that, get the 1% bin, they'll be bimodal at 1% above and below rating, sort em and find two that match to the degree you need"

That's kind of analogous; do you need to try to hit a particular value (accuracy) or do you need things in a consistent relation to one another (precision)?