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The official term is yard hold. This is nightmare for any engineer who’s part is responsible for yard hold. The vehicles are made, but not allowed to be shipped

The official term is yard hold. This is nightmare for any engineer who’s part is responsible for yard hold. The vehicles are made, but not allowed to be shipped to a dealership. And everyone’s breathing down your neck unless the issue is fixed and they are allowed to leave. Issues can be anything from simple part squeaking to major design flaw. Each vehicle is test driven over a course before the manufacturing teams give it a ‘ship it’ tag. Door fit is a major issue for anyone and everyone. You simply cannot engineer doors to fit right, the assembly line guys always have to pull it, twist it and ‘align’ it. Tolerances exist, but the tighter you go the more parts you’ll reject, the more the cost of that part will be i.e. cost of your car will go up. Everything can be fixed and it’s never too late, the only problem is the cost of the fix. The later in production a fix is issued, the higher is the cost.

beamatronic 6y ago
How does Toyota do it? Their doors seem to fit.
- klodolph 6y ago
  There are a lot of differences in the way Toyota manufactures cars compared to, say, typical US manufacturers and the differences are extensively studied in the literature. These techniques have been adapted to other fields, even software development. If you ever heard the term “kanban board”, well, that system is based on Toyota’s manufacturing system. One of the principles of Toyota’s process is that they will stop the assembly line to fix defects. This sounds simple, but other manufacturers will keep the assembly line moving, putting pressure on workers to complete their steps faster. https://en.wikipedia.org/wiki/Toyota_Production_System https://en.wikipedia.org/wiki/Toyota_Production_System https://en.wikipedia.org/wiki/The_Toyota_Way https://en.wikipedia.org/wiki/The_Toyota_Way One of the classic case studies is the Fremont Assembly plant in Fremont, California, which was run by GM until 1982 when it closed due to production problems. It was considered an embarrassment to the US automotive industry. Cars from the Fremont plant would come off the assembly line with major defects and they couldn’t be shipped to dealers. When I say “major defects”, think “this car can’t be shipped to a dealer, because it is missing a door.” https://en.wikipedia.org/wiki/Fremont_Assembly https://en.wikipedia.org/wiki/Fremont_Assembly Toyota needed to manufacture vehicles in North America and created a joint venture with GM called NUMMI, which reopened the plant in 1984—manufacturing both GM and Toyota vehicles. The existing workforce was sent to Japan to learn Toyota’s manufacturing system. The defect rate dropped dramatically after Toyota’s involvement. GM attempted to take what they learned from Toyota and bring it to other factories in the US, but failed. https://en.wikipedia.org/wiki/NUMMI https://en.wikipedia.org/wiki/NUMMI For various reasons, the plant shut down in 2010. It is now a Tesla plant.
  - Erlich_Bachman 6y ago
    > For various reasons, the plant shut down in 2010. It is now a Tesla plant. It probably wasn't intended that way, but that's such a beautiful irony. Similar to the dark humor of writing of Catch 22 and other books. Describe all the technological and managerial achievements and progresses of the system that is supposedly so much better than the one mentioned before (Tesla), and how it documentedly better, and produces so many good results and tolerating so many struggles, only to find out that it still was replaced by none other than Tesla. I guess they bet on the things that mattered even more.
    - philwelch 6y ago
      Except for Toyota having since become the world’s leading manufacturer of automobiles, sure.
      - tempestn 6y ago
        Although Tesla did recently pass them to become the largest car company in the world by market cap.
        sneak 6y ago
        I don't think that market cap, an entirely fictional number (constructed by multiplying two non-fictional numbers), is a reasonable or sufficient measure of "largest $X company". TSLA is doing well, but that has little or nothing to do with Tesla the auto manufacturer, and it certainly doesn't dictate their "size".
      - beamatronic 6y ago
        Toyota/Lexus fan here. They make the worlds finest previous-generation automobiles. It kills me how close they get to the mark (ie new 2021 hybrid Sienna WITHOUT plug-in) and just don’t hit it.
        toomuchtodo 6y ago
- dawnerd 6y ago
  If you measure they will still have variances between doors, Toyota is just more strict with allowable tolerances.
abeppu 6y ago
> Door fit is a major issue for anyone and everyone. You simply cannot engineer doors to fit right, the assembly line guys always have to pull it, twist it and ‘align’ it. I know nothing about manufacturing for cars or anything else, but ... why can't doors be engineered to just fit? In terms of absolute tolerances, I'm guessing all the stuff in the engine or transmission for a typical car is far more stringent, right? Is there something specific to the manufacturing process for doors or frames that is less controlled or precise?
- throwaway201103 6y ago
  I would guess it is because doors are large pieces of stamped sheet metal, as are the other body parts they mount to. They span a fairly large opening. There's probably a certain amount of flex and variation compared to cast and CNC machined engine parts. Doors in a house always need to be shimmed during installation to get the frames square and latches working properly. A car door will have tighter tolerances, but similar issues. The point is these adjustments are (or should be) made in the factory, not with post-delivery reworking.
- jacquesm 6y ago
  Because of material inconsistencies that are hard to get rid of (sheet metal is rolled to thickness out of a non-uniform billet, and cools non-uniformly as well due to edge effects, so you get small hardness and thickness variations) the material will deform in unpredictable ways during stamping. This causes very small deformities but over the size of a whole door it adds up leading to door being off by up to a few mm even when using exactly the same tooling during manufacturing. Welding then further deforms the door, even when it happens robotically and in a jig. The chassis typically suffers from the same effects. When the chassis warps one way and the doors warp in the other you can end up with poor fit. So manufacturers will do what they can to control for this but it will always be an issue as long as the input material is as inconsistent as it is. Unlike software, the real world is messy, and while of course it is technically feasible to mill a whole door and a chassis out of a billet it wouldn't be economical. So we adjust during manufacturing to cover the variations.
  - 6y ago

beamatronic 6y ago

How does Toyota do it? Their doors seem to fit.

klodolph 6y ago
There are a lot of differences in the way Toyota manufactures cars compared to, say, typical US manufacturers and the differences are extensively studied in the literature. These techniques have been adapted to other fields, even software development. If you ever heard the term “kanban board”, well, that system is based on Toyota’s manufacturing system. One of the principles of Toyota’s process is that they will stop the assembly line to fix defects. This sounds simple, but other manufacturers will keep the assembly line moving, putting pressure on workers to complete their steps faster. https://en.wikipedia.org/wiki/Toyota_Production_System https://en.wikipedia.org/wiki/Toyota_Production_System https://en.wikipedia.org/wiki/The_Toyota_Way https://en.wikipedia.org/wiki/The_Toyota_Way One of the classic case studies is the Fremont Assembly plant in Fremont, California, which was run by GM until 1982 when it closed due to production problems. It was considered an embarrassment to the US automotive industry. Cars from the Fremont plant would come off the assembly line with major defects and they couldn’t be shipped to dealers. When I say “major defects”, think “this car can’t be shipped to a dealer, because it is missing a door.” https://en.wikipedia.org/wiki/Fremont_Assembly https://en.wikipedia.org/wiki/Fremont_Assembly Toyota needed to manufacture vehicles in North America and created a joint venture with GM called NUMMI, which reopened the plant in 1984—manufacturing both GM and Toyota vehicles. The existing workforce was sent to Japan to learn Toyota’s manufacturing system. The defect rate dropped dramatically after Toyota’s involvement. GM attempted to take what they learned from Toyota and bring it to other factories in the US, but failed. https://en.wikipedia.org/wiki/NUMMI https://en.wikipedia.org/wiki/NUMMI For various reasons, the plant shut down in 2010. It is now a Tesla plant.
- Erlich_Bachman 6y ago
  > For various reasons, the plant shut down in 2010. It is now a Tesla plant. It probably wasn't intended that way, but that's such a beautiful irony. Similar to the dark humor of writing of Catch 22 and other books. Describe all the technological and managerial achievements and progresses of the system that is supposedly so much better than the one mentioned before (Tesla), and how it documentedly better, and produces so many good results and tolerating so many struggles, only to find out that it still was replaced by none other than Tesla. I guess they bet on the things that mattered even more.
  - philwelch 6y ago
    Except for Toyota having since become the world’s leading manufacturer of automobiles, sure.
    - tempestn 6y ago
      Although Tesla did recently pass them to become the largest car company in the world by market cap.
      - sneak 6y ago
        I don't think that market cap, an entirely fictional number (constructed by multiplying two non-fictional numbers), is a reasonable or sufficient measure of "largest $X company". TSLA is doing well, but that has little or nothing to do with Tesla the auto manufacturer, and it certainly doesn't dictate their "size".
    - beamatronic 6y ago
      Toyota/Lexus fan here. They make the worlds finest previous-generation automobiles. It kills me how close they get to the mark (ie new 2021 hybrid Sienna WITHOUT plug-in) and just don’t hit it.
      - toomuchtodo 6y ago
dawnerd 6y ago
If you measure they will still have variances between doors, Toyota is just more strict with allowable tolerances.

abeppu 6y ago

> Door fit is a major issue for anyone and everyone. You simply cannot engineer doors to fit right, the assembly line guys always have to pull it, twist it and ‘align’ it. I know nothing about manufacturing for cars or anything else, but ... why can't doors be engineered to just fit? In terms of absolute tolerances, I'm guessing all the stuff in the engine or transmission for a typical car is far more stringent, right? Is there something specific to the manufacturing process for doors or frames that is less controlled or precise?

throwaway201103 6y ago
I would guess it is because doors are large pieces of stamped sheet metal, as are the other body parts they mount to. They span a fairly large opening. There's probably a certain amount of flex and variation compared to cast and CNC machined engine parts. Doors in a house always need to be shimmed during installation to get the frames square and latches working properly. A car door will have tighter tolerances, but similar issues. The point is these adjustments are (or should be) made in the factory, not with post-delivery reworking.
jacquesm 6y ago
Because of material inconsistencies that are hard to get rid of (sheet metal is rolled to thickness out of a non-uniform billet, and cools non-uniformly as well due to edge effects, so you get small hardness and thickness variations) the material will deform in unpredictable ways during stamping. This causes very small deformities but over the size of a whole door it adds up leading to door being off by up to a few mm even when using exactly the same tooling during manufacturing. Welding then further deforms the door, even when it happens robotically and in a jig. The chassis typically suffers from the same effects. When the chassis warps one way and the doors warp in the other you can end up with poor fit. So manufacturers will do what they can to control for this but it will always be an issue as long as the input material is as inconsistent as it is. Unlike software, the real world is messy, and while of course it is technically feasible to mill a whole door and a chassis out of a billet it wouldn't be economical. So we adjust during manufacturing to cover the variations.
- 6y ago