Obviously a tongue and cheek post on my part. Some of you sure do hate MC. Please don’t cancel me.
Any company can be guilty of poor quality control from time to time. The fit and finish of my MC fenders is top notch.
Ya had one little job, WTF?
- Thread starter mrblaine
- Start date
Obviously a tongue and cheek post on my part. Some of you sure do hate MC. Please don’t cancel me.
Any company can be guilty of poor quality control from time to time. The fit and finish of my MC fenders is top notch.
I always assumed the aftermarket was manufacturing off of SEMA CAD files now.
Are they really just tearing apart a Jeep and going after it with a tape measure and a carpenter's square?
That has no bearing on whether they actually give a fuck or not, but I was just curious about industry standard design practices, I guess.
@J.Pierce - thanks for mentioning that database. I wasn't aware of it. It looks like for $500 a year you get access to a database of soild models for many, many vehicles. Very cool:
https://www.semagarage.com/techtransfer/index
https://www.semagarage.com/techtransfer/index
OP
I'd never assume that. Not sure that most even know those files exist.
OP
Forgot to mention that our casting engineer modeled our steering knuckles for the brake kits off of the SEMA CAD files. He didn't know enough about the application to understand that whoever uploaded them got lazy and just mirrored one part to produce the other side. That works just fine if the OEM makes a left and right ABS sensor but they don't, they use the same one for both sides and just flip it over so the mounting screw is opposite. We caught it on the pair of samples delivered for fitment and dimension checking and changed it in our CAD files.
It is always some little detail.
Isn't it, though? The younger engineers we hire get sick of me saying, "The devil's in the details!" These days, laziness prevails in our population, and most people naturally quit at about 90% done (and I'm being generous at 90%)...
OP
With a single exception, no one I have ever designed parts for has appreciated my attention to detail. In fact it irritated most of them to the point of just being crappy with me about it. All they saw was the upfront cost and time not realizing that it would pay huge dividends on the back end with fewer customer complaints, higher durability, and almost no fitment issues.
Also why I had to do the knuckles myself. None of them would have paid for or approved the 3D printed samples I used to check accuracy before building 15,000 dollar molds.
What I see with the young engineers is that they were taught how to use the software but not how to draft/design. They are really good at producing a model, but when it comes time to produce the 2D dwgs which will be used by the fabricator/assembler/mechanic, they don't understand how or why, they especially don't understand GD&T, and they don't understand quality control and the expense or effects associated with tolerances. Whatever the computer spits out is what they provide. It seems that teaching design practices was replaced by teaching software.
Luckily a few of the kids are pretty impressive and they listen and learn. Others seem like they can't be bothered and they know better. But I think every generation has that same make up.
Us end users appreciate your attention to detail. When we bolt up or install a part that fits perfectly without modifications, like it should, we are very happy.
Beyond the design/engineer phase you then have to find a manufacturer who also has similar attention to detail.
It should be required that engineers have to spend time in the field and on the production floor before they get to design anything. Maybe it would help some of them to understand why some of us call them inappropriate things when we are dealing with their lack of attention to detail.
I see this all the time in the forklift industry. They put shit in some dumb ass places. Making a simple job very difficult. Sometimes they put things in great places, but I think those are accidents. Lol
OP
You should see me and my knuckle machinist going over the first production pieces of every batch. I have a fixture, it has a center rod and a disc that slide into pieces of tube in the end of the axle tube. We bolt a knuckle up on OEM ball joints in an OEM inner C and slide the rod in through the knuckle hole. The hole has to be .010- .015 larger at the bottom of the disc than at the top. That means it is .005-.008ish below centerline. I want the error to be in favor of wear and goobers who overtighten the lower ball joints and move the knuckle higher than it should be.
When we started, he was convinced I was loony for that spec but he can nail it every time now. He explained over and over that machining tapers that close to an exact height is difficult and a half a thou moves the knuckle up and down a fair bit. Yeah, what's your point? We know all that and we know that's why tapers suck.
Of course, sending back 50 sets of out of spec parts convinced everyone that I was serious and now I get exactly what I want.
B00mb00m
The Church of Cutting Brakes of Atlas-Front Digs
Supporting Member
Ride of the Month Winner
The whole thing got worse when they started allowing model authority for building and partially dimensioned drawing with a generic tolerance for everywhere else. You don't design a part until you apply tolerances on every single aspect. People think if you make a tolerance it has to be something special. No, it can be a large tolerance but you have to decide as the designer don't just shove that shit on the guy running the mill he doesn't know the how's and why of the part. If you're not using math to create tolerances than you're just playing with adult crayons.
Oh man... If I had a dollar for every part that doesn't fit because some dummy doesn't understand tolerance and Max material conditions, is be a very rich man.
Just because you know it needs to be "close" doesn't mean you should just apply +/- 0.005 to a dimension...
Just because you know it needs to be "close" doesn't mean you should just apply +/- 0.005 to a dimension...
OP
The other side of that is if I had the same for every time I spec'd out +/- .125 and they held .005, I'd not be far behind you.
Here, cut these tie rods to length 35.25 and thread them. What's the tolerance? Give or take an eighth. Oh, we don't do that. We'll get them within .005. I really don't need that, I have 2" of adjustment. Sorry, that's the only way we do it.
Paul Land
TJ Enthusiast