Tuesday, November 15, 2011

pushing the limits of perfection

I received an email from a younger aged welder ( like myself ) with a bunch of questions. He was asking about different levels of measurement tolerances on welded parts I work on and tips about fixturing projects.

 Its really not a very specific question that I could give an answer to because every project I do is so very different and working with such a huge range of materials causes it to be always changing, especially being a prototype fabricator because its more sometimes about the look and relatively close tolerances for testing with great efforts to keep the cost of time and money down.

A good example is the Top Speed bike I am building. The tubes on that bike are first rolled with a slight curve then some how with my tricky ways, machines, a bit of magic and wacky bending dies, I am able to put tight bends on the long curved tube. This kind of bending is very complex in a lot of ways both in measuring and in manufacturing.
The odds of hitting exact numbers that Solidworks is giving me on the blueprint is next to impossible, I am close but never exact, it then become more visual and getting the look and flow of the frame then getting the exact numbers ( I would have a pile of bad chromoly tubes touching the moon if I tried to get it perfect like the computer model )

Love my Starrett stuff - worth every penny!! 

But when it comes to other projects for clients of the aerospace, medical, and science world, the level of expectations are very high so I then turn the attention to the numbers and getting it near or exactly what the customer expects.

Thats my job, and I think I do a good job at it !

Some projects come in that almost make me cry looking at the blue prints, because they expect near perfect things ( most of the time it seems these are not important things needing perfection and sometime are just errors on blueprints )
Learning from the old dudes over the years has stoked me out and stressed me out ( more on the stressed ) because there is those days where you build for days, weeks and months on a project only to find out things moved while welding, machining or handling and now you gotta fix them.

Some of the ideas we come up with to fix them scare or surprise me, thats when the years of experience come in...
Thats will be a great blog post of another day...

On a normal day to day I find myself holding very tight tolerances of measurements mostly because I make a lot of laboratory stuff where mishaps can throw everything off.  Some times the worst looking weld seems to be the straightest and strongest and other days when you don't drink 15 cups of coffee and 2 cans of Mt. Dew at 5 AM before welding, things look great and are some times straight too.

Either way the lesson is " Metal loves to move " ( people in to having fun in large groups while drinking a lot of beer (  if you read that without the punctuation, it covered 2 lessons in one))

These Titanium Elbows have very tight measurements in all ways so the fixturing is design  to be very restrictive to hold them in to the shape while welding and cooling. That leads to another problem of being able to get the torch in there to weld the parts and preform good quality welds.
 If you seen the fixture that I use to weld these, you would ask how do you even weld it all in there, there is no room for the torch ? I was kinda happy with the welds for how restrictive the fixture was to welding, no show winners but defiantly not leakers and thats what matters to the customer.  The tolerance is .008 +/-

I should have put a penny next to these Titanium parts so you know how small they are!
The Ti tube going in to and the bottom is a bit smaller then a wood pencil.

 the part on the left is boarder line being to short 
the part on the right is board line being to long
They both pass but on the limits
 ( side by side makes it easier to compare for the photo)

The measurement tolerance on these Titanium parts is .003" +/- or about 0.08 mm +/-
For you kids out there - thats the thickness of a piece of paper
 Titanium tubes with 2 - 360 deg. welds holding parts to the blueprint specs while being leak-free
I love these... I do thousands of them in all different sizes and shapes
Skill testers and good time to listen to books on tape!

Well that didn't answer any questions so now that I am done writing I see its kinda a waste of a post.
But its getting posted anyways regardless.

Espresso Machine build is coming soon!!! 
Get ready

1 comment:

  1. Please don't hesitate to get in depth like this more often. I think you may find most of the folks who read your site are as interested in fabrication as you, but not as skilled. Posts such as this are very informative, please keep it up.