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Lerps and Curves and Splines, oh my!


Aaron Eberhard
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I just ran across this absolutely BEAUTIFUL video explaining some of the math behind Bezier Curves.   For anyone who has ever created a spline, or a toolpath on a spline, this explains what's going on behind the scenes.  This is the sort of thing that a lot of us know fundamentally due to experience, but if you've ever wondered why the vector spacing on your surface toolpath isn't exactly like what you'd want, this may explain it.  If you've ever created guide curves to make lofted surfaces, here's how it's working, etc.  

Warning:  25ish minute video:

https://www.youtube.com/watch?v=aVwxzDHniEw

 

I thought it was cool, anyway :)

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Funny had a project a few years ago for a rocket engine. The Rocket Scientist gave us a spline to cut the feature from their CAD software that only 65 control points on the spline over a 42" long detail. We needed to hold .002" profile tolerance over the whole feature. When you programmed in CAM you were getting as much as .003" deviation and no one could understand why. I had to convert the spline in 1510 control points and then reprogrammed. We were able to hold .0001" profile output from the CAM. I had to sit down and explain this very principle to them. They didn't realize a machine tool really cuts in point segments and not spline segments. The less points you give the feature the courser the outcome. Once we tighten the point spacing we were able to machine it correctly. Then 35 year employee heard what I did and said oh yeah that is what they use to do back when we first started making these part was give them more control points.

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This is one of those video's that gives you the realization that there are many people out there in other industries that have a DEEEEP knowledge directly applicable to our profession and possibly have more creative and or efficient means of solving the day to day problems we run into, many of which problems most of us don't even know we have.... 

I am deeply frustrated with the leadership of our nation in the last 40-50 years and how they have classified machinists.  If you look into it, machinists are generalized as being the lowest IQ, even considered barely "functional" members of society.  While there may be grunt labor in the machinist labor force, I have found this to be far from true, I would consider most of these people to have been either under challenged during their education, or not mature enough when in school to realize the application or importance of a good foundation.  I feel lucky that I had people challenging me and gave me a healthy appetite for learning about what interested me, but at he same time, I wasn't mature enough to realize the importance of the foundational knowledge that I have been exposed to but can't recall as I wasn't invested to learn at the time.

This general classification our government has put on "machinists" has made it very difficult to attract talent that is willing and able to think at the level of the young woman who created this presentation.  I feel if there were more high level thinkers in our industry who were willing and able to encourage and nurture the "under challenged" folk, our industry in the country would evolve into something more sustainable.  I realize that there are some of us on this forum that possess both some of the hard and soft skills required to be those mentors, but we are few, and typically not at the same place of employment, only to collaborate on improving our collective trade on forums such as these.

Hopefully my ramblings are coherent, getting the jumbled mess that is my thoughts onto paper isn't even close to a linear process....

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11 hours ago, huskermcdoogle said:

I am deeply frustrated with the leadership of our nation in the last 40-50 years and how they have classified machinists.  If you look into it, machinists are generalized as being the lowest IQ, even considered barely "functional" members of society.  While there may be grunt labor in the machinist labor force, I have found this to be far from true, I would consider most of these people to have been either under challenged during their education, or not mature enough when in school to realize the application or importance of a good foundation.

Yeah, these people that look down on us... they are the people eating Tide Pods. They are the people that say "... just make iPhones in the USA. Problem solved." And last but not least, these are the people that say their food comes from the grocery store. ROFLMFAO!!!!

As if any of us care what those petulant fools think anyway. I almost pity them. Fortunately for many of us, by the time those fools realize how truly stupid they were we will have escaped this life and they will be captive to places like China because they don;t know how to make stuff that they can't 3D print.

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First, this was an excellent video, thanks for posting it Aaron!!!

As Freya rolled the credits, this link caught my eye:

https://pomax.github.io/bezierinfo/index.html

This particular site is like an extension of the mathematics, which underlie that video. There are a bunch of interactive applets, which allow you to "visually play" with the underlying math. Pretty cool.

 

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5 hours ago, GoetzInd said:

James, no need to be salty just because 3d printing is taking your job. 😜 Maybe you should focus your energy into developing a better tasting Tide Pod?

 

Mike 

 

New flavored Tide Pods are gonna make me rich. ;P

I'm never worried about technology taking my job because I'm either keeping up with it or moving ahead of it for the most part, but yeah, I'm salty AF and proud of it. <laughter>

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