Mis Programmed CNC Laser Cutting Machine

Discussion in 'Embedded Systems and Microcontrollers' started by Glenn Holland, Jul 31, 2015.

  1. Glenn Holland

    Thread Starter Member

    Dec 26, 2014
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    110
    This is a prime example of the phrase "Computers don't make mistakes, people do".

    I ordered a batch of custom made parts from a shop that uses a CNC laser/plasma machine to cut steel and other metals.

    With laser/plasma cutting, there has to be a tolerance for the "burn out" which is a small gap (about 1/16" to 1/8") between the raw material and the actual dimensions of the finished part. Very Important: The burn out tolerance is determined by whether the critical dimension is on the inside or the outside of the part and that detail must be properly entered into the CNC guidance instructions.

    For example, is the machine cutting a circular hole in a finished plate (and the circular piece is scrap) or is the finished part itself circular and the plate will be scrap. This makes a Hell of difference in setting the burn out tolerance!!!

    Cutting to the chase, I received the finished parts and there is a constant 1/8" error throughout every part. After analysis, it looks like the operator reversed the burn out tolerance for both the inside and outside dimensions. As a result, the outside dimension of the part is smaller than specified, but the holes are oversized.

    The bottom line: Whether you're running a CNC or manual shop, remember the old saying "Measure twice, cut once".
     
  2. nerdegutta

    Moderator

    Dec 15, 2009
    2,515
    785
    This is so true. I've been working in building and construction. I've seen a lot of carpenters measuring and cutting ply-wood plates once and twice, and started to cut another plate...

    So, are the pieces crap, or can you use them? What are the parts for?
     
  3. Glenn Holland

    Thread Starter Member

    Dec 26, 2014
    353
    110
    I labeled the defects and took a photo of the defective parts.

    I'm going to send it to the manufacturer and hopefully, they will make new ones free of charge.

    The parts are actually for a shaft support for an old fashioned seismograph recorder like the one shown in my avatar. The shaft seen on the right side is resting on one of these supports. Although these old style recorders are totally obsolete for scientific use, I build them for public exhibits about earthquakes.
     
  4. nerdegutta

    Moderator

    Dec 15, 2009
    2,515
    785
    Let's hope they understand, and take it on the house. - They should.
    Good luck.
     
  5. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    Guess they aren't ISO9000... First Article Inspection would have found that before it went out the door..
     
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