usually the risk to do severe machine damage is too great even if the outside programming were free or the outside programmer gave money for the privilege of creating free programs.
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even if you knew exact cnc model you obviously would also need to be aware of every parameter setting as a cnc can act quite different with different parameters.
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usually programmer starts with being a cnc operator thus is very aware of the cnc and the parts typically made and the companies typical standards and expectations after a decade of experience
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or outside programer puts up a $1,000,000 (or more) insurance bond and when a machine crash happens he gives up to bond for the cost of crash
Why are you so always "off the wall"??
First, I get you run
big machines, that probably make big crashes and costs lots of monies....
Second, I don't think a whole lot of us here (from my reading) are running those big machines, so your experiences probably only apply to maybe 10% of us. Don't misunderstand me, if I ever find myself doing your type of work (30ton castings not level with hardspots and 40" long tools), I will probably ask your advice if I run into a problem.
Third, bad programming or not, I would say the whole not crashing thing is (mostlly) on the setup guy. If he sees something odd/funny
HIT FEED HOLD! If something looks off, or 'weird'
HIT FEED HOLD! If you don't understand what is happening (IE a too small drill for a tap)
HIT FEED HOLD!
Even as a noob programmer back in the day, I am pretty sure most of mistakes could/would have been caught by a good setup guy. Not to say I don't make mistakes today.
But they are few and far between. AND most of them I could point back to "well if you saw this xxxx why did you continue running the program and not come get me?"