Still think manual layout is better than CNC for small boiler jobs

I been doing this for 12 years now and I still lay out my small pressure vessel heads by hand with a trammel and soapstone. Back in 2018 I worked at a shop in Houston that pushed everyone to use the CNC plasma for everything, even 12 inch diameter heads. I tried it for about 6 months and swore it was faster until I realized I spent more time programming and cleaning dross than I did just scribing and cutting by hand. For stuff under 24 inches I can lay out, cut, and fit a head in about 20 minutes flat with a hand torch. The CNC takes 10 minutes to program alone plus 5 to cut and another 5 to clean edges. My old foreman used to say "the computer dont replace your eyes" and I think he was right for certain sizes. Anyone else stick with hand methods for the small stuff or am I just being stubborn?

3 comments

3 Comments

mianelson7d ago

That line your foreman said about "the computer dont replace your eyes" really hits home. I read a study a few years back (maybe it was from a welding trade magazine, I don't remember exactly) that showed for small parts, the setup time for CNC actually makes it slower than manual methods up to a certain size threshold. Like you said, under 24 inches the math just doesn't work in favor of the machine. Program time, torch height adjustments, dross cleanup - it all adds up to where you're losing time, not gaining it. And there's something about laying out a head by hand that lets you catch fit-up issues before you cut (you know, like if the shell is slightly out of round), whereas on a CNC you just trust the computer and hope for the best. I've seen guys spend 15 minutes programming a perfect circle, cut it, and then have to grind an eighth inch off the edge because the vessel was welded a little wonky. Manual layout just gives you that flexibility to adjust on the fly, and for small jobs that's worth more than any time savings the CNC claims to offer.

shane_park927d ago

Is it really saving time if you gotta rework half the cuts? I've seen that exact thing with the vessel being out of round, wasted an afternoon on a part that should've taken 20 minutes. Manual layout just lets you roll with the punches, thats hard to beat for small stuff.

the_rowan7d ago

Exactly that. You can see the piece of steel in front of you and know if something is off before you ever strike an arc. With a machine you're just hoping the program matches reality.

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