waterjet vs. cnc plasma for blanks...

nine9jack9

nine9jack9

Active Member
Gentlemen,
Anybody who can weigh in on their experience with regard to having blanks cut out on waterjet vs cnc plasma. I know waterjet will have cleaner edge finish and no HAZ, but I am also looking at things like cost, time to market, turnaround time, etc. Will HAZ (heat affected zone) be an factor in heat treating, grinding, etc.. Will I have to take into account HAZ when designing blanks on CAD files to take into account loss from HAZ? As always thank you for your time.
 
Will HAZ (heat affected zone) be an factor in heat treating, grinding, etc.. Will I have to take into account HAZ when designing blanks on CAD files to take into account loss from HAZ? As always thank you for your time.
Click to expand...

Yes, HAZ will be a factor in just about everything. Considering the fact that you're likely going to have to remove up to 3/32" around the entire profile (how much you need to remove is going to depend on the individual plasma machine used for the cut, and how good the operator is at programming the feed/speed/amps of the plasma.)

After having a couple of runs of blades/parts plasma cut (by two different outfits), I found that the money/time you think you can save via plasma/laser cutting is eaten up in all the belts and time it requires to eliminate the HAZ. If you're having holes pierced or cut with a plasma/laser, you might as well plan on buying all carbide bits to clean out the holes (and be ready to scrape them afterward). If any of the holes are planned for threading....forget it. While taking the time and effort to fully anneal all the parts/blanks works SOMETIMES, it never worked for me with the higher alloy steels. I learned the hard way..... ended up trashing 40 blanks that simply could not be finished due to my choice to use plasma/laser cutting.

Although waterjetting is generally more expensive compared to plasma/laser cutting, its like comparing apple to oranges...... For what we do, with knife steels, waterjet is by far the most efficient and cost effective method to utilize.
 
I've had an OK experience with laser cut blanks, which would probably be very similar to plasma. Ed's right, the holes, jimping, choils, anything you can't get to with the grinder are hardened and will cause you grief. If you know that going in, and just use the cuts for the profile or any lightening holes, I don't think its too bad.

I've had 1095 and O1 lasered, with holes, jimping, etc. I did add a little to the cutting edge on my drawings, and always grind off the HAZ on the edge after annealing, just to be safe. I put them in a SS heat treat foil pouch, 10 at a time, and run them through an annealing profile in an Evenheat oven. I haven't had any trouble at all with them so far, but that's just 2 steels. They may not all be so easy.

My motivation for trying laser was the cost. It was less than half the cost of waterjet. If you have a programmable oven, annealing is a breeze, so I figure I save about $5-$7 per blank overall. You're not alone with your question, I too have been eyeballing a plasma table for quite some time.
 
Plasma cutters are going to have a much bigger HAZ than laser and a rougher cut for sure.

For knifemakers, I think waterjet is the way to go. YMMV
 
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