Is there really a practical difference between laser and waterjet cutting?

[Nsled]

I haven't really tried both to an extent that would let me determine either way, but in a practical sense is there a difference between waterjet and laser cut blanks?

I understand that the laser cut parts will have a heat effected zone, but does this notably effect the processing time and consumable costs? enough to outweigh the added cost of waterjet?

 

[JoeBusic]

Laser is cheaper. HAZ on a hardened peace is small but should be considered. HAZ on a unhardened peace is irrelevant.
On both machines there are differences in the cut based on power and speed. A lot of power and fast speed is considered a severance cut. It is wise to add size for it and grind the edges of. 1/2mm to 1mm is enough. Other cuts are related to wanted finish. If one wants a clean finish, sanding is necessary anyways so faster is better as cheaper. Slower can get a nice finish but not smooth. And it costs a lot as machine time is related to price. Quicky grinding fixes it all.
Water is better for composites. Other than that, price determines the choice.
I tried both and decided to go for laser.

 

[ea42]

The only area I've found laser cuts to be an issue is the tang holes. You want them undersize to be opened or reamed later, and the hardening effect on those hole edges seriously beats the hell out of bits and reamers. You don't find that issue at all with waterjet.

Eric

 

[A.McPherson]

Another option would be cnc plasma cut. Dunno if you've considered that or not.

 

[JoeBusic]

The only area I've found laser cuts to be an issue is the tang holes. You want them undersize to be opened or reamed later, and the hardening effect on those hole edges seriously beats the hell out of bits and reamers. You don't find that issue at all with waterjet.

Eric

Forgot about those. I skeletonize the handle and make handle holes in plastic inserts to avoid any drilling in steel.

 

[REK Knives]

Also, this hasn't been mentioned yet but almost all waterjets will cut and leave a taper... That means any jimping will be slanted after you square it up on your grinder

 

[Blade Lab]

I'm not a knife maker, but I know that Brian from Transparent knives switched from waterjet to wire EDM because he found the latter to be much more accurate.

 

[C_Claycomb]

I'm not a knife maker, but I know that Brian from Transparent knives switched from waterjet to wire EDM because he found the latter to be much more accurate.

I have regularly drawn work to be wire EDM cut and require surface profile tolerance of 0.05mm over 4” plus depth of cut. Seems kind of overkill on a fixed blade, but makes very good sense for folders, particularly reblading as Brian does. It is a slower and more expensive process than the others mentioned.

 

[JoeBusic]

I have regularly drawn work to be wire EDM cut and require surface profile tolerance of 0.05mm over 4” plus depth of cut. Seems kind of overkill on a fixed blade, but makes very good sense for folders, particularly reblading as Brian does. It is a slower and more expensive process than the others mentioned.

Price goes down significantly with stacking. On a bigger machine 50 can be cut at once.

 

[Alpha Knife Supply]

Also, this hasn't been mentioned yet but almost all waterjets will cut and leave a taper.

If you choose to have parts cut with by waterjet, ask the shop if their waterjet has a dynamic head. The dynamic head compensates for the taper so the parts have straight edges.

Chuck

 

[C_Claycomb]

Price goes down significantly with stacking. On a bigger machine 50 can be cut at once.

Sorry, I see now I wasn’t clear that I was assuming that stacking was a given. Cutting one at a time would be nuts.

What was your per blade price stacking like that? I am wondering anbout optimal number and thickness where one gets best price per, beyond which the additional time needed for prep and the greater cut depth starts to cost more than the benefit of more blades.

How were the individual pieces of steel prepared before stacking? Last time I looked at this for something stacked that wasn’t 0.3mm iron, they wanted layers to be ground flat for good electrical contact.

 

[JoeBusic]

Sorry, I see now I wasn’t clear that I was assuming that stacking was a given. Cutting one at a time would be nuts.

What was your per blade price stacking like that? I am wondering anbout optimal number and thickness where one gets best price per, beyond which the additional time needed for prep and the greater cut depth starts to cost more than the benefit of more blades.

How were the individual pieces of steel prepared before stacking? Last time I looked at this for something stacked that wasn’t 0.3mm iron, the layers needed to be ground flat for good electrical contact.

When I was investigating options for CNC, EDM was brought to attention. For fixed blades it was always very expensive but for folders they said it was competitive and that EDM would give more precision. We were talking about 3mm stock. They didn't mention preparation, but all stock would be bolted.

 

[Mike Read]

Laser - only tried it once and binned everything they did. Probably fine for fixed blades but as has already been said - the HAZ is not good if you need to ream pivot holes etc for a folder. I do think the company I used were unfamiliar with air hardening steel and didn't know the best settings for their machine, so maybe it is not always as bad as my experience.

Water Jet - No HAZ but you do get a bevelled edge. In theory accuracy is good but where you have to grind off the bevelled edge, the accuracy is only as good as your grinding. If you have a complex shape or a lot of holes it saves a lot of time marking out and reduces waste from errors. If you cut your holes the right size you can remove the bevel and get your correct hole size in one hit with a reamer.

EDM Overkill for fixed blades but the dogs danglies for folder parts. Very expensive - stacking does make it cheaper but not as much as you might think as it takes much longer to cut a stack. I have had it stacked 10 high - 4mm stock with a mill finish, it didn't need to be ground but was bolted through I believe.

I worked it out once for a batch of parts I needed, getting them water jetted was cheaper than just the cost of the saw blades, belts and drills needed to do the job by hand. So you save the time to mark out, cut up, drill and grind out your parts. Because the parts can be nested so close you need significantly less raw material also fewer errors are made and there is far less dust flying around your workshop - so healthier too.