Laser vs Waterjet vs EDM

[REK Knives]

I've used waterjet before and it was decent. But the downsides were accuracy, taper, and kurf (wasted material). I found a great local shop for laser cutting which I'm leaning towards, but read some stuff in another thread here where the head can harden the edges of stainless steel blades where it cuts. I like that it is much more accurate, 90° (no taper) and much less waste - and I can have some nice fine triangular jimping cut in. EDM is probably the premium option but it costs a lot.

So, can anyone school me on laser, or if that's not my best option? This is for a liner lock I'm making.

I was told laser cutting titanium (w/ nitrogen) will leave a burr on the opposite side, any experiences w/ this?

 

[Drew Riley]

My understanding is that HAZ can be minimized with slower speeds, and different types of setups, though on blade steels it shouldn't be much of an issue if you're heat treating afterwards anyway. Although, if you're reaming out holes that are spotted by the laser, you might want to use carbide tooling depending on the steel type. As for things like liners, I imagine you'll still want to cut things oversized to account for both the machining of your lock face, as well as final finishing, whether you do laser OR waterjet. EDM will get you closest to a final finish, though cost is usually the prohibitive factor.

 

[JTknives]

I would shop around if your not happy with your waterjet. Laser generally does not produce as nice of a cut and you have to grind that surface any way. With waterjet you don’t have haz. With a laser you will have a small bur on the backside. And the skin around the profile is hard as Glass. Not super thick but you can’t file it so it has to be ground away.

 

[P.Brewster]

I've made well over 10,000 laser and waterjet cut knives and I've used well over 10 different vendors. I've also worked extensively as a waterjet and laser programmer, estimator, and operator.

The issue is predicability, reliability, and severity of failure. A laser can produce wonderful results - but not reliably. A laser can turn a $1000 plate of knife steel into scrap in minutes. Every shop is eager to tell you about how great the cutting will be, but not so eager to get out their checkbook when they destroy your material. The HAZ is the least of your concerns. When the laser cutting goes south, it is extremely difficult to salvage your parts because the failure is so severe - often the parts will be welded into the sheet, have huge globs of rock-hard metal fused to the backside, and/or have lost features. Once a laser loses the cut, it often never recovers - which means if the cut goes south on part number 9, then all subsequent parts will be trash. Often the operator isn't watching your job, and even if they are, it can be difficult to tell that the cut is bad. The right way for the operator to handle these jobs is to (a) cut test parts and tweak the laser settings, and (b) stop the machine every 10 parts to evaluate.

Yes, it is common to see a burr ("dross") on the backside of laser-cut titanium, aluminum, and even stainless steel. In theory, a sufficiently powerful laser can be adjusted to cut cleanly, but it can take hours to dial in the settings. Most shops don't want to spend that time, so they just run the machine and allow the dross.

Waterjet, on the other hand, is much more predicable and reliable. Bad cuts are much easier to remedy. If the cut goes south (often due to a glitch with the abrasive feed), it will usually recover on the next pierce. The machine runs slower, which means the operator has a bigger window to catch problems and remedy.

You definitely want to (a) clearly and unambiguously communicate your requirements, and (b) clarify what will happen if your requirements aren't met. Make sure your vendor knows their money is on the line.

 

[REK Knives]

First, thanks everyone for chiming in!!

Let me ask you guys this... one of the reasons I'm interested in laser cutting is because I saw Spyderco did the same thing... if you go to 12:02 in the video below they are laser cutting their blades w/ the jimping in it I believe. Is this just because they were able to dial everything in perfectly by taking the time to do so?

Here's a quick render of the blade. Should I change the jimping up so it can be waterjet?

 

[Natlek]

There are many laser around ....... there are CO2 laser and there are Fiber laser Power is another story

 

[P.Brewster]

First, thanks everyone for chiming in!!

Let me ask you guys this... one of the reasons I'm interested in laser cutting is because I saw Spyderco did the same thing... if you go to 12:02 in the video below they are laser cutting their blades w/ the jimping in it I believe. Is this just because they were able to dial everything in perfectly by taking the time to do so?

Here's a quick render of the blade. Should I change the jimping up so it can be waterjet?

Yes, Spyderco is cutting relatively thin material and they have put the effort into getting a very clean cut. There are certainly shops out there that can do excellent work. However, even they are going to have breakdowns and problems. The question is - will the problem happen on your job, or someone else's?

Your jimping looks very doable for a good laser shop, assuming the material is on the thinner side.

 

[REK Knives]

Yes, Spyderco is cutting relatively thin material and they have put the effort into getting a very clean cut. There are certainly shops out there that can do excellent work. However, even they are going to have breakdowns and problems. The question is - will the problem happen on your job, or someone else's?

Your jimping looks very doable for a good laser shop, assuming the material is on the thinner side.

Thank you! your input is very helpful!

 

[tim37a]

I have my blanks cut on a 5 axis waterjet. The sides are vertical and the edges can be smooth. I elected to have slightly rougher edges so the operator can cut faster. I have quite a bit of jimping which came out very nice. No HAV to worry about. I would recommend it.

 

[Tin.Man]

I agree I think you need to shop around for waterjet.

I've used 3 places. First two kerf and edge quality was so bad it was almost comical.

Third place I think it took 28 minutes to cut 8 blanks and 90 degree edges and 30 seconds with blue scotchbrite belt and cant even tell it was waterjet.

 

[Maelstrom78]

What was this third place?

 

[Drew Riley]

I've had several things cut via waterjet by Mark at Leading Edge Fab. If you have a .dxf file ready to go, you might give him a call or send him an email and see what he can do for you.

 

[tim37a]

I also used Leading Edge Fab and was very happy with them. Didn't mention them by name because I have been chastised for mentioning names.

 

[REK Knives]

Thanks for all the input guys. Can water jet be used to spot 2-56 holes in g10? I read some negative issues with water jetting g10 so wasn't sure. How about laser with g10?

 

[Drew Riley]

Thanks for all the input guys. Can water jet be used to spot 2-56 holes in g10? I read some negative issues with water jetting g10 so wasn't sure. How about laser with g10?

I had asked Mark about doing some G10 a while back, and I think he prefers to stay away from it, due to the inherent headaches. G10 likes to blow out and delaminate all day long, if not properly supported underneath. I did have one guy successfully prototype a G10 part for me with a waterjet, but he drilled a hole for lead in, and he had some 1/4" lexan or some other rigid material underneath it to help with blowout and delam. As for spotting a hole, it's probably possible if you supported the piece properly, but hard to say you'd have a clean hole every time. That's assuming you find a waterjet operator that even wants to mess with it, and they're probably gonna charge extra.

 

[Tin.Man]

What was this third place?

Heart of Texas metal works.

 

[P.Brewster]

I had asked Mark about doing some G10 a while back, and I think he prefers to stay away from it, due to the inherent headaches. G10 likes to blow out and delaminate all day long, if not properly supported underneath. I did have one guy successfully prototype a G10 part for me with a waterjet, but he drilled a hole for lead in, and he had some 1/4" lexan or some other rigid material underneath it to help with blowout and delam. As for spotting a hole, it's probably possible if you supported the piece properly, but hard to say you'd have a clean hole every time. That's assuming you find a waterjet operator that even wants to mess with it, and they're probably gonna charge extra.

Bottom support is not sufficient to stop delam on G10 in a waterjet - in fact, bottom support has little to do with it. The delam happens during the pierce - i.e. before the jet has cut through the material.

EDIT - I should say that the most severe delam happens during the pierce. Less severe delam can occur during the cut, and it is remedied by bottom support.

 

[REK Knives]

Yes, I te

Bottom support is not sufficient to stop delam on G10 in a waterjet - in fact, bottom support has little to do with it. The delam happens during the pierce - i.e. before the jet has cut through the material.

Yes I read that there's a way it can be done if the operator knows what they are doing.... Is this true? What about in ti? Can the water jet spot small holes?

 

[P.Brewster]

Yes I read that there's a way it can be done if the operator knows what they are doing.... Is this true? What about in ti? Can the water jet spot small holes?

There are certainly tricks and tweaks that greatly reduce the delam problem in G10 and similar materials.

Ti is totally different than G10 in terms of delam problems.

The water jet is generally Ø0.03 to Ø0.05" in size, so in theory, it can spot a small hole as small as the jet diameter. In practice, it's not so straightforward and I personally wouldn't ask for anything smaller than Ø0.090.

However - I can't speak for any particular shop out there. No one can make black-and-white blanket statements about the capabilities of any machine or process. It is best to focus on and communicate the end result you desire, and let the prospective shop worry about how they will achieve that end result.

 

[kuraki]

However - I can't speak for any particular shop out there. No one can make black-and-white blanket statements about the capabilities of any machine or process. It is best to focus on and communicate the end result you desire, and let the prospective shop worry about how they will achieve that end result.

Absolutely this.