Hopefully… I’ll need to cut some 1mm - 3mm steel for a neighbor, some friends and myself. Nothing’s firm yet. So, am contemplating putting my dust covered LR3 to work…
@DougJoseph, curious about your thoughts/advice? Given you’ve built LR2, several LR3 and LR4 machines. You’ve done Plasma cuts for a few years now, and I’m curious how your Fiber laser adventures are turning out?
Curious whether, in my situation, you’d add Plasma torch to my existing LR3, or, build a new LR4 based gantry for reason(s) ? Or, skip Plasma altogether if trying to cut 1mm to 3mm steel without major warping. Cheers!
When are you cutting, and what size are the parts (besides thickness)?
You can now find large lasers in some makerspaces (the local big makerspace has a 5Kw laser at full sheet plus size). Local shops can often do this work cheaply as well.
That said, there is no need to explain the DIY spirit to me.
Below, I’m endeavoring to add a table in markdown format, which used to work here.
So, the tradeoffs between my LR3 plasma versus my small 30w galvo fiber laser are:
Cut Speed / Cut duration
Kerf width
Accuracy
Edge Straightness
Cut Area
LR3 plasma
Fast, Short time (1 pass, very deep)
Wide
OK, but not the best
Can be OK if you are careful.
Huge
30w galvo fiber laser
Fast, Long time (many passes, not deep)
Narrow
Very good
Very good
Small
The plasma can cut steel, deeply and quickly, in a single pass, supposedly as deep as 5/8" but I’ve never cut pieces that thick.
The 30w galvo can cut metals, in multiple passes, although not as deep as the plasma. I’m still waiting on metals I ordered to arrive for testing its carving and cutting on materials such as bronze or brass. Aluminum is quite reflective which works against on cutting. I don’t know if it’s the right tool or amount of power, to cut steel.
Plasma does not need a lot of rigidity like a CNC router, because it’s not fighting against deflection forces as with a router bit. An LR3 is a splendid beast for plasma. Especially given that my toolholder add-ons for plasma, including supporting floating Z with touch-off, are parts that are all already designed and shared on Printables, you could have an LR3 based plasma put together pretty quickly. And especially if you got an orphaned LR3 laying around, great way to repurpose it.
That said, someone around here did remix the tool holders etc for LR4. I cannot remember right now who it was.
The Clough42 YouTube channel has some great content on CNC plasma cutting including pointing out that most people who think it cannot be accurate on cut dimensions are folks who never bothered trying to measure the kerf or try to compensate properly for it. I found his conclusions to be spot on.
That’s way too little optical power to do a good job in steel, in my opinion. Especially if you don’t want to heat up and warp the part with lots and lots of passes.
For 3mm single pass at reasonable speeds , most folks I’ve met that are doing laser cutting were running around 2Kw of optical power for 3mm. That’s scary dangerous for a hobby machine.
Plasma seems like a better option for 3mm steel, in my opinion.
I’ve seen hobby plasma cutters that produced production grade results. Tuning, setup and understanding the material and the cutter are the important parts, just like we see with various woods or soft metals on a router.
3mm is what I threw my plasma gantry together for. Seemed to be ok even without THC. I bet any thinner would be a struggle though.
This is what I was expecting/hoping to be the case since I managed a usable, if ugly, part with a cheap torch turned all the way up, a chiron frame and a bunch of zip ties, so I should think some time tuning a LR3/4 based rebuild will get me pretty good parts. Though I might yet go down the route of milled aluminium
