Cutting foam sheets... with a needle!

[jhitesma]

Nice cutting David...guess I'm going to have to cut a grid soon

I gave another quick try at my cardboard over lunch. It didn't go great.

I slowed it down to 150mm/min at full power:



Pretty much immediately it started to char and burn. But I let it complete the cut anyway just to see:



And even with that it didn't go through the bottom layer:



Now, I admit I didn't double check the focus and didn't do a fine focus test before this run...but...still this is about what I seem to get when I try anything in the 100-300mm/min range with cardboard That's why I ran my cuts at 650mm/s but then had to up the passes to get it to go through. Feel like I must be doing something wrong...or maybe it is just the G2 lens making the dot "hotter"?

 

[GremlinRC]

I slowed it down to 150mm/min at full power:

I think that's too slow Jason, hence the card catching fire. I've tried cardboard in the past at 400mm/min full power and IIRC 3 passes went through some thick card. I'll try again this evening and see if it still works.

Cheers

Dave.

 

[jhitesma]

I think that's too slow Jason, hence the card catching fire. I've tried cardboard in the past at 400mm/min full power and IIRC 3 passes went through some thick card. I'll try again this evening and see if it still works.

Yeah, definitely seems too slow

But given the other David's comment earlier:

What is the thickness of your cardboard? I'm cutting 3mm cardboard (actually the boxes DTFB comes in) in just one pass... full-power (255) at 100 mm/min and getting clean through-cuts.

I figured I'd give it a try. I didn't go all the way to 100mm/min since I knew that was asking for fire...but figured I'd give 150 a go.

I'll give 400 with 3 passes a try. I'm sure my 650/7 passes isn't ideal it was just the first I found that worked.

Basically First I did a set of ten 50mm lines at different speeds from 1000 to 100 in 100 step increments. The 100 line burned, the 200 line was close to catching. 1000 gave the cleanest line - but didn't even cut through the top layer of the cardboard. 700 was where it seemed like I was still getting the cleanest line with the most cut. So I took than and then ran a set of 6 test lines with multiple passes (1-6) The 6th line with 6 passes just barely started to cut the bottom layer so that was what I tried first for the dino head. But it wasn't enough to cleanly release so I upped it to 7 passes. That still wasn't quite as deep on the bottom as I wanted so I slowed the passes to 650 and it was just barely what I consider acceptable.

Just trying to zero in a sweet spot where I use the fewest passes but still get the cleanest cut and got tired of experimenting and wanted to actually do some cuts I'll do more experimenting tonight to see if going to lower speeds with fewer passes can improve things much more.

 

[dkj4linux]

Nice cutting David...guess I'm going to have to cut a grid soon

I gave another quick try at my cardboard over lunch. It didn't go great.

I slowed it down to 150mm/min at full power:

View attachment 80594

Pretty much immediately it started to char and burn. But I let it complete the cut anyway just to see:

View attachment 80595

And even with that it didn't go through the bottom layer:

View attachment 80596

Now, I admit I didn't double check the focus and didn't do a fine focus test before this run...but...still this is about what I seem to get when I try anything in the 100-300mm/min range with cardboard That's why I ran my cuts at 650mm/s but then had to up the passes to get it to go through. Feel like I must be doing something wrong...or maybe it is just the G2 lens making the dot "hotter"?

Jason,

One of the purposes for having a shroud around the laser and a fan directed at the laser spot is to extinguish flames before they have a chance to flare up... that, and clearing the smoke. I, too, had little luck with cardboard at first for the same reason (especially on small features or acute corner where the beam dwelt too long) but with the shroud and a good stream of air (not the air-assist) I rarely have had that problem anymore. Your laser is similar in power to mine and I know you should be able to go that slow... I kid you not, I'm cutting those 3mm dinosaurs at full-power and 100 mm/min in one pass.

I do get a good focus on the material as well... it seems sometimes, when you run Ryan's focus script, that some of the near-but-not-quite-focused lines may generate more smoke more than others but they still don't flare up in flames...

I'll do some more cardboard tests and see what I can see. -- David

 

[x33]

Bottom completely and cleanly cut... no staining, charring, etc. except where it crossed a bed wall. Also compare to previous, neighboring cuts... on old plywood spoilboard. Thanks again, Joachim!
-- David

You're welcome!

You have to watch this video...and you can imagine what this 4KW beast will do with a flat bed
---> at 7:30 ---> cutting 20mm steel in ONE pass!!!
https://youtu.be/pMSyGOoesfM

 

[GremlinRC]

Jason,

I've been doing some tests. 400mm/min 3 passes 3.5mm cardboard. There was one or two "holding tabs" but very little.

I have a conclusion. While cutting cardboard, air assist is essential. Without it, I just set fire to the cardboard on the second pass, had to literally pick it up and chuck it outside.

 

[GremlinRC]

Jason,

One of the purposes for having a shroud around the laser and a fan directed at the laser spot is to extinguish flames before they have a chance to flare up... that, and clearing the smoke. I, too, had little luck with cardboard at first for the same reason (especially on small features or acute corner where the beam dwelt too long) but with the shroud and a good stream of air (not the air-assist) I rarely have had that problem anymore. Your laser is similar in power to mine and I know you should be able to go that slow... I kid you not, I'm cutting those 3mm dinosaurs at full-power and 100 mm/min in one pass.

I do get a good focus on the material as well... it seems sometimes, when you run Ryan's focus script, that some of the near-but-not-quite-focused lines may generate more smoke more than others but they still don't flare up in flames...

I'll do some more cardboard tests and see what I can see. -- David

Sorry, I missed your reply to Jason. That's interesting, because not even the shroud is enough to stop my cardboard catching fire. I have to use the air needle. I'm wondering if your fan is putting through more air than mine because you seem to be having much better results with the same shroud.

Dave.

 

[dkj4linux]

Jason cardboard tests...

Okay... here's what I do to set up for cutting cardboard (actually any material). Please understand I am not using "air-assist" here (the compressor or aquarium pump) but am relying on the shroud and internal fan only to clear smoke and suppress flames. They are crucial IMO. I personally don't think the real air-assist (using the compressor) adds anything but noise to cuts in cardboard.

First, I run the focus script and then lower Z back down to best focus on the top of the material... here about 16mm... and leave it there.



Then I run a series of 10 lines... starting at 1000 mm/min down to 100 mm/min.



Flip the test piece and find where the earliest, cleanest through-cut occurs... here, 200 mm/min might work but 100 mm/min will insure through-cuts...



Then cut the parts. These all look nice and fall out on their own. There's a slight crown in this piece of cardboard that I usually can just ignore (focus is reasonable over range of 6mm or so) if it's not too severe or abrupt...





In honesty, I think I need to run some parts such as Dave is showing... stars with sharp points, etc... before declaring this "foolproof" but it definitely has been working for me. -- David

 

[GremlinRC]

One think I like to do is admit when I got something wrong and after reading your words of wisdom, I tried again but this time I spent 5 minutes getting the focus absolutely spot on and what a difference it made. 1 pass 150mm/min and it cut beautifully. Only the cone shroud was assisting. So it seems to me that when cutting cardboard, the focus is the most important thing.

 

[jhitesma]

Well heck...I'm starting to think there's something about this girl scout cookie crate cardboard that's making this extra hard. I mean one of the first things I cut was cardboard and it "just worked" until I hit part of the design that went over the same area twice in quick succession and started it burning....

First thing I did was refocus. Then run the focus script to really dial it in. So focus is dialed now for sure. It was close before, well within David's 6mm leeway.

Next I ran the speed test like David suggested. None of them cut through all the way. And the last one set it all on fire:



I tried it at 400mm/min 3 passes. Cut wasn't as clean as what I get with 7 passes at 650 and didn't go all the way through

Either I got a lower output diode than you guys...or I'm running mine more conservatively...or my lens is dirty...or the G2 lens just isn't all it's cracked up to be.

It could be the fan...but I tried with and without my shroud and still get the same results. Maybe my shroud just doesn't direct as much air as effectively. I tried blowing on it while it cut but no real difference there either.

I still have a sheet of the original cardboard I had decent luck with...going to give it another try.

Oh - and Instructables announced the final results. I got a 2nd! New DeWalt 611 router coming my way! Sweet! Kind of better than 1st or grand for me since I don't know where I'd put another CNC machine anyway

 

[jhitesma]

Ok, tried my original cardboard to rule that out.

Not great but better. GS cookie crate on the left, sheet of "plain" cardboard HK once sent me as packing material on the right:



Those were both 400mm/min 3 passes. Neither went all the way through but the plain cardboard came closer:



I also tried cutting the thin non-corrugated cardboard of an actual GS cookie box much like David's cereal boxes. Not much luck there either. Only the 100mm/min cut came close to going all the way through...but it also started to smolder. Both with and without my shroud.

Think I'm going to have to make a better shroud next...or try with real air assist in here.

 

[GremlinRC]

Oh - and Instructables announced the final results. I got a 2nd! New DeWalt 611 router coming my way! Sweet! Kind of better than 1st or grand for me since I don't know where I'd put another CNC machine anyway

That's fantastic news Jason. Serious congrats. There were a lot of great instructables in that competition which makes your achievement even more remarkable. :applause::applause::applause:

Dave.

 

[Michael9865]

Oh - and Instructables announced the final results. I got a 2nd! New DeWalt 611 router coming my way! Sweet! Kind of better than 1st or grand for me since I don't know where I'd put another CNC machine anyway

Congratulations!

 

[dkj4linux]

...
Oh - and Instructables announced the final results. I got a 2nd! New DeWalt 611 router coming my way! Sweet! Kind of better than 1st or grand for me since I don't know where I'd put another CNC machine anyway

Well done, Jason! :applause: :applause:

Now you can start printing a mount for that new router... yet another tool to hang on your MPCNC -- David

 

[dkj4linux]

One think I like to do is admit when I got something wrong and after reading your words of wisdom, I tried again but this time I spent 5 minutes getting the focus absolutely spot on and what a difference it made. 1 pass 150mm/min and it cut beautifully. Only the cone shroud was assisting. So it seems to me that when cutting cardboard, the focus is the most important thing.
View attachment 80613

Outstanding, Dave! I think you've verbalized it for us. It's not just power, feed, and fan... focus, Focus, FOCUS!



For completeness sake, I found a USAF roundel (new word for me!) with some pointy bits (I need to find another one... this one has a bent upper-most point on the star ) and committed it to gcode. As hoped, it worked a champ! For this particular cardboard, it looks as though I could speed up to 150-200 mm/min and maybe get a little less soot on the edges. I noticed that handling the dino pieces you'll get a bit of black soot on your hands...









-- David

 

[dkj4linux]

...
Think I'm going to have to make a better shroud next...or try with real air assist in here.

I think this is the problem, Jason. To test, I'd set up a real cooling fan to blow across the area where you're cutting... and try those 100 mm/min tests again. I'm thinking there's so much smoke, it"s attenuating the beam's energy... possibly the lens is clouded with soot as well... but the external fan is a quick test. And Dave's test, along with my own experiences, pretty conclusively prove that, with good focus, just the shroud and internal fan are enough to clear the smoke, suppress the flames, and allow single-pass cuts in thinner cardboard.

This is also the reason not to leave the laser running unattended... if the fan/air blast ever fails, fire is imminent! -- David

 

[GremlinRC]

For completeness sake, I found a USAF roundel (new word for me!) with some pointy bits (I need to find another one... this one has a bent upper-most point on the star ) and committed it to gcode. As hoped, it worked a champ! For this particular cardboard, it looks as though I could speed up to 150-200 mm/min and maybe get a little less soot on the edges. I noticed that handling the dino pieces you'll get a bit of black soot on your hands...

David feel free to use mine. I cant upload a .dfx file here but heres a d/l link;
https://drive.google.com/file/d/0B17H2V7mbN-MV3N0N1Vab2lCV0k/view?usp=sharing

Cheers
Dave.

 

[RAGII]

I got my laser mount completed late last night. Hooked it up over lunch (working from home today while attending to a sick child) and am currently running a image2gcode file I created. I will post pictures a little later. Now I have a lot of wiring cleanup to do so I can easily go from needle cutter, to laser, to router. Or maybe I need a dedicated MPCNC for each

Jason, congrats on the win and have fun with that new router.

Rob

 

[x33]

Hi, while you guys were burning paper with a laser, I did some more tattoos on foam

I made up my mind to make all the control surfaces for the small shocky from EPP and not from Depron...EPP is much more flexible an will not break at minor crashes (our gym for indoor flying is very small and the walls are moving fast, trying to catch the planes )

Milling EPP is nearly not possible...it is "soft" and the milling drill has to be very, very sharp...
====>>>> But no problemo for the needle cutter!!!!!! The only trick is to find the right RPMs according the travel speed of CNc

The parts

Can you see the slits and holes for the Carbon Spars and the control horns?

CloseUp - the EPP is 3mm

Every thing is fine ...no sanding or cutting needed

I was grinning the rest of the evening!

Cheers
Joachim

 

[GremlinRC]

I got my laser mount completed late last night.

Hi Rob, Hope your feeling a bit better. Congrats on getting it all up and running. Looking forward to seeing the results of the "first light".

Dave.