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Cutting foam sheets... with a needle!

I think I now understand what's going on here and thus how to judge "how much is enough" when it comes to the air. This is really about ember removal, and smoke to a lesser extent. What you want to see, is tiny flecks of ash being ejected from the cut. Embers which would otherwise put out more heat and smoke inside the cut. Also the ash would then reheat on a subsequent pass reducing the actual cutting action. Therefore you should see the benefit more on cuts with multiple passes. The key is focusing the air blast right down into the cut

David you asked about air pressure. Mine is just open. Although my airbrush compressor has a regulator, it needs something totally blocking the airflow to allow it build up to the set pressure, with an open needle that can't happen. By squishing the end of the outlet, you get more than enough pressure, its enough to blast any loose light particles pretty much clear of the machine. I think an aquarium pump would be enough and has the benefit of working off 12V so it can be tied into the same power source as the laser. I'll be popping down to the local pet store to take a look at what they've got.
 
I think I now understand what's going on here and thus how to judge "how much is enough" when it comes to the air. This is really about ember removal, and smoke to a lesser extent. What you want to see, is tiny flecks of ash being ejected from the cut. Embers which would otherwise put out more heat and smoke inside the cut. Also the ash would then reheat on a subsequent pass reducing the actual cutting action. Therefore you should see the benefit more on cuts with multiple passes. The key is focusing the air blast right down into the cut

David you asked about air pressure. Mine is just open. Although my airbrush compressor has a regulator, it needs something totally blocking the airflow to allow it build up to the set pressure, with an open needle that can't happen. By squishing the end of the outlet, you get more than enough pressure, its enough to blast any loose light particles pretty much clear of the machine. I think an aquarium pump would be enough and has the benefit of working off 12V so it can be tied into the same power source as the laser. I'll be popping down to the local pet store to take a look at what they've got.
Thanks, Dave. I'm printing an air-assist holder right now... to hold an inflation needle, connected to a length of aquarium hose and a pump (pumps here just plug into the wall AC). I have noticed, even with just the shroud, that small embers occasionally fly off the cut area... so I just expect to see more of the same if I get the air-assist "aimed" properly ;) -- David
 
I'm a believer!

All,

Set up an "air-assist" test... took a couple of shots at printing a air-assist nozzle (an inflation needle... anyone shocked?) holder and began cutting some of the same pieces I've done in recent days. First pass holder on the right...

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I first tried the aquarium pump (with first-pass holder) and wasn't at all impressed it was doing anything...

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Set up my small 3-gallon air compressor and set the regulator as low as I could get it (5-10 lbs pressure) and started seeing more action at the point of attack... small embers running away, barely audible air "blast", etc. but needed better "aim".

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Printed the 2nd-pass holder that put the air-assist closer to the laser spot...

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and engraved a ruler (uppermost copy)... greatly improved finish, little smoke staining...

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So, decided to really give it something to do. The nema17 motor mount I've cut a bunch of... 5 passes, full power, 100 mm/min, focus on top of material all passes. Got similar result... but in only 4 passes! That's it laying on top of previous cuts that didn't cut fully through... little smoke stain on top, clearly cut through on bottom. 20% fewer passes with air-assist through 4.75mm plywood!

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I then decided to try once more with the aquarium pump... it's better than "no assist" but not as good as the heavier "air assist" from my air compressor... 4 passes, slightly smoke stained, and not-quite-complete through-cut.

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So, there you have it... I'm a believer in "air-assist"! The 40mm fan and shroud alone, while better than no shroud at all, does not give the full benefit of "air assist". YMMV! ;)

-- David
 
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Hi David. Glad you have seen the improvement air assist can offer. Your 20% fewer passes ties in pretty much with my experience too. I suspect that the performance improvement is probably due to both the ash and thick smoke (it probably gets pretty thick at the cut point) being removed before it can absorb the energy from the laser. Thanks also for saving me a few bucks buying an aquarium pump that likely is not powerful enough for the job. I'm sure there are probably more powerful ones out there that can duplicate at least the lower end pressure on a compressor.

BTW I had to look up YMMV:)

LSNED;)

Dave.
 
OK, another question regarding the hook up as I continue to wait on my heat sink. I modified the firmware for the fan output and all looks good there. Now, what method did you guys do to connect the TTL signal from the Ramps card to the laser driver. I have some JST connectors coming for the laser driver, but where would I find a connector for the Ramps card?

I do not trust my soldering skills yet to solder directly to the ramps card.

Rob
 
I got the remainder of the laser parts today (heat sink) so I am only in need of the JST connectors (due tomorrow) for the connections. I tore apart an old desk top computer and found some connectors I can use for the TTL signals. Last night I did the firmware changes and tested that the fan speed went from 0-5 volts so that is all good. Getting close to making some light.

Kids have Basketball tomorrow night so nothing will get done until Friday night. Wife volunteered me to put in a bathroom floor at the in-laws on Saturday so that is out, and Sunday is football. Need to see if the Packers can pull out a victory against the Cowboys so not much will get done over the weekend.

I am also still debating on my next "toy". I think I finally got my MPCNC square (needed to file out the roller supports as I believe they were shifting the conduit) so I am really looking into 3D printers. I have no knowledge of them or how to use them. I have been watching a lot of You Tube videos trying to get to learn. My biggest hurdle will be modeling parts. While I am good at 2D AutoCad, I have zero 3D modeling experience.

Right now I am leaning towards the WanHao Duplicator i3 v2.1. The only real complaint I have seen is leveling the bed is not the greatest. Not sure I want to spend the extra money to get a self leveling unit.

Hopefully my next post will have some "light" associated with it.
 
Just piddlin' around...

Found a good dxf of a triceratops for the grandkids. Scaled to 3mm slots with Inkscape and used JTech laser plugin to generate the gcode. I ran the air-assist although I don't think it had any real effect on cardboard cutting speed... I checked cut speed before running and it was almost identical to previous runs without air-assist.

Anyway, a couple of videos showing the air-assist nozzle in use and the finished product. Turn down the sound on first video... my air compressor kicked in just as I as about to start the video :(


Without flash washing out the picture the shroud glows brightly as the laser is firing...


Parts fit nicely together...

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The completed triceratops...

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-- David
 
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Right now I am leaning towards the WanHao Duplicator i3 v2.1. The only real complaint I have seen is leveling the bed is not the greatest. Not sure I want to spend the extra money to get a self leveling unit.
I got one about 2 weeks ago and I'm over the moon happy with it. Saying that I've never had a 3d printer before so I've nothing to compare with, but it's everything I hoped it would be. The bed level is not an issue on the 2.1. Apparently previous versions came with fiddly wingnuts which were not very good. The 2.1 has thumbwheels which make the job so much easier. One small complaint is the bed springs can shift. However that's easily fixed by printing a set of centering cups which keep those springs centered. There is another mod which everyone seems to be doing which is to strengthen the Z gantry with some printed parts and threaded bar. I've done the mod and it certainly seems to keep the Z gantry more stable. However out of the box I got first class prints. I'd have no hesitation recommending it.
 
Last bit of foolishness..

Tri -- that's what I call him -- seemed lonely. So I started the wheels of progress churning as never before... under Tri's watchful eye and supervision...

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Breaking a sweat... really! [It was 18 degF (-8 degC) two days ago... today it reached 80 degF (27 degC)... :confused:]

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Unfortunately, I didn't realize that this cardboard was 4mm rather than 3mm...

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But, with sufficient force and a pair of round-nose pliers, 4mm cardboard can be made to act like 3mm cardboard... kinda. And... voila! A suitable playmate is found for Tri... :rolleyes:

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I'm not sure Tri approves...

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A happy ending! I found them playing ball together this morning... ;)

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-- David
 
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You sure those dinos are for the grandkids???? Think you might be enjoying them a little too much to give them up...
Hey, Ryan! Tri, sad to say, has surely met his demise... last I saw of him, my 3 year old grand-daughter had him by the mid-section and was waving him like a flag. He seemed "shaken" by the whole ordeal :eek:

Notice the air-assist? I know that was a topic over on your forum... we've had our own round of recent discussions and practical testing to determine that it really does work. I'm a believer :D

BTW congrats on another incredible machine design... your LowRider looks amazing! Unfortunately, I don't have the strength and energy to handle big sheets of anything... so I'll leave it to you young'uns. There's enough other, more light-weight, things to play with, anyway ;) -- David
 
Hi, folks! I just visit the Forum to wish a happy and sucessful 2017 to all of you.
Nice to see a lot of progress in your projects and developments. I am planning to restart my MPCNC developments very soon. I just need to finish the overhaul works in our house that is being done since October.
Very soon I will turn on my machine to cut some depron sheets.
Big hugs for all
Silvio
 
Hi, folks! I just visit the Forum to wish a happy and sucessful 2017 to all of you.
Nice to see a lot of progress in your projects and developments. I am planning to restart my MPCNC developments very soon. I just need to finish the overhaul works in our house that is being done since October.
Very soon I will turn on my machine to cut some depron sheets.
Big hugs for all
Silvio
Hey, Silvio! It's good to hear from you. I'm sorry you've had the deal with the house so much... that's not nearly so much fun as cutting some foam and flying your planes. Welcome back! And only best wishes for you and yours in 2017 :D -- David