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Cutting foam sheets... with a needle!

Interesting notion. Have you tried this out? Sounds like it would tighten the orbit by 10mm (plus wire coil). That's what? 50% reduction? Looking at the specs for the motor, the prop holes are 12.5mm from center. It's something to consider.
Steve,

With my flywheel cutters, I've always tried to equalize the needle flex to each side... striving for a symmetric needle "blur". In my experience it reduces the friction within the needle guide. With larger needle loops that surround the bearing race, I've always used round-nose pliers to center the needle's exit angle rather than coming off at a tangent...

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the "blur" with needle coming off tangentially...

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and coming off centered...

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-- David
 
Thanks David, sometime you get a little tunnel vision and need a light shined. So I took my backup needle (still long) and put a bend in it and cut to size. Worked great on the first sheet. Then the motor wouldn't spin up. Wasted a whole bunch of time looking at the PSU. Turns out it was a fault in the ESC. Replaced the ESC. Cutting the 2nd sheet as I type. Better than a laser. Well faster at least. lol. Pretty close on the cut.
 
So that needle didn't last very long. I didn't see it break but since it came completely off of the bearing as well as breaking off by the mig tip, I'm hoping that it broke as a result of it coming off the bearing. I was worried about that. Looking at it after bending to center you can see that when the needle strikes it would tend to push even more on the coil.

I needed a retainer of some kind. Then I remembered these flanged bearing I had. Also 10mm in diameter. And I have 10 of them. Ran it through a sheet of DTFB and no complaints. Needle 1.jpg Needle 2.jpg Needle 3.jpg Needle 4.jpg
 
I really appreciate the work you are doing here, Steve. Keep it up!

A couple of things I might mention... not to argue but simply things I do differently to what you are doing here. I've never had problems with broken needles or needles coming off the bearing when I exercised appropriate care when fabbing and mounting them. I have bent/broken a few needles when torturing them while trying to cut cardboard and coroplast -- light cardboard actually cuts okay, coroplast not so much -- but in normal use with DTFB and fanfold foam I've never really had any problem with the needles. That said, I've never cut the large quantities of foam that some of you cut and I've not tried cutting any of the new waterproof foam board at all. I detailed the procedure I use to fabricate needles and mount them on the bearing way back in post #26 of this thread.

First, I do no annealing, or other heat-treating, of the needle at all. I trust the heat-treatment of the music-wire steel from the factory and feel the springiness of the steel helps keep the needle in place around the bearing. Another thing is that I always grind a shallow groove in the outer race of the bearing to help retain the tight loops of needle. And finally, I used a "mandrel" (a drill bit shank) about 2/3 the OD of the bearing to wind my loops around... about 1-1/4 to 1-1/2 turns and I usually leave a little tail/handle, which makes it easy to slightly spring open the loops to go around the bearing race. The loops spring back a bit when removed from the mandrel but, when fitted around the bearing, it "snaps"/settles and holds in the shallow groove in the outer race simply by its own spring pressure.

I recognize that many folks have had difficulty fabbing needles and grooving the bearing race as I've described... and have experienced many more needle-related failures than I have. But this is the procedure that has worked well for me. And, as always... YMMV :)

-- David
 

jhitesma

Some guy in the desert
Mentor
I wasn't able to groove my bearing and seriously considered ordering some flanged ones instead (I didn't have the right size on hand.)

But...instead I tried a tiny drop of super glue (because I didn't want it getting into the bearing) and it worked great. Even using the needle on cardboard after that it didn't come loose.

I also haven't tried annealing yet, I've considered it right from the start - but the more I researched the properties of music wire and proper methods of heat treating/annealing....the more I found good reasons not to. I forget the details of what I found, but the short version was that due to the size of wire and the way it's treated from the factory it's VERY VERY difficult to anneal effectively and it's more likely to make things worse than better for our purposes. Not impossible...but...much trickier than annealing larger pieces apparently.
 
FWIW, I just use TWO regular bearings with a washer between them that is slightly thinner than the needle wire - the needle wire loop sits in the 'groove' that is formed.
I've NEVER had a needle wire come off, and like David, never broken one either (although I only cut 6mm depron) - nor do I anneal them - they get enough use that I'm sure they've annealed themselves by now :)
Bearings are 8mm OD, 2mm thick, 3mm ID

Neil

Needle Bearing.png
 
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I've cut probably 150+ sheets of DTFB & WPFB. I've had a few needles break. Especially back when experimenting with some of the less successful methods like the crank wire around the motor shaft. I'm always looking to improve on my designs. But don't take this to mean that I'm any troubles that I haven't overcome.

Annealing the needle is a process where you're relieving the stresses you put into your needle from bending it into a coil. It's allowing the crystals in the steel to realign to its new shape. 500 degrees isn't all that hot. It's not like I'm putting it a forge until it's red hot. It's about 50% of a full anneal. So it's not going to remove the temper. If you don't want to do it, then don't. This thread is about sharing information, it's not a dick measuring contest.
 
There's absolutely nothing wrong with sharing what works for you and your use model. That is indeed what this thread is all about. That's what I'm doing... and have been doing all along. And I think that is true of most everyone who's contributed to this thread from the beginning. But there's never just one way of doing things and the testimonies/experiences -- and myriad successful cutters -- shared in this thread serve as clear proof of that. Please do what works for you... i.e. what works for me may not be suitable for you and your purposes.

I do understand what you are saying about relieving the stresses produced while creating the loops/bends (I used to make my own woodworking lathe tools/chisels from files and other metal bits...) but in the years I've been playing with the needle cutter -- as a hobbyist -- those stresses have never been so severe as to create a problem... so I've never sought to relieve them. Had I been cutting large quantities of foam board in a production environment, I'm certain my experiences would have been different, and the information I've shared would reflect those experiences. This thread is full of ideas and tidbits -- many different, some even contradictory -- that almost anybody, regardless of their experience level and interest in CNC and cutting foam, might find useful... and you never know which ones are going to grab the fancy of someone, somewhere, who'll take it, run with it, and come back to tell us all about it. What fun!

You've already contributed greatly and I, for one, thank you. -- David
 
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FWIW, I just use TWO regular bearings with a washer between them that is slightly less thick than needle wire - the needle wire loop sits in the 'groove' that is formed.
I've NEVER had a needle wire come off, and like David, never broken one either (although I only cut 6mm depron) - nor do I anneal them - they get enough use that I'm sure they've annealed themselves by now :)
Bearings are 8mm OD, 2mm thick, 3mm ID

Neil

View attachment 116521
Neil, what do you use that Servo for?
 
Neil, what do you use that Servo for?
My setup is a dedicated depron cutter, not a modified CNC system with a full Z head. Consequently, all I need is to be able to retract the needle assembly - which is what the servo does (and a bit simpler/faster than a regular Z mechanism with leadscrew). The head has a copper heatsink/shoe which constantly rides on the surface of the depron giving essentially a 'zero clearance insert' (like on a table saw - or a bit like a presser foot on a sewing machine ). There are a few posts with pics further back in this forum - the machine with the sexy clear blue acrylic laser cut parts LOL :D
Cheers
Neil
 
Here's Neil's depron cutter and the presser foot posts from earlier in this thread... a really slick machine.

Recently, I purchased one of the Eleksmaker A3 2.5 watt laser machines from Banggood. I'm thinking of a simpler, more compact, laser machine for my daughter's cross-stitch projects and some stylized engraving... they don't have a lot of room. These machines are similar to Neil's machine in that they do not implement a fully-functional Z-axis... and as a dedicated laser machine it really isn't necessary. But, of course, I prefer having a functional Z-axis, so I stole the printed linear stepper slide assembly (https://www.thingiverse.com/thing:2813896) from my CoreXY machine and fastened it to the acrylic tool plate.

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I'd love to keep the Grbl firmware and controller board that are on it but, since she'll often be using gcode files I create on my MPCNC laser engraver, I think it best for compatibility reasons to go ahead and set it up with the RAMPS/Marlin combo I normally use. The EleksMana SE control board doesn't have a third driver for the Z-axis anyway so I'll probably, for simplicity's sake, just do a wholesale cannibalization of the CoreXY machine's Z-axis and controller hardware and reflash it with the MPCNC firmware and then modify the steps/mm settings for the Eleksmaker machine.

Here are examples of the cross-stitch and stylized engravings we've been messing around with...

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-- David
 
Interesting stuff David ! I thought at first that you were personalising steaks LOL, but you were just using the grill frame :)))
Lots of interesting things, I've setup and played with an A3 LED laser I was given to sort out for a local woodworking initiative, they hadn't a clue what to do with it. I ended up using Easel (again :) as it's just a GRBL controller that's fitted). Now they engrave folks wooden floors as you can just plonk it down on the woodwork and hit the button - nice earner I'm told :)
I've done a number of cross stitch sheets for people (in lots of materials - hard stencil card card is their favourite for some reason - maybe because it smells of linseed oil LOL) - I tend to use octagons rather than circles as my laser can rattle through these at a high rate of knots compared to circles and it's of no consequence to them. The photomechanical nature of your engraved photos is quite nice - I should have a go at some arty farty stuff rather than continually cutting wing ribs and model aircraft parts :))
I noticed your engraved ruler, this is a real pet penchant of mine - a decent ruler - here in the UK for some obscure reason, nearly ALL the ruddy rulers and tape measures have metric AND imperial - we stopped using imperial in the 50's (I'm 68 and haven't used imperial measurements since I was six !!!). IMHO, it makes them ALL essentially useless as the top of the ruler is invariably imperial. Steel rulers are even worse, imperial at the top with metric on the bottom - the first 150mm usually has HALF MILLIMETRE marking rendering the first 150mm useless - arghhhhhhhh - have you ever tried to measure using half millimetre markings, it just merges into a mashup (nearly as bad as 1/100" markings on imperial rules :)) ! I have to buy my tape measures and rulers from the EU to get what I want (Belgium/Germany usually) - unbelievable really :)
I designed a 300mm rule(r) - 0 to 300 on the top, 300 to 0 on the bottom with the text fully readable (unlike yours which you have to rotate :). The opposite side is the opposite - 300 to 0 top 0 to 300 bottom - again readable. Only full millimetres and SQUARE ENDS so you can do inside measurements whatever side of the ruler you're using. Why aren't rules all like that ?? #soapboxRant :)))
It's a pity that the LED lasers can't cut white foam - spraying them with watercolour only helps for the first few mm's :) Grey depron is ok though - but nowhere as nice as the needle :)
Cheers
Neil
 
Thanks, Neil, for the kind words.

IMO it seems inherently right and proper to engrave a useful and reasonably accurate ruler when setting up and calibrating a CNC laser engraver... and I have them laying all around so one is always easy to find. Virtually all my 3d prints and milled CNC parts need to interface with standard hardware and my enjoyment level goes up by leaps and bounds when well-fitted parts, fabbed on calibrated machines, mate easily and accurately with the hardware that holds it all together.


Before you ask, most of my rulers are 152mm (plus a fraction)...it's an "artifact". My very first rulers were 6" rulers, of the "imperial on one side, metric on the other" variety you mentioned. When I chopped off the "inches"-side, I was left with a 152mm scale, which I then duplicated and flipped, to create the "2mm offset sides" ruler shown below...

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I honestly wish that the US had completed the transition to the metric system that was being pushed when I was young but, alas... they didn't and, an older US citizen now, I grew up using imperial measure almost exclusively. Once I made the decision to pursue engineering in school, however, it didn't take long to become comfortable with metric measure and I realized quickly that it is a far easier/better system to work with. I use it almost exclusively with my technical, hobby-related, activities -- 3dprinting and CNC -- but, even now, I must admit it's still easier for me to picture/judge a 100-yard [American] football field and play golf with yards to the hole rather than meters. Oh, well...

Thanks for the tip regarding oil-board/stencil-card... I've got a small quantity on order now. I use craft sticks for a lot of stuff but cross-stitch patterns really weaken the wood, especially along the grain... and thin plywood takes longer to cut with a diode laser. Also, I'll have to try your octagons vs circles trick...

I've gotten the Eleksmaker A3 converted over to Marlin/RAMPS from the GRBL-based firmware and controller that came with the machine. I know that some will say that is a step backwards but it now has a fully-implemented Z-axis and, being for my daughter, it is compatible with my Marlin-based MPCNC machines that I've used for most of the cross-stitch and stylized image work I've done so far. Here's the new Z-axis running over its 60mm of total travel... it's a bit noisy yet (it uses BB "bearings") but it's reasonably smooth and getting quieter with use


The stylized images I've been playing with are *vector* images created with a neat set of Python extensions... called "Blackstripes Python Extensions" out on Github

https://github.com/fullscreennl/blackstripes-python-extensions

There is a thread over on the V1Engineering forum where I first learned of this... you may want to check it out

https://www.v1engineering.com/forum...res-into-stylized-svgs-suitable-for-plotting/

A great advantage is that, being vector images, they are relatively quick to print (vs. raster) and yet still quite recognizable. Effects utilized are crossed, spiral, and sketch... crossed and spiral are my favorites so far.

Later.

-- David
 
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Anyone using LightBurn? https://lightburnsoftware.com/ I had looked at a few other suggestions from JTechPhotonics, but I was sold instantly on trying it. My wife burned her first cutting board with some basic instruction. I'm no expert on laser software, I highly recommend trying the trial.

"If you're new here, we want to be sure that LightBurn will work for you, so to give you a chance to really use it, we offer a 30 day trial period, with no restrictions. Make some things on us. Have fun - this is the full deal, no watermarks, no limits.

If you decide to buy it, we'll send you a license key that unlocks it permanently, allows installation on up to two machines, and gives you access to free updates for a year.
"
 
Here's Neil's depron cutter and the presser foot posts from earlier in this thread... a really slick machine.

Recently, I purchased one of the Eleksmaker A3 2.5 watt laser machines from Banggood. I'm thinking of a simpler, more compact, laser machine for my daughter's cross-stitch projects and some stylized engraving... they don't have a lot of room. These machines are similar to Neil's machine in that they do not implement a fully-functional Z-axis... and as a dedicated laser machine it really isn't necessary. But, of course, I prefer having a functional Z-axis, so I stole the printed linear stepper slide assembly (https://www.thingiverse.com/thing:2813896) from my CoreXY machine and fastened it to the acrylic tool plate.

-- David
David,

I would like to add a laser to my MPCNC to cut plywood for my firewalls and control horns. Would this laser be able to cut 3/32 hobby plywood?
https://www.banggood.com/EleksMaker...s=detail-left-hotproducts__7&cur_warehouse=CN

I experimented with the blackstripes extension with the needle cutter. I would like to try it out with a laser now.

Thank you for your input,
Britt
 
It's not going to cut thin ply very easily. I bought a 3.8W laser from JTechPhotonics with the idea of cutting thin ply and feel that 3.8W is probably the minimum for the job. It still takes too many passes for my taste. I wish I had the option to buy their new 7W laser, despite the cost jump between the models, but it wasn't available when I bought mine. Banggood has a 7W for $299. I'm sure you can find a happy medium in there. But 7W will cut thin ply fairly quickly. It comes down to how many passes you're willing to put up with.

A laser from JTechPhotonics isn't as inexpensive as Banggood. But their service and support is fantastic. I feel that they have a safer product as well.
 

jhitesma

Some guy in the desert
Mentor
The problem with the higher wattage diode lasers is that the spot size gets larger unless you spend enough to get into CO2 laser range. And spot size is key to good cutting. Not only for accuracy, but also for cutting power.

This page has a great explanation: http://www.parallax-tech.com/faq.htm

The relevant parts of the page for this discussion are:
Let us say you have a 50 Watt laser. Let us also say that the 50 Watt beam of this laser, measured at about one (1) meter away from the laser head, has a beam diameter of 6 mm =1/4 inch. The area of a 6 mm circle is 28 sq mm. Hence your beam at that position has a power density (called intensity) of 50/28 =1.8 Watt per sq mm (or an intensity of 180 Watt/sq cm).

If there was something you could cut with this intensity, say some kind of thin plastic, then (a) the width of the cut would be 6 mm (one diameter) wide, which would not be a precision cut, and (b) you would have to go rather slow, which would then allow heat of the beam to propagate and set things on fire and that would not be good either!
It is like slicing bread with a very wide and dull knife.

Let us say you could turn a knob and increase the power of your laser to 500 Watts! Then we know that you spent upwards of $50,000 on this laser and both (a) and (b) above are still problems.

Maybe it would be easier, cheaper and wiser to reduce the area of the beam. That of course is done by using a lens in front of the beam. If you get a lens that can reduce the beam diameter from 6 mm to 0.6 mm ( i.e. 10 times smaller) the area would become 100 times smaller and therefore the power density (intensity) would be 100 times larger or 18,000 Watts per sq cm or 180 Watts per sq mm! Now we are up to something.
I've used my 3w diode to cut ply...and it's tedious. I needed 5 passes with air assist to cut 1/8" ply. It worked...but it took a long time and isn't something I'm in a rush to try again. I've seen others have better luck - so there could be some variation in material and lens and power settings...but overall the diode lasers just aren't great for cutting. The "40w" chinese laser I'm currently playing with goes through ply WAY easier faster and cleaner and I haven't even finished dialing it in yet. But...a cheap chinese laser isn't going to do as much as a CNC, and is going to require a lot of of work and expense to make a usable machine...and still won't be big enough to do foam board. Mounting a CO2 tube and power supply to a CNC is possible...but tricky to so safely.
 
Air Assist is definitely on my To-Do list. 5 Passes isn't a horrible number. I don't know squat about laser theory. So if you can do 1/8" in 5 passes with a 3W laser, shouldn't you be able to reduce the number of passes by (aprox) 50% if you increase the power by 50%?

After reading your post, I checked the specs on the JTech 3.8 and 7w laser kits. Spot Size = 0.011 on both. 6mm spot size? Death Laser?
I don't see myself needing a CO2 laser anytime soon.

Also, from what I've read on Banggood https://www.banggood.com/EleksMaker...-p-1127310.html?rmmds=search&cur_warehouse=CN and elsewhere, 7W laser can even mark stainless and aluminum. That would be plenty enough for me. But I'm very nervous about Banggood at $300 and choking on JTech at $625.