Cutting foam sheets... with a needle!

FlyerInStyle

Elite member
the problem is I do not have a 3d printer
and am looking for some service that will make it cheaper then buying a 3dprinter and printing it all.
 

dkj4linux

Elite member
I'd suggest getting onto the ERC FB group (and peruse the FT thread) to see what others -- without a printer -- are doing. I'm sure this isn't an uncommon problem.

If you are an avid DIY'er, a 3d printer is IMO the single most valuable tool in your toolbox... and well worth looking into getting. Beyond my earliest machines, I couldn't have done any of the machines/mechanisms I've done in this thread without one. Please note also that though Edward has made a monumental effort to document his machine and provide step-by-step direction to build it... it is still a DIY project, i.e. not so much a traditional "kit" as a collection of all the parts necessary to build/duplicate his machine.
 
Last edited:

iGull

New member
Anti-Gravity Foam Wing Cutter Controller

Hi All

Probably not the place to post this (it's the only thread I know with intelligent folks in it :) ), but for now, I'll put it here to see if there's any interest - if so, I'll do up some schematics and stuff and move it to where it might need to be .

It's been a while since I visited this thread and much has happened since. I didn't completely waste my current lockdown .
This is a quick show of what is in essence, an electronic emulation of a gravity drop-arm foam cutter (similar to the old Tekoa style of arm).
The original cutters had a weighted drop arm calculated in percent - to which were attached cables/clips and a multitude of pulleys and wheels.
There was much 'faffing' about swapping cables over when you had finished doing one wing then swapping to the other - this just has a button.

This IS NOT a CNC controller - more a kind of mandraulic controller  I haven't seen anything like this around, otherwise I would have made one - let me know if this is the case !

I've attached a couple of pix and a link to an amateurish video to show the operation. The metre stick in the video emulates what would be the hotwire bow with a foam block to be cut in front of it (tip set at 75% chord of the root) - there would be aerofoil templates either side of the block for the hotwire to ride on of course.
The controller is an arduino nano with a couple of A4988 stepper controllers - a few pots and pushbuttons - plus the ubiquitous 3D printed enclosures and parts of course  Motors are just a pair of nema17's I had lying around (as with the rest of the parts really). Version 1 used geared motors (el cheapo  ) - worked perfectly except that at slow speeds, the motors had too much stiction and occasionally stopped. I tried various cheap motors - all the same really. A pair of ultra expensive swiss geared maxxon motors worked perfectly of course :mad:
Version 2 is what you see here.
Control is simple, setup you motors/cords across the width of the foam block, set the basic hotwire speed then dial in the (pre-calculated) ratio of the root to the tip (root is always 100%), switch on the hotwire and hit start. Wait until it exits exactly parallel to the trailing edge, then hit stop. Rinse and repeat for the bottom template. For the opposite wing, same thing, setup your hotwire again, press the swap button (swaps root/tip speeds) then hit start again.
Root to tip ratios are not as simple they sound, there are MANY other things to take into consideration ! I wrote an app around 20 years ago to do this very job and it's still just as valid today (I had a set of plans for an agricultural mechanical version of this controller on my old website back then). It was written in RealBasic (nee Xbasic) - it's now called Xojo (why???) I have the code repaired in the latest version, but no longer own a licence - it can compile to mac/pc/web/android/ios etc these days. You can run it in the IDE (it's free to do anything, just can't compile sans a licence) - if you have a licence, that might be useful to the community .

Let me know if there is any interest in this project.

Cheers

Neil

Link for video ...

 

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CartCurt

Member
Anti-Gravity Foam Wing Cutter Controller

Hi All

Let me know if there is any interest in this project.

Cheers

Neil

I would be interested in this type of project. I was looking at the old gravity system. Always looking for something new to try.

Curtis
 

FlyerInStyle

Elite member
Anti-Gravity Foam Wing Cutter Controller

Hi All

Probably not the place to post this (it's the only thread I know with intelligent folks in it :) ), but for now, I'll put it here to see if there's any interest - if so, I'll do up some schematics and stuff and move it to where it might need to be .

It's been a while since I visited this thread and much has happened since. I didn't completely waste my current lockdown .
This is a quick show of what is in essence, an electronic emulation of a gravity drop-arm foam cutter (similar to the old Tekoa style of arm).
The original cutters had a weighted drop arm calculated in percent - to which were attached cables/clips and a multitude of pulleys and wheels.
There was much 'faffing' about swapping cables over when you had finished doing one wing then swapping to the other - this just has a button.

This IS NOT a CNC controller - more a kind of mandraulic controller  I haven't seen anything like this around, otherwise I would have made one - let me know if this is the case !

I've attached a couple of pix and a link to an amateurish video to show the operation. The metre stick in the video emulates what would be the hotwire bow with a foam block to be cut in front of it (tip set at 75% chord of the root) - there would be aerofoil templates either side of the block for the hotwire to ride on of course.
The controller is an arduino nano with a couple of A4988 stepper controllers - a few pots and pushbuttons - plus the ubiquitous 3D printed enclosures and parts of course  Motors are just a pair of nema17's I had lying around (as with the rest of the parts really). Version 1 used geared motors (el cheapo  ) - worked perfectly except that at slow speeds, the motors had too much stiction and occasionally stopped. I tried various cheap motors - all the same really. A pair of ultra expensive swiss geared maxxon motors worked perfectly of course :mad:
Version 2 is what you see here.
Control is simple, setup you motors/cords across the width of the foam block, set the basic hotwire speed then dial in the (pre-calculated) ratio of the root to the tip (root is always 100%), switch on the hotwire and hit start. Wait until it exits exactly parallel to the trailing edge, then hit stop. Rinse and repeat for the bottom template. For the opposite wing, same thing, setup your hotwire again, press the swap button (swaps root/tip speeds) then hit start again.
Root to tip ratios are not as simple they sound, there are MANY other things to take into consideration ! I wrote an app around 20 years ago to do this very job and it's still just as valid today (I had a set of plans for an agricultural mechanical version of this controller on my old website back then). It was written in RealBasic (nee Xbasic) - it's now called Xojo (why???) I have the code repaired in the latest version, but no longer own a licence - it can compile to mac/pc/web/android/ios etc these days. You can run it in the IDE (it's free to do anything, just can't compile sans a licence) - if you have a licence, that might be useful to the community .

Let me know if there is any interest in this project.

Cheers

Neil

Link for video ...

what is that even for?
 

FlyerInStyle

Elite member
LOL, for cutting foam wings - here's a random vid link from youtube, you can see all the cables and drop arm from the old Tekoa setup.
My system does away with all the mechanics.


Cheers

Neil
oh sorry did not really realize that straight away. just saw the ruler and was confused
 

Dudley1001

Member
most led lasers will not cut the white foamboard, it will cut the top paper layer and that's about it. The white foam just disperses the laser. Black foamboard with black foam core cuts fine on my 7.5 watt output neje laser. This are my findings, other may vary.
 

RHill051

New member
Does anyone else use CNC.js to control their CNC? I'm asking because I'm curious if there would be any interest in me sharing how I set up CNC.js and my Raspberry Pi to send a push notification to my cellphone when the CNC finishes cutting out a sheet of foam. I've been using it for a few days now and it is sooooo nice being able to start a sheet and leave the room to do other chores and then when I get the update on my phone I just go swap a new sheet onto the CNC and repeat. I'm sure it's possible to do something similar if you use Octoprint but I haven't looked into it. If there is interest I'll work on putting together a short'ish how-to
 

dkj4linux

Elite member
I use CNC.js and Grbl to control most of my DIY machines... but I use the v1pi image from Jeff Eberle (@jeffeb3) of V1Engineering/MPCNC fame. It has CNC.js and Octoprint both pre-installed, comes in hotspot and non-hotspot versions, and it's very convenient and easy to set up and use.

Your push notification really sounds neat. Are you needle-cutting?

I'm not an alarmist but, since I don't know you or your setup, I feel I need to add a word of caution here... I often ran my needle-cutters pretty much unattended -- or at least within earshot -- and never had a mishap; i.e. I got away with it. I also trust my 3d-printers enough to run unattended quite often. But I DO NOT recommend unattended operation, however, of any other CNC machine -- router, laser, etc. -- because of the inherent fire hazard it presents. I've been in the CNC "game" long enough and frequent enough forums to know that the fire hazard is real and can be catastrophic. Please take care.

BTW... welcome to the party! Tell us more about yourself and what you're up to.

-- David
 

RHill051

New member
I use CNC.js and Grbl to control most of my DIY machines... but I use the v1pi image from Jeff Eberle (@jeffeb3) of V1Engineering/MPCNC fame. It has CNC.js and Octoprint both pre-installed, comes in hotspot and non-hotspot versions, and it's very convenient and easy to set up and use.

Your push notification really sounds neat. Are you needle-cutting?

I'm not an alarmist but, since I don't know you or your setup, I feel I need to add a word of caution here... I often ran my needle-cutters pretty much unattended -- or at least within earshot -- and never had a mishap; i.e. I got away with it. I also trust my 3d-printers enough to run unattended quite often. But I DO NOT recommend unattended operation, however, of any other CNC machine -- router, laser, etc. -- because of the inherent fire hazard it presents. I've been in the CNC "game" long enough and frequent enough forums to know that the fire hazard is real and can be catastrophic. Please take care.

BTW... welcome to the party! Tell us more about yourself and what you're up to.

-- David

I completely agree with the word of concern/caution surrounding the importance of being aware of what is happening with the CNC. Correct me if I'm wrong but there isn't really any way for the needle cutter to fail catastrophically causing a fire. The only issue I've ever run into with my needle cutter is the needle flying off the bearing which has ruined a sheet of foam but that was it. I share a similar opinion of my 3D printer running unattended. I have my CNC set up using the V1Pi Image as well and Marlin. I also have a spindle that I've swapped onto my CNC but that is always run where I can watch and abort any unexpected behavior.

I've dropped in here with a few questions before. I'm very grateful for all the help this group and thread have provided. I've been able to get my CNC set up so it will auto start both my shop vac and my need cutter at the same speed every time I run a job and I also recently added a small fan to the bottom of my need cutter to direct cool air over the copper welding tip to help keep it cool which I think prevents the foam dust from melting inside the tip and then jamming the needle causing a job failure. (The fan is literally zip-tied to the bottom of my needle cutter lol but it works sooooo well)

PXL_20210518_145655342.MP.jpg

Link to an album of my CNC https://photos.app.goo.gl/pcE4hQ4qc8MfRX6fA
 

dkj4linux

Elite member
I completely agree with the word of concern/caution surrounding the importance of being aware of what is happening with the CNC. Correct me if I'm wrong but there isn't really any way for the needle cutter to fail catastrophically causing a fire. The only issue I've ever run into with my needle cutter is the needle flying off the bearing which has ruined a sheet of foam but that was it. I share a similar opinion of my 3D printer running unattended. I have my CNC set up using the V1Pi Image as well and Marlin. I also have a spindle that I've swapped onto my CNC but that is always run where I can watch and abort any unexpected behavior.

I've dropped in here with a few questions before. I'm very grateful for all the help this group and thread have provided. I've been able to get my CNC set up so it will auto start both my shop vac and my need cutter at the same speed every time I run a job and I also recently added a small fan to the bottom of my need cutter to direct cool air over the copper welding tip to help keep it cool which I think prevents the foam dust from melting inside the tip and then jamming the needle causing a job failure. (The fan is literally zip-tied to the bottom of my needle cutter lol but it works sooooo well)

View attachment 200356
Link to an album of my CNC https://photos.app.goo.gl/pcE4hQ4qc8MfRX6fA
We're on the same page here. The needle-cutter is such a delicate/fragile tool that almost certainly the worst that can happen is the needle goes flying and/or the guide drags, and the foam sheet is spoiled. The only high-speed part is the flywheel/motor and it's pretty safely out of the way and represents IMO a very miniscule fire risk. I've built probably 100+ needle cutters over the past 11+ years, during its development, and not a single fire has ever occurred so I grew pretty comfortable letting it "hum" away in another room... and trusting a distinct change in the sound to alert me to something amiss.

Lasers and the high-speed rotation of the collet on a powerful router/spindle OTOH can easily start a fire however and IMO are the primary reason to remind ourselves -- and others -- that unattended operation of our machines is generally not a good idea and caution should be exercised.

Since I'm talking to another MPCNC'er I know you are aware of all the great folks and advise to be had over on the V1Engineering site. I love your Primo and its enclosure. I never achieved a setup so refined as I ultimately seemed more interested in building the machines themselves than in using them to produce planes... though early on, my late fishing/golfing/flying buddy and I needle-cut, built, flew, and crashed whole fleets of foamy aircraft out in my pasture. What great fun we had!

Those days are now gone however... and, at this late date, I'm pretty much out of the needle-cutting business. I do keep up with what's going on here but, thankfully, the needle-cutter idea took on a life of its own and there are now many folks out there who use and support it... and I've been able to retire.

Thanks for dropping in over here and sharing your setup.

-- David
 

RHill051

New member
Absolutely :) as I mentioned I got a lot of help looking back through this thread and since a lot of people here might have come looking for advice specifically on the needle cutter (though I know there has been a lot of talk surrounding lasers lately) I thought I'd see if anyone else was interested in knowing how to get push notifications. So for those who are interested here it goes:

The process of getting the push notifications integrated into CNC.js involve:
  • Setting up a free account on "Pushover"
  • Downloading the free app for either Android or iOS
  • Creating a python script on the Pi
  • Adding an "event"
So first as I mentioned you would want to go over https://pushover.net/ and create a free account. Then download the free mobile app where you'll be able to find your "User Key" in the settings area. (This is used to tell pushover what device to send the push notification to). While you are still at the pushover site you will also need to create an "Application". While you are logged into the site you can scroll to the bottom of the home page and select "Create an Application/API Token" as shown in the blue here below.

1621362016248.png


All you really need is a name but if you want to give your CNC a custom logo I believe that will be displayed next to the push notification when you receive them. For my CNC I just called it "CNCjs" to keep it simple.

Now that you have the application you also have an API Token that will be used in the python script next. For these steps, you will have to make changes on the raspberry pi that CNCjs is running on. I'm assuming you are able to do this either directly on the Pi or over an ssh connection with something like PUTTY. You can create the python script by executing the command
Code:
nano [name of your file].py
There is an example of a python script on the Pushover site:
Python:
import httplib, urllib
conn = httplib.HTTPSConnection("api.pushover.net:443")
conn.request("POST", "/1/messages.json",
  urllib.urlencode({
    "token": "APP_TOKEN",
    "user": "USER_KEY",
    "message": "hello world",
  }), { "Content-type": "application/x-www-form-urlencoded" })
conn.getresponse()
You will want to change the values for the "token", "user", and "message" for your situation. I changed the "hello world" of the example to "CNC job is complete." as an example. Now you should be able to save the file and move on to the next step which is getting the file path and using that in the event we will create in CNC.js. A sure-fire way to make sure you have the right file path for your script is to execute the following command. (if you don't use the absolute file path the event won't be able to execute the file, ask me how I know lol)
Code:
readlink -f [name of your file].py
This will give you the absolute path of the file so you can execute it from the event. Copy that path and head over to CNC.js.
  1. Open the "Settings"
  2. Select "Events"
  3. Click "Add"
1621363612158.png

You want to select "G-code: Stop" for the Event and then "System" for the Trigger and past in the Linux command unless your file path is different. This is the home of my python script as seen in the below screenshot.
Code:
python /home/pi/[name of your file].py
1621363650490.png

Now, as long as the event is enabled you will get a push notification as soon as CNC.js completes a gcode file. In the tests I've done the push notification is almost instant but could vary slightly due to wifi/cellular connections.
 

RHill051

New member
Hello guys, So I'm a bit stumped. I was running my needle cutter pretty much flawlessly for a total of maybe 30 sheets of foam? and then I took it off to cut some wood with my spindle. I decided to put it back on for a few more planes this past week and made a modification to my vacuum board that included a few bolts holding the corners down but I didn't recess them enough and my needle hit it which bent it and cause the bearing to seize and melt the flywheel (it is a flywheel right?). I have since replaced the wheel with a new one and for the life of me, I can't get a needle to stay on.. I have snapped several needles now and I don't know what is causing it. The last two broke right on the bearing leaving a little ring of wire around the bearing. I suspect my bearing are just garbage because there is a ton of play in them. Maybe I'm not maintaining them correctly or maybe they are just not good enough for the high 9500rpm they are running at. I was wondering what others use for bearings or if anyone else has noticed the bearing on their needle cutter being super sloppy. I've thought of just buying a really nice one like the ones that are used on racing drones but I don't know if it would survive the needle cutter conditions. Any advice/feedback is greatly apprecieated.
 

Dudley1001

Member
try taking off the top 2 bearings and you may want to try a printed needle holder such as THIS. The 6mm bearings are made very cheaply and can wear out. Some rc helis use them and they are usually a better quality. Lubing the bearing can help before use but once they are worn, they are garbage.
 

kilroy07

Legendary member
Hello guys, So I'm a bit stumped. <Snip>. Any advice/feedback is greatly apprecieated.
I would suspect the bearings. I once got a bad batch from Banggood (Which I refuse to buy from any longer) and they felt rough right out of the package. They went in a 3D printer project I was working on and within a week they literally disintegrated. It was almost as if the bearings were made of powder. Bearings like that would last minutes if not seconds in an application like an needle cutter.

For such a critical component of your setup, it might be well worth spending a bit more coin on some quality bearings.
 

Dudley1001

Member
The other bearing to watch is the front bearing inside the motor. I toasted the shaft and bearing on mine. Luckily the motors are cheap. The vibration and impact load probably took its toll on it. I had cut close to 100 sheets on it and my balance on it wasn't the greatest. The motor was still running but noisy and when I checked it ,the bell had side play and found a worn out shaft with about 1mm of wear on one side of the shaft
 

sirjaymz

Member
...snipt...
I can't get a needle to stay on.. I have snapped several needles now and I don't know what is causing it. The last two broke right on the bearing leaving a little ring of wire around the bearing.
...snipt...

I ran into this same problem... so I created the different flywheel, using the same bearings as you are using, but the attachment is different and is a friction fit, versus the ;wrap around the bearing' method. I have NOT broke a needle since I created this and started using it.