CNC Needle Cutter

An area to discuss model engineering outside of general balsa and foam bashing
Post Reply
Site Admin
Posts: 171
Joined: Mon Dec 17, 2012 4:45 pm

CNC Needle Cutter

Post by Colin » Wed Nov 23, 2022 2:54 pm


For a while I had been wanting to expand into CNC manufacturing of model parts following experiences with 3D printing.

David Cowley had very generously lent me his CNC milling machine to experiment with and I had managed to produce foam ribs and ply parts without too much trouble.

This was a typical ebay Chinese hobby machine and it worked well, the main problem I found was simply due to the size limitations - I could not cut a decent sheet size.

I handed the machine back to David and put the project on hold until I sorted out my garage and put in a second bench.

Move forward 18 months and now I was in a position to pick this up again so started to look around. Remembering the size issue I had three options -
  • Buy a larger machine - raises the initial costs
  • Buy a smaller unit and replace the frame - wasted materials
  • Build from scratch - gives most flexibility and bang/buck
The third option was the favourite and so I started to look online for ideas and answers - for example, do I go for milling or laser?

With regards to this question whilst laser was an interesting proposition there were two major problems. Firstly the cost, and secondly certain materials are problematical owing to their reflectivity e.g. white foam.

(There is a solution to the second problem in that the foam could be sprayed dark to begin with, or else covered with dark paper prior to cutting.)

On balance I decided to go for a machine where I could start off with a milling solution and then add on a laser module at a later date and so started looking at articles on this and this is when I came across the concept of needle cutters...

Site Admin
Posts: 171
Joined: Mon Dec 17, 2012 4:45 pm

Re: CNC Needle Cutter

Post by Colin » Wed Nov 23, 2022 3:06 pm

Needle cutters explained

The concept of needle cutters is very simple. Think of a sheet of postage stamps and how a stamp is separated by tearing the perforations. Well if the perforations could be done in the shape of a part then a part could be torn off the same way.

And if the perforations could be very close together so they are actually touching, or even overlap, then the parts would not be perforated, they would actually be cut and this is what happens with a needle cutter.

The perforator itself is actually a needle attached to a regular brushless motor driven via an ESC. This is attached to a head running on XY arms controlled by an Arduino CNC controller.

By using a motor speed of around 8000 rpm and a feedrate of 600 mm/min the perforations come out as a continuous cut line.

There are a few designs out there but mine is based on the design by Edward Chew published on Thingiverse at

Site Admin
Posts: 171
Joined: Mon Dec 17, 2012 4:45 pm

Re: CNC Needle Cutter

Post by Colin » Wed Nov 23, 2022 3:12 pm

ERC TimSav

With Edward's design the main parts are all 3D printed from PLA and uses 4020 and 2020 aluminium extrusions for the XY arms. All necessary files are on thingiverse to download.

He has done a video here to give an overview...

Site Admin
Posts: 171
Joined: Mon Dec 17, 2012 4:45 pm

Re: CNC Needle Cutter

Post by Colin » Wed Nov 23, 2022 5:16 pm

My initial version

I will not describe the build itself as Edward's videos do a far better job and I built exactly as per his design other than the arms which I made 1m and 0.5m to fit my bench. This gave me a cutting area of 860mm x 340mm.

The actual process of getting a plan to the cutting stage I will describe in later posts - I will simply focus on the mechanical side here.

So version 1 is built and working but I encountered a few problems...
  • Needles breaking
  • Needles being thrown
  • Sloppiness in positioning
  • Problems in continuing jobs following a needle issue
Needles breaking
The needles are made from sharpened lengths of 0.6mm piano wire which I used straight from my stock and I found that I would be lucky to get them to last more than one session. The piano wire was obtained from model shops and shows and I tried a number in case I was using a particularly brittle item.
The solution was in the local B&Q where I found that they stocked 0.6mm piano wire in 34m reels. Since using this I have only had one needle break and that was after around 8 sessions.
Not only is the wire more durable, it is also a lot cheaper. From SLEC a 3' length is 52p (58p/metre) whereas a reel from B&Q is £4.20 (12p/metre).

Needles being thrown
As designed the motor has a flywheel fitted with 2 small bearings. The needle is attached by fashioning a loop at the end of the needle and then fitting that over the end of the bearings.
53baef25c0498a1ba9222d3d8b1e387f5b727755_2_666x500.jpeg (145.68 KiB) Viewed 405 times
The issue is the loop. Initially i found it hard to make the loops consistent using pliers or a mandrel. I invested in some round nose plies which sorted that problem but the issue was then that the loop was hard to get on the bearings when made to the correct size, or didn't grip the bearings properly if slackened off.
The answer was to modify the flywheel to use a link stopper as used in small models to attach pushrods. This gave two benefits - firstly attaching was simpler and more secure, and secondly meant that needle length was no longer an issue as it could be easily adjusted in situ.

Sloppiness in positioning
I found that the gantries downloading from Thingiverse were not quite right for my extrusions so the wheels could not be really tight against the extrusions. This meant that the end of the Y arm had demonstrable play here.
This was resolved through the use of eccentric nuts which could be adjusted to take up this slop.

Problems in continuing jobs following a needle issue
The problem was that my cutter was not fixed to my bench unlike the foam which was taped down. This meant that when replacing the needle it was easy to knock the relative positioning. The answer, not yet implemented, is to fit the cutter to a baseboard that also holds the foam.

So now I have a reliable cutter so it's on to the process of going from plan to parts...

Site Admin
Posts: 171
Joined: Mon Dec 17, 2012 4:45 pm

Re: CNC Needle Cutter

Post by Colin » Fri Dec 02, 2022 11:54 am

Now we come to the complicated bit where we go from plan to cut parts which will take quite a while to write up. In this first post I will describe the steps required and then list the software that I use.
Following posts will focus on each step in detail.

Of necessity the flow involves a number of stages...
  1. Obtain digital plan of model
  2. Convert it to DXF format,.
  3. Manipulate the plan to fit the cutter
  4. Create the cutting plan
  5. Convert the DXF to gcode
  6. Send the gcode to the cutter
For steps 2 to 4 I use a combination of Inkscape and Fusion 360.
For step 5 I use dxf2gcode and for the output to the cutter I use Universal Gcode Sender
Links for all these are below. There are alternatives and I will discuss these in the relevant posts.

Inkscape -
Fusion 360 -
dxf2gcode -
Universal Gcode Sender -

All these are free and well reviewed.

Site Admin
Posts: 171
Joined: Mon Dec 17, 2012 4:45 pm

Re: CNC Needle Cutter

Post by Colin » Fri Dec 02, 2022 1:01 pm

Obtaining plans
There are thousands of plans out in the internet so the challenge is knowing where to look.
If you are looking for a specific model, then remember Google is your friend. As an example, let's say I wanted to build Ed Kazmirki's 'Taurus'.
I simply put 'taurus rc plan' into Google, and the very first entry that comes up is what i am looking for...
plan search.jpg
plan search.jpg (231.61 KiB) Viewed 328 times
Alternatively there are a number of sites that host collections of plans. A list of these is below.

Ideally you should look for PDF or DXF plans rather than bitmaps, (jpg, png, bmp etc). This is because PDF plans are often cleaner and more accurate, whereas bitmaps are usually just scans of paper plans which may need a lot of cleaning up.

Some of these are free, some need subscription or membership. There are a great many more, and google can take you to them, so I am just listing those that I have actually used as a source. Some cover all aspects of aeromodelling, some focus purely on RC foam... The last one on the list is run by a chap called Julius Perdana who is an Indonesian graphic designer. He has a YouTube channel well worth watching as examples of what scratchbuilt foam aeromodelling on a limited budget can achieve. Take a look at this for instance

Post Reply