Cable cutting machine

KamBys 22 Dec 2024 11:04 21 4521 Cool? (+25)

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TL;DR

A wire cutting machine for model railway electronics cuts kynar wire to a set length and quantity.
It uses an Arduino Nano CNC shield with two stepper motor controllers, a 16x2 I2C display, and a membrane keyboard.
The BOM includes an Arduino Nano for 10 zł, a CNC Shield for 12 zł, and 2x stepper motor with cables for 22 zł.
A modified 3D-printer extruder feeds the wire, scissors make the cut, and the firmware repeats the cycle while trimming the first excess section for accuracy.
The cutting motion should be reversed downward to stop fragments scattering, and the enclosure still lacks space to store the power supply.

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For my own purposes, I made a wire cutting machine to complement the electronic boards I offer for model railways. The premise was to cut the wires to a set length and quantity.

Electronics .
To speed up the build, instead of making a PCB I used off-the-shelf solutions: a CNC shield for an Arduino nano with two stepper motor controllers. To this attached after I2 a 16x2 display and a membrane keyboard (ready-made from Alliexpress).

Mechanics .
After reviewing similar solutions, I decided to feed the wire with the mechanics of an extruder from a 3D printer. As the kynar is thin and quite delicate, the drive had to be modified: the toothed roller has grinded teeth, and instead of a concave roller I put a bearing. To prevent the kynar from slipping off the rollers, I glued a truncated meat injection needle onto the input. On the exit, instead of a piece of bowden - a piece of pen nib. The last two modifications ensured stable guidance of the flexible cable.

I carried out the cutting with scissors - a very important advantage of this solution is that after cutting you can continue with the closing movement of the pliers, unlike with typical clippers. There are Stanley clippers available, or replacement clippers that work with scissors, but I don't need to cut thicker wires, plus the scissors were easy to attach. Scissors without handles mounted in a 3D printed mount, the movable arm has a handle instead of a handle, which is articulated to a wheel attached to a stepper motor. The motor is arranged so that it can perform a full rotation freely. The whole, unlike the solution based on clippers, is not sensitive to the wear of the mechanism, its play, etc. (the scissors do not close at zero, they make a further movement, which will always eliminate tolerances, the influence of wear, etc.).
Motor mounts from 3D print, Roller on kynar - 3D print reinforced with M3 pin. Display and keyboard in canopy 3D print, all encased in foamed PVC.

Firmware .
The display shows a menu where you select the variant to be cut, then the number of wires or sets per board. In the next step, the program moves the wire according to the preset length and then the stepper motor responsible for cutting performs a full rotation. The cycle repeats itself a pre-programmed number of times, and the start of the programme always begins by cutting the excess wire so that the first section is exactly the set length.
The last menu item allows the length of the sections to be cut to be specified manually.

What I would change .
I would reverse the cutting motion - so that the movable arm cuts downwards rather than upwards - here I needed to eliminate the scattering of cut fragments by the canopy tray catching the tossed fragments.
At the back of the case I would have given space for the power supply, so as to store the whole thing in a compact form.

BOM
Arduino Nano 10 zł
CNC Shield 12 zł
2x stepper motor controller 18 zł
display 1602 with I2C expander 10 zł
membrane keyboard 5 zł
2x ENema17 stepper motor with cables 22 zł
12 V power supply from demobilu
scissors from demobilu
M3 screws, washers, nuts from drawer
2 sheets of foamed PVC 60 zł
(prices from alliexpress, allegro)

A video of how the device works:

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Assembled device:

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Kynar feed drive:

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Cutting drive:

Cutting drive.

Entire mechanism:

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Back of case

About Author

KamBys wrote 805 posts with rating 39 , helped 32 times. Live in city tczew. Been with us since 2003 year.

Comments

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gulson 22 Dec 2024 11:18

Thank you for sharing an interesting design! Are you using the cut wires in any way more wholesale? Or is it more of a machine for the purpose of testing yourself and your capabilities? Has there been... [Read more]

TechEkspert 22 Dec 2024 13:06

Very interesting! A lot of experience can be gained from such practical realisations, and in the future you can think, for example, about miniaturising solutions and increasing their durability when, after... [Read more]

slaw0 22 Dec 2024 18:41

Doesn't this feeder imprint teeth on the cable? [Read more]

KamBys 23 Dec 2024 08:46

. I cut about 100 pcs a week - the amount I use for my semi hobbyist production of electronics for models. This is perhaps not a prototype, but rather a one-off pilot series. As something comes out in... [Read more]

michasinny 23 Dec 2024 23:50

Hey. Super project and cool that you are sharing your knowledge with the rest of your colleagues. Thanks. Have a healthy and peaceful Christmas. Hi. Michael. [Read more]

rb401 24 Dec 2024 02:17

. Your build is beautiful, carefully crafted and impressively worked. I like it very much. But somehow I don't see the practical sense of e.g. saving time or increasing production efficiency, with such... [Read more]

KamBys 24 Dec 2024 08:40

. Well, and I can see - as far as my case is concerned, it's quite a convenience for me, it takes me off a laborious, boring job that I simply don't like. And this is where the greatest added value lies... [Read more]

clubber84 24 Dec 2024 08:42

Hello. . And this is where I see the first (quite serious) wear and tear in this razor - the cutting surfaces will quickly dull/chip in this one spot. I suggest using a guillotine-style cutting mechanism... [Read more]

KamBys 24 Dec 2024 08:49

. Nothing like this is occurring at the moment, and I used the scissors deliberately: - The kynar is thin, I don't cut anything thicker than that. - Typical knives for cutting in this type of machine:... [Read more]

clubber84 24 Dec 2024 09:04

And see, now I know you haven't explored the subject of cutting. I was writing about the guillotine mechanism, where nothing is clamped (it doesn't work like a sheet metal or paper cutter) just cooperates... [Read more]

KamBys 24 Dec 2024 09:13

And you see, now I know that after 12 years the electrode does not fail. :D . I know perfectly well what you wrote about and I referred in the second dash to it. [Read more]

clubber84 24 Dec 2024 09:19

OK, in that case you used scissors because typical guillotine mechanisms were too expensive. But. In your scissors drive solution, a guillotine made of two stainless steel plates with a notch to match... [Read more]

TechEkspert 24 Dec 2024 10:54

Here https://www.elektroda.pl/rtvforum/topic4077229.html I have had the opportunity to test and pass on for testing wire cutting scissors, they have a serrated surface and I suspect are suitably hardened.... [Read more]

KamBys 24 Dec 2024 11:22

. I considered this, even drew the mechanism (prototypically I wanted to use blades from trapezoidal knives), but more time, complication of the system (ensuring free movement while pressing the blades... [Read more]

clubber84 24 Dec 2024 11:57

. With this cable cross section, the current solution (free arm on the wheel) would calmly suffice. One guillotine blade fixed, the other movable, on guides, coupled to the arm or to a scissor mechanism... [Read more]

rb401 25 Dec 2024 05:50

. I understand this aspect of weariness perfectly. But I still feel a serious dissonance between the number of cut episodes you write about and the reported tedium. I simply don't understand how one can... [Read more]

KamBys 25 Dec 2024 09:49

. Propulsion is not a problem, some issue (as I wrote) would be to build the mechanism so that the blades rub against each other to pick up the slack in between, while at the same time not providing much... [Read more]

jajacek44 25 Dec 2024 10:50

In the manual wire preparation machine for mini-winding by O.K. Industries scissors were just used to cut the kynar. https://obrazki.elektroda.pl/6319229100_1735120175_thumb.jpg . [Read more]

sukovenkoartem 02 Jan 2025 17:07

I'll be honest, it's much more convenient to do it the traditional way. [Read more]

FAQ

TL;DR: For small-batch electronics work, this DIY cable cutting machine automates about 100 wires per week and, as the builder put it, "it takes me off a laborious, boring job." It uses an Arduino Nano, CNC Shield, 2 stepper drives, a modified 3D-printer extruder feed, and scissors to cut thin Kynar wire to preset lengths without a PC. [#21360822]

Why it matters: This design shows how a low-cost, fully offline wire cutter can remove repetitive manual work and improve repeatable wire length in semi-hobbyist electronics production.

Approach	Main advantage	Main drawback	Best fit in this thread
Scissors on stepper wheel	Simple mounting, easy replacement, tolerates wear/play	May wear at one cut point over time	Thin Kynar, current build
Side cutters / clippers	Familiar tool format	Crimping action was rejected here	Not preferred for this machine
Guillotine blades	Higher durability potential	More complex blade guidance and preload	Considered for a later redesign
Specialty fiber/wire cutters	Likely harder cutting edges	Higher cost, lower availability	Optional upgrade path

Key insight: The most important design choice was not the controller but the wire path: blunted drive teeth, a needle guide at entry, and a pen-refill guide at exit made thin, flexible Kynar feed reliably enough for repeatable cuts. [#21358409]

Quick Facts

Approximate BOM cost was 137 zł plus a 12 V power supply and scissors from surplus: Nano 10 zł, CNC Shield 12 zł, two stepper drivers 18 zł, 1602 I2C display 10 zł, keypad 5 zł, two NEMA17 motors 22 zł, and foamed PVC 60 zł. [#21358409]
The machine was sized for about 100 wire pieces per week, and the builder estimated it saves about 30 minutes weekly, or about 25 hours per year. [#21360822]
The cutter is fully offline: menu selection happens on a 16x2 display with membrane keypad, without needing a computer during normal use. [#21358432]
Mechanical guides were improvised but specific: a trimmed meat-injection needle at the feed entry and a piece of pen refill at the exit stabilized the thin wire path. [#21358409]

How was this cable cutting machine built using an Arduino Nano, CNC Shield, two stepper drivers, a 1602 I2C display, and a membrane keypad?

It was built from ready-made modules instead of a custom PCB. The controller stack uses an Arduino Nano on a CNC Shield with 2 stepper motor drivers, plus a 1602 display over I2C and a membrane keypad. One stepper feeds the wire, and the second stepper drives the cutting mechanism. The builder chose these parts to speed construction and keep the machine independent from a PC during normal work. [#21358409]

What is Kynar wire, and why does it need a modified feed mechanism compared with typical insulated wires?

"Kynar wire" is a thin insulated hookup wire that is used for compact connections, with a flexible, delicate form that makes guiding and traction more difficult than with typical thicker insulated wires. In this build, the wire was thin enough to slip or wander off a standard extruder path, so the feed path needed extra guiding and gentler roller contact. That is why the builder modified both the drive roller and the entry and exit guides. [#21358409]

Why were scissors chosen instead of side cutters or a guillotine mechanism for cutting thin Kynar wire in this machine?

Scissors were chosen because they were simple, available, and tolerant of mechanical play. The builder rejected typical cutters because they crimp and do not continue through the closing motion the same way scissors do. He also considered guillotine-style blades, but rejected them for higher cost, lower availability, and the extra work of building a proper blade mechanism. For thin Kynar, easy replacement mattered more than maximum durability. [#21360835]

What modifications were made to the 3D printer extruder feed to stop the wire from slipping or being damaged?

The feed was modified in four practical ways. The toothed drive roller had its teeth ground down, the original concave roller was replaced with a bearing, a trimmed meat-injection needle was glued onto the input, and the Bowden section at the output was replaced. These changes reduced marking, kept the wire centered, and improved stability for thin flexible Kynar during repeated feeds. The drive body itself still came from a 3D-printer extruder concept. [#21358409]

How does the firmware handle preset lengths, quantities, and the initial trim cut so the first wire section is accurate?

The firmware uses a menu-driven cycle. 1. The user selects a stored variant or enters a manual section length. 2. The program advances the wire by the preset length and then commands the cutting stepper to make one full rotation. 3. Before starting the run, it trims the excess wire so the first finished section matches the programmed length. The cycle then repeats for the selected number of wires or board sets. [#21358409]

What is a Bowden tube, and why was it replaced here with a piece of pen refill at the wire exit?

"Bowden tube" is a flexible guide tube that routes filament or wire between mechanisms, keeping the path constrained while allowing remote drive placement. In this machine, the builder replaced a Bowden piece at the exit with a pen-refill tube because it better stabilized the thin Kynar at the last stage before cutting. Together with the needle at the entry, it stopped the wire from slipping off the rollers or wandering sideways. [#21358409]

Scissors vs guillotine cutter for a DIY wire cutting machine — which approach is better for thin flexible wire like Kynar?

For this build, scissors were the better practical choice. They were easier to mount, easy to replace, and their over-travel helped cancel tolerance and wear in the mechanism. A guillotine could be more durable, but several commenters noted it needs good blade guidance and contact pressure to work well. The builder had already considered such a redesign, yet kept scissors because the machine only cuts thin Kynar and not thicker cable. [#21361747]

Why doesn’t the feeder imprint gear teeth onto the cable, even though it uses an extruder-style drive roller?

It does not imprint because the roller teeth were deliberately blunted. The builder ground down the toothed roller so the teeth were no longer sharp, and he also noted that even typical insulated wires do not show marks easily in this kind of feed. A commenter asked directly about tooth marks, and the answer was clear: with beveled teeth, nothing was being imprinted on the cable. [#21359571]

What did the builder say they would change in the next version of the machine, especially regarding cutting direction and power supply placement?

He would reverse the cutting motion and redesign the enclosure layout. Specifically, he wanted the moving arm to cut downward instead of upward, because the current direction throws cut fragments into the canopy tray and scatters them. He also said the back of the case should include space for the power supply, so the whole unit stores as one compact device rather than as separate parts. [#21358409]

How many wire pieces per week was this machine designed for, and how was its payback time estimated?

It was designed around roughly 100 cut wires per week for semi-hobbyist model electronics production. The builder estimated the machine saves about 30 minutes each week on a disliked repetitive task. He then translated that into about 25 hours per year and argued the machine would amortize in under 1 year, even including development time. That estimate was central to his defense of the project’s practical value. [#21360822]

What was the approximate BOM cost of the machine, and which parts came from AliExpress, Allegro, demobil, or 3D-printed sources?

The listed hardware total was about 137 zł before counting surplus tools and supply parts. The BOM named Arduino Nano 10 zł, CNC Shield 12 zł, 2 stepper drivers 18 zł, 1602 I2C display 10 zł, membrane keypad 5 zł, 2 NEMA17 motors with cables 22 zł, and 2 foamed PVC sheets 60 zł. Prices were said to come from AliExpress and Allegro, while the 12 V power supply and scissors came from demobil, and multiple mounts were 3D-printed. [#21358409]

How many prototype iterations were made before the final version, and what changed during feed-drive testing?

There was no full formal prototype series, but there were several partial iterations. The builder said he tested the feed motion separately, and that test revealed the need for the injection-needle guide at the input. He also tried 2 different drive-ratio variations with different lengths and shapes before assembling the final machine. So the main iteration work happened in the feed path and transmission geometry, not in a long chain of complete prototypes. [#21360977]

What problems come up when trying to adapt this design from wire cutting to insulation stripping, especially for PTFE/Kynar/tefzel wires?

The main problem is that stripping is a different motion and control problem than cutting. A commenter stressed that stripping thin PTFE-type wires is a real technological challenge, and the builder agreed the current machine was not designed for it. He noted that a more versatile design would likely need a servo and front-back wire movement, plus a tool that cuts insulation without damaging the conductor. In short, cutting sections is solved here; automated stripping is not. [#21361747]

Which alternative cutting tools mentioned in the discussion, like Stanley-style cutters, optical fiber scissors, or custom stainless guillotine blades, are worth considering for better durability?

Three alternatives stood out. Stanley-style replacement cutters were mentioned early, but the builder did not need them for thicker wire. Later, commenters suggested stainless guillotine blades with a notch matched to wire diameter, aiming for higher durability and simpler service. Another participant pointed to hardened, serrated scissors similar to optical-fiber cutters as a potentially longer-lasting option. For a serviceable small-batch machine, those alternatives make sense if scissor wear appears later. [#21360956]

Why might a fully offline wire cutting machine be preferable to a PC-connected solution for small-batch electronics production?

A fully offline machine is easier to deploy, quicker to start, and avoids tying a simple repetitive task to a computer. One commenter explicitly praised the offline module and the fact that the machine is completely independent of a PC, noting that many devices now require computer connection or charge extra for standalone operation. In a small-batch workshop, a local display and keypad can be enough for preset lengths, quantities, and repeatable cuts. [#21358432]

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