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Using the CNC Hot Wire Cutter

Using the CNC Hot Wire Cutter

1: First Use Setup

To use the CNC hotwire you need 2 different software, those are GRBL hotwire, and JEDIcut. Both of them have installation managers to download but there is some settings you need to change when first opening.

For JEDIcut:

Open JEDIcut in administrator, none of the changes will save otherwise

Start by going to tools → options. Under communication change the mode from CNCnet to gcode.dll, this will allow Jedicut to make gcode files that can be read by GRBL

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Then under CNC controller change your speed settings to match this

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The main changes will be cut speed and max speed. When making your routes for cutting, cut speed will be the speed of the wire while in the material, while fast speed will be the speed when moving outside of the foam.

After this go to Heating and deselect the checkmark for enable/disable heating control

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Then change the values of v1 and v2 to 200, sometimes these values will override the cnc velocity to ~0.2mm/min if you dont change.

Finally you can go to Name of axes and change them to XYAZ, this is because grbl has the axis set on XYZA, rather than XYUV, and ensures that the gcode can be read.

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2: Cutting Preparation

2.1: Gcode generation

JEDIcut can use either .dxf or .dat files to generate gcode, depending on the complexity of the airfoil one might be much easier to work with than the other. Generally, if you are using a standard airfoil (NACA, HT, EPPLER, etc) you can find a .dat file in Airfoiltools, while custom airfoils or anything non-standard should be done with a dxf.

2.1.1: .dat Creation

On Airfoiltools go to the database search (should be what the hyperlink goes to) and type in the airfoil you are using

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After finding the airfoil click on and download the source .dat file.

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2.1.2: .dxf Creation

Dxfs can be created directly from the CAD model you have, right click on the face that you want to create a DXF from, and click export to DXF/DWG. Make sure to save as type DXF and not DWG.

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Depending on the complexity of the face you may need to simplify the dxf, this can be done in AutoCAD, this should be done for anything on the inner profile, spars are much easier to add in JEDIcut than work with from the dxf.

2.2: Back to JEDIcut!

In Jedicut create a new wing cut (not profile) and click on the file button on the right of the textbox below wing root

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Select the filetype you saved the profile as (dxf or .dat) and import it. Click on symmetrical profile for the wing tip and edit all of the properties of the wing on the right. The only things I would recommend changing are the root chord, and the skin thickness (set to 1.4mm) and the start/release height, keep in mind that the zero of the hotwire is at ~12mm so the entrance height should keep that in mind, the release height should be ~10mm above the entrance.

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Example Settings

 

2.2.1 Adding Spars:

Spars can be added by going to tools → ribs manager and clicking on the circle icon. The all of the settings should be done based off the geometry of your model, but the diameter should be offset by ~2.5mm (eg a 12mm hole should be cut w a diameter of 14.5) and the entrance angle should be 0 degrees from the bottom

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Example Settings

2.2.2: Creating the pathing

Go to tools → cycle of cut manager. The default cutting pattern cuts the top, goes back around to the front, and then cuts the back, you could technically use this but I would really advise against it. Start by deleting everything below Extrado and the pause between vertical and horizontal then click on the symbol for the bottom arc

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After this select the Intrado and click the up arrow to move it above the Extrado, then click on the Extrado and hit the checkbox for inverse. Then add a horizontal and change its value to -20, and go back to the first horizontal and change it to +20, your cut should now look like this, hit apply and then escape.

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Finally you can click the cut button and export as gcode

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3: Cutting time!

Connect the usb to your computer and connect to the pico in GRBL, then click on the file icon to import your gcode. Before starting the cut ensure that the machine is zeroed and all of your axis are zeroed.

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After this set your wire temperature to ~50% and turn the wire on, ensure that its actually on by placing some foam on the wire. If everything looks good you can click on the play button to the right of the file import to start running!

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3.1: Manual Control

If you need to move any of the carriages it can be done using the jog function, try to move at a feed rate of 200mm/min and make sure the jog is set to the distance you want, if the carriage gets run into either hard stop the lead screw will strip the coupler and it will need to be reprinted and replaced. If something goes wrong you can click the stop button to pause it.

3.2: Enjoy!

If you did everything right you should now have a cut wing, if not you can check out the troubleshooting section below.

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Troubleshooting (ping @Jakob Boelling or @Jackson Barber for more help)

 

Physical Part Does Not Match GRBL Preview (trailing edge got clipped short, spar entry too wide, overall too small, etc)

  • 99% of poor cuts are from kerf/width of cut being too large, try running colder

  • Overall too small: adjust skin thickness in JediCut. May have to tune, have.

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Skin Thickness Adjustment Box

  • Leading edge clipped short: with the leading edge being so thin, kerf affects it really badly. Try adding a rectangle to the back (easily done in AutoCad), which can get trimmed with an exacto knife after. Cutting trailing edge first can also help, see this video (we dont use this software since it cant take dxfs): https://www.youtube.com/watch?v=uWO8kMGxqGU

    image-20260327-024545.png
    Trailing Edge Extension Rectangle To Help With Kerf

  • Spar entry too wide: Run colder, play around with entry angle in JediCut, Tools->Ribs Manager Angle. Position->Below also helps

    image-20260327-025011.png

Cut-Path Preview in GRBL Does Not Match Input

Jedicut:

  • Spars are too small: when changing skin thickness, JediCut also offsets spar diameter. Increase the spar diameter in Jedicut by 2x skin thickness, i.e 2mm skin thickness, 12mm spar → 2*(2mm offset)+12mm = 16mm

  • Improper axis names: Under tools (top left)->options->GCode, ensure axis names are XYZA and not the default XYUV

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    See top-right, should match these letters

  • Complete garbage, halves are flipped relative to eachother: Under tools-> cycle of cut manager, look at cut cycle and make sure no steps are incorrectly inverted (check box on right side)

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Extrado tool path incorrectly inverted

CNC isn’t moving

Physical Problems:

  • A and X axis (horizontal travel for either side) connectors are very loose, fall out of enclosure sometimes (make sure you have metal part of connector facing the ceiling, and order follows AXYZ based on motor labels)

  • Grime on linear rod can stop the motors, unplug motors and manually turn lead screw past sticky point, wipe off grime

  • Stepper shaft-lead screw coupler can strip/loosen, re-tighten or swap to extra ones in the cnc-box

  • Steppers can get prohibitively hot, has soft-locked cnc after 5-6 hours of run time

  • Lead screw nuts can pop out of carriages if not glued in properly

GRBL:

  • Sometimes softlocks, try clicking reset, stop, or unlock, and disconnecting and reconnecting within GRBL

  • Make sure axis direction are correct, could be driving carriage into the hardstop (change in second tab, invert axis)

  • Motor current isn’t too low (should be 1000-1500 mA)

Jedicut:

  • Open the G-Code file, check the number after F, which is feed rate in mm/min. If JediCut was not configured following the upper guide, the default speed will be set by tools (top left)->options->heating->V1 or V2. By default V1 and V2 are absurdly slow, ~0.0006mm/min.

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Speed should be ~F200, not F0.0006

  • Jedicut has built in dwell times, under tools->options->cycle of cut manager, delete pauses. Looks like this in G-Code, GRBL reads it in seconds, so it pauses for 2000 seconds. Just delete from G-Code and reconfigure in Jedicut for the future.

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2000 SECOND long pause, causes random stops

Wire Wobbling

Physical Problems:

  • Dirty wire: heat up the wire and wipe with a spare piece of foam to get rid of melted globs

  • Alligator clips dragging on something: any weight or friction on the alligator clip wires will cause the wire to move, tighten zipties on sides of vertical carriage

  • Stray wires can drag against the wood base plate: just watch both sides of the wire as it cuts

  • Tension is too low: can be caused by wire unravelling or elastic wear

  • Vertical axis is wobbly: double check that lead screw is not being bent in or out by the vertical carriages (look for a bowed shape in the vertical lead screw). If its bowed, send a message on discord and we can work on a fix

GRBL/Heating problems:

  • Too cold: If alligator clips are spaced as far apart as possible (general setup), below ~25% is too cold, and the wire will get bent by the foam

  • If both stages are moving smoothly, but the wire is still wobbling: crank up heat to ~70% for a second, then cool down

  • Ensure bottom of airfoil is cut last, it can sag and cause wobble