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Sketch to G-code for a CNC router on iPad

You can go from an Apple Pencil sketch to G-code for a CNC router without leaving the iPad. Draw the part with real dimensions, set the cuts and the bit in PencilCAD’s Cut toolset, scrub through the toolpaths, then upload the G-code to your controller over Wi-Fi, or hand the drawing to your router software.

Safety first. Test every new job on scrap, and check the capped feeds against your bit and material. PencilCAD only uploads files: it never starts the machine, and you stay with it while it cuts.

1. Draw the part with dimensions

600 600 write a size on a line
Write 600 on a line and it becomes 600 long.

Pick CAD in Settings → Tools, then close every outline you want cut. The parametric sketching guide covers constraints, and the woodworking guide covers parts.

2. Set the operations and depths

Cut Engrave Score, Draw Skip profile, frees the part pocket, adaptive or V-carve shallow groove on the line left uncut
In Operations, each layer or shape gets a job.

Choose Cut in Settings → Tools or More, and give each layer an operation and a depth. Relief SingleLine lettering cuts one stroke per line.

wide: deep thin: shallow V-bit the depth follows the width
V-carve, with a V-bit: deeper where the shape is wider.

3. Set up the Job: machine, bit and material

pass 1 pass 2 pass 3 Z0: top of the stock or Z0: bottom of the stock (spoilboard) step-down depth
Each pass goes one step-down deeper.

In Job, pick the machine, a bit (flat, O-flute, V-bit or ball), the material and the step-down. Feeds are capped: treat them as a careful start.

Ramp in tab part climb milling: clockwise round the outline
Tabs hold the part; Ramp in eases the bit into the cut.

4. Plan, then scrub the preview

open outline
Check
Planning… Stop
Plan, with Stop
Scrub the preview

Check flags open outlines, parts off the sheet and depth problems, most with a one-tap fix. Edit the drawing and you plan again before you send.

5. Get one G-code file per tool

the job 1 of 2 · 6 mm flat load, zero, start 2 of 2 · 3 mm flat load, zero, start GRBL can’t change tools mid-file
One file per bit, named in the order you run them.

GRBL can’t change tools mid-file, so two bits make two files, such as “1 of 2 · 6 mm flat”. Each is GRBL-safe G-code: tool-centre paths and arcs.

6. Send the files

Send… Wi-Fi upload AirDrop or iCloud Drive FluidNC, grblHAL, ESP3D, Onefinity, Buildbotics uploads, never starts Carbide Create, Easel, Mach4 G-code DXF
Upload over Wi-Fi, or hand off a DXF.

Send uploads to FluidNC, grblHAL, ESP3D, Onefinity and Buildbotics over Wi-Fi, or hands Carbide Create, Easel or Mach4 a DXF to toolpath itself. Export for also writes a Shaper SVG.

7. At the machine: load, zero, start

6 mm flat
Load the bit
Z0: where the Job says X0 Y0
Zero X, Y and Z
you press start
Press start

Run the files in order and check the first part. More in the laser cutting guide, Cricut cut files on iPad, sheet metal flat patterns and on the features page.

Questions

Can an iPad make G-code for a CNC router?

Yes. PencilCAD plans profile, pocket, engrave and V-carve toolpaths from your drawing, plus adaptive clearing, and writes a GRBL-safe subset of G-code, one file per tool. You can upload it over Wi-Fi to FluidNC, grblHAL, ESP3D and Onefinity/Buildbotics controllers.

Does PencilCAD start the machine?

No. It only uploads files. You load the bit, zero the machine and press start yourself, for every file.

Why do I get more than one G-code file?

GRBL machines can’t change tools in the middle of a file, so PencilCAD writes one file per tool, named in order, such as “1 of 2 · 6 mm flat”. Load, zero and start each one in turn.

Can I use Carbide Create, Easel or Mach4 instead?

Yes. Choose one in Send and PencilCAD hands off a DXF of the drawing with AirDrop or iCloud Drive. That program then sets its own toolpaths and offsets.

Shaper, Carbide Create, Easel, Mach4, Onefinity and Buildbotics are trademarks of their owners; PencilCAD isn’t affiliated with them.

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