Reference · CNC toolpaths and machine code

3D Milling on Digital Cutters with Grasshopper

With LARGER.slicer, our Grasshopper toolkit, a Zünd digital cutter mills continuous 3D surfaces. Grasshopper calculates the toolpath and exports it as an HPGL/PLT file that the Zünd runs directly. We tested the workflow on the Zünd G3 L-2500 in the model workshop of the Münster School of Architecture, FH Münster.

Developed at therobotics.lab, MSA Münster School of Architecture

Digital cutter milling a 3D relief into a wooden board

Finished 3D-milled lettering relief set into a solid-wood panel on the cutter table

Machine

Zünd G3 L-2500 in the model workshop of the MSA, FH Münster

Setup

Working area 1800 × 2500 mm · routing module RM-A, 1 kW

Our part

LARGER.slicer: 3D toolpaths and HPGL/PLT export

Tools

Rhino, Grasshopper, Zünd Cut Center

Freeform surfaces instead of flat cuts.

Zünd digital cutters are built for cutting and 2D routing. Continuous 3D surfaces, where the router moves in X, Y and Z at the same time, are not part of the standard workflow.

With LARGER.slicer they are. The plugin generates 3D milling toolpaths in Grasshopper and writes them as an HPGL/PLT file. Many shopfitters and interior workshops already own a Zünd. This lets the same machine mill reliefs and textured surfaces.

Digital cutter modelled in Rhino next to the LARGER.slicer Grasshopper definition

The machine as a model

The Zünd G3 L-2500 is modelled in Rhino, next to the Grasshopper definition. You reference the 3D geometry and check that it fits the working area of 1800 × 2500 mm.

One component, one continuous toolpath

The CNC Program component takes a Brep or a mesh from Rhino. It calculates a zigzag toolpath (boustrophedon) across the surface.

Every point of the path carries its own Z height. The router follows the freeform surface instead of milling in flat steps. Material thickness, pass depth, stepover, tool and spindle speed are set as inputs.

Zigzag 3D milling toolpath of the lettering relief in Rhino with the generated HPGL code in Grasshopper

Digital cutter with routing module and workstation in a university model workshop

A file the cutter runs directly

The exported PLT file already contains everything the machine needs: tool selection, spindle speed, vacuum control, Z positioning, extraction height and underlay compensation.

In Zünd Cut Center you load the file, fix the material with vacuum, calibrate the tool height and start the job.

Milling in X, Y and Z at once

The router follows the freeform surface in all three axes at the same time. The result is a smooth relief instead of flat steps.

The test piece: the MSA lettering, set into a curved surface.

Routing module milling a curved relief pocket into a softwood board

Hand pointing at the raised lettering on the smooth 3D-milled surface

Tested on a production cutter

The workflow was developed and tested at the Münster School of Architecture (MSA). A Grasshopper template and a quick start guide are included in the LARGER.slicer download.

GitHubLARGER.slicer, open source LARGER.slicerThe full toolkit robotics.labMSA, FH Münster

Working area1800 × 2500 mm
Max. milling height50 mm, limited by the gantry clearance
Routing moduleRM-A with 1 kW spindle
Tool changeAutomatic router bit changer
InputHPGL/PLT file from LARGER.slicer

Workflow in five steps

01Reference

Reference the 3D geometry in Grasshopper and check that it fits the working area.

02Set up

Set material thickness, pass depth, stepover, tool and spindle speed.

03Generate

Generate the toolpath with the CNC Program component and check it in the Rhino viewport.

04Export

Export the HPGL/PLT file.

05Mill

Load the file in Zünd Cut Center, fix the material with vacuum, calibrate the tool height and start.

Video · MSA, FH Münster

The cutter milling a relief

3D simultaneous milling on the Zünd G3 at FH Münster. Toolpath and HPGL file from LARGER.slicer.

What it is for

Reliefs, textured panels, mould and prototype surfaces: anything that needs a smooth 3D surface rather than a flat cut.

Toolkit and workflow PARAMETRIC.solutionsDeveloped at robotics.lab, MSA, FH MünsterMachine Zünd G3 L-2500Photos and video Moritz Wesseler

Using a digital cutter in your workshop?

Many shopfitters and interior workshops already have a Zünd cutter. We adapt the workflow to your machine, tools and materials, so you can use it for 3D surfaces as well.

Tell us about your machine