1. Simple planar slicing

A general introduction of the concepts organization of compas_slicer can be found in the introduction tutorial.

This example describes the planar slicing process for a simple shape, consisting out of a shape with a single contour (also known as a ‘vase’). Its files can be found in the folder /examples/1_planar_slicing_simple/

1.1. Imports and initialization

The first step is to import the required functions:

import time
import os
import logging

import compas_slicer.utilities as utils
from compas_slicer.pre_processing import move_mesh_to_point
from compas_slicer.slicers import PlanarSlicer
from compas_slicer.post_processing import generate_brim
from compas_slicer.post_processing import generate_raft
from compas_slicer.post_processing import simplify_paths_rdp_igl
from compas_slicer.post_processing import seams_smooth
from compas_slicer.post_processing import seams_align
from compas_slicer.print_organization import PlanarPrintOrganizer
from compas_slicer.print_organization import set_extruder_toggle
from compas_slicer.print_organization import add_safety_printpoints
from compas_slicer.print_organization import set_linear_velocity_constant
from compas_slicer.print_organization import set_blend_radius
from compas_slicer.utilities import save_to_json

from compas.datastructures import Mesh
from compas.geometry import Point

Then we initiate logging to make sure that messages generated by compas_slicer are printed in the terminal.

logger = logging.getLogger('logger')
logging.basicConfig(format='%(levelname)s-%(message)s', level=logging.INFO)

Next we point to the data folder. Compas_slicer assumed there is a folder named data where it looks for the model to slice. The model to slice can be of type .stl or .obj. In the data folder compas_slicer will create a folder called output, where all the intermediate and final outputs of the slicing process will be saved. Therefore, we run the command get_output_directory(DATA), which checks if the output folder exists and if not, it creates it.

DATA = os.path.join(os.path.dirname(__file__), 'data')
OUTPUT_DIR = utils.get_output_directory(DATA)  # creates 'output' folder if it doesn't already exist
MODEL = 'simple_vase_open_low_res.obj'

1.2. Slicing process

In the next step we use the Compas function Mesh.from_obj to load our .obj file. We then move it to the origin, but this can be any specified point, such as a point on your print bed.

Next, we initialize the PlanarSlicer to initialize the slicing process. You need to specify the layer height and the slicing_type that defines the methods for generating the ‘slices’. Currently, the following methods are supported:

default: Uses only standard compas functions, without external libraries, but can be a bit slow.
It works for both open and closed paths.
cgal: Uses the ‘compas_cgal’ package, this is a very fast method but requires you to install compas_cgal.
It only works for closed paths

slicer = PlanarSlicer(compas_mesh, slicer_type="cgal", layer_height=1.5)
slicer.slice_model()

We also align the seams so that the start of each path is as close as possible to the start of the previous path

seams_align(slicer, "next_path")

After the model has been sliced, several post processing operations can be executed. One useful functionality is generate_brim, which generates a number of layers that are offset from the bottom layer, to improve adhesion to the build plate (see image). Also, a raft can be generated using the generate_raft command.

../_images/01_brim.jpg — *Left: Without brim. Right: With brim*

generate_brim(slicer, layer_width=3.0, number_of_brim_offsets=4)
generate_raft(slicer,
              raft_offset=20,
              distance_between_paths=5,
              direction="xy_diagonal",
              raft_layers=1)

Depending on the amount of faces that your input mesh has, a very large amount of points can be generated. simplify_paths_rdp_igl removes points that do not have a high impact on the final shape of the polyline. Increase the threshold value to remove more points, decrease it to remove less. For more information on how the algorithm works see: Ramer–Douglas–Peucker algorithm

simplify_paths_rdp_igl(slicer, threshold=0.6)

Currently the ‘seam’ between different layers of our shape is a ‘hard seam’, the printer would move up almost vertically to move to the next layer. To make the seam more ‘smooth’, and less visible we can use the seams_smooth function. This function simply removes points within the specified distance to enable a smoother motion from one layer to the next.

seams_smooth(slicer, smooth_distance=10)

To get information on the current state of the slicing process we can print out information from the slicing process.

slicer.printout_info()

Since we are now done with operations involving the PlanarSlicer class, we can save the slicing result to JSON. In the next steps we will use the PlanarPrintOrganizer class to organize our print for fabrication.

save_to_json(slicer.to_data(), OUTPUT_DIR, 'slicer_data.json')

1.3. Print organization

In the next steps of the process we will use the PlanarPrintOrganizer to make our slicing result ready for fabrication. First, we initialize the PlanarPrintOrganizer and create PrintPoints. The difference between PrintPoints and the compas.geometry.Points we were using in the previous step is that the PrintPoints have all the necessary additional information that is needed for the fabrication process.

print_organizer = PlanarPrintOrganizer(slicer)
print_organizer.create_printpoints(compas_mesh)

We can add these additional functionalities to the printpoints by calling different functions.

set_extruder_toggle: Adds a boolean extruder_toggle to the PrintPoints. True means the extruder should be on (printing), whereas False means the extruder should be off (when traveling between paths).
add_safety_printpoints: This function adds a ‘safety point’ (also known as ‘z-hop’) before and after print paths, to make sure the extruder does not collide with the print. This is recommended for prints consisting out of multiple contours.
set_linear_velocity: Sets the linear velocity (printing speed) for the print.

set_extruder_toggle(print_organizer, slicer)
add_safety_printpoints(print_organizer, z_hop=10.0)
set_linear_velocity_constant(print_organizer, v=25.0)

Again we can print out the information about the print_organizer.

print_organizer.printout_info()

After adding all of the fabrication-related parameters we will convert the Printpoints into a dictionary of data and then export it to a .JSON file.

printpoints_data = print_organizer.output_printpoints_dict()
save_to_json(printpoints_data, DATA, 'out_printpoints.json')

Once the slicing process is finished, you can use the compas_slicer grasshopper components to visualize the results, described in the grasshopper tutorial.

To view the results of the slicing process, open the planar_slicing_master.gh file in examples/1_planar_slicing_simple. This loads the json and txt files that have been produced and displays them as Rhino-Grasshopper geometry. You will only be able to visualize the results after you have run the python file that generates them.

1.4. Final script

The completed final script can be found below:

import time
import os
import logging

import compas_slicer.utilities as utils
from compas_slicer.pre_processing import move_mesh_to_point
from compas_slicer.slicers import PlanarSlicer
from compas_slicer.post_processing import generate_brim
from compas_slicer.post_processing import generate_raft
from compas_slicer.post_processing import simplify_paths_rdp_igl
from compas_slicer.post_processing import seams_smooth
from compas_slicer.post_processing import seams_align
from compas_slicer.print_organization import PlanarPrintOrganizer
from compas_slicer.print_organization import set_extruder_toggle
from compas_slicer.print_organization import add_safety_printpoints
from compas_slicer.print_organization import set_linear_velocity_constant
from compas_slicer.print_organization import set_blend_radius
from compas_slicer.utilities import save_to_json

from compas.datastructures import Mesh
from compas.geometry import Point

# ==============================================================================
# Logging
# ==============================================================================
logger = logging.getLogger('logger')
logging.basicConfig(format='%(levelname)s-%(message)s', level=logging.INFO)

# ==============================================================================
# Select location of data folder and specify model to slice
# ==============================================================================
DATA = os.path.join(os.path.dirname(__file__), 'data')
OUTPUT_DIR = utils.get_output_directory(DATA)  # creates 'output' folder if it doesn't already exist
MODEL = 'simple_vase_open_low_res.obj'


def main():
    start_time = time.time()

    # ==========================================================================
    # Load mesh
    # ==========================================================================
    compas_mesh = Mesh.from_obj(os.path.join(DATA, MODEL))

    # ==========================================================================
    # Move to origin
    # ==========================================================================
    move_mesh_to_point(compas_mesh, Point(0, 0, 0))

    # ==========================================================================
    # Slicing
    # options: 'default': Both for open and closed paths. But slow
    #          'cgal':    Very fast. Only for closed paths.
    #                     Requires additional installation (compas_cgal).
    # ==========================================================================
    slicer = PlanarSlicer(compas_mesh, slicer_type="cgal", layer_height=1.5)
    slicer.slice_model()

    seams_align(slicer, "next_path")

    # ==========================================================================
    # Generate brim / raft
    # ==========================================================================
    # NOTE: Typically you would want to use either a brim OR a raft,
    # however, in this example both are used to explain the functionality
    generate_brim(slicer, layer_width=3.0, number_of_brim_offsets=4)
    generate_raft(slicer,
                  raft_offset=20,
                  distance_between_paths=5,
                  direction="xy_diagonal",
                  raft_layers=1)

    # ==========================================================================
    # Simplify the paths by removing points with a certain threshold
    # change the threshold value to remove more or less points
    # ==========================================================================
    simplify_paths_rdp_igl(slicer, threshold=0.6)

    # ==========================================================================
    # Smooth the seams between layers
    # change the smooth_distance value to achieve smoother, or more abrupt seams
    # ==========================================================================
    seams_smooth(slicer, smooth_distance=10)

    # ==========================================================================
    # Prints out the info of the slicer
    # ==========================================================================
    slicer.printout_info()

    # ==========================================================================
    # Save slicer data to JSON
    # ==========================================================================
    save_to_json(slicer.to_data(), OUTPUT_DIR, 'slicer_data.json')

    # ==========================================================================
    # Initializes the PlanarPrintOrganizer and creates PrintPoints
    # ==========================================================================
    print_organizer = PlanarPrintOrganizer(slicer)
    print_organizer.create_printpoints(generate_mesh_normals=False)

    # ==========================================================================
    # Set fabrication-related parameters
    # ==========================================================================
    set_extruder_toggle(print_organizer, slicer)
    add_safety_printpoints(print_organizer, z_hop=10.0)
    set_linear_velocity_constant(print_organizer, v=25.0)

    # ==========================================================================
    # Prints out the info of the PrintOrganizer
    # ==========================================================================
    print_organizer.printout_info()

    # ==========================================================================
    # Converts the PrintPoints to data and saves to JSON
    # =========================================================================
    printpoints_data = print_organizer.output_printpoints_dict()
    utils.save_to_json(printpoints_data, OUTPUT_DIR, 'out_printpoints.json')

    printpoints_data = print_organizer.output_nested_printpoints_dict()
    utils.save_to_json(printpoints_data, OUTPUT_DIR, 'out_printpoints_nested.json')

    end_time = time.time()
    print("Total elapsed time", round(end_time - start_time, 2), "seconds")


if __name__ == "__main__":
    main()

1. Simple planar slicing

1.1. Imports and initialization

1.2. Slicing process

1.3. Print organization

1.4. Final script

COMPAS