Laser Cutting Techniques Waffle, Tabbed and Notched Joinery

1. Adv.LaserCuttingJoineryPrimer
The City University of New York
Architectural Technology Dept.
written by Mauricio Tacaoman
and Michael DiCarlo
Waffle, Tabbed, and Notched Joinery
April 12, 2014

2. 2
This material is based upon work supported by the National Science Foundation
under Grant Numbers 1141234.
Any opinions, findings, and conclusions or recommendations expressed in this
material are those of the author(s) and do not necessarily reflect the views of the
National Science Foundation.

3. Adv.LaserCuttingJoineryPrimer
Fig. 1 -Surface Based in Rhino
Waffle Structure Joinery
Step One:
The first step in creating a waffle structure is to
create a base surface. Ideally it is better to have a
surface that does not have exaggerated peaks and
valleys as this will result pieces that are too thin.
The surface itself can be any size, but eventually
it will need to moved into a laser cutter. The laser
cutters in Architectural Technology Department are
limited to 32” x 18”, so it is best to accommodate
your model to those dimensions.
Step Two:
At this point the initial contours in both the
X and Y axes can be created. To begin, create a
layer for the X-contours, and Y-Contours.
Step Three:
Now to create the sections use Rhino command:
Contour. It will prompt you to select object for
contour, so pick the surface you created. Then it
will ask you for the contour plane base point, pick
either the X or Y direction. After you have chosen
a direction type in the distance between contours.
(The larger the distance the lower the amount of
pieces and the lower accuracy of the final model.)
Step Four:
Repeat the same process to create the contours
along the other axis.
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Fig. 2 -Contours along the Y-AxisFig. 3 -Contours along the X-Axis
Fig. 4 -Contours along the Y-AxisFig. 5 -Contours along the X-Axis

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Waffle Structure Joinery
Step Five:
You may need to join the curves making up each
contour cut. Select them individually and us Rhino
command: Join (Ctrl + J).
Step Six:
Use Extrude Curve>Straight command
(ExtrudeCrv) to create surfaces from the contour
curves.
Step Seven:
Move the Y-Axis surfaces vertically half the depth
of the extrusion made on the previous step.
Step Eight:
Use the Surface> Offset Surface command
(OffsetSrf) to give the surfaces thickness, this
thickness is determined by the thickness of the
material being used. (i.e. .0625” chipboard).
Step Nine:
Use the Boolean Split command on both the X and
Y axes extruded contours. This will result in a slots
that allow you to join the parts.
Fig. 6 -Y-Axis Member with notchesFig. 7 -Sectional Members
Fig. 8 -Sectional Curves on a Cartesian Grid Fig. 9 -Extruded Sectional Curves
Fig. 10 -Detail of extruded sectional curves Fig. 11 -Shifted sectional planes

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Waffle Structure Joinery
Step 10:
Use the contours of the sectional mebers as your
laser cutting profile, assemble.
Fig. 12 -Separated Sectional Members Fig. 13 -Sectional Members After Make2D

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Unrolled- Tabbed surface Joinery
Step 1-
Once you have a 3dimentional shape or object
you want to reproduce, it’s important to make sure
it is “closed” meaning all the edges are touching
with no gaps, think “water tight”. You can check or
openings using the
“SelOpenSrf” command, if no surfaces are high-
lighted that means you’re good to go, if surfaces
do become highlighted, that means they are not
closed and you should check your geometry. If the
object is a type of panel or part of a system, there
may be open edges at its extents, that is fine too.
Step 2-
Select the polysurface and run the “UnRollSrf”
command, make sure that the sub-command “ex-
plode” is set to “No”, this will keep adjecent edges
aligned, as shown in the image to the left.
Step 3-
After successfully completing the unroll and ad-
justing any overlaping geometry you should create
4 layers,; Surfaces, Score lines, Cut lines, and an
“construction line” layer.
Then, select the polysurface and run the “DupBor-
der” command, this will give you a curve outline of
the geometry, this curve should be exploded and
entered into the construction line layer.
Step 4-
Take the unrolled polysurface and explode it into
it’s subsurfaces. Then run the “DupBorder” com-
mand again on all the subsurfaces, the resulting
curves will make up the score lines for each face.
Fig. 14 -Tetrahedrom, sold geometry Fig. 15 -Unrolled Surfaces
Fig. 16 -DupBorder
Fig. 17 -Explode Surfaces

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Unrolled- Tabbed surface Joinery
Step 6-
The lines should be exploded and the “SelDup”
command run, all duplicates should then be
deleted and the left over curves moved into the
“score lines” layer.
Step 7-
For now hide the score lines and bring up the
construction lines. Here you will begin creating
the cutting profile that includes the tabs. Indi-
vidually select the curve segments and run the
“OffsetCurve” command, you can choose to “Cap”
the offset which will create a connection to the
endpoints of each line.
Step 8-
Also, you can choose not to “Cap” the offset then
manually chamfer the ends and trim the excess,
as you can see in some areas the offsets may
over lap.
Step 9-
After the tabs are created and tailored to your
needs in the “constrction line” layer, you should
run the
“BooleanCurve” command. In Top view, highlight
the whole object, press enter, then click outside of
the object, this will creat a single polyline around
the perimeter of all the curves, this line is your
“Cut” line, and should be positioned in that layer.
Step 10-
The score layer should be set to green, and the
cut layer set to blue, hide or delete the construc-
tion lines, scale appropriately for your piece and
you should be set to sent your item(s) to be cut.
Fig. 18 -DupBorder of exploded surfaces
Fig. 19 -Offset border Curves
Fig. 20 -Clean up over laps
Fig. 21 -Establish Cut lines Fig. 22 -Establish Score lines

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Unrolled- Tabbed surface Joinery
Step 11-
Create a bounding box the size of the machine’s
printable area, in this case 24”x48” and a sec-
ond box the size the the material, in this case
14”x17”. Position your material in either the upper
right or left hand corner of the printable area. Set
your layers to their appropriate colors, at citytech
green=score, blue=cut and red=etch.
Step 12-
Select print, set your scale and position the “print
window” over your printable area box. Send to
plotter.
Step 13-
Remove material, fold along score lines and glue
along tabs.
Fig. 23 -Organize the print layout Fig. 24 -Send to cutter
Fig. 25 -Cut Pieces Fig. 26 -Cut single piece
Fig. 27 -Fold Tabs Fig. 28 -Glue

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Notched Joinery
Step1-
Starting with a simple geometry, like this box, de-
cide which edges need to be joined to create the
desired object, forthis example we’ll go throught
joining this single edge.
Step 2 -
Next you will need to divide the edge curve, us-
ing the “Divide” command we divide the edge to
be joined into 7 equal length segments, this will
give us all the division points, then the points on
the edge should be offset along the surface the
distance of what ever material the you are working
wth wil be. For this example we are asuming the
use of 1/4” acrylic or craft plywood.
Step 3 -
After Offseting the points accordingly, draw a ploy-
line accros each set of points to create this sort of
“tooth” pattern
Step 4 -
Once the lines defining the notches is drawn
over ech surface you can use them to “Trim” the
negative spaces. The left over surfaces should
be the profiles necessary to cut with. You can us
the “unrollsurface” command to project each to the
C-plane.
Step 5 -
Once projected to the C-plane use the “DupBor-
der” command to extract the perimeter curves,
color them blue, and for more complex geometries
labeling which surface is which may be helpful.,
use the text tool to type any identifying informa-
tion, the text will be filled in and not “cuttable”, to
create vector out-lines, select the text and “ex-
plode”.
Fig. 29 -Solid base geometry Fig. 30 -Divide Edges
Fig. 31 -Outline the notch pattern Fig. 32 -Trim the excess
Fig. 33 -Flatten/ Unroll the faces to cut Fig. 34 -Prepare for cutting and label if needed

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Notched Joinery
Also, for pressure fits you will need to take into ac-
count the kerf width. The “kerf” is the width of the
material removed by a cutting device, like a saw
or laser.
The kerf of the lasers at Citytech are around
1/64”, though there is some variance between the
machines,
material choice and power settings.
The offset of the “tooth” curves should move in
the direction of the opening and the distance
somewhere in the nighborhood of 0.002”, to get
a perfect fit will require a little testing, It’s wise to
conduct a material/ power test with a small piece
of or selected material.
Fig. 35 -Fit together