Laser Cutting: Advanced Joinery

Adv. Laser Cutting Joinery Primer

The City University of New YorkArchitectural Technology Dept.

written by Mauricio Tacaoman and Michael DiCarlo

Waffle, Tabbed, and Notched JoineryApril 12, 2014

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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.

Adv. Laser Cutting Joinery Primer

Fig. 1 -Surface Based in Rhino

Waffl e Structure Joinery

Step One:

The fi rst step in creating a waffl e 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 fi nal 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

Adv. Laser Cutting Joinery Primer3


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



Step 10:

Use the contours of the sectional mebers as your

laser cutting profi le, assemble.

Fig. 12 -Separated Sectional Members Fig. 13 -Sectional Members After Make2D


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 fi ne 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



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 profi le 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 surfacesFig. 19 -O! set border Curves

Fig. 20 -Clean up over laps

Fig. 21 -Establish Cut lines Fig. 22 -Establish Score lines



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


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 defi ning the notches is drawn

over ech surface you can use them to “Trim” the

negative spaces. The left over surfaces should

be the profi les 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 fi lled 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


Notched Joinery

Also, for pressure fi ts 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 fi t 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