This is a very
interesting discussion of how Rob uses the Sketchup 3D drawing
software (from Google) to do CNC projects with his ShopBot. The talk
is taken from the Sektchup BaseCamp meeting that was recently held
on the Google campus (June 2008). Rob's talk is the 3rd in the
series in the YouTube video this link will take you to. If you are
interested in Sketchup, all three talks are good. But Rob's specific
talk starts at 34min:40sec. You can scan forward to it. His talk
lasts about 35 minutes, so sit back and enjoy.
[Click Here to View.]
Loading Heavy Sheet Goods aka the ShopBot Salutation! -
Aug 2008
Sheet goods can be awkward and heavy.
Depending on your shop configuration, manually loading even moderately
heavy sheets alone can be cumbersome at best. This ShopBot Salutation is
a technique which, for me, is the easiest, fastest, and safest way of
manually handling and loading sheet goods.
Everyone is different and you know your body and capabilities best. But
if you can almost touch your toes and you don't throw out your back
everytime you lift something wrong this might work for you. Keep in
mind that, while this technique works well for me it might not be best
for you. Practice with light materials until you get the hang of it -
and go slowly. Once you do get the hang of it, if you are like me
you'll never go back.
However be warned! You may be laughed at.
Starting the Magic -
June 2008
"Any sufficiently advanced technology
is indistinguishable from magic." - Arthur C. Clarke
ShopBot makes amazing
tools, and while they aren't really magic, they can seem that way. A
ShopBot is a 10,000 trick pony and in this column we are going to
explore techniques and patterns that can make your ShopBot
experience more productive, more fun and maybe even magical.
A Design Pattern is a description of a solution to a particular
problem. And a collection of design patterns is called a Pattern
Language. This column is devoted to defining a ShopBot Pattern
Language: a collection of useful design patterns which used together
in a composition can help solve problems and reduce complexity in
your digital fabrication projects.
While one pattern may stand alone, another may only make sense
within the context of a composition of patterns. In either case each
pattern defines a good solution to a particular type of problem.
With each entry we will describe the problem, why the given design
pattern is a good solution, and present a real world example of the
pattern in use.
So let's get started building out
our vocabulary and seeing the components in use ...
1. The Puzzle Joint
Sometimes a design
presents itself in which flat parts cannot easily be cut as a single
part. Either the part is too large to cut from the material
available, exceeds your ShopBot capacity, or maybe would simply be
too wasteful to cut as a single object. Puzzle joints provide a fast
and easy way to accurately attach flat parts together to create
larger parts.
Turning MDF back into Trees: A Puzzle
Joint Example
I was presented with a design problem which involved producing over 52
linear feet of a 5 foot tall articulating and branching tree shapes for
an indoor garden of a local restaurant.
The design,
provided by the architect, resembled an artistic, silhouette
tree-scape. The
contractor I was working with was conscientious about material waste
and so I suggested that we break the trees into parts which could
then be assembled onsite like a giant jigsaw puzzle. This would
increase our yield from 30% to 80% - a significant improvement.
It took me just under three hours using Sketchup to break
the design down into manageable parts and to align and scale
the puzzle joint geometry to the parts. In the end there
were 127 parts. Every part had a number and of course I
provided the key for assembly. We joked with the contractor
about just dropping off a giant pile of parts and letting
him figure it out - somehow he didn't see the humor.
Unfortunately the special 1/2" fire-proof MDF was only available in
4'x10' sheets so I precut each into 4'x5' sections for nesting. In
the end only 3 sheets were required. Here's an example of one of the
nesting patterns. This was done by hand and while somewhat tedious
it didn't really take very long.
I stopped by the jobsite to take some pictures and make sure
everything was coming together well.
The contractor has been apprehensive that this approach would be
difficult and time consuming for him.
I stopped by the jobsite to take some pictures and make sure
everything was coming together well.
The contractor has been apprehensive that this approach would be
difficult and time consuming for him.
And while he probably wasn't so happy about all the edge sanding the
assembly portion of the job came together quickly and easily.
Here's a picture of the first sub-assembly being test fit. One of
the three puzzle keys has been taped to the wall for reference.
And at last the trees were done. These were taken minutes before the
opening night party.
They were a huge success!
And there's the magic - turning MDF back into Trees!
How to construct a Puzzle
Joint
Breaking a part down into
smaller parts which interlock via puzzle joints is fast and easy. Here's
how I use Google Sketchup
(a free version can be downloaded from their website) to create a puzzle joint design. Any decent
CAD software should be able to perform equivalent operations.
First I've designed and saved a model of a generic puzzle joint. There
are many possible variations on this form. This just happens to be one I
generally start with. You can
download a zipped dxf
file of this joint here.
Then, starting with the model I want to break up into smaller parts I
import my puzzle joint geometry. In Sketchup, when one model is imported
into another, the imported geometry is encapsulated into its own
component. This is handy since for the moment we want to move, rotate
and scale the puzzle joint without interfering with our base model
geometry.
Move the puzzle joint so that one endpoint is coincident with a point on
the model where you want the joint to begin.
Rotate the puzzle joint about that first point such that the other end
is in alignment with the opposite point you wish the joint to span.
Scale the joint along its axis to bridge the two points. When scaling
always have care that the curves of the joint never become too small for
your intended cutting tool to properly machine.
Explode the puzzle joint component thereby merging its geometry with the
rest of the part. Separate the two parts from one another. These parts
are now ready for nesting and toolpathing.
