Digital molds: looking beyond 3D printing - Benjamin Peters at TEDxBeaconStreet

A digitally controlled, re-configurable mold is a device often seen in science fiction. Like the common pin art toy, a digital mold is made up of a dense array of parallel, moving pins and can quickly generate any desired surface shape. Realizing the potential benefits such a device could have for manufacturing and prototyping, Ben has developed technology that makes a low cost, high resolution, digital mold a reality.

So let's start by talking
about 3D printing.

3D printing is a lot like
normal printing,

but it's in 3D.

(Laughter)

Not that kind of 3D.

But more like this.

3D printing refers to additive
manufactoring techniques

that build objects layer by layer,

starting from nothing

and ending up with
a completed physical object.

A common exageration is

a 3D printer is just like
a Star Strek replicator,

you can make anything.

Although you can make
very complex geometries

with a wide variety of materials

like plastics, powders and metals.

3D printing does have its limitations.

This is why we have
so many kinds of 3D printers.

These are a lot of
different varieties that exist,

of different kinds of additive
manufacturing techniques

that fall within
the field of 3D printing.

The true magic of 3D printing

isn't it being a Star Trek replicator.

It's how we use it.

A 3D printer is used by designers

to generate their parts
in the real world.

So, you can take a design,

plug it in the printer
and it'll print it out for you.

And you can take
that part in your hands,

make adjustments to it,
change your design

and print another one.

So it's used for iterative design,

and it actually checks parts
with the real world.

So it's a really useful tool.

A disadvantage of 3D printing
is that it's actually pretty slow.

So we have a really nice
little 3D printed cup

over here on the left
with an integrated straw.

Pretty cool!

That takes about the same
amount of time to print

or to manufacture
as these plastic cups

or a hundred packs of 50 plastic cups,
so 5,000 plastic cups.

So it's about the same amount
of manufacturing time,

That's low-balling it.

So, this layer by layer
additive process is pretty slow

compared to a formative
manufacturing technique.

So, I started to gain interest
in 3D printing,

when I was in
my senior year at MIT.

And I wanted to make a printer

that was really fast and really cheap

and printing with
a wide variety of materials.

So I was a little disappointed
to find out

that these goals were kind of

what the entire 3D printing industry
was already working on.

(Laughter)

So, I decided, I needed to take
a different approach

if I was going to make
a big impact in this field.

So, I kinda looked at the trends
that exist within fabrication tools

and you can plot them
on this graph here

where the flexibility and speed
of a fabrication process

are inversely proportional.

So 3D printing on the left is
very flexible, but pretty slow,

and injection molding on the right,
making legos is very fast,

but can only make the parts
the mold is designed to make.

And I needed something
that was both fast and flexible.

Instead of our breakthrough technology

that jumps out of the curve
and then I found out

about a little known field called
reconfigurable pin tooling,

probably haven't heard of it.

Essentially, the idea
is to have a bed of pins

that are adjustable in height

and with those pins,

you can generate a surface
for use in molding

or for other applications,

this is from science fiction,
this isn't real.

(Laughter)

I was surprised to find out
interesting facts though.

This is the first patent
in reconfigurable pin tooling,

in 1863, that's 150 years ago.

But in comparison to 3D printing,

the first pattern in
3D printing was in 1984,

that's 29 years ago.

So, if reconfigurable pin tooling is
so cool and such an old idea,

why are there no
reconfigurable pin tools?

While so many different 3D printers
exist on the commercial shelves.

Well, it turns out there are
just really hard to make.

So, this is a pin art toy,

you'll probably be familiar with this.

This is the most classic example
of a reconfigurable pin tool.

And if I were to make this
electronically reconfigurable,

I would have to add a motor
to everyone of these pins, right?

And there's about a thousand pins
in this sort of cheap desktop toy.

A thousand motors
is a lot of motors

and that's a really significant
engineering challenge.

You probably or you might
have seen this video

which actually came out
this last week.

This is a really cool example
of a reconfigurable pin display,

that some of my friends
made at the MIT media lab.

And this device
is individually actuated,

so all the pins have
a single motor on each one.

There's 900 pins within
3 inches resolution,

and it was used for haptic interface

and for making experimental services.

So, if I wanted a surface
that was high resolution to use as mold,

why can't I do this?

Why can't I make this surface
super high resolution?

Math. That's why.

(Laughter)

Math is fighting me on this one.

When I increase the resolution,

I get this quadratic scaling
of the area,

so length times width is area,

and that's a nonlinear term.

So, when we get
to high resolutions,

this becomes a really big problem.

We get huge numbers
of pins to control,

massive numbers of motors

and it just becomes
totally unfeasible,

and everything falls apart.

So faced with this hopelesness,

I decided to do this
for my PhD and Masters.

(Laughter)

And undergraduate thesis.

And I've been working on it
for about 3 years now.

And I've developed
a number of techniques

to actuate pins and to move pins.

These are some of the prototypes

and I actually won
an award for one of them,

which is the reason I'm here,

because I got picked up after that.

I was kinda disappointed
in all of them so far.

Until recently, and that's kinda of

what I wanted to talk
to you about today.

So, I had an interesting idea

when I was working
on a different project,

not the reconfigurable
pin tooling project,

but I was working on a machine

that had a lot of vibrations in it

and what happened is that
I was attaching a part to it

and the screws in that part
kept on coming loose.

And it was really frustating at first,

but then I realised that
I could actually use

this pattern vibration to turn out screws,

which is actually a really good way
of getting linear actuation.

So moving something along its axis.

So, what I decided to do is apply this
to reconfigurable pin tooling.

And here it is.

It actually works pretty good.

This an array of screws,

that has a specific pattern
of vibration applied to it,

and that causes selective screws
within the array

to actually turn out and
turn them back in as well.

And it works like this:

this is a schematic
of the actuaction here.

We have dislocations within
the square array of screws

and if you dislocate it just right,

around the screw you want
to turn and you reset it,

you get a non linear torque
applied to one of the screws,

and you get motion,
so pretty cool.

And the coolest thing about this
is that the only actuator you need,

the only motor you need
for this array is for the edge pieces.

So the edges are always
going to scale linearly

with the resolution versus
the number of pins scaling

this huge quadratic term.

And all the pins actually
are just little screws.

Screws are very cheap,

and you get can cheap
linear actuators on the edges

for vibration.

And this works really well
at high resolutions

because that ratio becomes
higher and higher,

as you get higher in resolution.

The ratio between linear and
quadratic terms within the array.

With me so far?

(Laughter)

So, after doing this project,

I'm actually pretty confident

now more so than
I have been in the past,

that this HD pin surface
could be a reality,

and you could see one of these
on your desktop

and download a file into it

and have it reconfigure its surface

into an arbitruary file
that you found online

and you use it as a design tool
because you could use it as a mold

instead of just 3D printing objects
layer by layer

or along with a 3D printer as well.

So, it's really just
a close cousin to 3D printing

versus any sort of replacement.

And here it is,
this is kind of the pitch,

the digital mold as the next tool

to help form and shape the future
of personal fabrication.

That's it.

(Applause)