Hi all,

... all the readings about warping and heated beds let me think about using this for developing of printable actuators and other parts ...

My idea is to build actuator-elements out of a heater embedded between sheets of different materials with different thermal behaviour - a 'normal' bimetal-setup, but with plastics, glass-fabric, ceramics and such.

This is a reprappable way to tools like grippers, tweezers or even piston-like elements ...

Viktor

That sounds... like a great idea!

But you'll need printable embedded nichrome.

Luckily, we're working on it!

[objects.reprap.org]

This is a reprappable way to tools like grippers, tweezers or even piston-like elements ...

Neat! What size range do you plan to explore with this?

Hi Sebastien,

... my tweezers and actuators are mostly some millimeters to centimeters in size and only partially suitable for bigger scaling ... here i atached images of some of the 'bigger' ones

But with some tweaking and redesigning you can build some ten centimeters big actuators too.

For a project with Fraunhofer and Festo i designed some elastc kinematics, pneumatic grippers and 'morphing fingers' in sizes from 5 to 20 centimetres, but with an optimized FEM and stronger materials you can build some really big morphers with meters in dimesnion ...

Viktor

why not just use nitinol?

... my comercial micro-grippers use nitinol with 0.1mm diameter - heating 0.5 seconds for closing, cooling 1.5 seconds for releasing again.

When applying two counteracting nitinol-actuators, you can reduce the moving time to 0.7 seconds in both directions, but it's mostly to slow either

My magnetic actuators didn't have a measurable delay, but they're much weaker (or the VC-magnets bigger).

PZT-actuators have very high forces (some ten to hundred Newtons) and actating-frequencies up to some ten kHz, but very low moving ranges (around 0.2 to 0.3mm linear travel).

I have some piezo-leg-actuators with 'propagating wave'-movement, which can travel 25mm, have an stall-force of maybe 4 Newtons, a resolution of 0,15 micrometers stepwize (or some nanometers in continuous high-voltage mode), but with below 10mm/s they're a bit slow ...

My best actuating material were some NiMnGa-blocks, what's called "magnetic shape-memory alloy", is activated by a magnetic field instead of voltage as with PZT, can morph/travel 5 to 10 percents of the actuator length (compared with max. 3% with nitinol and 0.3% with PZT), can apply some hundred Newtons force and activating frequencies in the kHz-range ... only two drawbacks - first: it was pricey, second: the company (www.adaptamat.com) isn't there anymore

But for reprapping you should think about fabbing hollow structures out from elastic resins/silicone for pneumatic and hydraulic morphing/bending structures ...

Viktor