3D printing: Shells and Infill (Part 3: Printing the 3D model hand)

Before we begin: In part 1 we described what are infills and shells. In Part 2 we did some testing.

We took what we learned from part 1 and part 2 and printed our 3D hand model! For your information, the 'original' model had 15% infill and 2 extra shells. The 'new' model was set to 0% infill and 1 extra shell. Lets look at the results.

The Main Hand Body
Original: 224 grams (24 hours), material: Red PLA
New: 54 grams (6 hours), material: Red PLA
Comments: The New model was four times lighter, more aesthetic and it took significantly less time to print! The improvement in weight was due to no infills. It looked better since we printed the new model standing (as shown in the pictures) but the original model was printed lying flat at the back of the hand with the palm facing upwards. It took only 6 hours to complete compare to 24 hours because less material was used.

New and Original hand body (Palm side)

New and Original Hand Body (Back of Hand)

The Fingers

Original fingers : 118 grams (13 hours), material: Red PLA
New fingers : 128 grams (13 hours), material: transparent PLA

Comments: The weight had increased and it took around the same time as before.  Furthermore, it looks really ugly. Each individual piece did not have a uniform material density. The bottom half of the printouts were solid (even though we set it to zero infill) and the top half had no infill. You can see in the image (bottom right) that the base is very yellow because transparent PLA turns yellow when it is densely printed, hence solid! The top part is slightly transparent because less material was used. We will probably have to print out another batch!

New fingers and Old fingers

Base was solid while the top has no infill

Conclusion: The body of the hand improved in weight however the fingers did not. Something went wrong and we will investigate further.

3D printing: Shells and Infill (Part 2: Testing)

Before we begin: In our last post, namely "3D printing: Shells and Infill (Part 1: Introduction)" we gave a brief account on what shells and infills are in the context of 3D printing. We intend to use this knowledge to reduce the weight of our 3D printed hand.

In this post we tested the 'shell' and 'infill' function and had some fun with more 3D printing!

Test 1: Rectangular cuboid

Infill: NONE

Extra Shells: NONE

Test 1: We found that it was very easy to break. This was MINIMAL material. We thought that we needed extra shells. 

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Test 2: 3D finger

Infill: 1%
Extra Shells: 3 layers

Test 2: The extra shells made it much thicker. It was very tough. The 1% infill was negligible. We didn't complete the print.

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Test 3: Another 3D finger with external defects

Test 3: Broke in half to look inside

Infill: NONE
Extra Shells: NONE

Test 3: Easy to break. Some defects visible and will be a problem. Looks like we need more shells to improve its hardiness. 

Conclusion: To reduce the weight of our 3D models we can have ZERO infill and ONE extra shell. We will attempt to print the 3D hand model with these settings. 

3D printing: Shells and Infill (Part 1: Introduction)

Before we begin: The aim of this short study was to decrease the weight/material of our 3D models (the hand). We have successfully printed a hand (link) however it was too heavy. If the hand was lighter, it will be more portable and easier to make future add-ons (such as wrist or arm).

In this post we will introduce the terms 'shells' and 'infills'. We believe that we can significantly reduce the weight by removing the unnecessary material inside 3D models.

The SHELLS, also known as perimeters, are extruded outlines defining the shape of the layer. Extra shells strengthen objects.

INFILL is what happens in the space left over.

It's usually extruded in some kind of pattern. The main setting we're dealing with here, though, is infill percentage. (refer to the image below)

More infill will make an object stronger. Less will make it lighter and quicker to build.

Objects for display often won't need more than 10% infill, while even objects that are going to see hard use rarely need more than 80% infill. Not using more infill than necessary will help us save time and plastic.

Source: http://www.makerbot.com/support/guides/printing/

Taken from http://blog.teambudmen.com/2013/09/understanding-shells-layer-height-and.html
Author: Isaac Budmen

Acetone Vapour Bath gives a shiny smooth finish

We can get rid off the annoying layers(rough surface) on the 3D printed objects by this method called acetone bath. But Acetone bath is only used for ABS plastic. So we cannot do it for our 3D printed hand.

Further doing some research, Yay! Instead of acetone, we can use tetrahydrofuran, or THF, as a solvent for PLA. The process for smoothing PLA with THF is the same as smoothing ABS printouts with acetone.

Here is the method,

The nExt biG Thing

Finally we were able to print an awesome 3d Hand. The heat issue that we have on our 3d printer caused some dodgy results. Some of them are,

However after fine tuning the 3d printer we managed to print a complete 3d hand (Thank you Andrew  \m/). Used rubber pieces for the hinges as the 3d printer doesn't support the flexible materials. It was bit of a challenge to shape those rubber pieces and also to drill the fingers so that we can put the thread in. Also I had to sand the sides of the fingers so that it has less friction for the movement. Here are some photos.

It already has a lot of fans. :)

GREAT JOB GUYS!

Printing a Robot Hand

We have found a very attractive 3D model of a robot hand call Flexy-Hand on Thingverse (link) designed by Gyrobot, published on the 4th of March 2014.

Here is a description from the website:

A proof of concept printable hand with "live hinge" flexible joints. Individually activated fingers using Filaflex filament as tendons.
Printed in Makerbot Translucent Red and Filaflex hinges.
Re-mix this idea into your own robotic or prosthetic project. 

• Fingers open automatically, no return tendons or springs needed.

• "Frictionless" articulation - no rubbing parts.

• Stretchable tendons offering adaptive grip on irregular objects (only one motor required to activate all fingers).

• Fully printable solution, no vitamins required.

• Tough and rugged.

• Realistic form under a surgical glove (see image above). 

We have spoken to a few people from different Engineering departments about using a 3D printer.  

Will keep you updated about its progress!