In this tutorial you'll learn how to download and 3D print the Ada robotic hand, for a tutorial on the assembly of the hand click here. The Ada robotic hand is the new generation of robotic hand, derived from our previous Dextrus robotic hand.
This tutorial is for:
- Hand: Ada V1.1
- Board: N/A
- Firmware: N/A
You will need:
Downloading the Ada hand
The Ada robotic hand is released under Creative Commons Attribution-ShareAlike 4.0 license, meaning that it is completely free to download and use, we only require that any modifications and improvements are also released to the community with the same freedoms.
To download the latest version of our Ada hand:
- Download the 3D files here
- Extract the downloaded ZIP file (ada-robotic-hand.zip)
This folder contains the components required for a left and a right Ada hand (8 STL files), each part is prefaced with 'L' or 'R' denoting whether it is a part for a left or right hand. A single hand requires the following 3D printed components:
- Palm - Ninjaflex
- Back cover - PLA/ABS
- PCB tray upper - PLA/ABS
- PCB tray lower - PLA/ABS
The palm is orientated to produce the best surface finish on the palm and the ventral (front) surface of the fingers, and also allows the finger joints to print correctly. With the part in this orientation, it requires support material between the print bed and the bottom surface; support material is not required for any of the internal parts of the palm.
The palm is printed with the fingers hyper-extended as this allows them to provide a more constant force when actuated and prevents the fingers from being too floppy at their naturally-extended position.
The back cover is orientated so that the face of the wrist connector is on the print bed, and the text prints facing the correct way up. This part requires (line pattern) support material both between the bed and the bottom surface of the cover, and for the internals of the cover.
PCB Tray (Upper & Lower)
The PCB tray prints as 2 separate components, which are then glued together. They are orientated with their flat faces on the bed and do not require any support.
Recommended PRINT settings
Print settings will vary between printers, If you have already dialled in your printer for using Ninjaflex and PLA, then we recommend you use those settings. Below are the print settings we have used to print the Ada hand.
- Ada Parts: Back cover, PCB tray upper, PCB tray lower
- Layer Height: 0.3mm
- Temperature: 205°C - 230°C
- Print Speed:
- Outer shell: 30 mm/s
- Inner shell: 70mm/s
- Infill: 70 mm/s
- Infill Density: 30%
- Overhang Angle: 60%
- Ada Parts: Palm
- Layer Height: 0.3mm
- Temperature: 230°C (Lulzbot Taz)
- Print Speed:
- Outer shell: 16 mm/s
- Inner shell: 20mm/s
- Infill: 20 mm/s
- Infill Density: 45%
- Overhang Angle: 30%
- Support Density: 25%
Please read the 'Tips for printing with flexible filament' section below for a more detailed discussion on printing with Ninjaflex, or visit the Ninjaflex website for their recommended print settings.
The support material on the back and inside of the palm needs to be removed, as well as any support material in the fingertips and in the motor slots.
Flex each finger in turn and make sure that there is no excess support material preventing the finger flexing.
Remove the support material from the inside of the back cover, the wrist connector holes and around the base of the back cover (support is highlighted in grey in the images).
The PCB tray is printed in 2 separate components, upper and lower. Use super glue to join the two flat faces together, making sure that the slots for the motor cables line up, and allow time for the super glue to dry.
tuning the STIFFNESS OF THE finger joints
The joints in the fingers have been designed in order that both of the joints close at the same rate, however the joint stiffness is greatly affected by the print settings. If one joint closes before the other, then you may need to manually adjust the joint stiffness, either by adding super glue or by slightly cutting the joint material with a scalpel. This step can damage the hand, so only adjust the stiffness of the joints if you feel that it is absolutely necessary.
When a finger is closed, if the proximal (bottom) joint completely closes before the distal (top) joint starts to close, or if the proximal joint seems overly floppy, you will need to stiffen the proximal joint. Use a toothpick or cotton bud to apply a small dab of super glue to the inside of the proximal joint. The tip with this method is to add a small amount of super glue, wait for it to dry, test the joint stiffness and then repeat.
If when the finger is closed, the distal joint closes completely before the proximal joint start to close, then you may need to reduce the stiffness of the proximal joint. Use a scalpel to create a small cut on the inside of the proximal joint (highlighted blue), this should loosen the joint.
If the motors appear to struggle to close the finger, you may need to loosen both of the finger joints. Use a scalpel on both the proximal and distal joints, as described above.
TIPS for PRINTING WITH FLEXIBLE FILAMENT
Our Printing setup
Our 3D printing arsenal comprises of the following:
We use all of these printed to produce the various components of the Ada hand. The Mini is primarily used to print the PLA parts (Back Cover & PCB Tray) and both the Ultimaker's and the Taz's are used to print the Ninjaflex parts (Palm). We have modified/upgraded both the Taz's and the Ultimaker's to allow them to reliably print flexible filaments such as Ninjaflex. Below are a few of our tips, modifications and techniques for printing with flexible filaments.
The force applied by the feeding the filament into the hot end creates pressure in the nozzle which forces the melted filament through the nozzle. The nozzle pressure is influenced by many different factors, such as the consistency of the material at certain temperatures, the extrusion speed, the nozzle size etc.
Flexible filaments require a low nozzle pressure to extrude reliably. One way to reduce this nozzle pressure is to increase the nozzle size. We use a 0.6mm nozzle on both the Ultimaker's and the Taz's. A nozzle size of 0.5mm still allowed us to print Ninjaflex reliably, however increasing the nozzle size to 0.6mm allows us to increase the extrusion speed, thus decreasing the print time.
extruding Flexible filament
An issue with flexible filament is that it can compress and buckle under pressure, which means that the distance between the extruder and the hot end should be as short as possible. There should also be as few gaps and pinch points as possible, such as the gap between the knurled bolt and the hot end.
The Taz uses a direct drive extruder, therefore it is relatively simple to modify to print flexible filament. You only need to the standard extruder with the flexystruder, which removes all of the pinch points and possible gaps in the extruder.
The Ultimaker uses a bowden extruder setup, which comprises of a stepper motor mounted on the frame of the printer which feeds the filament through a length of tubing connected to the hot end. This setup reduces the mass and size of the print head, thus increasing the possible print speed. However this setup is not suitable for printing flexible filament as flexible filament tends to buckle in the bowden tube and the amount the filament can compress and stretch over the large length results in a less responsive hot end.
To modify the Ultimaker to print flexible filament we have used a Flex3Drive. The Flex3Drive uses a flexible drive shaft connected the frame mounted stepper motor, which also connects to an geared extruder assembly mounted on the print head. This means that the print head still has a small mass and footprint, but reduces the distance between the extruder and the hot end, effectively turning the configuration into a direct drive setup.
The Ninjaflex website suggests that Ninjaflex is printed at 230°C (225°C - 235°C). We currently print Ninjaflex on the TAZ at 230°C, and at 195°C on the Ultimakers. The temperature of the Ultimaker is so low to prevent strings and to allow it to print bridges relatively successfully.
As detailed above, we need to keep the nozzle pressure relatively low in order to allow for reliable extrusion. Another way to reduce this pressure is to print slowly. We use print Ninjaflex at around 1/3 of the speed we use for PLA.
Flexible filament compresses as it is extruded and stretches when retracted. This means that the retraction speeds and distances need to be increased to prevent stringing on the print.
We have found that the settings for printing Ninjaflex differ slightly between colours, for example we have found the following Ninjaflex colours to print inconsistently.
- Sapphire Blue
Take this information about material inconsistencies with a pinch of salt, as there may have been other contributing factors causing the print inconsistencies.