Delta
Release status: unknown
| Description | Delta type parallel kinematic manipulator setup to be used as repstrap
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| Based-on | [[]]
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Contents
Introduction
The Clavel- or Delta-robot is mostly known for its use in pick-and-place work in PCB fabrication and generic packaging applications. It features fast and accurate positioning and is relatively easy to build. We, User:Energetic and User:Reinoud teamed up to create a both easy to fabricate and light on the budget RepPrep/RepRap. Our goal is to be well under the current prices for Mendel and/or Darwin RepRap's.
We decided to design and develop the bot trough a series of prototypes, learning and refining on each iteration.
Prototype 1
The initial prototype designed and lasered by User:Energetic. It was cut out of 1 cm acrylic sheets by a shop. It proofed the concept of the magnetic ball bearings and the overall structure of the design. Regretfully it was never driven by an Arduino/Sanguino other than simple stepping.
Prototype 2
Lessons were learned from prototype 1. It proved to be hard to reproduce the machine since non-standard 4mm shaft Nema17 motors were used and needed some intricate drilling in the side of the sheets to receive the bolts and nuts. Since acrylic also turned out to be quite expensive, we decided to go for plywood. We replaced the 10 mm acrylic with a set of three sheets of plywood with the respectively thickness of 3, 4, 3 mm so to easily accommodate the 4mm nuts and bolts.
The structure was also modified to accept larger upper-arm ranges to give it a larger work-space. As 4mm shaft steppers are hard to find, the design was modified to use the standard 5mm shaft Nema17 steppers.
Although we've learned a lot of this prototype to justify a prototype 3, we'll first try to get it to work first. We might stumble on other unforeseen challenges!
Calibrating
The bot can detect the arms being in the start position. However, due to various causes the exact start angles of the three arms are not known but a rough estimation. Start angles being wrong result in a severe warped space that is far from flat nor the right size. The prototype therefore needs to be calibrated at least once in its life or when its reassembled.
Prototype 3
Will most likely not feature the timing belts and pulleys. They proved to be too hard to get and can hopefully be replaced by either higher resolution microstepping or by a lasercut gear system. It will most likely also not feature the current ball-bearings used to hold up the cut-out wheels since the ball-bearing, but also the bolts attaching them also turned out to be hard to get.
The plan is to make this one either the next prototype, or the final, of the laser-cut Delta RepPrep.
Prototype 4
Well.. speculation here... First RepRap-able version?
Firmware
User:Reinoud has written a ReplicatorG compatible firmware that does both the needed coordinate transformation and the real-time control. The goal is to have the complete bot, including the extruder, running on either a single Arduino or on a single Sanguino with standard Polulu stepper controllers and standard Nema17 steppers. As for SDD card recording and playback support, a Sanguino might be required since the imported implementation of the FAT/MSDOS FS alone takes about the half of the Arduino 32Kb flash program space and currently just doesn't fit with the rest.
Is http://deltafimware.googlecode.com/svn/trunk/ the lastest version of that firmware?
Firmware Math
TBD
Mailing list
Existing Designs
"Mjcbruin" from the Netherlands designed the this delta bot for $70. It is driven by 3 hobby servos, and is controlled by an Arduino. The code has been published at the letsmakerobots link. Video Design + code
User:Reinoud has built a similar design with servos.
- Ugly Stewart Platform ( http://builders.reprap.org/2006/09/ugly-stewart-platform.html ) : crude prototype for hydraulic Stewart platform.
- first stab at a Stewart platform RepRap: http://blog.reprap.org/2006/02/reprap.html
- Biollante: a few more stabs towards making a hydraulic Stewart platform RepRap: http://burningsmell.org/biollante/
- Biollante posts: http://builders.reprap.org/search?q=Biollante
- Volksrobot: http://sites.google.com/site/volksrobot/
- "Delta robot kinematics" by mzavatsky goes into excruciating detail on the math, has some nice illustrations, and ends with some sample code in C and a Lego implementation.
- Tripod positioners such as the SpoonPod, the Helium Frog Delta Robot, and Viktor's tripod repstrap demonstrator have many similarities to Delta positioners, as does the TRap.
- Forrest Higgs prints nice herringbone racks and pinions on his RepRap, and speculates that perhaps they will be useful in a Delta or Stewart RepRap.[1][2]
Files
Tooling
Lasercutter and standard tools are sufficient to make the current repstrap version
