I don't think so..
I desired a bit more of a challenge. How about using the 6x6x6 print to create all the custom bits for a simple, elegant and fully functional CNC machine? I am not talking about a conventional 3-axis gantry-type CNC mill, but something a bit more exciting. I set myself the challenge to design and build a machine based on the Delta Robot, capable of milling/drilling in soft materials, and have all the main custom components for the motion platform fit in the 6x6x6 inch envelope of the awarded 3D print.
This inctructable has initially been published after the completion of the design phase. The first few steps will discuss the objectives, background, software & electronics, mechanical design and conclusions. In addition there are several steps to be completed afterwards, showing the actual build of the machine. A change log is attached to this first step. Current version: V0.11
Step 1: Objectives
- An important objective is to create a design for a Delta-robot based CNC mill, where the majority of custom components for the motion base will fit in a 6x6x6 inch envelope.
- The components in the 6x6x6 envelope must be printable on one of the Objet 3D printers at Instructables.
- Elegance is high on the agenda. Not only for the way the machine looks, but also in the way the motion base moves.
- As I already have a large CNC machine, I will initially try to 'borrow' as many parts as I can in order to keep the cost down.
- The motors must be powerful enough for the machine not to lose any steps, without having to resort to gearing.
- Speed is not the biggest priority.
- The accuracy of the mill should be sufficient for drilling small circuit boards (think free version of Eagle PCB) and milling small items.
- Last, but not least, it should be fun to design, build, and use the contraption!
Step 2: Background: Delta platform
- There are no costly linear slides, only pivot points.
- All the important motion mechanisms can easily be located above the work piece, away from debris.
- Simple mechanical concept, with low variety in components.
- The way a delta works is just more interesting than the majority of linear platforms...
The picture in this section is from the original patent, which expired a few years ago. Further reading: http://en.wikipedia.org/wiki/Delta_robot
Step 3: Software & Electronics
In order to be fully flexible for development purposes, I have two different options for connecting the stepper drivers to the PC. First of all there is the Arduino, which currently is loaded up with GRBL. The second option is the connection over parallel port using a 5-axis interface board. The last option should enable me to run LinuxCNC.
At the moment I do not know how to go about sorting out the software. I will worry about that after I have an actual mechanical assembly I can play with. Some links I found suggest that I do not need to start from scratch:
Step 4: Mechanical Design
You will notice there is nothing in the model holding the rod ends onto the shafts. I am planning to sort this by using elastic bands or tension springs between a pair of links. The doors can be lifted out. Hinges are universal, ie. not handed. Take out the pins from one end, place them in the opposite positions, turn the door around and the door opens the other way around with the only thing wrong being the text on the handle now reading: 9x9x9... Hinge locations not being used as hinges can be used to lock a door by inserting thin pins.
Attached to this step is a small movie file. Open it up to see a short animation of the motion base. There are some random oscilations on the motors in order to generate movement.
Step 5: Conclusions
If I would have designed the parts for being produced on a more basic printer and without the 6x6x6 inch restriction, I would have designed everything in a slightly different way. For example, I would not have had to split the motor base and tool holder into three separate parts. Still, having designed functional 3D printed components for the first time, I now want to do more! I am certain I could increase the accuracy of the Delta by adding some gearing... The tool holder could be replaced with a purpose designed unit with integrated light weight 3D print extruder... I am sure now: Stage 1 is to get permanent access to a 3D printer, Stage 3 is world domination. No idea what Stage 2 is though!
Step 6: The Build, 3D Printed Parts
More will be added to this step, as soon as there is progress on this front. For now, see the pictures for my suggested print. I left a gap of at least 0.5mm between components in order to prevent them from sticking to each other. I still have to generate a final STL file, but will do so at the moment that it is needed. I am planning to publish the as-built design files after actually assembling a machine myself.
Step 8: The Build, Fabrication
Step 9: The Build, CNC Machined Parts
Step 10: The Build, Mechanical Assembly
PS. Can you spot the most important tool in the picture? It is the one with the wooden handle...