For quite some time I have lusted after a 3D printer with the following specifications:
- A 20x20x15cm build area
- A heating print bed
- A heated build chamber (ambient to 100C) to possibly eliminate warping.
- A respectable print resolution and speed
Over 12 months ago I made my first serious attempt at satisfying these by designing and half building a rep-strap based on the mantis CNC design. However serious limitations in the design and a lack of free time have resulted in the ‘gunstrap’ collecting dust for over 12 months. Among others, the problems with the gunstrap were:
- High rolling resistance due to metal on metal sleeve baring
- Slow speed due to needing to physically move the heavy print bed and print head. assembly.
- Poor resolution due to the design of the Z and Y axis.
- Extruder stepper located within the build chamber.
To overcome each of these limitations I have spent some time designing a replacement in SketcUp, as seen below.
What you see above is a fully enclosed build chamber that will be constructed from 12mm wood fibre board or similar. The blue transparent section is a double layer glass viewing window that is opened by the handle below it.
When opened, the two axis print head and print bed are accessible. To the right of the window will be a 16 character 2 line LCD display for temperature readouts and the like.
This design features the following:
- All electrical components and motors (ex end stops) are located outside of the heated build chamber.
- Print head weight has been reduced to as little as possible to increase print speed and resolution.
- Rolling resistance is lowered through the use of ball bearings.
- Scissor lift Z axis for increased stability
The scissor lift Z axis will be constructed by modifying a lab jack similar to the one shown here. If the wooden shell, which also acts as the main structure of the printer, is removed then the workings become more clear. The modified lab scissor jack coupled to a stepper motor can be seen below (click image to enlarge).
Looking from the front top down on the two axis print head stage its seen that its composed of stainless steel shafts for guides like a Mendel, a PTFE sleeve bearing for the print head holder similar to a Ultimaker. Rather than an expensive belt I plan on sourcing some fine braided wire to use as a pulley which I have seen work quite well on older mechanical pen plotters for lab work. I plan on cutting box section aluminium from corner to comer to make L pieces to hold the guide bearings.
Feeding filament into a wades extruder on the side of the printer will be a mounted filament spool. The wades extruder will force the filament up a PTFE tube which enters the printer at a hole located at the top of the printer.
Finally, in a side compartment insulated by double thickness paralleling will be the electronics. This includes a RAMPS based stepper driver system, ATX powersupply and cooling fans.
As no low melting point plastic components or electrical equipment is contained within the build chamber I believe the high build chamber environment of 100C should be achievable. The heat will be provided by the heated print bed and print head only and will be actively circulated by a fan at the top of the chamber.
I am plananing on sourcing the bearings from smallparts.com.au and modifing them to include a flange. The stepper motors will come from robotgear.com.au for around $85 for 4, including shipping within Australia. I have a month off before starting a PhD in 2012 so hopefully that allows enough time to get this all built and calibrated.
You can find a copy of the 3D model from here. Some parts of the model were sourced from Googles 3D warehouse including the Steep Reel, bolt, Arduino Mega, character display and ATX powersupply.
I would love to hear what people think of this design and so welcome all comments and criticisms. If you have any suggestions for improvements or alternative ideas please leave a comment!
Happy new year to all!
