Ceramic Extrusion
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Release status: Experimental
| Description | Unfold Ceramic Extrusion, extruders and materials
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This page describes the research done by Unfold on extruding ceramic materials with a RepRap. The development platform used is a Bits from Bytes Rapman so all extruder cad files are designed for this machine or machine independent. The CAD files or general principles should be easily adaptable to Mendel or other machines. This page describes experiments with various types of paste extruders, ceramic clay recipes and other related topics. We keep a blog about progress on ceramic 3d printing and other topics at [1].
Forum thread
http://forums.reprap.org/read.php?180,21047
Status
Experimental, documentation under construction, in fact I just lost half of my edits :(
Extruders
Claystruder 0.1 (Stepper Driven Plunger)
Description
This design never left the drawing board but was based on the principle of a plunger being driven down a syringe barrel using a (stepper) motor. This can be done either with an expensive linear stepper engine like on the Fab@Home Model 1 Syringe Tool or with a more standard rotational stepper. Examples of the later are the Fab@Home Model 2 Syringe Tool, a very early Syringe Pump Prototype by Adrian Bowyer, Zach Hoeken's Frostruder MK1 or Viktor's (VMX) Syringe Tool. We never had any experience using this type of extruder on clay paste so this is an incomplete list of (dis-)advantages:
Advantages
- Compatible with most software, firmware and electronics due to the use of a stepper engine
Disadvantages
- Paste oozing source
- Assembly height is at least double of syringe length making it rather impractical for larger volumes
- Inflexible in syringe size
Claystruder 1.x (Time-Pressure Valve)
Description
Based heavily on Zach Hoeken's Frostruder MK2, Claystruder 1.0 is the printhead that we used extensively for over a year to successfully print earthenware and porcelain ceramic objects. Basically instead of a mechanical plunger, you use timed pulses of air pressure to drive the material out of the syringe hence in the industry this is called a Time-Pressure Valve. The only difference with the frostruder apart from the physical design is that we use one double action 3/2 solenoid valve instead of two 2/2 single action ones. The 3/2 valve will pressurise when powered and automatically de-pressurise when power is removed. Its cheaper and requires only one controller output to operate. The double 2/2 gives possibly a greater flexibility in pressure timing. We also use a rubber plug that comes with your syringe on top of the material to prevent air pressure from digging a canal true the last 10-20cc of material. Without it you loose the last bit of printable material but worse the resulting air jet will shoot a hole in your model (or even more destructive). You can build a Claystruder 1.0 for RapMan following the instructions below, create your own design or use a Frostruder from Makerbot to get similar results. note: We have never tried but expect more trouble getting decent ceramics prints with machines that have a moving bed like Makerbot Cupcake or RepRap Mendel. The resulting movement of your complete model which is still plastic for the duration of the build can result in a collapse. A bed that moves only along the Z axis might be preferable, alternatively you can try using slow build times and the acceleration features of recent firmwares.
Build Instructions
Also on Thingiverse: It is important to note that it was never designed with elegance or easy printability in mind, its just a quick and dirty prototype. The Claystruder 1.1 is designed on top of a spare RapMan extruder mounting plate that we had around. The DXF for the mounting plate is attached. Laser cut out of 5mm material. The claystruder base that holds the syringe is glued on top of the mounting plate. Two feet fit in appropriate holes of the plate. (see, not very elegant...) The two STL's that make up the claystruder need to be printed with support turned on. It is kept to the minimum but its not completely without overhangs. You can fit most 50-60 cc syringes in the base of the Claystruder. The cap is also a mounting base for a 12v DC 6012, 3/2-Way Miniature Solenoid Valve from Burkert: link. You will also need two screw on connectors for the tubing. On short tube goes straight down true the cap and should end 5-10 mm below the bottom. Here you can fit a rubber plunger cap from a 60cc syringe that you perforate to guide the tube true the rubber cap. This will make sure that your syringe is air tight. On top of the valve goes your tube that runs from the compressor. At the front of the valve is the pressure release outlet. I always use two small clamps to hold the cap and the base together. You will need to fit something on the base plate to trigger your limit switches. I use a threaded rod and a few bolts. Like for the Frostruder, you need a compressor, 10 bar max, for it to work.
Advantages
- Simple straight forward design
- nearly instantaneous start/stop capability
Disadvantages
- Less compatible with most software, firmware and electronics due to the use of a solenoid valve
- Air compressor or other source of compressed air needed
- Difficult to control flowrate
Claystruder 2.x (Auger Valve)
Description
This is the current head under development and not based on previous RepRap developments but rather on extensive research of industrial dispensing solutions. The aim is to solve some of the issues observed during extensive testing of v1.0.
Print Materials
Preparing Clay
Filling a syringe
While I was going through the excellent documentation of the Frostruder at Makerbot I found the following photo's of Zach filling a syringe:
I used this method exactly once :) Its totally unusably for getting a syringe filled with clay and trying to avoid any trapped air. So here's the method we hacked together in a few minutes.
The Syringe Transfer Tool!
The STT is a syringe from which the front is cut of and that is used to suck up material.
You still need a canister or lump of air free material but thats easier than to try and get the material compacted in every syringe individually. turns head-does not adjust speed-back to typing.
Next step is to fully insert the plunger in the syringe and suck up material. The trick is to pull the plunger while simultaneously pushing the syringe in the material. After 100 times you can do it one handed while taking a picture :)
Now you detach the plastic plunger stick from the silicone plunger cap without letting air in (tricky part). After that you smooth the clay and taper it a bit, I always put little pit in the top to make sure air escapes before the clay reaches the nozzle when transferring the clay in the print syringe.
Onto the magic transfer move.... You make a nice stack of pssst-turns head-perfect print finished. A nice stack of plunger stick - STT - empty syringe and you push the clay out of the STT into the empty syringe, et voila!
Porcelain
Images
First printed ceramic vessel
Gcode toolpath
Various tests
Notes
- designboom: "unfold and tim knapen: l'artisan electronique" "Z33 art centre in hasselt, belgium ... on show until may 30, 2010. the installation enables exhibit visitors to make their own forms using the device."
