Chocolate Print head for i3 quick change printer

thingiverse

As it says in the title. This is a 3d print head for printing chocolate things. This is in progress it is one of my quick change units or will be. Primarily i will use a Syringe (with insulated jacket) and use the plunger to push out the chocolate onto greaseproof paper attached to the bed using bulldog clips. I started to design this, partly because i demonstrate printing occasionally and I struggle to find prints that are liked by a whole range of people from the young to the old, and male and female. The chocolate printer seams to get every one interested. For me the more people that can be inspired to participate in science or engineering the better Notes, Chocolate starts to melt at body temperature. Printing from a syringe onto greaseproof paper clipped to the print bed means it is easy to clean. the nozzle is large about 2mm and a print height of 2mm is reasonable prints can be completed in 10 to 15 mins depending on the size white chocolate appears to give a better finish than milk or dark. Bubbles can be a problem. Instructions I decided from the beginning that i would use the extruder driver to move the Syringe plunger (in the paste extruder). This lead to first problem the extruder has a built i safety feature and will not work below 180 degrees C. To solve this I will use a Pot on the Carriage to simulate 200 degrees. I have noticed people have used external circuitry to control there paste extruders, this is for me not the ideal solution. It lacks any elegance and is not using the available resource of the printers extruder. Using 2 small stepper motors (28BYJ-48-5V) wired in parallel as in the z axis of the prusa i3 to drive the plunger up and down. Assembly, 1, Cut two 3mm perspex strips 40mm wide 210mm long 2, insert 4 bearings into the top_plate and the middle plate. insert 2 M6 nuts into the plunger plate and glue on the 2 washers to prevent the nuts from coming out, take care not to glue the nuts. also add 2 M4 screws to operate the micro switches. 4, layout the the top, plunger, middle, and bottom plates with the 2 perspex strips and familiarise there orientation and positioning. Carefully glue one 40mm strip into the guide of the middle plate ensure exactly 90 degrees in all 3 planes. and the location 150mm from the end. 6 Repeat step 5 on the other side. 7, Glue on the top to the long ends of the perspex. 8 Insert threaded bars through top, plunger and middle plates. Thread on nuts as you go. Update 2nd July15 the chocolate printer was used in earnest last week, I preloaded syringes with Dark, milk and white chocolate the day before, the heater box was set at 35 degrees c (not sure how accurate the sensor was but within a degree or so). The printer itself performed perfectly, however the chocolate didnt, the Dark chocolate solidified too quickly, the milk chocolate printed 3 or 4 layers then new layers just stayed moulten and the white chocolate didnt cool any where near fast enough to use. in conclusion i think finding a blend of dark and milk chocolate that works best is my next project.