Our precious crucible cart has undergone its final transformation into what will likely become the key element of our glass printing machine. Unlike portland, refractory does not use good ol’ H20 for its chemical bound, so for refractory, firing is a key step.
Next time you see our crucible cart it should be mounted on our machine!
One last chapter before we can begin our crucible cart’s dryout schedule: the top. We need a bomber top to handle ladling of molten glass blobs into the crucible as well as way to fix the loose electrical terminals. The insulating refractory won’t cut it in these departments so its time for some more 3000F rated refractory to coat on top.
After its fired we can get it mounted to the machine and should be showtime!
Now that we have that big (potentially) hot heater coil wrapped about our crucible, its time to give her some insulation to keep those precious BTUs where we want it – melting glass (or whatever else we may find ourselves melting with our new contraption – mooohahaha).
Alright, so now after carefully placing our crucible cart onto our vibrating table we clamped forms around the sides ready for filling. In all places where there was potential wood contact, we covered said wood with plastic bags to prevent it from adsorbing an unfair of moisture from the curing refractory.
Then we get to flip it over and finish the top side – next episode.
Of course, if we are to melt glass, we are going to need some heat, a whole lotta’ heat indeed! So we are pleased to finally outfit our crucible a 220V 2KW heat coil and packed in a jacket of 3200F rated refractory.
Next up – fill this baby with some insulating refractory to keep our needed heat in.
We got the cart all built today. The crucible isn’t much good if we can’t steer it around, and that is the the cart’s primary task. The secondary task is to provide a frame that will fill with high temperature insulation (refractory).
The third task is to provide a thermal heat break from the 2000F crucible. We selected stainless steel for that task and in addition, the stainless doesn’t make full contact with the steel it will be mounted to. So the stainless is about 1/4″ away and only make contact where it is bolted.
Our first nozzle heater coil attempt failed miserably. The refractory selected for the task was far too course and we were unable to fill the nozzle cavity properly. So when it heated up, the heater coil sagged and shorted out. But – we did learn from our mistake(s)!
One missing step was to measure the resistance of the heating wire before it is hidden from view. This lets us keep an “eye” on the coil even when its buried in refractory. So if we get the resistance readings after packing refractory, we know for sure that the coil has not shorted out. The first coil didn’t short out, but it wasn’t packed satisfactorily.
Another thing we learned is; it was difficult to pack the coil in place. So to help to that end, we decided to pre-pack the heater coil (after stretching of course). Between the proper refractory and the pre-packing we are confident this second attempt will work.
We are very excited to get the last hot-end machining done. It was stopping us from packing the nozzle heater in refractory, and getting this show on the road. She’s really starting to look like a lean mean glass printing machine!
One thing we really wanted from day one is to be able to actuate the nozzle. It will allow for much more complex pieces to be printed beyond single wall items (such as vases) than the glass printer as described by MIT. There are some ideas presented by the Glass Lab, though this is our stab at the task.
As eager as we are to get the nozzle glowing yellow; we took the time to put it in now. We are quite pleased with the outcome so far (to be tested of course). We wonder if aluminum and copper will be printable with this setup?!?
The main reason we bit the bullet now is the crucible assembly will be much more fragile after its all been fired, so we needed to do it now if it is to be done with our initial setup.