Preparing the printer
Place containers under both chutes. These will capture excess material that can be reused later. A tarp can also be placed under the printer. Some dust will fall down different holes and gaps in the printer while printing and it will make cleaning the printer later a bit easier.
Next set the printer to preheat. Preheating the printer will make the powder spread better and will leave the part stronger when it leaves the printer. A good starting point is 60°C. Leave the printer for about fifteen minutes. The sensor is not in the powder but on the printbed, so if the sensor says 60°C, it does not necessarily mean that the powder is 60°C yet.
Before printing can be started on a 3DP printer, the printer needs to be filled with material. The amount of material needed depends on the height of your part. Ideally you will need the height of the part in feed material, but the printer works better if there is some extra. Before starting, it might be wise to remove the cartridge. Filling the printer will make some of the powder spurt. If this powder gathers on the nozzle it will negatively impact the printing.
First lower both feed pistons by an amount that is at least the height of the part to be printed, with quite a bit extra for compacting and safety. Next lower the build piston by 5mm.
Next fill the printer with material. This step is pretty self explanatory.
Use special compacters or something like a spoon to compact all the powder. Compacting is an important step that should not be skipped. If the material is not compacted, it will shrink when the spreader moves over it, effectively reducing the amount of material (in volume). This will eventually ruin the print, by not getting enough material on the print.
Next create a smooth surface. Raise the feed pistons to the height of spreader. Then, either by hand or by the printer, mover the spreader to the other side. Some material might overflow into the chutes on either side. Repeat raising the feed pistons and moving the spreader until the entire surface is smooth. Doing this step with layers to thick will actually tear up the printing surface, so do it in small (smaller than 1mm) layers.
Then, just before printing, insert the cartridge with the binder. Now everything is set for printing.
Insert a micro SD card containing the print file in the SD card slot on the megatronics.
REMEMBER: the file on the SD card that will be printed has to be named “print.txt”. Any other files will simply be ignored.
Estimate the file and use a thin rod like a screwdriver or a caliper to check if the amount of material in the feed hoppers. If this amount is less than the amount of layers multiplied by the layer thickness, the printer will not have enough material to print. The printer does not check its piston positions, so this could damage the printer.
The printing density needs to be selected before the print is started. The density changes depending on material, binder, cartridge age and how strong the model needs to be. 100% In the case of a 96DPI cartridge means the printer will deposit 96 drops per inch in the sweeping direction. Raising this value will increase the amount of droplets per inch. With HP6602 cartridges, printing at 100% will leave gaps in the print most of the time. During the tests prints were made with percentages ranging from 200% to 300% with double sweeping. This gave good results on strength and shrinkage.
The last step is also the easiest step, press print to start printing. If the first few layers turn out good you can leave the printer. The first few layer may slide around a bit, this is not a disaster. It will stop after the first few layers. If the first layer is completely obliterated though, it might be wise to stop the print and restart it with thicker layers.
post printing processes
After the printer is complete, it will enter a heat cycle. This heat cycle is an important step of the printing process, without it the part will be very fragile. After the heat cycle the part will be stronger, making it easier to handle and clean. 30 minutes is enough in most cases, but an hour is best. Overriding the heat cycle and manually setting the heat (maybe even to a higher value) is also sometimes required.
When the heat cycle is completed, the part can be removed. First dig most of the remaining material from around the model. Then use a spoon to scoop up the part. Then, using a tube or a source of compressed air, blow of the remaining loose powder from the model. Doing this in a closed box (see the depowdering station) will make this job less messy.
The last step is to infiltrate the model to bind the model. This will give the model it’s final strength. There are several options, ranging from waxes to epoxy resins, but the easiest infiltrating liquid is CA (Cyanoacrylate, super glue), the thinner the better. Wear a mask while doing this, Some of the CA will vaporize during this process and breathing it in not make you happy. Place the model in a disposable container and apply the CA to the model. When CA makes contact with the porous printed model, it is rapidly absorbed and instantly cures. Do infiltrate the model in a well ventilated room or outside, since the fumes released by the CA are not something you want to breathe in if it isn’t necessary. getting a bottle of CA with a brush is a wise investment (even just for the brush), because a brush can deliver CA a lot more accurately than simply dropping it on. Then either use CA activator or let the part cure for some time to fully cure the model. Now the model is at full strength.