I originally intended to make this guide for other architects in my office who intend to use the 3d printer. I decided to make it public on instructables, so that its available to anybody who could benefit from the advice. I think due to the size and cost of the machine I have found very little discourse on the subject.
A quick disclaimer, this machine is expensive and fragile, you should not use it without a proper induction. This documentation covers how to improve your workflow, use the machine efficiently and produce better quality prints in less time.
This Instructable covers the process from setting up the print through to post-processing.
Step 1: Model Placement on the Print Bed
Sectioning the Model
One feature of the Projet that I find very helpful, is the ability to crop models simply by moving them out of the print bed area. Sometimes sectioning a complex model can be troublesome and lead to many errors that require extensive manual fixes to make printable. In the pictured example I move the model down by half its height (-50mm). The machine will give you an error to alert you to your mistake, but it will still allow you to print your model if you wish.
The orientation of your model has a large impact on the print time, due to the speed of the different 3D printer axis. As the Projet does not need to print 'scaffold' material like other 3D printers, you are free to rotate your model to make it print as fast as possible. The quickest axis is the x-axis (side to side), followed by the y axis (front to back). And the slowest is the vertical z-axis (as every new layer, you need to pull out a new layer of Core powder. You should generally avoid printing vertically) So when placing your model on the print bed, rotate and move it to be as short and as close to the back of the print bed as possible.
There is a second factor that help choose where to place your model that most often compliments the previous decision, but occasionally does not.
Essentially the rear of the bed is more reliable and accurate than the front edge of the bed. As every new layer of powder is pulled from the rear, it guarantees that powder there is always the most dense and compact area of the bed. This increases the reliability, especially for very fine tolerances/details.
So unless your model is very large it should already be orientated along the back edge for the fastest print speed, also making it the most accurate. If your model is too large and takes up the whole bed you should make sure the side with finer details is at the back.
You should also try to orient your model so that small details are pointing upwards. This means that when the model is being printed, the finest details are printed onto a solid base. As opposed to being printed directly onto loose powder.
The rear edge of the print bed is the fastest and most accurate location. The taller the model the longer it will take to print. Aim to have finest details on model facing upwards.
Step 2: Orientation Speed Comparison
If in doubt the best method is to check for yourself. You can find the 'Print Time Estimator' in the tools tab.
To illustrate the importance of model orientation I created a simple side-by-side speed comparison for the print time on each axis, its only an estimate, but you can see in the images how much the time can vary for exactly the same print.
X-axis = 5 Hours 59 mins (recommended)
Y-axis = 6 Hours 45 mins
Z-axis = 9 Hours 47 mins
The recommended X-axis orientation across the back of the machine is approximately 60% quicker.
Step 3: Extracting the Print
My preferred method for extracting the model, is by excavating most of the powder, and sliding the model onto a mat/tray.
I have broken most models in the transfer process from print bed to post processing area, so i now i prefer to use a mat. Usually the model is still obscured by loose powder, it is very easy to apply force to the wrong part and break it. By sliding the print onto a mat, it spreads the pressure across the whole print, reducing chance of breakages.
The first step of extracting the print from the bed is very straight forward. Start from the opposite corner of the bed from the print, and vacuum as much powder away as you can. Familiarise yourself with the location of the print on screen, so you know what shapes to expect. Once you have cleared all the bed around the print, you can swap the to a smaller hoover nozzle to get into smaller spaces.
At this point its helpful to raise the print bed, it will give you better access to your model, as well as allowing some excess powder to be cleaned away in the corner. You can see from the image that powder will spill out of the bed. You can control the bed height from the machine console by twisting the main dial.
Transfer to Mat
As the model has not bee Infiltrated yet, it is still very fragile. You need to remove enough powder from the model so that its not too heavy when you lift it out. But equally alot of the extra powder is acting as support material. So you need to think carefully about the shapes of your model, remove any excess powder on top of the model, but generally leave powder that is within the model, or acting as a support structure.
Place the mat next to model, gently pick the print up a fraction, and move the model across. You can now easily move the model across to the post processing chamber. Once the print is fully removed from the print bed area, you can do a complete and thorough clean of the print bed. Not only is it good manors, but it is also essential to future machine performance.
Step 4: Cleaning the Model
The main tactic with the air hose is do not rush. The air pressure from the hose can still break parts of your model, if they are thin enough.
The method to using the air hose, is to start approximately 10cm away from the model, and make gentle sweeps side to side. As you get more confident about the shape of the print you can move closer. If you have a very fragile area, that you need to clean, you can reduce the pressure by unscrewing and removing the tip of the air hose.
The mat that the model was lifted on comes in handy for rotating the model without touching it. Once you have removed most of the powder, you will be able to see the best way to pick it up without breaking it. Pick the model up and repeat the same cleaning process but from different angles.
Once finished, the chamber needs to be cleaned, this can be completed by either using the Air Hose or the Vacuum from the build chamber. It doesn't make a difference as the powder is recycled by both back to the hopper.
Step 5: Infiltration
The final step of the process is infiltration. Essentially coating the print in glue. The porous model will absorb the glue and set hard and strong. There are a choice of infiltrants you can use. Personally i have never had any success with Water/Epsom salt combination, and prefer to use the Strong ColorBond Instant Infiltrant.
Please make sure you are wearing all Health and Safety equipment at this point, as this is industrial strength glue. Gloves and Goggles are a must.
The Projet 660pro does provide a fold down post-processing tray in the Post processing chamber. But I would only use this tray for infiltration if you are lacking an alternative well ventilated location.
In general you should keep the glues away from the machine. It is also not a particularly comfortable space to try and infiltrate in. While you don't want to make any mistakes full stop, doing this procedure within the machine adds unwanted stress to the process.
If you are going to proceed in the post processing chamber, you can should switch on the extraction from the main console dial.
Dipping or Drizzling
There are two techniques for applying the glue to the model. Dipping and Drizzling. Both are pretty self explanatory. Unless you have a small print, Drizzling is the preferred method. As Dipping requires you decant large amounts of Infiltrant at once to submerge the model.
Make sure you have enough Glue ready, before you start. If the bottle you are using is only half full, it may be best to open a second in case you need to use it. Do not be concerned about wastage, all unused infiltrant will be re-bottled at the end of the process.
Hold the model within the container, and pour over the ColourBond liberally. Do not worry about getting it on your hand, the gloves will protect you. The process is exothermic, so do not be surprised if the model starts to heat up. Put the model down if its becomes uncomfortable.
Rotate the model as you pour, to cover every bit of surface. You will get the best results if you can completely cover the model in a single continuous pour. This will give a consistent finish once it dries. If you are too frugal with the glue areas will start to dry, and end up with multiple layers. This is when you will have visible drips and marks on the finished print.
Once the model is totally covered, remove it from the container and dab it lightly with a paper towel, removing any liquid on the surface. Keeping drying with a paper towel until the paper comes away dry.
While still wearing your protective gloves and goggles you need to re-bottle the infiltrant that collected in the container. While still over your drip tray, use a funnel to pour the infiltrant back into the bottle. Screw the lid back on securely. Now pat down all your equipment with paper towels in case of any drips or splashes.
Step 6: Drying
You must now leave the model to dry. Drying times are dependent on the size of the model. If you place it in the post process chamber, you can switch the heater on to help. I would leave it for at least around two hour, but large models may require longer, you may need to leave it for longer.
Step 7: Finished
You are finished!