Getting our hands dirty with 3D Printing (Part 2)

Over the last 10 years, Stratasys Strategic Consulting have spent a lot of time developing software to analyse the cost of 3D printing. Labour is still a big element of the cost and so to refine our cost models further, we sent our Senior Consultant, Loic Le Merlus to the Stratasys EMEA demo centre in Baden Baden to spend a week learning about the work activities within the 3D printing process chain. Over the next few weeks he will discuss what considerations are important when analysing the cost of labour in 3D Printing.

In our previous article, we talked about  how important it is to prepare the print file and how time consuming it could be. This week we are going to talk about the 3D printer itself: how to prepare the printer before a print, how to do maintenance operations and how to remove parts from the 3D printer.

Preparing the machine

On most printers, you need to prepare the machine before being able to print. On PolyJet machines you need to clean the print heads manually with a silk cloth and ethanol to remove any material that tends to stick to the print head from previous jobs. You also need to clean the platform with ethanol as a thin layer of support material might still be there. Once this is done, you can start the print on the computer connected to the machine. This whole operation takes between 5 and 10 minutes.

On an FDM machine it is easier, you just need to put a new print base sheet into the chamber and then select the next job for printing. However you have to make sure there is a good seal between it and the print bed otherwise sufficient vacuum wont be generated by the pump. One trick is to let the print sheet warm up a bit in the chamber making it flexible and helping to create a much better seal. Once this is done, you can check that the starting position of the extruder and make any necessary adjustments. This takes between 1 to 2 minutes depending if you’re able to get a good seal on the base sheet first time around.

Once the machine is printing there’s no real need to do anything else freeing you up to remove other builds or prepare the next build on the computer.

 

Cleaning platform
Cleaning the platform on an Objet500

 

 

Removing the printed parts from the printer

Removing parts from a professional FDM machine like the Fortus couldn’t be any easier as you only have to remove the print sheet or tray from the chamber. Even for the biggest machines there are no issues except maybe the weight of the part itself. For a PolyJet machine it can take a bit longer as you need to remove the parts manually one by one from the machine. There is also a support structure between the part and the platform which is soft enough to break easily be requires the use of a spatula to scrap through it. With bigger machines such as the Objet 1000, parts can get very heavy and need specialist equipment to remove them from the machine. All in all removing parts from the machine takes between 1 and 3 minutes

removing tray from fortus 400
Removing the build tray from a Fortus 400

Maintenance of the printer

Like all manufacturing machines, 3D printers require maintenance. It can be as common as changing or refilling material to changing the print heads themselves. On a Fortus FDM machine, it is necessary to change the tip after a certain amount of use. For example after every 800 inches of ABS filament or 300 inches of Ultem. Changing the tip can take between 10 to 15 minutes and every time the tip is changed the machine needs to be recalibrated. This is done by printing a special pattern which allows you to measure with calipers any misalignment in each axis as well as the width of the filament extruded. Once the measurements are taken they are entered into the machine which will then automatically correct itself. This process is repeated 2 to 3 times to ensure a good calibration. This generally takes about 15 minutes to printing the pattern and 10 minutes to measure it each time. Reloading material is easy if you are printing with the same material and the same tip size. If you want to print with a different material however, the tip needs to be changed which means the calibration needs to be redoing. Also depending on what the previous material was and what the new material is, a chamber heat stabilisation process must all be run. For instance the worst case is changing from ABS to ULTEM which takes 6 hours for the build chamber to stabilise at the new temperature.

Changing tip on Fortus900
Changing the tip on a Fortus900

 

With Polyjet processes, the roller and blade need to be cleaned every 1000 machine hours or any time issues with the part are noticed. This cleaning takes about 30 minutes. The longest operation however is changing a print head which can take 2 hours but this is only done when there is something wrong with it. After changing the printhead or when changing materials, it is important to recalibrate the machine. This involves printing special patterns and then weighting them on a scale which is linked to the machine as well as printing patterns on paper which are then scanned for the machine to interpret. This process takes about 20 minutes to print and 30 minutes of technician time. Changing materials is not that straight forward, as the old material need to be purged from the system first. This can take about 1 hour and then the machine needs to be filled with the new material which takes about an hour as well.

Calibration of an Objet 500
Calibration of an Objet 500

How will this look in future?

As we have seen, maintenance and preparation are still manually intensive, even though the calibration process has been somewhat automated on the recent versions of the Polyjet. In the future, robotics can be integrated in the machine which would allow minimal labour for loading and unloading the machine as well as automatic calibration. For other processes, big service bureaus have developed centralised material feeds to make the reloading of the material totally automatic as well as making sure the machine will never run out of material in the middle of a print. As 3D printers enter more and more factory floors all those process will be streamlined and become more automatic thereby reducing the workload of skilled technicians who currently are required to run the machines.