This week I have done the final few prints for the radiopacity project. I have been working on this project since June and it is satisfying to see how far the project has come since then. The paper is also coming together nicely, and I am excited for when I can post the results of the project.
In research, things rarely happen as originally planned, often due to completely unforeseen factors. I have decided to focus this blog on how real timelines are often quite different to the plan. This week was my second time ‘hacking the printer’ on my own, and this time I was much more confident. This week, I had three things to print:
- Print a hand with radiopaque bone (within TangoBlack, a black rubber material to represent the soft tissue of the hand)
- Samples for mechanical testing the material (5 of each)
- Samples for a second mechanical test (5 of each)
The hand was the biggest job (4 hours) and I originally planned to get the two mechanical testing samples done in a second print job (1.5 hours). Here is my original plan for the two days:
This plan wasn’t being super optimistic, either. I gave myself extra time to make the material and set up before printing, with an hour between prints to clean and setup for the next print. Friday was block booked for cleaning and getting the printer back to full working condition for Monday morning. ‘Test and clean’ from the timeline means checking how badly the printer had been blocked up while printing the radiopaque material, unblocking the print heads and making sure there are no issues before beginning the next print. This is the part that I had rushed in previous prints, cutting corners and continuing with the print even though heads were blocked, because I thought that ignoring one or two blocked heads (out of ~100) would not affect the end results. This was a huge lesson for me, as I now know that this step is crucial. One or two blocked heads at the start can ruin an entire print and result in repeating the entire job, which in the long run, is more time consuming, and also a waste of material. I made sure to mix my material after any break in printing – as I had not done this last time. This time, after mixing well before every print, there were hardly any blockages.
So, this time I did not cut corners with the cleaning step, but the real timeline was still quite different from the planned timeline:
The ‘reality’ timeline was going perfectly (almost too perfectly!) until 13:30, when I realised the hand part was printing but no bone was showing up. I cancelled the job and checked the printer for blockages, but there were no print heads blocked. We had this problem a few months previously, and to be honest we are still unsure what went wrong. The 3D hand file (consisting of two parts – the bone and the surrounding soft tissue) successfully printed with clear ink as the skeleton and black rubber material as the soft tissue, but would not print the radiopaque material. Eventually, I decided to swap the cartridge tag to trick the printer into thinking that it was printing just clear ink (as I knew it had already successfully printed the skeleton from this cartridge earlier in the week). I tried a tiny hand first – ‘Test print’ in the ‘reality’ plan (shown below, the hand is less than 1cm long). This print was successful so I started the print of the hand at 18:00 and went home while it continued to print.
While trying to resolve the hand issue, I split ‘print 2’ from the plan into two parts. I thought two smaller prints would make more sense because if the print failed again, there would be less material wasted. The first small print (Print 2 in the reality plan) was successful but the second (Print 3) was cancelled as parts did not reach the correct height. By 16:00 I had the idea about swapping ID tags so the hand skeleton could be printed, so I abandoned print 3 and printed the hand.
The following morning I saw that the hand was printed successfully. I removed the hand from the print tray, made up some more material, and attempted print 3 again – the final print. Again, this print did not reach the height that it was supposed to. I tried again, and this time the print was fine.
Overall, I was very happy with these two days of work. Even though the printing took nearly twice as long as I had planned, I still managed to get them all done before the weekend. Most importantly, there was very little blocked heads during the print – I am going to credit this to the fact that I took more time to set up/ clean the printer before plowing ahead and printing as I had done previously. I also think that mixing the ink before every single print helped to reduce blockages, and was worth the extra time as this reduced the clean up time after each print. I look forward to getting the hand x-rayed next week to show exact radiopacity of the print!