GMASS - Tungsten, X-ray shielding filament from Turner Medtech
Posted: March 21st, 2016, 8:27 pm
So, I we received a spool of Tungsten filament the other day and here is my preliminary review of this interesting material.
This ABS-filament with tungsten particles is marketed as printable radiation shielding and also as a dense plastic that can be printed to weigh down things: http://turnermedtech.com/gmass.html
At the moment, it only comes in 1.75 mm, which means you need a rebuild kit if you are an Ultimaker user.
We intend to use this for printing components for our X-ray diffractometers, here is an example of a test piece I made:
(This one does not have a particular purpose other than testing how well this filament prints)
I was also interested in how this works with ruby nozzles, as I heard horror stories about this basically being unprintable with brass nozzles because of the rapid nozzle wear.
If any of you consider testing this filament, here are a few comments:
- The printing temperature stated in the instructions is 200-230 C, which is surprisingly low. I have never managed to print ABS well below 240 C and I mostly print at 260. I had to increase the temperature to 260 for the GMASS to print well too.
- Using the TESA Easy Stick glue to make it stick to the glass plate works well just as with other ABS filaments.
- A nozzle size of 0.5-0.6 mm is recommended, it does print with the 0.4 mm nozzle too though.
- This filament has really odd extrusion characteristics. I am still confused to how difficult it is to extrude.
I had to print at 20 mm/s (0.15 mm layers) as my direct extruder would skip at higher speeds.
My boron carbide filament as a reference, which has a much larger fraction of particles both by weight and by volume, extrudes quite similar to pure ABS. So either Turner Medtech used some really weird ABS grade for this filament, or there is some effect of the particles that I don't yet understand.
- There seems to be a very wide range of particle sizes in the filament, some of them are HUGE, at least 0.1 mm.
I would therefore recommend at least 0.15 mm layer height (as the manufacturer does) with no less than 0.3 mm initial layer.
The last point means the ruby is not safe anymore. Tungsten may be softer than Ruby but the sheer size of some of the particles means you can still break chips off the ruby. Here is how the tip looked after a few hours of printing:
That wear will not affect the printing quality and the nozzle will likely survive for a long time, but it is good to be aware of this.
I used diamond lapping film to polish the bottom surface of a print to check for large grains and here is how it looks.
The line width of this first layer became a bit uneven, but the average of two lines is 0.8 mm. You can imagine when I started printing at 0.2 mm initial layer, which was more like 0.1 mm in reality, and those huge particles get caught between the glass plate and the ruby (you will hear it 
)
That is why I would not print with less than 0.3 mm initial layer.
For weighing down things I would actually recommend using Colorfabb bronze/brass/copper-fill instead as it has similar density but is much cheaper, easier to print and does not wear the nozzle at the same rate.
For X-ray shielding this thing is, although a bit difficult to handle, still highly interesting!
This ABS-filament with tungsten particles is marketed as printable radiation shielding and also as a dense plastic that can be printed to weigh down things: http://turnermedtech.com/gmass.html
At the moment, it only comes in 1.75 mm, which means you need a rebuild kit if you are an Ultimaker user.
We intend to use this for printing components for our X-ray diffractometers, here is an example of a test piece I made:
I was also interested in how this works with ruby nozzles, as I heard horror stories about this basically being unprintable with brass nozzles because of the rapid nozzle wear.
If any of you consider testing this filament, here are a few comments:
- The printing temperature stated in the instructions is 200-230 C, which is surprisingly low. I have never managed to print ABS well below 240 C and I mostly print at 260. I had to increase the temperature to 260 for the GMASS to print well too.
- Using the TESA Easy Stick glue to make it stick to the glass plate works well just as with other ABS filaments.
- A nozzle size of 0.5-0.6 mm is recommended, it does print with the 0.4 mm nozzle too though.
- This filament has really odd extrusion characteristics. I am still confused to how difficult it is to extrude.
I had to print at 20 mm/s (0.15 mm layers) as my direct extruder would skip at higher speeds.
My boron carbide filament as a reference, which has a much larger fraction of particles both by weight and by volume, extrudes quite similar to pure ABS. So either Turner Medtech used some really weird ABS grade for this filament, or there is some effect of the particles that I don't yet understand.
- There seems to be a very wide range of particle sizes in the filament, some of them are HUGE, at least 0.1 mm.
I would therefore recommend at least 0.15 mm layer height (as the manufacturer does) with no less than 0.3 mm initial layer.
The last point means the ruby is not safe anymore. Tungsten may be softer than Ruby but the sheer size of some of the particles means you can still break chips off the ruby. Here is how the tip looked after a few hours of printing:
I used diamond lapping film to polish the bottom surface of a print to check for large grains and here is how it looks.
)That is why I would not print with less than 0.3 mm initial layer.
For weighing down things I would actually recommend using Colorfabb bronze/brass/copper-fill instead as it has similar density but is much cheaper, easier to print and does not wear the nozzle at the same rate.
For X-ray shielding this thing is, although a bit difficult to handle, still highly interesting!
