Unicorns

Further Adventures in 3D Printing


Our 3D printer has not had much use lately, due to a number of reasons; the main one being that we’ve simply been too busy with other things. However, we recently received a new sample of masking tape for the print bed, and we thought that this was as good an excuse as any to dust off the 3D printer and start printing off some more stuff.

If you’ve read our previous blog post on 3D printing (http://www.makerspace-uk.co.uk/3d-printing/), you’ll have seen that our previous attempts have been a little hit and miss. In general, the results have been very good. However, with a lot of the things that we’ve printed, we’ve suffered from the prints warping, and lifting slightly off the print bed, so we’d been determined to get to the bottom of why this was happening, and to try and find a solution. To see how we got on, please read on.

Having received our new sample of masking tape, we were really keen to have a go at printing off some new things. For a start, however, we thought we’d check that everything was working ok by printing off some old favourites like our unicorn and elephant. Unfortunately, our first attempts with the new tape really didn’t turn out at all well, and we found that all our prints simply refused to adhere to the tape; even ones like the elephant which had previously caused us no problem at all. The image below shows the results of one particular attempt where the print lifted from the print bed and formed a sticky mess under the extruder:-

Initial attempt

Initial attempt

Clearly, we had a bit more investigation to do.

The first thing we tried was to move the printer to a more stable platform, as the table on which it was located was a little on the wobbly side. This, however, made little or no difference.

Having completely run out of our old masking tape, there was no way of checking whether or not the new tape sample was the cause of our problems; and having waited so long to receive our new sample of masking tape, we didn’t really want to wait for another different sample. However, we did think that it was perhaps worth trying a different type of tape to see if this might work. The only thing that we had readily available in a decent width was some Gorilla tape, so we thought it might be worth a try. However, although we did find that the prints adhered really well to the Gorilla tape (probably due to the initial layer effectively being melted into the tape itself), this caused a problem with the surface of the tape remaining stuck to the print when the print was removed from the print bed; as can be seen from the image below:-

Gorilla tape print

Gorilla tape print

Clearly, if we were going to make any progress with what we had available, we needed to really go back to basics.

One of the things that we had noticed when printing the elephant (the GCode for which we had received with our 3D printer) was that the print head cooling fan was on right from the very start of the print. However, with the other prints that we’d tried, we noticed that the fan only came on after the first 2 layers had been printed. We were fairly certain that this would make a difference, as previously our elephants generally printed better than all our other print attempts. However, there was clearly something else that we needed to do also, as we were now finding, with our new sample of masking tape, that even our elephants would not adhere to the print bed.

Something that had been suggested to us some time back was that it might be worth rubbing down the print bed with some form of alcohol to ensure that there were no greasy residues which might prevent our prints from adhering properly. Luckily, we had relatively easy access to 250ml bottles of Isopropyl alcohol (http://cpc.farnell.com/ambersil/230015080/isopropyl-alcohol-250ml/dp/SA01224), so we got hold of a bottle and some paper towels and tried cleaning the surface of the print bed, and also the layer of tape that we placed onto the print bed. This made quite a difference to our first attempt at printing an elephant, and we actually think that it was one of the best things we’d managed to print.

Elelphant - base layer

Elephant – base layer

Elelphant - top layer

Elephant – top layer

Satisfied that our newly found knowledge was helping to improve the quality of our printed elephant, we decided to further investigate how to ensure that the fan would be running at the start of our other prints. This meant digging into some of the more expert settings within our slicing program, Cura.

The expert settings within Cura are accessed by means of the ‘Open expert settings…’ dropdown from the ‘Expert’ menu. Pressing Control-E will also provide a shortcut to the expert settings. Within the expert settings, there is a ‘Cool’ section, within which one of the settings is ‘Fan full on at height (mm)’, for which we had a setting of 0.5mm. We reasoned that by changing this value from 0.5mm to 0.0mm, this should cause the fan to come on from the very start of the print. Examining the resulting GCode showed that a GCode of ‘M107’ was replaced with a GCode of ‘M106 S255’. We decided to try this with our printed unicorn, and, sure enough, we found that changing this setting had the desired result of causing the print head cooling fan to come on right from the beginning of the print, and this provided much better print bed adhesion.

Really pleased with the progress we were making, we decided to investigate some more options within the Cura slicing program. One of the other issues that we’d had with our printed unicorn was that the rear end of the unicorn was not printing very well because there was no support for areas that were not in contact with the print bed. We’d noticed that there was a ‘Support type’ option under the basic settings within Cura. For the prints that we had done, we had opted for a setting of ‘None’; i.e., no support. We thought we’d have a go at printing one with a support type setting of ‘Everywhere’. The trade off for this setting was that the print would take an additional 7 minutes, however, the finished result was well worth the extra time, as can be seen in the image below:-

Unicorns

Unicorns

The unicorn on the right was printed with no support, whereas the one on the left had a support type setting of ‘Everywhere’. This causes the print areas not in contact with the print bed to be supported by means of a small platform, which can simply be snapped or cut off once the print in complete.

One final thing we wanted to do was to ensure that the print head would always automatically go to the home position prior to starting the print. We found that this was simply a matter of adding the GCode line ‘G28’ (Move to origin/home) prior to the ‘G29’ (Probe bed) GCode line in the ‘start.gcode’ on the ‘Start/End-GCode’ tab within Cura.

Following these final tweaks, we are finding that the majority of our prints are coming out far better that our previous attempts. However, as always we will continue to try out new things and carefully monitor our results; and we’ll be sure to let you know of any new discoveries we make along the way.