One thing I’ve always struggled with has been printing overhangs and to some extent bridges due to inadequate part cooling. The problem is, with a monstrous hot end assembly such as mine, where can I fit a fan without losing too much travel in X or Y?
My answer has been to exploit the fact that there is some space in between the two X rails on the Y carriage (at the very ends of the X rails).
So I designed the X under carriage with “wings” on the side and ducting to channel the air from two tiny blower fans onto the part being printed.
So when the carriage is at X min or X max, these tiny fans just fit in the gap in the Y carriage and I don’t lose any X movement. The problem is that these fans being 30mm x 30mm x 10 mm only have a rating of 1.24 cfm which was probably being restricted to even less than that by the narrow ducting that I first designed.
Therefore, time to upgrade. After a lot of searching , I managed to source a couple of 40mm x 40mm x 10 mm fans with an airflow rating of 3.0 cfm. With one fan each side, I previously had (1.24 x 2=) 2.28 cfm in total but probably less due to the restricted ducting. These new fans will give up to 6 cfm (3.0 x 2) so about 260% more (providing I could modify the ducting). I did lose some movement in X due to the bigger fans. The final result was that I now have 344mm travel down from 360mm with the 30mm fans. So I’ve lost 16mm but I can live with that.
The featured image at the top of this post shows the final OpenScad design. I managed to get the ducts enlarged significantly but it’s all very tight. Here is the the part with a model of a V slot wheels in place.As you can see, this is a big as I could make the ducting as there isn’t much clearance.
Here is a side view of one of the ducts. There is one on each side or course.
and this is the end view. The top is about 3mm thick at the front but gets thinner, as do the sides – down to about 1mm in places in order to maximise the available space.
and from underneath, it looks like this. The airflow is directed down and towards the nozzle but not directly at the nozzle.
I printed it with E3D edge but it was over a year old and I hadn’t done a very good job of keeping it dry, so the quality isn’t great. However, it did a pretty good job of making an unsupported 40mm wide bridge.
and this is what it looks like with one of the new fans in position (but not fixed).
Of course it was a fairly major job to strip down the complete carriage assembly and fit the new part but I got it done in record time (I’ve had a lot of practice by now).
Here is a not very good picture of how it fits in the gap between the X rails on the Y carriage at X max..
I haven’t yet run any test prints but I have high hopes. 6.0 cfm might not sound very much but when it’s focused as it is, there is quite a considerable blast of cold air – much much more than I had before. Oh and they are quieter than the 30mm ones too. They had a very annoying whistle at full speed which these ones don’t have. Both types of fan are 12v and I run them through a DC-DC conveter at a PWM frequency of 10 Hz, which gives me surprisingly good control if I want to run them slower. I’m looking forward to seeing what sort of torture tests I can do with them ………..