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As I have built a closed chamber for my UM2 (http://umforum.ultimaker.com/index.php?/topic/5921-um2-greenhouse-edition/), I have been particularly interested in improving cooling of the printing head. Kris posted some really inspiring analyses here:

http://umforum.ultimaker.com/index.php?/topic/5953-idea-on-underextrusion/

...and I felt like trying my luck with more powerful fans. These were the most powerful ones I could find, given the size constraints:

http://www.yeahracing.com/catalog/yeah-racing-tornado-high-speed-25x25mm-ya0201-p-2520.html

http://www.yeahracing.com/catalog/yeah-racing-hacktronic-tornado-high-speed-ball-bearing-25mm-htn304-p-3471.html

In an attempt to maximize the heat dissipation, I got the aluminium blocks black anodized. The anodized layer is removed from the joint surfaces between the two lowermost blocks in order to improve thermal conduction:

Aluminium parts, black anodized (1/2)

 

To avoid excessive absorbing of heat from the nozzle unit, I removed the anonized layer from the bottom of the lowermost block:

 

Aluminium parts, black anodized (2/2)

 

...also, the holes for the nozzles are drilled slightly bigger from underneath (except for the last 1mm or so) in order to reduce the absorption of heat from the nozzle unit.

 

I installed 2 of the Yeah Racing Tornado fans to the printing head:

New fans

 

Both fans are blowing from the front to the rear - in other words, I inverted the airflow.

 

Arctic Silver was used between the two lowermost aluminium blocks.

 

Printing head assembled

Printing head in action

I had to make small dents to the lowermost plastic block in the printing head for wiring purposes.

If i wouldn't have the dome around my printer, the noise from the new fans would drive me nuts. Fortunately the high-frequency noises are absorbed quite nicely by the PC and acrylic windows, so the increase in noise level is subtle.

My first impression is - I certainly need to find a new balance for retraction settings. I'll post an update after some testing.

 

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After initial tests, I feel quite good about the hack... My starting point is a bit peculiar due to the closed chamber:

dome (thermal image)

As the outside surface temperature of my dome is around 38C (in air-conditioned room), I believe the air inside the dome must be over 45C - and above to the heated bed naturally more. The image above was taken when printing ABS at 260C, having the build plate temperature at 90C.

Unfortunately I don't have before and after images of my printing head, but here are some thermal images after installing the Tornado fans:

printing head, front corner view (thermal image)

printing head, front view (thermal image)

printing head, lowermost visible point of PTFE (thermal image)

printing head, uppermost visible point of PTFE (thermal image)

I need to install an additional lens to my thermal camera to get more precise images... However, if the front fan temperature is around 65C and the PTFE temperature varies around 63C-74C, it looks like the ventilation is quite efficient.

Unfortunately I have no way to observe the temperature on the back side of the PTFE part. Also, there are some tricks with the measurement, as I need to open the front window of my printer in order to capture thermal images. This will naturally start cooling the chamber immediately, unless I placed the printer to my sauna. At that point my wife would probably start calling around for some professional help.

Further updates after further tests - now it looks like retraction works without issues and ABS warping is well under control.

 

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Actually, this comparison I should have realized to do already earlier - here are thermal images from the front and from the rear, taken from the fans:

front fan

rear fan

I took several images from front and from rear, having the printing head in different areas of the build plate. The temperature difference was consistently 10C. Given that I have 2 fans (each 5.13 CFM - I know they don't equal to having a 10.26 CFM fan) replacing the original 3 CFM fan, I think the temperature difference is significant. At least the PTFE part gets much cooler air than it would get with the original setup. Of course, my closed chamber makes my setup difficult to compare with the original setup without the dome.

My firsts tests with challenging (from warping point of view) ABS prints are very encouraging. I'll try to get some photos uploaded tomorrow...

 

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Right... I haven't yet had time to play a lot with PLA. It looks like I need to use higher temperatures than before in order to use same retraction settings as before. I don't know whether this is logical or not - maybe I should start trying different retraction settings.

What comes to ABS, I'm very happy. As ABS is more important for me, I have used much more time to try it out. Here are a few photos of my most challenging print so far:

work in progress

ready, still at print bed

bottom with raft 2/3

bottom with raft 3/3, strong shadows

bottom view, without raft

top view, without raft

There's quite a bit of retraction involved - also some overhangs are quite tricky. Prior to my closed chamber hack, I also suffered from warping. Now the geometry aspects seem to be in order. The photos above have been taken using sunlight and flash in a way any problems would get accented. In real life the piece feels fairly smooth and very solid.

BTW - with raft, the size of the basis is 203x203mm. In order for me to get it printed, I needed to bend the clips holding the glass bed in its place - otherwise they hit the print head.

 

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A word of warning for anyone going for a similar hack... It seems to be easy to drain too much current from the fan output. I don't know exactly how much power consumption is too much, but the 2.8W taken by two Tornado fans did cause some headache for me:

http://umforum.ultimaker.com/index.php?/topic/7067-temperature-oversampling/

Now I have a completely separate power supply for the fans. The good thing is - now I can adjust their operating voltage independently.

 

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No need to worry about the 5V fan connector, you can safely draw more then 2A out of it.

 

I don't know why the 2 Tornado fans cause a problem - is their load not purely resistive or what - but the impact on the temperature reading fluctuation is very clear. When the 2 fans are connected, the temperature on LCD varies +-10C (20C from peak to peak, approximately) - without the fans, it's barely +-1C.

 

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Yes, I'm using a similar power source for the fans now. However, as the Tornado fans use 5VDC as their operating voltage (and up to 7DC), I also use one of these for regulating the voltage:

http://www.ebay.co.uk/itm/331125688871

Very good combo, in my opinion.

 

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