Silicone sock interfering with part cooling?  

RE: Silicone sock interfering with part cooling?

Posted by: @jonas-borgstrom

Since I upgraded my printer to mk3s+ I've been struggling with some PLA curling issues. Printing a Benchy usually result in it being knocked of the bed when the nozzle runs into curled up piece at the top of the arches. I know this could at least partially be due to bad bed adhesion, but it also got me to investigate how effective the part cooling fan was.

I finally found a fan duct with air flow that I prefer, but I'm still on an OG Mk3 setup.

RE: Silicone sock interfering with part cooling?

A few things that make a difference:

After adding a sock, you should run a PID Calibration to 230C to allow the printer to re-tune the heating algorithm as the hot end now has a blanket on it.

I changed to this brilliant fan shroud as it gets airflow the whole way around the nozzle and the sock doesn't interfere. I'm not 100% sure if it is a direct bolt on for and MK3S+ though. Preferably printed in PC Blend or similar.

https://www.thingiverse.com/thing:4124587

This fan shroud for the part cooling fan:

https://www.prusaprinters.org/prints/38001-prusa-mk3s-improved-45-degree-fan-shroud

And this fan shroud for the hot end fan reduce air being pulled from the heated bed, which can cause cold spots that lead to other issues.

https://www.thingiverse.com/thing:3533859

The other one that helps is this shroud for the extruder to reduce heat creep on long prints. If you do this one, do the one without the temp sensor, use a Noctua 5V fan and install the fan so it is pulling the air through the shroud.

https://www.thingiverse.com/thing:4280200

PETG is fine for all the shrouds except the one I said needs PC (ABS or ASA would suffice). PLA is not suitable for any of them.

RE: Silicone sock interfering with part cooling?

Posted by: @morphias

I changed to this brilliant fan shroud as it gets airflow the whole way around the nozzle and the sock doesn't interfere. I'm not 100% sure if it is a direct bolt on for and MK3S+ though. Preferably printed in PC Blend or similar.

https://www.thingiverse.com/thing:4124587

I can recommend a remix of that one, which I feel has a better means of support on both sides:

https://www.thingiverse.com/thing:4588226

I printed this in PC Blend and it has been working fine with a sock.

RE: Silicone sock interfering with part cooling?

Posted by: @jonas-borgstrom

Since I upgraded my printer to mk3s+ I've been struggling with some PLA curling issues. Printing a Benchy usually result in it being knocked of the bed when the nozzle runs into curled up piece at the top of the arches. I know this could at least partially be due to bad bed adhesion, but it also got me to investigate how effective the part cooling fan was.

Unfortunately to me it looks like a good part of the direct air flow is blocked by the around 1.5 mm extra material the silicone sock I have installed adds around the heater block. The fan shroud might work well without a silicone sock, but with a sock installed it looks like the fan shroud is not located low enough for the majority of the air to reach the printed part.

Anyway, to test my theory modified the stock mk3s+ fan shroud to sit 1.4 mm further down and printed it. It's still too early to tell how much of a difference this makes, but I was at least able to print a full Benchy without it being knocked of the bed.

Anyone else that has noticed reduced part cooling when installing a silicone sock?

My modified fan shroud is available here if anyone would like to give it a try:

https://www.prusaprinters.org/prints/53982-sock-friendly-mk3s-fan-shroud

Thanks for posting this. I found the same when "upgrading" my Mk3S with the MK3S+ extruder cover and Mk3S+ fan shroud. Printing out your model now.

I think the Mk3S+ shroud can be further improved as follows:

• restrict the airflow towards the "front" of the nozzle and direct more flow to the sides
• extend the "left and "right" airflow channels by 2mm to get more coverage "behind" the nozzle
• increase the interior width of the left/right airflow channels by 2mm - this won't impact pinda fitment but would allow for less restriction. Don't want to get closer to the sock so need to expand outward
• add vanes for the left and right airflow channels to reduce turbulence
• add a chamfer or fileted bottom edges of the model to minimize chance of catching on the print

I do think this one probably solves most of these issues so I'll try that next: Prusa MK3S and MK3S+ Fan Duct with PINDA Support by kalleknall - Thingiverse

RE: Silicone sock interfering with part cooling?

@dan-3

Dan: Nice find.  I keep looking for the best shroud and this might be it.  

RE: Silicone sock interfering with part cooling?

This is the same one that I had recommended above.  It is well supported and works great.

RE: Silicone sock interfering with part cooling?

@g-monkey

I glossed over your post - sorry.  Great find.  

RE: Silicone sock interfering with part cooling?

Ok a few minor drawbacks with the kalleknall style shroud:

• The fan is only held in place with one bolt instead of two. For me this means the fan is able to vibrate and makes printing noisier. Using a zip-tie on the free bolt location helps.
• You need ~4mm more slack in the fan cable compared to the Prusa shroud due to a slight change in fan location.
• This shroud is more restrictive so max airflow is reduced. You can tell this by the fan's RPM change compared to the Prusa shroud. Unless you're printing super fast, max airflow is not the issue - the direction of airflow is more important for detail work. For high-speed functional prints without steep overhangs, the Prusa shroud will probably perform better. Swapping back and forth between these isn't too difficult but you do need to change the fan mount in addition to the shroud itself so don't toss your old fan mount!

RE: Silicone sock interfering with part cooling?

I have not had any fan vibration issues with mine.  There is only one bolt for the fan but it is well seated in the shroud itself, and the shroud is well supported by two bolts.  I don't understand your point on the 'rpm changes', as there is no air flow sensor - fan speed is set in the slicer and then put into the gcode, not dictated by airflow.

RE: Silicone sock interfering with part cooling?

@g-monkey

RPM will pitch a bit higher with more resistance to the airflow, given the same driving current.

RE: Silicone sock interfering with part cooling?

Posted by: @kenryan

@g-monkey

RPM will pitch a bit higher with more resistance to the airflow, given the same driving current.

No, the fan does not increase speed with increasing load.  This fact is easily demonstrable by putting your finger on it while it is turning.  The resistance of your finger will slow it down.  If you are able to detect (or even better measure) an increase in fan speed while using this shroud it will be due to lower resistance/better airflow than the standard shroud.

RE: Silicone sock interfering with part cooling?

Quoting an informative article on the topic of centrifugal fans:

https://hvacrfundamentals.blogspot.com/2009/08/understanding-centrifugal-fan-motor.html

...Fan motor performance is one of the most often misunderstood aspects air conditioning systems. The amp draw on a centrifugal fan goes down as resistance to airflow is increased. For most people this seems counterintuitive. It is easy to picture the fan motor pushing harder to overcome the resistance and increasing in amp draw. However, this is exactly backwards. Centrifugal fans move air by throwing the air outwards through centrifugal force. The amount of air the fan is moving decreases as the resistance to airflow increases. If the fan blades are moving less air, they can actually spin easier because there is less air to sling. This causes the motor RPM to increase and the motor amp draw to decrease...