Bed Fan Duct

The place to discuss your hardware and software/firmware modifications...
User avatar
quaver
Posts: 53
Joined: Fri Feb 27, 2015 4:32 am

Bed Fan Duct

Post by quaver » Sat Oct 08, 2016 6:20 pm

In the process of updating to an E3Dv6 hot end. As this requires a new extruder mount I decided to try a duct for my 50mm bed fan. I have attached a few shots of the design. Thoughts/comments/suggestions? I am not convinced that a bed fan duct really helps cooling or improves print performance but it seems many users have adopted them. The duct improves containment of the airflow but it also causes a pressure drop which lowers mass flow. Perhaps a duct with a higher capacity fan (20mm thick vs 10mm) is better but it seems simply using the same fan with a duct could potential reduce printing performance.
Attachments
E3DV6_Bed Fan Duct1.jpg
Bed Fan Duct Xsectn
E3DV6_Bed Fan Duct2.jpg
Bed Fan Duct

User avatar
quaver
Posts: 53
Joined: Fri Feb 27, 2015 4:32 am

Re: Bed Fan Duct

Post by quaver » Sun Oct 09, 2016 6:06 am

Finished the attachment design and fan guard. Mounting bar (green) is held to the extruder mount (brown) by two machine screws. Duct (blue) attached by means of a dove-tail tab. Should be easy and quick to install/remove. Fan guard is a new design intended to reduce noise level and improve airflow. I plan to use the E3D provided heat-break fan and shroud (not shown) oriented with the fan to the side or rear.
Attachments
E3DV6_Bed Fan Duct4.jpg
E3DV6_Bed Fan Duct5.jpg

User avatar
insta
Posts: 2018
Joined: Tue Sep 16, 2014 3:59 am

Re: Bed Fan Duct

Post by insta » Mon Oct 10, 2016 1:07 am

Very nice!

Make one for the V4 :mrgreen:
Custom 3D printing for you or your business -- quote [at] pingring.org

User avatar
quaver
Posts: 53
Joined: Fri Feb 27, 2015 4:32 am

Re: Bed Fan Duct

Post by quaver » Tue Oct 11, 2016 12:01 am

Thanks Insta. For grins and giggles I ran a simple CFD analysis on the duct assuming a 0.1" H2O static pressure at the inlet. Distribution looks nice and it seems the tongue in the center nudges air to the perimeter on either side which is what I was hoping would occur. The simulation does not take turbulence from the fan into account so everything looks nice and uniform. I will likely add a .25" straightener in the section of the throat just below the flange face to help reduce turbulence.
Attachments
duct_fx4.jpg
CFD on duct

User avatar
quaver
Posts: 53
Joined: Fri Feb 27, 2015 4:32 am

Re: Bed Fan Duct

Post by quaver » Wed Oct 12, 2016 4:14 am

CFD of the fan guard looks promising as well. Very little pressure drop (<0.09" H2O) and good distribution. Knock off a few of the sharp, interior downstream edges and it should be in good shape.
Attachments
bed_fan_guard_CFD1.jpg
Velocity vectors and pressure gradient
bed_fan_guard_CFD3.jpg
Trace paths

User avatar
insta
Posts: 2018
Joined: Tue Sep 16, 2014 3:59 am

Re: Bed Fan Duct

Post by insta » Wed Oct 12, 2016 5:20 am

Which is fantastic, but doesn't solve my v4 problem ;)
Custom 3D printing for you or your business -- quote [at] pingring.org

User avatar
quaver
Posts: 53
Joined: Fri Feb 27, 2015 4:32 am

Re: Bed Fan Duct

Post by quaver » Fri Oct 14, 2016 6:48 pm

To beat a dead horse... I decided to run a CFD check on the whole bed fan system as an assembly. Interesting results. Found turbulence downstream of the fan motor support plate (see graphic). This structure is the same diameter as the hub of the fan. Gluing a simple cone to the back of this surface (yellow part in section view) solves this problem improving flow performance and likely reducing noise. Hope to build parts and test within the coming weeks.

It also looks like I will creating a version for the V4 for Insta... ;)
Attachments
bed_fan_sys_cfd1.jpg
Turbulence at fan hub w/out tail cone
bed_fan_Wtc_cfd2.jpg
Low turbulence at fan hub due to cone
bed_fan_Wtc_xsctn.jpg
Tail cone

User avatar
zemlin
Posts: 444
Joined: Thu Feb 04, 2016 9:32 pm
Location: Indianapolis, Indiana

Re: Bed Fan Duct

Post by zemlin » Sat Oct 15, 2016 3:11 am

Nice looking rig, and interesting analysis. I'll try the cone thing on my duct setup.

User avatar
insta
Posts: 2018
Joined: Tue Sep 16, 2014 3:59 am

Re: Bed Fan Duct

Post by insta » Sat Oct 15, 2016 4:03 am

quaver wrote:It also looks like I will creating a version for the V4 for Insta... ;)
I will trade you a PEI MIC6 bed for a 50mm fan duct STL that fits my setup and can be printed without much in the way of supports.
Custom 3D printing for you or your business -- quote [at] pingring.org

User avatar
kartcrg
Posts: 93
Joined: Tue Jul 14, 2015 10:30 pm

Re: Bed Fan Duct

Post by kartcrg » Sat Oct 15, 2016 5:43 am

insta wrote:
quaver wrote:It also looks like I will creating a version for the V4 for Insta... ;)
I will trade you a PEI MIC6 bed for a 50mm fan duct STL that fits my setup and can be printed without much in the way of supports.
If he doesn't take you up on that, I will ;)
NgDJWoql.jpg
2GUBel2l.jpg

Post Reply