Fan backwash problem - new parts to fix

Hi All

There was an old thread in which Markus revealed that the fan backwash causes distortion of large area printing.

Now it seems several of us have been working on possible solutions.

I am going to post the fruits of my work here and I ask others to do the same, at present the discussion resides in a thread about cheap filament.

Rory

Just printing a 80x110 tool holder for my CNC and just noticed it's curling big time

This may take some time as I am not sure if I can display links in body of post.

My work stems from a suggestion by David Crocker DC42 that it might me possible to capture the backwash from the fan. No account has been taken of possible clearance issues. The earlier work on the fan duct is also included. It was my view that the gaps in the heatsink needed to be filled to get a good flow to the nozzles. What flow this new design will give is not known as I have not been able to build the parts. The extended fan nozzles will need adjustment in length and angle plus shaping of the ends to clear the bed and hot block.



[tinkercad.com]#



[tinkercad.com]#

If anyone is willing to build prototype parts for me I would be delighted, particularly if they are near Norwich.

Rory

Yes the back wash or perhaps more accurately fan inlet draft is a problem. For the moment I have the following solution via used kitchen roll holder.

Dave M

Dave

Effective yes, beautiful well that's in the eye of the beholder. What is the Microchip Logo all about?

Rory

Rory

I know its ugly but its functional just like me

The Microchip is a Pic chip programming kit that I might get around to playing with one day though its old technology now!

Dave M

Hi all,

based on my conclusions of the fan backwash warping problems described here I tried to find a design change which distributes the heat on the heated bed sufficiently for large prints (esp. on the Y-axis), is easy & quick to print, easy to mount and without necessity to change the Duet board mounting.

First the problem:

When the fan is on there is a fair amount of backwash which degrades the heat distribution on the heated bed and causes warping of the print on the part which is left to the fan (see pictures in the thread mentioned above). The following picture shows the thermal distribution of the heated bed with the fan ON (nozzle position: X110 Y150 Z3, heated bed temperature set to 57°C):



To exclude that the poorly heat distribution is caused by the heated bed, the heat plate, the aluminium plate or the glass layer I did a thermal scan with the fan OFF (same settings as above):



Given the marginal space between the fan and the Duet board mounting a solution like the fan duct I build from baking paper was no option. While chatting with rayhicks and Ian about the problem, rayhicks thought about some deflection of the backwash with the help of blades like the ones used in louvers. I also thought about circled holes pushing the backwash in the upper direction but then went for the easy to design fan louvers.

I used openSCAD to draft a latch type fan louver with only 1.2mm depth, so that it's either no problem to home the X-axis nor does it need a complex production of the part. To deflect the air I put in slots with an angle of 30° directed upwards. This also ensured enough room to get sufficient air into the fan.



I took me some tests to get a decent print:



The plate is attached using the four pins. The lower pins are pushed into the holes of the caphead screws for the allen key, the two upper and longer ones are pushed into the upper holes (now we know why there are no screws used ). Everything is quite tight, but to provide reliable fixation some kapton tape is used. That looks like this:



I printed the part (Arduino Mega2560 plate) which was the source of the discovery of the fan backwash problem with exactly the same settings as I did it before:



The result of the nearly four hour print: No warping at all, homing the X-axis without problems, mission completed

While printing I did some IR thermometer measurements on the edges of the print and the temperatures only differed by about 3°C maximum. The plastic part which fixes the hot end to the X-carriage had about 28-30°C.

Oh and this was my scientific experimental setup for taking the thermal pictures



More on the Arduino thermal cam here

Happy New Year and always have fun!

Markus

[EDIT: Added .scad and .stl files]

DISCLAIMER: This design is not proven to be without harm for your printer. So use it on your own risk, I will take no responsibility for any damage. Especially the aerodynamic consequences of the plate directly mounted on the fan inlet should be researched.

Edited 2 time(s). Last edit at 01/01/2014 03:49PM by markbee.

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XBee & electronics blog: [lookmanowire.blogspot.com]

Markus

Great work, I would be interested to know if your device increases to flow from the output of the fan by organising the inlet flow better?

Rory

Markus

Any chance you could post up the STL file so I can print one out

H

Hi hughesie,

added both files to my posting above.

Markus

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XBee & electronics blog: [lookmanowire.blogspot.com]

Excellent Markus,

Thank you very much I will print one of these out now whilst I try and find a bottle of Glenfiddich.

Dave M

Excellent!

Thanks Markus, i'll be printing of of those next

Like you transparent Duet case btw

Matt

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Limited Edition Red RS Ormerod 1 #144 of 200 - RRP 1.09fw
iamburnys Ormerod Upgrades Github
Follow me on ThingiVerse My Designs

Nice work Markbee. Rory I certainly prefer your design from an artistic view point but obviously its not as slim.

I presume that lugs could be added to MarkBees design so it clips over the fan or could even replace the front of the fan.

I should do it rather than talk about it but still twiddling about so not tried printing yet. ( Tomorrow I hope as I have finally arrived at that point in the manual )

Anyway great stuff. This is what its all about aint it ?

EDIT:

Had a rough go at adding a skirt and lugs to the part in OpenSCAD. File attached. fan_backwash_plate_with_skirt_lugs.scad

regards
Andy

Edited 1 time(s). Last edit at 01/01/2014 09:32PM by kwikius.

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

Just a thought on this fan backwash issue, but will a louvred vent work on an input to a fan?

I'm "thinking out loud" and not an expert here, but would a smooth 45 degree 'pipe bend' be better as it sucking from higher up and more remote from the sensitive area.

The louvre effect will obviously have an effect, but thinking of the local air motion a short distance from this plate will it have a big impact on that flow?

I guess you have tried it out and seen it working, but that was my concern.

(off topic comment) Building this printer has broadened my horizons and introduced me to OpenSCAD an interesting CAD option. I currently prefer DesignSpark Mechanical as it is so intuitive, but I'm intrigued by the 'instruction' alternative.
Also I like Kiacad, certainly as a viewer. I tried a few edits, but they did not go as planned and 'Find' seemed to lock me out, but that's probably down to inexperience!

@Rory

Can't measure that with the means I have at hand. I'm still a bit concerned about the aerodynamic consequences this design has. I measured temperatures while doing the four hour print and could not observe any irregularities to printing without the backwash plate. Call it a pragmatic approach.
I would welcome if anyone has more insight into the aerodynamics part of this (I only knew aerodynamics/ backwash from flying single engine piston planes. The "fan" is a bit bigger though ).

@Matt

Thx Matt. Simple lasercut from the .dxf files provided in the Ormerod master design files.

@Andy

Great! I also had some tries with parts that could clip on the recesses of the fan. But the plastic is quite stiff and it's hard to clip it on. So I went for the tape. I printed your design but can't get it on either.

@Treth

That's why I did a disclaimer on this whole idea. I did some tests and measured some things and it was all in the typical data envelope. But as said I'm not into aerodynamics, so use it at your own risk and consider it as a workaround one level above my baking paper/ kapton tape idea.

Markus

Edited 1 time(s). Last edit at 01/02/2014 03:04AM by markbee.

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XBee & electronics blog: [lookmanowire.blogspot.com]

Quote
markbee
[...]
@Andy

Great! I also had some tries with parts that could clip on the recesses of the fan. But the plastic is quite stiff and it's hard to clip it on. So I went for the tape. I printed your design but can't get it on either.

Oops! I did say it was rough, just meant to show what I was talking about. The lugs werent really in the right place. Perhaps a design similar to the little tangs on the connectors ( e.g the thermistor connector under the bed) might be more bendy.

Quote
markbee
But as said I'm not into aerodynamics [...]
Markus

The one thing I know re aerodymanics is that air doesnt like going round sharp corners( else it has to try go infinitely fast so leading to turbulence and noise),so the leading and trailing edges should be radiused if possible.

regards
Andy

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

Exhaust Duct Mark I

Needs some modification I think, I made the 1mm thick to keep the weight down, maybe increase that to 1.5mm



Tinkercad Model

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Limited Edition Red RS Ormerod 1 #144 of 200 - RRP 1.09fw
iamburnys Ormerod Upgrades Github
Follow me on ThingiVerse My Designs

Hi iamburny,

Nice! Could you provide the .stl file so that I could compare your duct to my backwash plate? How did you fix the Duet board?

Markus

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XBee & electronics blog: [lookmanowire.blogspot.com]

@iamburny
Looks good, thanks for sharing.
I have my electronics in the same location, just using two "T" bolts on the far end.

Kevin

@markbee

You can download the STL from the tinkercad link (Download for 3D Printing) and I have attached to this post aswell.

my duet is fixed the same as Treth with just the 2 screw on the right hand side, holds fine, only a teeny bit "flappy" on the left end.

Matt

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Limited Edition Red RS Ormerod 1 #144 of 200 - RRP 1.09fw
iamburnys Ormerod Upgrades Github
Follow me on ThingiVerse My Designs

Quote
markbee

@Andy

Great! I also had some tries with parts that could clip on the recesses of the fan. But the plastic is quite stiff and it's hard to clip it on. So I went for the tape. I printed your design but can't get it on either.
Markus

I have done another version. This time I just added some clips which are a bit bendier and no skirt. I cant print it out tonight ( get complaints about the noise! ) but will try tomorrow. My take some fine adjustment yet..
Here is the file so far anyway..

fan_backwash_plate_with_clasps.scad

regards
Andy

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

I don't want to put a dampener on markbee's design - which looks excellent to me - but I should point out that the fans supplied to some of us do not have recesses in the screw holes, so the screw caps sit proud:



The only way I can use that design is to cut the lugs off, drill holes in it and countersink them, and then use countersunk screws to hold the louvre/fan/fan duct/heatsink assembly together in place of the cap screws. This will also make it unnecessary to stick it on with tape.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

@Matt

I will print the part tomorrow and measure the temperatures at the heating block with the various designs. This is the crucial point/ part where the temperature shoud be controlled accdg. to Ian

@Andy

Let me know if it clips on. I then will test it an compare it with the other variants

@dc42

It looks that there are some design differences between the printers even in the batch with the first 500. I have #004 and I'm not sure how many things have changed since then. I don't think there is any kind of list where design changes since the start of selling the Ormerod are documented. But this complicates any design change proposal like the fan duct.

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XBee & electronics blog: [lookmanowire.blogspot.com]

Am still at it I think Ive taken dc42's issues into account.

Here's where I'm at so far. In order to incorporate bigger holes Ive had to make it a bit bigger. Prob need slots by the clasps so they are more bendy



Also Looking into making a bit of a smoother wing section.

regards
Andy

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

Hi all,

Still continuing to remodel the fan backplate. Sadly my lugs or clips were just too small and didnt come out very well well at all really. However I did manage to get an aerofoil section to the thing in OpenSCAD.

Now looking to alternative ways to fasten it on though..

Anyway here is the print. This is only me second ever print ( 1st was the right angle thing) so quite chuffed!


Also attached are the OpenScad files for the part. You will see I made it a bit deeper and various stuff like that.

regards
Andy

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

Here's one I made - it's a push-fit over the fan. Requires 5mm clearance between fan and Duet enclosure.

Pics and design files attached (DesignSpark free CAD prog & STL) - can't figure out how to embed the photos in this message like you other clever buggers have done (it's late ).

@dmould, that looks good, thanks for sharing. I too will be using DesignSpark Mechanical so thanks for supplying the source doc.

re insert image. After you have attached the file a box/button appears next to the attachments name "create link in message"

@Treth - Yes. I clicked the "create link in message button" but it didn't appear to do anything.

Hi again,

Dmould. That print looks great. I have a long way to go to do that well. I spent a while cleaning mine up!

Anyway Here is my V2 offering, which is my 3rd ever print.
This time I used cylinders for the lugs and a bit of maths to get them in the right place. I added a skirt and I changed the aerofoil to an arc, but with radiused ends.
Anyway this one fits nicely so I'm calling that my final entry to the fan backwash Challenge!

I've enclosed the SCAD, STL, and the gcode so have a go. It doesnt take too long to print either being so small.

EDIT Btw, if you try it, the best way to get it on is to put the bottom lugs on then gently snap the top lugs in place.





regards
Andy

Edited 1 time(s). Last edit at 01/04/2014 06:38AM by kwikius.

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

I downloaded your file and when I click "Create link in message" the following text appears. I have changed the square brackets [ ] as I assume it will just insert the picture!
(open square bracket)attachment 24058 100_1796.JPG(close square bracket)

and the actual text:


perhaps there is a forum Q&A somewhere?