Fans & Cooling

[jorwex]

Hi all,

What size fans do you have in your printers and where are they mounted? Specifically on your extruder and heated bed. I don't fully understand why fans are mounted to heated beds when you can control their temperatures independent of the hot ends. There doesn't seem to be a ton of info about fans on the RepRap wiki. 

Are you limiting their voltages at all so they don't operate at full blast? Is there a target temperature I want the hot end's PEEK to stay below so I can experiment on my own? 

Fairly confident in the passive/heatsink cooling on motor drivers after tweaking their current limiting resistors. I picked up a small assortment of 12V fans from Fry's (50, 60, 120 mm) earlier to play around. 

Oh and this is for my in-progress Graber if it matters. Thanks again everyone,

Jordan 

--
Jordan W

[Elliot]

Jordan,

You're still building your Graber? I might actually be back at the
meetings before too long, if you need any help. If you need pieces
printed, let me know.

To answer what I think are your main questions:

* The j-head hotends shouldn't get hotter than 248c, I think:
http://reprap.org/wiki/J_Head_Nozzle#Nozzle_Holder
* If you're using a NEMA17 motor as your extruder, you probably don't
have to worry about putting a fan on it. I put a fan to cool my
extruder motor because it's a NEMA14 that's being pushed pretty hard.
If you're using a geared extruder, I think you have to worry even
less.
* If you have a PLA extruder body, you will want a fan to keep it from
warping. Smart reprap people (whosawhatsis among others) say you
should not print an extruder out of PLA. It's worked well for me so
far, but I only print PLA and I have a fan keeping stuffs cool.

To answer the other questions:

I use either a 50mm or 60mm fan mounted on my extruder motor, cooling
the extruder motor, PLA extruder body, and the top of the J-head
hotend. I don't print crazy overhangs or bridges anymore, so I don't
actually point the fan at the print at all.

If/when you print ABS, you don't want a fan near it at all.

If you're doing ABS, you don't want a fan near your print.

I don't use a fan on my heated build plate these days; I just wait for
it to cool on its own once the print is done.

The piece that I use to mount the fan on the extruder motor is:

https://github.com/elliotf/reprap-fan-mounts/blob/master/motor_screw_mount.stl

download link:
https://raw.githubusercontent.com/elliotf/reprap-fan-mounts/master/motor_screw_mount.stl

Elliot

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[jorwex]

Hi Elliot

I am indeed still building my Graber. I haven't had very much free time lately. 

Thanks for the temperature notes and links.  

-The wiki says "PEEK nozzle holders have a maximum working temperature of roughly 248degrees Celsius. Due to many variables, it is highly recommended that this temperature is not to be approached. Above this temperature, PEEK will melt and the hot-end will fail." 

-I'm printing only PLA for now (not near 248), then I don't need to worry about cooling this portion? Or is that range close enough to "approaching" the PEEK max?

-I'm using a geared extruder driven by a NEMA17 motor.

-I had an ABS extruder printed. 

-I was asking about bed fans because I saw Bill had (I think) a 120mm fan cooling his delta's bed at the last meeting I went to (a while ago). I didn't realize it was for cooling prints. 

So it sounds like I may not need any fans!.

All that's left to finish my printer is leveling my heated bed and fixing the slack in my y-carriage belt (I think some of the teeth got rounded off). Shouldn't be long. 

Glad to hear that you may be back soon. Hope all is well

Jordan

--
Jordan W

[Elliot]

Jordan,

I believe that you'll still want a little fan to cool the top end of
the J-head. If you're printing PLA with the j-head, the PLA can swell
and jam the hotend. Other hotends (prusa, e3d) use a tiny TINY
~20-30mm fan.

I've not tried it without the fan (due to the PLA extruder body) so
I'm not sure how necessary it is. Also, it might the sort of thing
that can happen a few hours into a print and cause very sad pandas.

Elliot

[jorwex]

So with the j head will one of these 50 or 60 mm fans do the job? Since it doesnt need to be a big fan, maybe I'll use the "quieter" one I grabbed it won't be screaming. 

Should I just connect it to a spare 12V line? or use the D09 pins on the RAMPS and control it that way? I'm still reading over the configuration.h options for Marlin. 

Thanks!

--
Jordan W

[Elliot]

A quiet 50mm should be more than enough. Just point it at the top of
the j-head, where the groove holes are.

I just wire it to the aux 12v, personally. It's right by the D2
diode, by the 12v input:
http://reprap.org/wiki/File:Arduinomega1-4connectors.png

[jorwex]

Wow I never noticed that header before. There's all sorts of pins and goodies on there. I'll give that a try.

I have to try a print again and watch closely, but I think my current issue is preventing the Bowden tube from getting pulled into the Hobbes bolt on my hinged Wade's extruder. I thought the spring loaded filament guide on the extruder would hold the tube, but it hasn't been.

You had said in the past that you don't terminate your Bowden with one of those pneumatic fittings, right? 

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Jordan W

[Elliot]

Ah, I think you're referring to the "reverse bowden" that goes from
the spool to the extruder, that helps with the >90deg bend that the
filament travels through. Is that what you're referring to?

The solution is probably to print out a little disc that you can fit
onto the end of the tube. If you look at the mendel90, it has a
little thing to prevent the problem you're having. You might be able
to see it in the picture:
https://lh3.ggpht.com/-o7lu7kZ9r0Y/UMD9kXzRMUI/AAAAAAAAGGU/vSKjuoqMtbM/s1600/Mendel90+Dibond.jpg

To be clear, it's not really a bowden. If you need help
designing/printing something to keep your extruder from eating the
(what we will call) guide tube, please let me know.

[Matthew Bennett]

There are videos on YouTube describing "that" as a cold-end Bowden.....

[jorwex]

Yes that is what I was referring to. I suppose Bowden is incorrect. I know it to refer to those cables on bikes and cars http://en.m.wikipedia.org/wiki/Bowden_cable

I will try to rig up something and see if I can print once the guide tube isn't getting pulled in. If that fixes the problem, I'll try to design something but may take you up on your offer. 

Thanks

--
Jordan W

[Elliot]

It sounds like it *is* a bowden, then.

As far as a design goes, I would hope/imagine that a simple open-top
tophat would do the trick:

https://github.com/elliotf/reprap-cold-end-bowden-retainer/blob/master/retainer.stl

All of the measurements are likely off, since I made up the numbers,
but the general idea is that the tube sits in the socket and the rim
keeps it from being eaten by the extruder.

[jorwex]

I was thinking it wasn't because the interior element doesn't drive any sort of mechanism on the end. 

Wow did you just design that? I need to experiment with modeling software. Just made my first successful print!

Thanks!

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Jordan W

[Elliot]

Congratulations on your first print!

Hrm, I don't think I understand what you're saying the problem is.
The good news is that I'm planning on coming tomorrow, so if you're
going to be there, we can talk it over.

Yes, I just "designed" that. Really, it's just a few cylinders,
though. I find openscad fairly easy to use.

I updated it a little to get the holes to be dimensionally accurate,
now, too. All I need to do is measure the inner/outer diameter of my
tubing.

[jorwex]

Eh it's not important + I'm tired and am probably not being 100% coherent. 

I won't be able to make it tomorrow, but will hopefully next week. 

--
Jordan W

[jorwex]

Printed spacexula's calibration 20x20mm half cube (10mm high). Happy day. 

--
Jordan W

--
Jordan W

[Elliot]

Congratulations!

[jorwex]

Hi Elliot,

One other temperature related question. I was reading http://reprap.org/wiki/Print_Troubleshooting_Pictorial_Guide#Part_Temperature and wondered if you have your setup configred to reduce the bed temp after the base layers are deposited. I am have zero issues with adhesion at the moment. 

Thanks

Congratulations!

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Jordan W

[Elliot]

Jordan,

If you're not having a problem, don't change anything. :) Are you
having a problem?

Elliot

[jorwex]

Oh I meant I'm not having problems with too little adhesion. Too much perhaps? Bottom of the print is a bit bulgy (not nearly as bad as the picture on that wiki link). Thought if the bed was turned down a bit after the initial few layers (not sure how to do this), then it wouldn't look a little smashed like it does now. 

I have some corner lifting at the top of the print, but I didn't have my new fan pointed at this thing he whole time either. 

--
Jordan W

[Elliot]

Jordan,

As long as you can get the print off the bed, you don't have too much
adhesion. Note that you will want to wait until the build plate is
cool before you try to remove your piece.

As far as the curling corners problem goes: I found that having a fan
helped. Turning the heat down might help as well, but there's the
possibility that your part might come loose, too. Of course, it also
might be that you're extruding too much (your e-steps are too high,
adjust with M92 E<number here>).

The first layer flattening is a problem for me at times, too. For me,
I think it's my laziness around setting my Z height correctly. For
you, it might be a combination of setting your Z height and extruding
too much.

Have you gone through
http://reprap.org/wiki/Triffid_Hunter's_Calibration_Guide#E_Steps_Fine_Tuning
?

Getting my e steps right was the tuning that took me the longest, but
it's really paid off with the quality and strength of my prints.

Elliot

[jorwex]

I have followed that Wiki link in the past, but I have since removed filament and taken apart the extruder a bit. Probably wouldn't hurt to do it again. 

If I recall, you use a glue stick for extra adhesion? Do the first few layers actually slide around a bit when you realize you need to put some glue down? 

Thanks again Elliot

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Jordan W

[Elliot]

In the worse cases, yes, the part will slide about or the filament
will just not stick at all. In most cases, though, it just looks
wrong (small circles in particular come out horribly) or there's
curling later on later on.

No problem, sir, and please do chime back if/when you find the
solution to your problem(s).