Adding a 40mm fan for the j-head.

I am adding a small 40mm fan to cool the top of the j-head. I was wondering if anyone has a clever idea on powering it rather than a couple of untidy looking extra wires.

Doesn't answer your question, but have you considered just adding a hole in the fan duct like [4.bp.blogspot.com]? I think nophead mentioned it in the most recent updates.

I have 200 by 190 prints and the fan duct is horrible. I actually don't know why it is there but that is possibly my ignorance :-) It seems to add a lot of noise and wobble and I didn't notice a change in print quality when I stopped using it. So all was fine for a few months but then with the colder weather the jhead started jamming. It doesn't make sense to me but it happens now with a new jhead I swapped in aswell so I'm going toward a solution without the duct and the 40mm fan seems to be a possible solution.

I assume that you have trawled this forum and Thingiverse but just in case, NumberSix has published this [www.thingiverse.com] you can read more on his blog [numbersixreprap.blogspot.co.uk]

You are always going to have to power a DC fan using two wires, whether they are untidy or not is down to the individual
One of the (so far) unused 'P' connectors on Nopheads circuit board can be used for such a fan along with a permanent +12V supply taken from the same circuit board from the adjacent 'H' terminal.

The fan duct is 'horrible' - in what sense? This is a very fine design to cool PLA prints as and when needed as it directs air exactly where it is needed - compare this to earlier "blow all over the place" solutions.

Alan

Edited 1 time(s). Last edit at 10/19/2013 05:04PM by Alzibiff.

If all you prints are large then you probably don't need it. It is only required when printing small to medium PLA objects. Once the layer time gets above a certain value the object cools enough anyway.

It isn't noisy in my experience, perhaps some fans are noisier than others. I also don't see any wobble. Are you saying the fan rotation vibrates the X carriage? I don't think the extra mass is significant.

I think all you need to stop PLA from jamming is the tape around the heater block. Odd it would jam more in cold weather though.

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[www.hydraraptor.blogspot.com]

Thanks for the responses.
Alzibiff, that is the design I'm using. The carriage fan is horrible for me as
1. Arranging the bulldog clips is difficult with large prints
2. It obscures a view of the print.

Chris - the noise and wobble are just intermittent and occur with infilling. Some sort of resonance seems to amplify the noise.
Perhaps the 40mm fan is overkill. Thermodynamics seems to be sometimes paradoxical.

Edited 1 time(s). Last edit at 10/20/2013 04:50PM by Ralph Hilton.

1)It clears the clips if you remove the top handles and use the amended fan bracket.
2)Yes that is the only thing I don't like about it when demonstrating the machine but it it isn't a problem when printing as you don't need to see what is happening. The only alternative is two or three fans to get even cooling.

This is the effect of having a fan blowing from one side only when you have a steep overhang.



What is actually wobbling? Does it affect the print?

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[www.hydraraptor.blogspot.com]

What is wobbling, or perhaps heavily vibrating says it better, is the whole extruder assembly. The carriage fan adds to that a lot. The print doesn't seem to be affected.
Would it be right to say that if the hotend is insulated then it is no longer necessary to direct the air flow away from it? Thus 3 40mm fans at 120 degree angles could be workable?

Yes if you insulate the hot end you can blow fans on it but I don't know how you would get three 40mm fans to fit under the carriage. Better to have one and a duct that creates a ring of air.

The first five kits had 30mm fans and a much smaller duct that mounted under the carriage. I changed to 60mm because they are cheaper and give a lot more air flow. The old design is still available on Github: [github.com]. It requires a version of the carriage with a bracket on it though.

When you say the fan adds to the vibration, what causes the vibration when then fan is not present? Why would three 40mm fans make less vibration than one 60mm fan? I am sorry but I don't understand what the problem is. Mine makes a rushing air sound mainly and I can't really hear it when the machine is running. I can feel a slight vibration if I put my finger on the fan duct, but not if I feel the carriage or the nozzle. Is this something you hear, see or feel?

Edited 1 time(s). Last edit at 10/20/2013 08:53PM by nophead.

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[www.hydraraptor.blogspot.com]

The vibration is on some prints where the assembly is moved rapidly back and forth. It is the fan duct that adds to the noise. I hear feel and see it. The creator of this things seems to have had the same situation. [www.thingiverse.com]

The main thing though is the visibilty of the print.
Especially at the moment when I recently had a lot of problems with jamming, I want to be able to see exactly what is happening at any time. I need to get about 100 hours of succesful printing done in the next 10 days or so then I can experiment a bit more. At the moment I have one 40mm fan mounted on the left under the carriage using a modified carriage with mountings for it. I started a 9 hour print an hour ago - if it works ok I'll leave it alone until more time is available!

That guy appears to have more than just a vibration problem - look at his lead screw pointers!

I have been running without my fan duct for a while now (ever since switching to ABS in fact) and I can still definitely hear something rattling on the X-carriage. At first I thought it was the fan mounting screws that are sitting with nothing attached but I fitted the fan bracket to keep the screws tight and there is still some vibration. I also printed those anti-vibration feet, and whilst that reduces the vibration across my desk when doing narrow infills it does nothing for whatever it is that is rattling. I've taken those feet off now because I started suffering from a print bed alignment issue that may or may not have been related, but reducing the acceleration to 2000 as per Chris' latest firmware has all but eliminated the "shake myself to bits" moves anyway.

Yes the machine needs to stand on a firm flat surface so those feet would be nightmare for keeping the bed level and the Z height correct. A stiff rubber strip or cork running the full length of the aluminium tubes would be better.

The main source of vibration is from the y axis as that is the heaviest moving mass. Changing the acceleration has a big effect on taming short infill. Using 4000 in the firmware was a mistake. I set it to the same value as I use with my own software, but that also has anti-resonance code so it slows down when doing high frequency zig-zags. Also my own software does not synchronise the extruder with the axis acceleration so it relies on fast acceleration to give good quality. Reducing Marlin to 2000 makes the machine a lot smoother and if anything improves the print quality. I haven't tried lower yet. At some point I would expect sharp corners to get too much plastic.

I am still not sure what Ralph's problem is. The carriage will vibrate if the g code tells it to. I.e. if you have fast zigzags it will move backwards and forwards at tens of Hz. The fan adds a little moving mass but not much. It could have a big effect on resonance though as it will lower the resonant frequency so could be the difference between resonating on a fast infill or not if if the resonant frequency was similar to infill frequency. Normally Y is the problem though as it has a lower resonant frequency. If X resonates first I would suspect the belt is not tight enough or the model only has short infill in the X direction.

When you say you can hear it are you saying something is rattling? Is the carriage loose in some way? Adding the fan to my machine doesn't make any noticeable difference to the amount of noise it makes or the amount of vibration it imparts to what it stands on, or the visible motion of the x carriage.

I have noticed sometimes the strain relief clip on the D connector can rattle because it has no wires under it. A spot of glue or some card jammed in the gap will stop it.

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[www.hydraraptor.blogspot.com]

It is a vibration, not a rattling.It is probably a resonance issue with the carriage fan. The 9 hour print finished with no problems. I've ordered a few 40mm fans to experiment with in a couple of weeks time. Using the single fan does seem to improve the smoothness of prints. The x carriage I'm envisioning with 3 fans mounted might look rather strange.

Have you reduced the acceleration to 2000 in the firmware? It simply doesn't match my experience of how the machine behaves.

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[www.hydraraptor.blogspot.com]

I reduced the acceleration to 2000 and put a couple of pieces of carpet under it. Much quieter now :-)