Fan for cooling printed parts (better bridges etc.)

Hi Guys,
I am currently using the latest iteration of the Smartrap from Serge with the J-head lite head and the 6mm steel rods.
I have noticed when building tall and really thin objects that the PLA overheats and starts to look like one of those curly type ice cream cornets instead of staying straight.
I also noticed that when bridging gaps if I blow on the PLA as it comes out I get a perfect bridge but if I just leave it to print then I get a spiders web where the first layer of the bridge is. The problem is that the PLA can't lose the heat fast enough and it falls out of shape before it hardens.
I think the solution is probably a fan to cool the build item as soon as it extrudes because i have seen similar issues on other printers but the J-head lite version of the Smartrap doesn't offer many places to add a fan on top of the fan thats required to cool the top of the J-head lite.
Has anyone else had this issue with their smartrap and if so did anyone find a solution?
Regards
Mike

Hey
Sounds like you're having some issues with pla cooling. I think the main problem is that the fan is directed at the top part of the hot end instead of on the print.

Unfortunately, the smartrap is constructed of a low melting point PLA, so active cooling of the hot end holder is necessary to prevent a melt down. Not an ideal situation.

Hey reg backemf christian, what do you think?

Edited 1 time(s). Last edit at 10/23/2014 11:01PM by Robert_Paulson.

This is (was?) currently an issue in the standard Smartrap, also because with the Huxley hotend it needs 2 independent fans, and this is (was?) not managed by the Marlin firmware provided with the printer. Serge will be more precise about this.

There have been several brilliant solutions proposed. It is a pity that they are spread in three different forums (either here or in the French thread which is now dead, or in the newer official Smartrap forum at smartfriendz.com). This would actually be the good thread to collect all these.

So here is my solution: since I am (very) lazy and I don't care too much about esthetics, I use a 2mm aluminium wire to hold the fan. It allows me to change position and direction arbitrarily and it can be attached anywhere on the X arm. Since I use Regpye's hotend, I keep the fan directed half way between the hotend and the piece, with some minimal low fan speed if I need to go beyond 200°C. I have put enough Kapton tape around the "hot end of the hotend" to avoid excessive cooling when the fan is turned on or accelerated by the slicing software.


I would also ask Serge: how should we manage these two Smartrap forums? If they are both open, there will always be somebody posting here and not reading there, and viceversa.

Edited 1 time(s). Last edit at 10/24/2014 05:53AM by cristian.

thank you christian..

yes. it's a problem about the two forums. We try to make the official one the main source, but it takes time.

on the other side, i like to have still a "house" here in reprap.org. I'm about to update the page here too to be more up to date . It's important to me to keep active in this place .

I got also thingiverse with 900 comments, so i'm used to browse on diferent places

next version will be on youmagine i think , and thingiverse would disapear after a while ( political reasons..i prefer ultimaker .

This is ok as we can make the smartfriendz forum the main place where people go to find infos, news and solutions. Those threads here should become more general threads.

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the Smartrap project

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Hi Guys,

In case you are interested I used this fan [www.thingiverse.com]. It has a nozzle to cool the print and a slot to cool the top of the hotend. I opened the slot with a hairdryer and a knife to blow more air over the hot end. I only used one of the screw holes to attach it but its very stable. It's not ideal but it got my machine to build this.
[slickpic.us]
I am currently working with blender and the tutorials so hopefully soon I can start to make my own parts when i need them.

Regards
Mike

Edited 2 time(s). Last edit at 10/24/2014 05:13PM by mikefiatx19.

I've never had to use a fan since I make my carriages out of plywood (5.5mm oak laser cut). Wood makes an excellent insulator for radiant temperatures around 200C. Not much help for the smartrap, unless a 1/2" ID x 3-4" OD wood disk can some how be mounted in between the heat sink and the PLA. That would free up the fan to tilt more toward the print. It'd be fairly easy and cost almost nothing, except for altering the carriage for M3 bolts maybe.