Printing small features can be challenging . Sometimes a layer is so small and takes so little time to print that it is still melted and soft when the next layer goes on. The plastic gets pushed around, and quality suffers. Another problem is overhanging perimeters. Sometimes loops that are only partially supported curl up as they cool. Later after they have hardened, the nozzle can bump into them with enough force to break fragile pieces, or knock them from the bed.
One solution is slow-down cooling. You set a minimum time per layer, and the extruder will slow down enough to take that much time to print, giving the plastic more time to cool. This can dramatically increase print times depending on the model.
The other way to cool the plastic is with a fan blowing into a duct that directs the air out through a ring around the nozzle. This cools the plastic as it is extruded. Slow down cooling may still be needed as well for very small featuers, but you can turn the minimum time down to something like 5 seconds when a fan is there to help out.
You can find a fan duct for the Solidoodle at Thingiverse – http://www.thingiverse.com/thing:30828 .
With ABS, keeping a fan on all of the time might not be a good idea. The layers need to be hot to bond together, and if they are cooled too quickly the print may turn out very weak. It’s best to save the fan for the very small layers, and also unsupported bridges. If a thread needs to be pulled over open space, cooling with the fan can prevent it from sagging. Slic3r and Cura can both turn on fans for layers under a minimum time, and Slic3r can also run a fan during bridges. To make this happen however, you need to be able to connect the fan in a way that allows it to be controlled by Gcode. This capability is built into RAMPS and Azteeg controllers, but not the Sanguinololu. It can be added, however.
I discovered this from Nophead’s blog post – http://hydraraptor.blogspot.com/2012/07/sanguinololu-fan-hack.html
You will need a Logic Level Mosfet such as this one – http://www.amazon.com/POWER-MOSFET-N-CHANNEL-TO-220-SWITCH/dp/B008UTXK78/ref=sr_1_3?ie=UTF8&qid=1351296606&sr=8-3&keywords=nte+2985
You will need to add some headers to the Sanguinololu. This isn’t too difficult, but if you haven’t soldered anything to a PCB before I recommend these tutorials-
The host is a bit eccentric, but the info is good. I had a go at it myself with a $6 solder iron and whatever solder and had a hard time of it. Then I watched the videos and followed his recommendation of a solder station, a chisel tip and the proper solder, and found that it was quite easy. If you are inclined to modify your printer to do great things, then some equipment and basic soldering skills are a good investment, and nothing to be afraid of.
One more thing you will need is a solder sucker, which is just a bulb with a tip. The holes for the headers are filled with solder which will need to be removed. Heat the solder from one side of the board and hold the sucker against the other side. When the solder melts, suck it up with the bulb. This would be easiest with a pointed tip that will fit through the hole. This way you can push the melted solder through and suck it out at the same time. Do this a couple of times from both directions to really get it cleared out.
You will need some straight headers, like http://www.amazon.com/30-Pin-Single-Row-Snappable-Header/dp/B0083COCZG/ref=sr_1_22?ie=UTF8&qid=1351297518&sr=8-22&keywords=square+header+.1%22 . Any self respecting electronics store should have them (which rules out Radio Shack).
At minimum you will need to solder headers into the four pins at the left end of the expansion area. I recommend you solder all of the pins while you are at it. At least add headers to the pair at the far right. This will allow you to plug in an SD card reader, should you choose to buy one.
Note the shaky work here due to diving in without the proper equipment or education. Still functional, if not a little ugly. You will need a couple of connectors like these http://www.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=50-57-9002&WT.term=50-57-9002&WT.mc_id=Connectors,%20Interconnects&WT.medium=cpc&WT.campaign=Connectors,%20Interconnects&WT.content=text&WT.srch=1&type=Phrase&WT.source=google&cshift_ck=452CDBE6-2610-4AC2-BEEE-57A4932EE148csDGEoepNp
This photo from http://www.thingiverse.com/thing:22202 shows where the MOSFET will connect to the board-
Solder some wires onto the legs of the MOSFET, with some shrinkwrap tubing at the ready-
The right leg is Source and it will go to GND on the board. The middle leg is Drain and will go to the black wire on the fan. The left leg is the Gate and will go to PWM B12 on the board. The red wire from the fan goes directly to 12v on the board.
You can switch the fan on and off by manually entering a M106 code in Pronterface, such as M106 S255 where S is the speed, expressed as a number from 0 to 255. Repetier host has a button and a slider to control the fan.
The fan may not already be activated in firmware, so follow the directions here for how to download and update the firmware. When you have the firmware open in Arduino, change to the Pins.H tab. This will probably be too far down to appear at the top of the screen, but on the right side there will be an arrow that pulls down the full list. Scroll about halfway down, looking for the section for Sangiunololu. In that section look for
#define FAN_PIN -1
and change the -1 to 4.