Syringe pump

I was looking for an syringe pump to automate the fertilization of my nano cube. My first try with http://www.thingiverse.com/thing:539490 failed. The mechanical part was not sufficiently stable. There are many syringe pumps projects at thingiverse but I decided to use the thing http://www.thingiverse.com/thing:536373.
Cause my printer has only a 80x80mm print bed this thing was perfect becauseall parts fits on my print bed.

But I've did some modifications so make the syringe pump works fine for me. There are some issues in the original thing:

• The distance of holes for the NEMA17 stepper are not OK. It is not possible to mount the motor.
• Cause the original thing is made as an extruder for a printer the motor holder has no holes to mount the syringe pump to a plate or something like this.
• At the syringe slider the shaft of the syringe is now fixed to the slider. With this its possible to push and pull liquids. This was important because I have to load the fertilizer then the syringe is empty without demounting the whole syringe pump.
• A mounting hole to add a M3 screw for an end stop. So signal that the syringe is empty.
• My used messing antriebsschraube has another dimension. Changed the dimension in the slider so the xxx fits now.

In my eyes it's necessary to use linear bearings for the slider. Changes the hole diameter to use an normal LM8UU bearing. Or maybe a self printed bearing ;-)
The syringe Pump is working very well, but with some limitation. There is a mechanical slackness when the direction is changed (From push to pull of from pull to push).
But for me it's not a problem, because I load the whole syringe and push a little bit fertilizer to reset that slackness. After this the direction is not changed because every day only 0.4 ml fertilizer is pushed into the fish tank.

Feel free to use this mechanical parts. I've made the electronic with an panStamp AVR module and connected it to my smart home system FHEM.
 

Print Settings

Rafts: No

Supports: Yes

Resolution:  0,2mm

Infill: 20% 

Notes:  Support is only needed for the slider. All other parts doesn't need support.
For me 20% infill works fine, there is no high force to the parts

Parts

• 2pcs. linear rods, 8mm diameter, 150mm lenght
• 2pcs. Linear bearings LM8UU or print your self
• 1pcs. NEMA17 stepper motor
• 1pcs. trapezoidal screw (T8 8mm, 150mm lenght) with brass copper nut (T8-1-D1)
• electronic to control the pump. I've choose panstamp AVR 1 connected to fhem
• Some M3 screws and nuts.

Print and assemble

Print all 3 parts. There is nothing special.
If you mount the linear rods try to align them in parallel. Otherwise the stepper may loose steps when the syringe is nearly empty.