Syringe Pump


A syringe pump

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I needed a syringe pump design for an open source laboratory autosampler project I’m working on. There were several good designs here on Thingiverse, but most only included STL files. Since I needed to customize the design for my needs, I used Openscad to create this design from scratch.

I wanted to be able to use a wide variety of brands and sizes of disposable syringes for use in transferring water samples from EPA Method 524 style 42mL glass septum topped vials.
Ended up using two syringes, both from McMaster Carr:
30mL polypropylene syringe
10mL polypropylene syringe

and to hook up the syringe to the sampler:
1.5″ Blunt tip dispensing luer lok 17ga. (nominal 1/16″) needle

The 30mL syringe is for extracting samples from the vial, and the 10mL is for adding calibration solution to the sample for quantitation by Gas Chromatography/Mass Spectrometry.

The bigger autosampler project will follow, but this portion should be useful.
The advantage to publishing the Openscad version, is that you can customize the syringe plunger and holder for the size of syringe you are using. The files have variables for syringe diameter, syringe body end flanges (major and minor dimensions, and thickness), syringe plunger end diameter and thickness, and plunger shaft diameter.

By entering these values into the Openscad files Syringe_Plunger_Stage.scad and Syringe_Support_End.scad, you can accomodate many different syringes. You will have to adjust some of the surrounding block dimensions to make the syringe “slot in” to place.

The design uses standard Nema 17 stepper motors with 8mm dia. 2mm pitch X 150mm leadscrews, which are about $15 on Ebay or Amazon. I used 5mm smooth rod for the guide rails, as I had a bunch hanging around. You could modify the ears on the stages for larger diameter rails in the scad files, if needed. The 8mm leadscrew end is held by a 608ZZ skate bearing sandwiched between the bearing end piece and the syringe support piece. 3mm metric socket head bolts and nuts are used throughout for mounting everything. There are ears on the base of the end stages with 3mm holes for mounting on your project.

I also used two vitamins from Things here on Thingiverse in the design:

Anet A8 solid Z coupler by user FerociousDesigns

This is to attach the stepper motor to the leadscrew.

The second vitamin is a plastic spiral linear bearing for the sliding stage:

By user aeropic:

I customized the spiral linear bearing using this thing, and the file is spiral_vase_linear_bearing.scad modified for 5mm ID, 12mm OD size.
This allows the slot in the support to clamp down and adjust the tension on the spiral bearing.

I also added a split end-stop switch mount (not shown in the photo) for homing the stages.

Please let me know what you think of the design. My Openscad programming skills are very disorganized, so the code kind of sucks, but this at least allows others to modify the design, hopefully for the better. I’m not a fan of “open source” projects which only publish the STL files, as it makes design changes nearly impossible.

NOTE: Updated files on 03/24/19. Replaced the three Endstop files with V2 versions. Relocated limit switch to the side of the stage to better hit the moving stage without interference. Added a photo showing the Endstop in fluorescent green filament.


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