The compression test used allows us to assess the actuation force needed to push liquid outside the syringe. Thanks to the adjustable workbench, it can be used for syringes with a diameter between 0.9cm and 2.9cm in diameter.
For this test, 4 different syringes from the same manufacturer are used (5mL, 10mL, 20mL and a special for insulin). The syringes are placed inside the workbench. Syringes are filled to the maximum with water to simulate an injectable liquid. A 20mm cylindrical probe is used to mimic the pressure of the finger on the plunger. The plunger is compressed all along the syringe body.
The determination of the actuation force via a compression test allows us to characterize the response of the syringes toward pushing.
In this case, the maximal strength (Fmax) can be correlated to the actuation force needed to push liquid through the syringe. As expected the presence of a small diameter needle (0.9mm) (red curve) at the end of the syringe increases the needed actuation force needed compared to syringes without needles (blue curve).
We can observe that, except for the 5mL syringe without needle, the others are quite linear all along the push. The final bump is due to the lack of volume inside the syringe when the plunger arrives at the end of its course.
We can see that there is no significant difference of comportment between the 10mL and the 20ml syringes when the needle is on (around 9N).
A linear course during injection is the guarantee of precision.