Reducing probability of glass breakage in drug delivery devices

A method for manufacturing drug injection devices, the method comprising:

• receiving, by one or more processors, a fixed set of parameters that specify physical properties of a syringe and a liquid drug;
• determining a set of parameters that specify physical properties of a drug injection device configured to deliver the liquid drug to a patient via the syringe, wherein the drug injection device includes a mechanism configured to drive a plunger rod toward a plunger of the syringe encased in a syringe carrier, wherein determining the set of parameters includes:
• (i) generating, by the one or more processors, a candidate set of parameters for the drug injection device,
• (ii) applying, by the one or more processors, the fixed set of parameters and the candidate set of parameters to a kinematic model of the drug injection device to determine a predicted peak pressure within the syringe, including determining the predicted peak pressure as a function of impact velocity of the liquid drug, and including using the kinematic model to model interactions between at least the mechanism, the plunger rod, the plunger, and the syringe carrier, wherein using the kinematic model includes (A) modeling the mechanism as a linear spring with an equilibrium length, and/or (B) modeling (i) a pre-impact stage at which the plunger rod has not come in contact with the plunger, and (ii) a first impact stage at which the plunger rod comes in contact with the plunger,
• (iii) determining, by the one or more processors, a probability of failure of the drug injection device using the determined predicted peak pressure,
• (iv) if the probability of failure is above a threshold value, repeating the steps (i)-(iii) with a modified candidate set of parameters, and
• (v) selecting the candidate set of parameters if the probability of failure is not above the threshold value;
• and
• manufacturing the drug injection device using the determined set of parameters.

A drug injection device configured to deliver a liquid drug to a patient via a syringe, the drug injection device prepared by a process comprising:

• receiving a fixed set of parameters that specify physical properties of a syringe and a liquid drug;
• determining a set of parameters that specify physical properties of a drug injection device configured to deliver the liquid drug to a patient via the syringe, wherein the drug injection device includes a mechanism configured to drive a plunger rod toward a plunger of the syringe encased in a syringe carrier, and wherein determining the set of parameters includes:
• (i) generating a candidate set of parameters for the drug injection device;
• (ii) applying the fixed set of parameters and the candidate set of parameters to a kinematic model of the drug injection device to determine a predicted peak pressure within the syringe, including determining the predicted peak pressure as a function of impact velocity of the liquid drug, and including using the kinematic model to model interactions between at least the mechanism, the plunger rod, the plunger, and the syringe carrier, wherein using the kinematic model includes (A) modeling the mechanism as a linear spring with an equilibrium length, and/or (B) modeling (i) a pre-impact stage at which the plunger rod has not come in contact with the plunger, and (ii) a first impact stage at which the plunger rod comes in contact with the plunger,
• (iii) determining a probability of failure of the drug injection device using the determined predicted peak pressure,
• (iv) if the probability of failure is above a threshold value, repeating the steps (i)-(iii) with a modified candidate set of parameters, and
• (v) selecting the candidate set of parameters if the probability of failure is not above the threshold value;
• and
• using the determined set of parameters to manufacture the drug injection device.