Pen injectors

Tailor-made solutions in springs, stamping & bending and assemblies for enhanced pen injector performance and patient safety

Inyectores de pluma
Feature

Dose-setting and drive springs engineered for accurate, repeatable dosing across every injection in the cartridge

Feature

Torsion, compression, and calibrated metal components for smooth dial-up / dial-down feel and reliable click feedback

Feature

Solutions for reusable, disposable, and connected pen platforms from a single dose to hundreds of cycles

Pen Injector Springs
PRECISION

Crafted for enhanced precision and prolonged use

Unlike autoinjectors, pen injectors ask the patient to attach a needle and set a dose by hand, so the mechanism must make that effortless and exact every time. A pen delivers multiple doses from a single cartridge, with the dose adjusted through a spring-driven setting mechanism. That places a different demand on the metal parts than a one-shot device: they must perform identically on dose one and dose three hundred, across the full range of high- and low-viscosity formulations.

Springs for Pen Injectors
PERFECTION

The spring is the dose

In a pen injector, the spring doesn't just push; it meters. Torsion springs strained during dose setting store precisely the energy needed to deliver the set volume, then release it in a controlled, repeatable stroke. Paired with calibrated ratchet and clutch components, they produce the tactile clicks and dial-up / dial-down feel that let patients set a dose confidently and correct it without wasting medication. We engineer these springs and stamped parts to hold their characteristics over the full service life of the device, so accuracy never drifts from first dose to last.

Pen Injectors Springs and Stamping and Bending Metal Parts
NEW PLATFORMS

Reusable, disposable, and connected platforms

Pen platforms are diversifying fast, and each type stresses the metal parts differently. Disposable pens demand ultra-consistent springs and stamped parts at high volume and low cost. Reusable and hybrid pens — a durable drive unit paired with disposable cartridges — cut waste but need springs and formed parts rated for hundreds of actuation cycles without wear or load drift.

Connected pens add conductive contact parts — battery, dose-encoder, and switch contacts — for dose logging and app pairing. We supply the full range from one source: high-throughput stamping for disposables, fatigue-rated drive springs and formed parts for reusables, and EMI/ESD-safe contact components for connected devices, all designed to ISO 11608 and ISO 13485 expectations.

PRODUCTS

Together, we make the perfect solution for your pen injector

The earlier we join your program, the more we can optimize dose accuracy, drive force, and feel against your cartridge format and drug viscosity. We co-engineer with pharmaceutical companies, CDMOs, and device manufacturers, validating spring behavior through load testing and simulation before scale-up. Manufacturing runs to ISO 13485 with clean-room cleaning and packaging, machine-vision inspection, and full material certification: from rapid prototyping to reliable global serial production.

Products
Compression springs
Wave springs
Constant force and power springs
Assemblies & power packs
Torsion springs
Tension springs
Stamping & bending
Contact springs

Frequently Asked Questions

How does a spring set and deliver the dose in a pen injector?
In most multi-dose pens, the spring meters rather than just pushes. A torsion spring is strained as the patient dials the dose, storing exactly the energy for that volume; pressing the button releases it to drive the plunger a controlled distance. It works against calibrated stamped ratchet and clutch parts that turn rotation into precise, repeatable steps and create the clicks and dial feel. Spring and stamped parts are engineered together so the mechanism holds its characteristics for the full life of the cartridge and, in reusables, for hundreds of cycles.
Which metal parts drive the dose-setting mechanism, and how are they made?
The dialing and dosing feel comes almost entirely from small, precise stamped and formed parts: ratchet teeth, clutch plates, drive sleeves, clips, and dose-window frames working with the torsion spring. RPK Medical matches the process to the part: progressive-die stamping for high-volume runs where cost per part is critical, and multislide (fourslide) forming for intricate, multi-bend components shaped from several directions at once. Multislide feeds the strip along its grain direction, which raises fatigue resistance, important for parts actuated thousands of times in a reusable pen. Consistent tooth geometry and burr-free edges keep the click feedback and dose steps identical across the device's life.
How do component requirements differ between reusable and disposable pens?
Disposable pens run one cartridge and are discarded, so the priority is ultra-consistent springs and stamped parts at very high volume and low unit cost, with tight control of spring rate and tooth geometry to keep dose accuracy identical across millions of units. Reusable and hybrid pens keep a durable drive unit and swap cartridges, so their springs and stamped parts must survive far more actuation cycles without load drift, wear, or fatigue. RPK Medical supplies both: high-throughput stamping for disposables, and fatigue-rated springs and formed parts for reusable drive mechanisms.
Which contact parts do connected or smart pens need?
Connected pens add electronics for dose logging and app pairing over Bluetooth or NFC, which brings two component needs on top of the mechanical drive. First, conductive contact (contactor) parts such as battery contacts, dose-encoder contacts, and switches that register each dialed or delivered dose must maintain reliable, repeatable contact through thousands of actuations. Second, EMI/ESD-safe stamped parts so static and interference do not disturb the electronics. Because RPK Medical forms contact parts and structural parts on the same multislide and stamping lines, the electrical and mechanical components arrive matched and can be integrated into one subassembly.
How do you keep dose accuracy consistent across every injection in the cartridge?
Dose accuracy depends on the springs and stamped parts behaving identically on the first dose and the last. RPK Medical controls spring rate and free length, and the tooth geometry and tolerances of the ratchet, clutch, and drive parts, then validates with load testing and simulation across the full stroke and the drug's viscosity range. That component-level control feeds the system-level dose-accuracy testing pens undergo as needle-based injection systems, so performance stays inside spec through the whole cartridge and the device's shelf life.
Can you co-engineer around our cartridge format and drug?
Yes. The earlier RPK Medical joins the program, the more we can optimize dose accuracy, drive force, dialing feel, and contact reliability against your specific cartridge format and drug viscosity. We co-engineer with pharmaceutical companies, CDMOs, and device manufacturers, designing the springs, stamped parts, and contacts as one system and validating through load testing and simulation before scale-up, from rapid prototyping to reliable global serial production.

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