Automated assembly system inserts stoppers in medical vials

Schmidt Technology has developed and built a custom assembly system for use by Albert Browne Ltd, a leading supplier of infection prevention products, to automate a critical stage in the production of protein detection kits for use in the medical and healthcare sectors. The new system, based on Schmidt Technology's latest 405 servo press, is providing extremely high levels of accuracy and applied force in a delicate application, while helping Albert Browne double productivity, improve working conditions and ensure product traceability.

Founded in the 1930s, Albert Browne is today part of the Steris Corporation and specialises in the development and manufacture of dedicated chemical monitoring and contamination detection kits for use in steam and chemical sterilisation and decontamination systems; these are typically used in hospitals for cleaning surgical instruments, gowns and endoscopes.

One of the company's main product lines is the Ninhydrin Protein Detection Kit, used for detecting protein residues that may remain on surgical instruments after they have passed through a washer-disinfector. A key part of the kit is the supply of small test vials containing ninhydrin reagent in a gel form; this reacts to show the presence of amino acids, peptides and protein residues.

Production bottleneck

Each vial measures 10mm in diameter and 150mm in length and is prefilled with gel before an airtight stopper is inserted and the vials packed with other test items and instructions. Until recently, the stoppers were inserted by hand. This was a time-consuming and relatively slow process, plus it posed a risk of repetitive strain injury (RSI) for factory staff, and was impossible to regulate consistently so that stoppers were always inserted with the optimum force to guarantee an airtight seal.

Steve Brown, Production Manager at Albert Browne, explains: "We recognised that we needed to automate this process to improve productivity, product quality and working conditions for our line-side staff. We had not previously worked with Schmidt but chose them for their proven press technology, ability to develop customised systems and their UK manufacturing and technical support."

The semi-automatic system developed by Schmidt incorporates a stainless steel rotary bowl feeder, a pick-and-place mechanism, a six-station rotary table and a 405 servo press. Individual vials are hand-loaded into inserts on the rotary table. As the table indexes, a stopper is first positioned by pneumatic grippers into the opening of each vial, before being presented to the press, which then forces the stopper home. Brown says: "It is critical that we strike a delicate balance between applying sufficient force to ensure that each stopper creates an airtight seal, preventing the volatile ninhydrin from evaporating, but not so much force that the relatively soft plastic stoppers spread in the neck of each vial and become impossible to remove by hand."

Closed-loop control

The press system developed by Schmidt uses dynamic closed-loop force control to regulate the force applied to each stopper as it is pressed into the vial to within +/-0.5N. The system is also capable of extremely fast ram speeds - of up to 200mm/s - to improve cycle times, but can be instantly controlled to reduce speeds over the final few millimetres of travel. Just as importantly, this can be achieved consistently, at a resolution of less than 2.4microns and a level of repeatability of under 10.0microns.

In addition, the system features a dedicated Schmidt large-area LCD Press Control that makes system configuration quick and simple without the need for special operator training. It also provides detailed diagnostics and analytical reports, which Albert Browne has now standardised as part of its plant-wide traceability systems; these are key to the company's role as a leading supplier to the medical sector.

The new system has delivered considerable benefit to the business, as Brown points out: "It has allowed us to double output and reduce reject rates to almost zero. Perhaps most importantly, it is improving the working conditions for our operators in this particular cell and enabling us to provide an even better level of product quality and traceability to all our customers".