Absolue encoder used on machine to cut millions of glass tubes

Danfoss Bionics A/S has designed a fast machine capable of cutting medical capillary tubes. One of the keys to the success of this project was a Newall SHG-A2 absolute linear encoder that helps Danfoss meet both strict length requirements and demanding volume throughput – millions of glass tubes will be cut every year at the company's production facility in Nordborg, Denmark.

Technical manager Per Brandt Rasmussen comments: "Danfoss has been involved in the medical sector for the past five years. For some time we have been working on a new product launch that will help improve the life quality and expectancy of life for diabetic patients."

The system devised by Danfoss designers in close co-operation with the newly founded company Danfoss Bionics A/S involves the cutting of small-diameter glass capillary tubes, in lengths ranging from 10-40mm.

Bespoke cutting machine

Mr Rasmussen states: "Unfortunately it is not possible to go out and buy capillary tube cutting machines. The only option was to either subcontract the design and manufacture of a bespoke machine or take the project on ourselves – so we chose the latter and I got the job of orchestration."

Accuracy of length was of paramount importance to the success of the project, as Mr Rasmussen explains: "Our previous experience of ordinary encoders was that sometimes they can lose a step. We knew that this outcome would not be satisfactory for cutting capillary tubes, so we did our research on absolute linear encoders from Newall. Immediately the SHG-A2 sounded like the right solution for our application."

Further enquiries from Danfoss Bionics led the company to the door of Kurt Rasmussen Machine Tools A/S, the Danish distributor for Newall products. After further discussions the company confirmed its order for the SHG-A2 absolute linear encoder.

Dependable and accurate

Developed to meet a wide range of feedback applications, the SHG-A2 provides a true absolute position immediately upon power-up; the encoder does not use batteries or static memory to retain the positional data. True position can therefore be re-acquired once power is applied, regardless of the duration for which the power has been off. The encoder has a travel of 200mm and can traverse at up to 8m/s giving 0.001mm resolution. The SHG-A2 has an accuracy grade of +/-0.01mm.

The encoder has since been fitted to the Danfoss Bionics machine at Nordborg, where it has been moved from the development laboratory to the production facility for final installation qualification.

Mr Rasmussen continues: "It is the first time we have used Newall and I must say we are impressed. We spoke to both KRMT and Newall during the build process and always received helpful advice, particularly regarding interfacing the encoder's output signal with the machine's PC. The products are also inherently resistant to contamination, which is crucial considering the amount of glass dust produced by continuous cutting operations. We would not have any hesitation using Newall products again."

About Danfoss Bionics A/S

Danfoss Bionics A/S is related to the global Danfoss Group, a leader in development and manufacture of mechanical and electronic products and controls. With 53 factories in 21 countries, Danfoss employs some 18,000 people worldwide, 6000 of whom are based in Denmark, the company's country of origin.