More traffic than usual will be turning into Drumoyne Road, in Govan, Glasgow, tomorrow. Some 200 business customers of Dorset Printers (Glasgow) Ltd have been invited to attend the formal opening of the firm's new purpose-built 20,000 sq ft printing factory, representing a #3m investment in the future and an increased size of more than three times compared to its previous location.

''We had grown to the point where we simply had to both move and fulfil our plans for new production equipment,'' said Stephen Cassidy, production director. ''We plan to demonstrate to our guests that Dorset Printers, already firmly established as in the first division of the Scottish printing industry, has now taken its place in the premier division.

''Our mission now is to grow Dorset Printers into one of the country's most successful printers.'' Tomorrow's opening ceremony will be performed by Ron Culley, chief executive of Govan Initiative Ltd. Hugh Boyd, managing director of Dorset Printers, has gone on record that his company owes a debt of gratitude to Govan Initiative and to the Glasgow Development Agency for ''much assistance, advice and support'' received in carrying out the firm's programme of expansion and development.

An initial three-year plan has been launched to double the current annual turnover of #3m a year and in the process increase the workforce from 30 to 50. Investment in new production equipment includes two #1m German-made Heidelberg B1 print presses and the establishment of a fully equipped finishing department.

A considerable programme of staff training has been carried out to match.

''This enables us to produce large volume books, bound and machine stitched, to suit a new wide variety of business functions including holiday brochures, company reports, newsletters and manuals of every kind,'' said Cassidy. ''We have also installed a computer network which fully integrates all estimating, production scheduling, purchasing, stock control, despatch and accounts functions. We possess fully digital ISDN lines.''

The firm, which holds IS0 9002 status, is proud of its all-round use of the latest technology in an industry which in a comparatively few years has changed almost beyond recognition. As the customers are shown over the new facilities - the full move began about two months ago - they will also hear of the way in which, while continuing to cater for customers as before, the Dorset management look to a broader future.

''We have built up a reputation for high quality commercial printing, with an emphasis on colour printing,'' said Cassidy. ''Our customer base covers all of Scotland and the North of England. Some of our work is for customers who then export it abroad.

''Now we are starting to expand, including a venture into calendars with a Scottish theme. We also plan to venture into the computer manual printing market, something which is steadily growing.

''Already much of our work, including glossy colour work, is for the GDA, local enterprise companies, and local authorities including Glasgow District, Renfrewshire, and South Ayrshire. We carry out contract work for many large advertising agencies.

A firm which runs a 24-hour working day, from Monday at 7am until Friday at 7pm, Dorset's quality of service guarantee has been built on a solid reputation for attention to detail.

''Printing today requires that attitude, along with a skilled staff. Part of our training programme for new staff, underlining that theme, is the way in which each employee is taken step by step and machine by machine through the entire process,'' said Cassidy.

''We get a tremendous feeling of job satisfaction from the whole process, even if it often amounts to extremely hard work. Looking back, from small beginnings we weathered the depression of the eighties, and came on from there.

''We're proud to show what we've got and what we can do.''