Internal quality control includes the entire process and all the products at the mill, using statistical measuring and follow up systems.
Customer is at the core of quality management. The primary goal of quality control is to ensure that customer’s requirements are met.
As a part of management system
Quality control can be based on a certified management system, which is based on ISO 9000 standard system. The aim of the process is to improve the quality and decision making as well as relationship management.
To achieve this, it is imperative to understand the needs of the customer and of other interest groups. Equally important is to ensure that the work environment is such that the entire workforce participates in the process: a well-managed delivery chain results in an even and high-quality products and services.
Internal quality control
© Metsä Group/Studio Tomi Aho
Internal quality control observes the properties and measurements of raw materials, and sawn timber’s properties at various stages of the process.
This collected data can prove that the quality requirements, including kilning, are met. This intermediate data is valuable, if something needs to be checked downstream e.g. if there has been a claim.
An important part of internal quality process is the control, calibration and maintenance of the measuring equipment.
Measuring and grading of logs
Logs can be measured in the forest, at the roadside, during transportation and also at the mill, usually at the log sorter.
The final measuring at the mill is the most common one in use. There are controls at the log sorting, usually by choosing randomly a smaller batch.
There are also specific requirements by authorities for goods imported from outside EU.
These vary according to species, origin etc, but the main aim of this is to prevent the spreading of diseases or pests. A phytosanitary document is required for importation of conifer timber from all Non-EU countries and Russia, Kazakhstan and Turkey. With conifers the phytosanitary documents are dependent on species and origin.
Debarking
Normally, the logs are debarked before sawing, especially if the chip by products are being used for pulp manufacturing. At smaller mills, where the by-products are used for instance for energy production, debarking is not needed.
Sawing
The quality control begins with ensuring that the log class – quality and size – is the correct one.
Then the most important aspects of quality control are the accuracy of sawing and the surface quality.
The dimensions of various sizes in production are checked in the process. This measuring can be manual, but there are also devices capable of doing this as well. The advantage of the machines measuring continuously the pieces is that the entire production is measured, as opposed to sample pieces taken during the process.
Sticking
If sticking is done poorly it may result in deformed pieces. Usually, the biggest reason for this is that there are too few sticks, or they are in a wrong place.
Usually, the batch on sticks gets an identification number, which helps to trace back the goods should there be any need for it.
Drying
Customers may have different requirements regarding the kilning, because the moisture content may vary according to end uses. In kilning the moistures can be monitored either with sensors attached to the goods or with manual moisture meters.
Best way of controlling the moisture is by taking sample pieces off the kilned goods and checking them by weighing or drying. When measuring the moisture content, it is important to take into account the temperature of the measured piece. There are also requirements set by authorities, especially when exporting timber outside the EU. The most commonly required standard is the ISPM15, which can be found at most mills exporting kiln dried goods.
Quality grading, packaging, protection and dispatch
Visual sawn goods grading at Nordic mills is based broadly on the Nordic Grading Book, the “Grey Book”. Quality grading has evolved over the years, the current version of the book takes into account all four faces of the sawn piece of Redwood/Pine (Pinus sylvestris) and Whitewood/ Spruce (Picea abies). There one gets introduced to mail qualities (Unsorted, Fifths, Sixths). However, it is important to note that many mills produce also customer specific grades.
Quality grading takes into account several parameters: technical properties such as size and moisture content, visual properties like knots (type, size, number) and defects like pitch pockets, grain, splits and shakes etc. Quality grading can be either visual or automatic, machine made.
Mills have different practices to monitor the success of desired grading. Typically, random packages are chosen from stock and then checked for size, moisture and other grade parameters like knots.
Dispatch is the final link between the producer and the customer. At this point the wrapping, binding and other visual aspects should be checked for the last time.
By-products
The sawmilling by-products’ quality is also monitored. The size of chips, size of sawdust particles and content of dry material are all measurable properties in by-products.
