1. Selecting the right wood
Only hard and tough woody plants such as beech or hornbeam can be used for the production of measuring instruments. Only the finest and also the smallest part of the trunk is used; the so called side timber.
2. Producing a semi-finished product
Blanks are carved out of quality side timber. Once again, unsatisfactory pieces are carefully discarded. The sorted blanks are neatly placed on pallets to form stacks.
3. Drying the wooden blanks
The stacks are initially stored in a roofed outdoor warehouse where the cut-outs are left to slowly dry out and stress in the wood to gradually decrease over a period of almost one year. Subsequently, the timber is subjected to second drying in chambers until it reaches approximately 8% moisture content. Finally, it is necessary to subject the timber to one more process – hydrothermal treatment, at a specific temperature and humidity.
4. Cutting into slats
Timber which has been hydrothermally treated is subsequently plane smoothed on four sides and saw again into individual slats, which are a fundamental part of any wooden folding ruler.
5. Dyeing the slats
The wooden slats are then dyed with several layers of 100% water-based paint. The method of roller coating ensures a quality and smooth surface of the slats.
6. Printing the scales
Next, a two-colour scale is printed onto the slats. Scale accuracy is achieved due to solid stamping dies made of synthetic rubber that are firmly attached to metal dies.
7. Lacquering and final surface treatment of the slats
Just like dyeing, lacquering is carried out by roller coating. The outer UV lacquer completely covers the print and the base colour of the slats and thus protects the product not only against water but also against basic solvents such as acetone.
8. Machining the slats in order to insert joint parts
Each type of folding ruler has a different kind of joint and therefore, the slats must also be machined in a different way. Precision machining of wooden slats by milling is a very difficult process. Accuracy in hundredths of millimetre must be achieved.
9. Inserting the joints
Individual parts of the ruler are inserted into milled parts of the slats. Again, it is a precision process.
10. Fitting the end slats with end pieces
The first and the last slat of each folding ruler are fitted with a steel end piece. It serves as an accurate beginning or end of the measuring instrument and also protects these ends against damage during use.
11. Folding ruler assembly
During assembly, all components of the ruler must "unite" at the same moment to form one harmonious whole. It is a very demanding operation performed by complex single-purpose machines. For instance, in the case of a 2 m BL52 folding ruler the machine must assemble 10 slats + 9 rivets + 9 washers at the same time. Each ruler is controlled by sensors and a worker during assembly. Next, it is cleaned and handed over to next operation.
12. Checking dimensional accuracy
Checking the length accuracy of a folding ruler as a legal measuring instrument is required by law. The same holds for checking the accuracy tolerance during transition between individual slat joints.
13. Folding the ruler
After inspecting, the assembled rulers are folded together. Formerly, the folding was carried out manually like most manufacturing operations. Today, this hard work is performed by single-purpose machines.
14. Machining and surface treatment of folding ruler ends
A folded ruler is not yet completely finished; the ends need to be treated in order to get the look we all know. The two ends of the ruler are machined and dyed. Thus treated, the rulers are much more comfortable to use.
15. Printing special characters or advertisements
This operation may or may not take place depending on the requirement. Virtually, any graphics can be printed on the folding ruler thanks to pad or UV digital printing. It may be a special character or, more frequently, a promotional message.
16. Final inspection and packing
Visual inspection of finished rulers. Here again, a human hand touches each individual product. The rulers are not merely packed into boxes and cartons; they are visually checked one more time. We use standard size packaging: boxes of 10 items or cartons of 100 items.