When screws are fed by vibratory feeders and driven by automatic screwdrivers, a deviation that nobody would notice in manual assembly can stop the whole line. This is why we treat the screw as a functional part of the system, not just a mechanical element.
What goes wrong on the line
In large batches every small deviation multiplies. Typical consequences are:
- Jamming on vibratory feeders – caused by head or length deviations and by foreign or mixed parts.
- Unstable tightening torque – caused by drive and thread variations.
- Bit wear – a poorly formed drive wears the bit faster.
- Cracked plastic or chipboard – caused by thread geometry that does not suit the material.
- More complaints and scrap on the line.
The parameters we control
- Head roundness and head dimensions – affect feeding stability and how the screw sits in the bit.
- Choice of drive – for example TORX versus PZ affects bit grip, tightening torque and bit wear.
- Thread profile – should match the material the screw goes into.
- Length and tolerances – for certain dimensions we achieve deviations of approximately 0.02 mm, depending on the dimension and project requirements.
- Drive concentricity – monitored with statistical process control (SPC) together with head diameter and height, thread profile and length.
Keeping the batch clean
Mechanical sorting and optical inspection remove non-conforming parts before packaging. Optical inspection is available on request, with a target of up to 50 ppm. For more demanding projects each packaging unit is inspected separately, which further reduces the risk of non-conforming parts reaching your production. We have three optical sorting machines – see Optical sorting.
Stability over time, not only on the first delivery
A sample that meets the drawing is only the start. We monitor tool wear, process stability and setting corrections, and we track deviations statistically, so that the hundredth batch behaves like the first. Read more in Series production and the risk of variation.
Work with us from the development phase
We help customers reduce line stoppages, scrap, bit wear and complaints through technical cooperation – analysing feasibility, advising on head, drive and thread geometry and on material choice. The development process is described on the Development page, and the page on Custom screws explains what we need to start.
Running an automated line with screw problems? Send us your drawing or specification – we reply within 1–2 working days.