Insight

Driven by a need to increase production capacity, Dimac underlines that the motivation for purchasing sorting machines is changing, with a focus on replacing obsolete machines and automating processes. Therefore the Tortona-based company is ensuring its high-quality machines are designed for the future with three new solutions for the defect detection in the thread of screws and bolts.

Guaranteed by rigorous design activity and state of the art hardware and software components, and devices, together with many years of expertise in the mechanical assembly and testing, according to existing regulations and customers’ specifications, Dimac produces nine different automatic 100% inspection and sorting machines for fasteners, as well as three SPC in process control measuring systems.

A fundamental aspect of all Dimac’s machines are the robust design for enduring performance. “We’ve engineered our machines by using high-quality materials and a modular, scalable approach to reduce stress on mechanical components,” explains Dimac Srl. “The result is
long-term reliability and lower maintenance costs.”

The Italian company has also looked to use advanced technologies to ensure lasting reliability, such as the new inspection stations for thread defects and surface defect controls. The new advanced solutions also include a linear camera station, multi-camera station and electro-mechanical roller station, now available on mcv sorting machines.

Dimac adds: “External thread inspection in screws and bolts is crucial for ensuring product quality and reducing false rejections, thereby lowering selection costs. Various technologies are employed for this purpose, each with specific characteristics suited to different situations.”

The traditional method for thread inspection is an optical profile control using rotating station and dimensional camera – the control station puts in rotation the piece while the dimensional camera captures multiple images. The profile analysis solution with a rotating station has two main limitations, the piece is not inspected over its entire surface, despite the increased number of captured images, and the rotation entails high machine costs and long selection times. To address these needs, Dimac has developed three advanced inspection stations.

The first solution, a linear camera control station, uses a line surface scanning camera that grabs a line of pixel for each trigger while the piece turns 360 degrees. The grabbed surface lines are then joined together to obtain the unrolled image of the cylindrical side surface of the thread. The surface line scanning camera is triggered by the 360° rotation station’s encoder to cover the entire piece surface and the resolution of the trigger pulses can be set to improve the accuracy of the surface inspection. 

The vision software analyses the thread using Dimac AI tools, identifying irregularities such as ‘z-thread’ or foreign hits and dents or excess of surface coating between crests. The high-quality of the acquired side surface image enables the detection of minimal defects, including those quite invisible to the human eye, such as head fine cracks. This method is very accurate but does not perform dimensional measurements, plus its scanning cycle time limits output rates. Dimac therefore recommends this method when high-quality controls are required, such as in aerospace applications.

The second solution is a multi-side camera station equipped with three or four side surface cameras positioned 90° or 120° to one another to look at the threaded shank surface, all around. Although the image quality is lower than the line surface scanning camera version, the multi camera station doesn’t require the piece rotation, enabling high productivity of up to 700 pieces per minute for M6 screws. Dimac AI tools are also used with this station to detect macroscopic defects, such as dents, scratches, open cracks and radial holes. 

The third technology, patented by Dimac in 2023, is electro-mechanical inspection using a gauging roller station, where a threaded master roller gauges the thread’s compliance. Designed for M6 screws, a group of two gripping rollers keeps the piece in rotation while the third threaded roller gauges the threaded shank simultaneously. The roller gauge sliding axis movement is checked to stay into a threshold envelope by a special sensor. Any defect impacting the roller gauging effort to spike out of the envelope is immediately identified, to define the thread quality. 

Thanks to a special control algorithm, the system is insensitive to core ovalisation, reducing the rate of pseudo-reject. The output rate is also lower than the other two solutions, but this station ensures the screwability of the conformed parts – making it reliable for fasteners used in automatic assembly lines as it helps to remove small burrs or dirt in the thread.

“We see important opportunities for Dimac to introduce automatic machines for high-speed 100% inspection and sorting fasteners with Artificial Intelligence (AI) features, as well as SPC systems for in-process data collection across all key industries. These markets are facing challenges concerning the continuous improvement of automation in production and control processes, together with data collection and analysis, as well as traceability and efficiency. They are also facing the challenges of eliminating manual sorting operations, which are subject to errors and too expensive,” states Dimac. “At Dimac we can help and our perspective automation can be the driver of the future.”

For instance, Dimac machines are designed to run unattended and be used by unskilled operators because they are user-friendly and intuitive. Furthermore, Dimac also offers periodic metrological verification using the MSA procedure as part of its after sales service, to ensure compliance with quality standards.

Dimac also ensures that its software platform is continually evolving to help guarantee stability and error-free operation. Each improvement is closely monitored for continuous and reliable performance. 

As well as these technological investments, Dimac is also committed to sustainability and creating a production site in 2023 that operates entirely on sustainable energy. The site’s roof has solar panels to power the geothermal energy plant, as well as provide heating and cooling to the building housing a new showroom, along with modern offices for the sales, marketing, service and R&D departments.

In terms of economic sustainability, in 2022 Dimac launched the Pay Per Use project in Italy. This initiative enables 100% inspection and sorting machines to be rented through a variable monthly fee based on the volume of fasteners sorted per month. The project aims to economically sustain sorting operations in low volume production contexts and promotes a circular economy by providing machinery as a service. After the usage period, machines are returned to Dimac and can be rented out to other customers.

Dimac has also recently launched a SPC-Dimac business unit, automating SPC control in production, to enhance its role as a consultant. Dimac is able to assist customers in managing quality control data, maintaining accurate and current control plans, as well as ensuring data validity for immediate use in optimising production processes. The challenge is not about the big data collection but in swiftly making the relevant data accessible and impactful. This approach promises significant future business development, offering benefits such as predictive maintenance, personnel savings, reduced waste and increased production flexibility. 

“With a drive for quality getting stronger, we believe that fastener manufacturers should be changing their mentality regarding quality control,” reports Dimac. “Instead of seeing an investment in inspection and sorting machines as an extra cost in the production process, companies should be considering the investment with the same weight as they would production machinery. Dimac’s role is to partner with fastener manufacturers to support investments and supply high-quality, accurate and reliable machines that are ‘born to last’.”