Covis relies on BIG KAISER for its precision machining: boring heads, roughing heads and the modular Smart Damper vibration damping system from the Swiss tooling supplier help Covis to adhere to very tight tolerances even on exotic materials and superalloys.

A complex, rigorous production process

Flawless quality assurance is a basic prerequisite in the energy and petrochemical sector. To meet the high standards demanded by its customers, Covis has to overcome multiple challenges in its day to day machining operations, requiring specialized techniques, tools and procedures.

"We are quite specialized and produce unique parts and components as one-off's, or at the very least in extremely small series runs,” says Soprana. “The production process is highly complex and exacting with many steps.”

"It consists essentially of three phases: first phase preparing the piece, followed by the material coating process, after which the piece is precision machined to the final finish,” says Soprana. "To complicate matters further, sometimes the material that is machined is exclusively Inconel or Super Duplex."

Inconel is a nickel and chromium based super alloy that is exceptionally resistant to oxidation, high temperatures and corrosion, but its hardness makes it extremely challenging to machine.

"The heat generated during the machining process flows into the tool, subjecting it to a sustained barrage of stresses and strains. Cutting speeds are low, contact times are long and machining sessions are protracted," says Soprana.

Medium to large parts for the energy sector are machined in the main production site, with diameters ranging from 500 to 2,500 mm. To achieve the best possible finishing result on such difficult materials, the machining process requires the additional use of vibration dampening systems. Further exacerbating the issue, the depth of the holes to be finished is substantial (8-9xD, f. e. 45x420 to 53x480) and tolerances are very tight, with finishing grades pushed down to a roughness of 0.4~0.2. 

Such conditions require the participation of a tooling partner such as BIG KAISER, capable of ensuring maximum precision and repeatability at all times, and eliminating vibration levels that could impact the company's high-quality standards.

Flanges for hydroelectric power plants in S355J2G3 with Al-Bz 8 coating. The most challenging holes on this piece are the 4 radial holes Ø58h6 with roughness 0.8 that are drilled with Smart Damper bars starting from the outside for a depth of about 400 mm.

Team effort delivers results

Every machine, every material, every machining operation and every cutting parameter is a potential variable that can affect the performance of a tool. A tool supplier like BIG KAISER who can swiftly adapt their solutions to differing conditions and requirements can make a significant difference.

"The boring heads are top-notch: 4 microns in the Vernier equal 4 microns on the machine,” says Soprana. "Delivery times with BIG KAISER are rock solid, which is quite a relief for us.”

“When working side-by-side on a project, we work as equal technology partners because at the end of the day, it is always a team effort that delivers great results," says Soprana.

“Working with partners such as Covis on challenging, complex projects, helps us at BIG KAISER to generate and evaluate real-world data, spot trends and continuously test and increase our knowledge base of tools, processes and materials,” says Enrico Zanghi, Technical Sales Manager at BIG KAISER.

"Our customers demand outstanding results, therefore Covis has a policy of working exclusively with premium suppliers,” concludes Soprana. "With BIG KAISER we know that we can rely on a technologically impeccable partner that provides first-class customer service."

In combination with the BIG-PLUS spindle system, which ensures simultaneous a double cone-flange contact between spindle and machine, Smart Damper bars substantially reduce the problem of vibrating surfaces. When working with deep bores and vibration dampening bars, it is important to add additional rigidity to the machine.

Solving the problem of vibration

Covis uses a variety of tools from BIG KAISER, including boring heads, roughing heads and the modular vibration dampening system Smart Damper. The Smart Damper bars have enabled deep boring with high precision finishes on valves with Inconel, with substantially better results than were possible using solutions from other suppliers.

All the machining centers in the workshop are also equipped with the BIG-PLUS spindle system, the only system in the world to guarantee double simultaneous cone-flange contact between the spindle and the machine. This is another important step that gives more rigidity to the machine and keeps vibrations under control.

"We switched to BIG-PLUS several years ago and the choice is really paying off,” says Soprana. "When working with deep bores and anti-vibration bars, it's important to add additional rigidity to the machine. After several years of having used BIG-PLUS and BIG KAISER's vibration-dampening solutions, I can honestly say that they have never let us down."

The weld seams have a strongly interrupted cut, which allows inserts with large radii to be used. BIG KAISER's tools ensure continuous machining, meaning that Covis does not have to perform adjustments or breakage checks at every hole, which saves time and resources.

In the hole-finishing and re-centering phases, there are several aspects that need to be taken into consideration. Firstly, the tool must reach the bottom of the hole within a certain cutting time; secondly, it must remain within tolerance and roughness specifications and thirdly, it must guarantee the concentricity of the hole. Soprana says, "It is not possible to obtain precise results on such demanding machining operations using reaming processes. That's why we rely on boring heads."

Roughing must also be done with attention to detail since a rough-cut piece with high roughness invariably impacts the quality of the finish. Covis has, therefore, invested into improving the roughing process by utilizing BIG KAISER roughing heads that have enabled high-precision finishes on pieces that have already been surface treated.

Smart Damper bars reduce vibrations, allowing Covis to process difficult materials such as Inconel.

The Smart Damper bars have made it possible to perform deep drilling with precision finishes on valves with Inconel coatings, with results that, in the past, could not be achieved with tools from other suppliers.