For best results in the machining of multiple material layers, cutting parameters must be applied for each different material. The new L-MAX, a portable drilling unit from SOMEX, a member of the SUHNER group of companies, can perform all of these functions in automatic mode.
Multiple material layers, also referred as stacks, can be composed of completely different materials, stacked up in layers of, for example: titanium, carbon or aluminum. To achieve optimal machining results, each material layer must be programmed with its own cutting parameters, ideally for each layer automatically. The spindle speed and feed rate must be adapted for each material transition to the next.
In the past, aluminum was the primary choice of materials used in the aircraft industry and portable, handheld pneumatic-driven drilling units were used as a common tool in this industry.
The application of these conventional pneumatic drilling units in today’s modern and innovative aircraft industry necessitates extreme compromises. In addition to large air consumption combined with high noise emissions, pneumatic-driven drilling units cannot perform feed and speed variations as required for different stack materials.
Consequently, only a portable, handheld NC-programmable drill unit is capable to deliver optimal results and high efficiency, since the aircraft industry imposes rigid quality standards including:
Concentricity/position between holes ≤ 40 μm
Surface quality between Ra 1.6 and Ra 3.2
Circularity/hole quality for rivets ≤ H8
Other requirements such as avoidance of delamination.
An L-MAX concept integrates two servomotors: The larger motor drives the spindle and the smaller servo regulates the feed. The feed rate is determined by the speed difference between ballscrew and ballscrew nut or, in other words:
If the speed (rpm) of the feed servomotor is higher than the spindle motor speed (rpm), then the L-MAX spindle will advance.
If the speed (rpm) of the feed servomotor is lower than the spindle motor speed (rpm), then the L-MAX spindle will retract.
Both servomotors are controlled by the control system IDM. It allows the user to regulate spindle speed and feed at any position of the total travel.
Furthermore, an adaptive drilling mode can be selected to help improve and optimize a drilling cycle. In this mode, the drill unit recognizes the transition from one layer to the next, automatically. Irregular material thickness of layers at any position are detected and matched with the correct cutting parameters. This way, cycle times can be minimized and machining quality and results optimized.
The control system includes a minimum quantity lubrication (MQL) system, which is directly mounted to the mobile platform.
Related Glossary Terms
Rate of change of position of the tool as a whole, relative to the workpiece while cutting.