CNC machining of core components of humanoid robots: 3 key machining points for lightweight design implementation

The commercialization of humanoid robots is stuck in the process of lightweight processing - this is a common feeling shared by many robot development teams when communicating with us. Many teams have already completed structural optimization design, achieving joint part wall thickness within 2mm and clear weight reduction goals. However, after being handed over to the processing plant for trial production, either the size exceeds the tolerance and cannot be installed, or the batch deformation cannot meet the service life requirements, and the design plan still cannot be implemented. As a CNC precision machining service provider specializing in the field of robotics, Shenzhen Huiwen Zhizao undertakes the machining verification of hundreds of core parts for humanoid robots every year. We have summarized that there are three key points in the machining process for the implementation of lightweight design.

Lightweight humanoid robots should not only reduce weight, but also balance strength and accuracy

Many people's understanding of lightweighting in the processing of robot core components still remains at the level of "digging grooves to reduce weight". In fact, the weight reduction of core components such as joints, shells, and transmission shafts of humanoid robots must be based on three foundations:

Firstly, the structural strength of the parts cannot be reduced, and they must meet the load requirements of long-term repeated movement;

Secondly, the fitting accuracy of the design cannot be changed, and the joint rotation clearance must be controlled at the micrometer level;

Thirdly, the dimensional stability after processing should be sufficient, and dimensional drift should not occur after three months of delivery.

These three requirements put forward completely different requirements for the process design of precision machining of CNC parts: ordinary machining only needs to machine the dimensions according to the drawing, while lightweight parts machining with humanoid robots requires advance prediction of the impact of machining deformation and stress release on subsequent use, and should be well prepared in the process stage. Huiwen Zhizao relies on the technical background of the Chinese Academy of Sciences and can cooperate with customers to optimize the structural process before processing, helping customers find a balance between weight reduction and processability.

The first key is to solve the problem of clamping deformation when clamping thin-walled parts

The lightweight core components of humanoid robots are mostly 1.5-3mm thin-walled structures, and clamping is the first difficult point that cannot be bypassed. Traditional pressure plate clamping results in high local stress, causing the parts to rebound and deform after loosening, and the dimensional deviation can easily exceed 0.01mm, directly leading to excessive fit clearance. In our long-term practice of machining robot core parts, we have summarized two clamping schemes suitable for thin-walled parts, which can be selected according to the structure: if it is a shell type part with a flat bottom surface, we use an integral vacuum suction cup clamping, which evenly distributes the force and does not require local pressure. For parts with a wall thickness of 1.5mm, the clamping deformation can be controlled within 0.005mm, fully meeting the accuracy requirements of joint installation; If it is a shaft type or irregular joint part, we use customized soft claws and process support to provide auxiliary support at the cutting force position to reduce deformation caused by cutting vibration, while controlling the clamping force to avoid clamping deformation. Last year, we processed a humanoid robot hip joint shell with a designed wall thickness of 1.8mm. Originally, the customer used traditional pressure plates for clamping, but the deformation remained stable at around 0.012mm, which did not meet the design requirements. We switched to using integral vacuum suction cups for clamping, and the deformation was reduced to 0.004mm, with all form and position tolerances meeting the standard at once.

The second key is stress release control, which must address the issue of dimensional drift in the later stages

Stress deformation is the second hidden pit in the precision machining of humanoid robot CNC parts: many parts are fully qualified after processing and testing, and are delivered to customers for half a month. When assembling, it is found that the size has changed, with a deviation of more than 0.01mm, and cannot be installed. This is essentially the deformation caused by insufficient release of internal stress in the blank and redistribution of stress after material removal during processing. In response to this issue, we have established a standardized stress relief process in small batch precision parts customization: whether it is aluminum alloy, magnesium alloy, or titanium alloy materials, as long as it is a thin-walled lightweight part, the process of "rough machining → natural aging → semi precision machining → vibration aging → precision machining" is adopted. After rough machining, a 3mm margin is left, and the stress is naturally released after 72 hours of constant temperature placement. After semi precision machining, residual stress is further released by 30 minutes of vibration aging, and finally precision machining is carried out. Through two stress releases, we can control the subsequent dimensional drift of the parts within 0.003mm, fully meeting the requirements of customer assembly and long-term use, without the problem of "factory qualification and assembly deviation".

The third key is complex surface machining, which must use five axis CNC machining to ensure accuracy

Nowadays, the lightweight structure of humanoid robots is becoming increasingly complex. Many joint parts adopt integrated molding design, including multiple angles of mating surfaces and curved surfaces. Traditional three-axis machining requires multiple clamping, and the cumulative clamping error will exceed 0.01mm, which cannot meet the requirements of fitting accuracy. Five axis CNC machining can complete the machining of all surfaces in one clamping, reducing the cumulative error of multiple clamping. At the same time, when machining curved surfaces, the tool always maintains the optimal cutting angle, and the surface quality is also better. As a precision machining service provider for CNC parts in Shenzhen, Huiwen Zhizao currently has 16 five axis linkage machining centers that can process core parts of humanoid robots with a maximum size of 1.2m. Whether it is an integrated joint housing or a complex shaped transmission shaft, it can be clamped and processed in one go, with a cumulative clamping error controlled within 0.005mm, meeting the accuracy requirements of complex lightweight structures. And we support small batch precision parts customization, with samples of up to 10 pieces delivered within 3 days at the fastest, to meet the rapid iteration needs of the R&D team.

The quality control of Huiwen Zhizao ensures the consistency of each batch of parts

In the research and development stage of humanoid robots, most of the requirements are small batch customization, and many small processing factories do not care about processing consistency. Each batch of parts has one size, which brings a lot of trouble to subsequent assembly and debugging. As a national high-tech enterprise and specialized new enterprise, Huiwen Zhizao has passed ISO9001 and IATF16949 quality management system certification. All CNC parts precision machining orders must undergo German Zeiss three coordinate inspection after processing, and all dimensions must be fully inspected and qualified before delivery. Small batch orders can also ensure dimensional consistency, and inspection reports can be attached with the goods, making customer research and development more worry free. At present, we have a standardized factory building of 10000 square meters and 150+precision machining equipment. We have provided robot core parts processing services for technology innovation enterprises and research institutions such as Huawei, Xinsong, Xiaomi Ecological Chain, and the Chinese Academy of Sciences. We have accumulated a wealth of experience in processing lightweight parts with different structures and can quickly adapt to customers' research and development needs. Huiwen Zhizao provides modular ODM services for robot body hardware design and manufacturing, covering the entire process of design (mechanical structure/electrical scheme design/process optimization), manufacturing (CNC machining/mold/surface treatment), assembly (component trial assembly/product assembly and debugging), supporting customers to choose single or multiple service modules as needed. It is a high-end robot full industry chain service provider with integrated design, manufacturing, and assembly capabilities.

summary

The lightweight design of humanoid robots has been implemented, and the precision machining of CNC parts must focus on three core aspects: controlling the clamping deformation of thin-walled parts, releasing internal stress in advance to avoid dimensional drift in the later stage, and ensuring accuracy with five axis CNC machining for complex structures. Only then can the design scheme truly land and achieve the dual goals of weight reduction and accuracy. If you are engaged in the research and development of core components for humanoid robots and encounter difficulties in lightweight machining, please feel free to send drawings and machining requirements for consultation. Engineers from Shenzhen CNC parts precision machining service provider Huiwen Zhizao will provide targeted process solutions and quotations within 24 hours.