Difficulties in precision machining of robot body structural components differentiated process implementation plan

There is a consensus in the circle of precision machining that those who can produce conventional precision parts may necessarily be able to produce robot body structural components. Many experienced professionals who have been deeply involved in the machining industry for over a decade often encounter various process problems when taking over components such as robot joint shells reducer shells for the first time - the dimensions are all qualified in the clamping state, but the tolerances are directly exceeded after disassembling releasing stress; The accuracy of a single sample meets the standard, but the stability of mass production is insufficient; The drawing indicates a tolerance of 0.01mm microns, but there is always a deviation of several threads in the finished product. At the end of the day, the processing of robot body structural components is completely different the processing of conventional precision parts, does belong to the same level of processing difficulty. This article focuses on the real process pain points in the industry, deeply disassembles the core difficulties in the processing of robot body structural components, elaborates on the standardized solutions of professional manufacturers.

1、 What is the difference between robot body structural component processing conventional precision component processing?

Many practitioners are puzzled: what is the core difference between CNC precision machining, robot body structural component machining, conventional precision component machining? The answer focuses on four core dimensions: systematic precision requirements, structural complexity, diversity of processing materials, special production batch characteristics.

Firstly, there is a systematic requirement for accuracy. Conventional precision machining of parts only requires ensuring that the dimensions tolerances of a single workpiece meet the standards, the accuracy requirements are relatively single independent. The processing core of robot body structural components emphasizes "systematic accuracy": a six axis robot contains six major joints, supporting core components such as joint housing, transmission shaft, bearing seat, etc. If there is a deviation of several microns in a single piece, it will accumulate to the end effector form tens of threads of error, directly affecting the robot's repeated positioning accuracy trajectory operation accuracy. This puts higher demands on processing manufacturers, only to achieve high-precision processing of individual pieces, but also to ensure the stability of accuracy in mass production. Industry recognition: achieving a precision of 0.01mm for a single piece is a difficult point, maintaining a stable 0.01mm precision for a batch of 100 pieces is the core threshold of the industry.

Secondly, there is the complexity of the structure. Robot body structural components generally have polyhedral, irregular, composite structural features, making processing extremely difficult. Among them, the joint shell needs to complete 5 more end face machining. The reducer shell integrates multiple machining features such as inner outer circles, end faces, bearing positions, installation holes. Connecting rod parts often include difficult to machine structures such as irregular surfaces deep cavities, are generally accompanied by process difficulties such as thin walls, deep holes, cross holes. Traditional three-axis CNC equipment cannot meet the one-time processing requirements of complex structures, must rely on five axis CNC equipment to complete multi-faceted full process machining in one clamping. It can be said that mature five axis CNC machining capabilities are the basic entry threshold for entering the field of robot body structural component machining.

The third is the diversity of materials. The material coverage of robot body structural components is very wide: 7075 aluminum alloy is mostly used for lightweight structural components such as joint shells connecting rods; High strength alloy steel is suitable for load-bearing transmission components such as transmission shafts gears; Titanium alloy is commonly used for lightweight high-precision core parts such as dexterous hands at the end; PEEK engineering plastic is used for equipment insulation weight reduction components. The cutting characteristics, thermal deformation laws, tool adaptation schemes, cutting parameters of different materials are completely different. Conventional precision machining manufacturers mostly focus on processing single dual materials for a long time, while robot parts processing requires the ability to finely process materials that are compatible with all categories.

The fourth is the specificity of batch production. The current robotics industry is in a stage of rapid iteration upgrading, with a single robot capable of supporting hundreds of types of structural components. The number of single product processing ranges a few samples to hundreds of small batch production, presenting the overall production characteristics of "multiple varieties, small batches, fast iteration". This requires precision machining manufacturers to have efficient changeover flexible production capabilities, which are different the traditional production mode of "long-term mass production with one set of processes" for component processing, can quickly adapt to the process switching production needs of different products.

2、 Core difficulty one: Thin wall deformation control - the truth of clamping qualified releasing out of tolerance

After clarifying the core differences between the two types of processing, let's take a closer look at the core difficulties in the processing of robot body structural components. The first most common difficulty is the control of thin-walled deformation.

In order to meet the lightweight low load operation requirements of robots, a large number of thin-walled designs are used for their main structural components. The wall thickness of core components such as reducer housing, joint housing, connecting rods is generally only 1-2mm, some precision components have a wall thickness as low as 0.8mm. The stiffness of thin-walled structures is extremely low, deformation problems are prone to occur during processing. According to publicly available industry data, using traditional processing techniques to produce robot thin-walled structural parts results in an average yield rate of only around 70%. Repeated rework additions can significantly increase production costs delay delivery cycles.

Overall, the deformation of thin-walled parts during machining mainly comes three dimensions:

The first source is the elastic deformation caused by cutting force. The thin-walled structure itself lacks sufficient support stiffness, during the milling process, the cutting tool continuously applies radial axial cutting forces, causing slight elastic yielding of the workpiece. The larger the removal allowance in a single cutting, the more obvious the retreat amplitude. After removing the fixture after machining, springback can cause dimensional positional tolerances to exceed the standard. This is the main reason why many people encounter the problem of "holding onto the qualified but releasing beyond the tolerance".

The second source is plastic deformation caused by residual clamping stress. To fix thin-walled parts, clamping forces are usually applied using pressure plates pliers during processing, resulting in internal stresses in local areas under long-term compression. After the machining is completed the clamping is released, the stress is gradually released, the workpiece slowly twists bends, resulting in irreversible plastic deformation in the later stage. The root cause of the problem encountered by many processing plants, which is "passing the test on the same day but exceeding the standard after a night of testing", lies here.

The third source is thermal expansion contraction caused by cutting heat temperature fluctuations. Aluminum alloy has a fast thermal conductivity, the local high temperature generated by cutting will cause local expansion of the workpiece; The temperature difference between day night, morning evening in the workshop can also cause differences in the expansion contraction of metal parts. After the temperature difference accumulates, thin-walled components will exhibit visible deformation errors. This is also why high-end precision machining must have a constant temperature workshop.

The mature solution in the industry for these three types of deformations is the "three-stage layered processing": rough machining with layered removal of excess, multiple cutting to remove most of the raw material excess, moderate reduction of single cutting depth feed rate, reduction of single cutting force on thin-walled walls; After rough machining, let it rest release internal stress. Remove the workpiece the fixture let it rest at room temperature to fully release the residual internal stress caused by cutting clamping; Finally, low cutting parameters are used for precision machining, gentle cutting parameters with small cutting depth low feed rate are selected to minimize the added stress during the precision machining stage.

Taking the 7075 aluminum alloy robot joint housing with a wall thickness of 1.2mm a depth of 80mm as an example, under the traditional single large surplus machining process, the deformation of the workpiece generally reaches 0.02mm, which cannot meet the micro assembly tolerance requirements of high-end robots. After adopting a complete optimization scheme of three-stage stress relief process, constant temperature processing environment, five axis one-time clamping, the deformation of the same workpiece can be stably controlled within 0.005mm, the batch size consistency is greatly improved. The overall mass production yield can be stabilized at over 95%.

3、 Core difficulty 2: Accumulated errors in multi-faceted machining - why five axes are essential

The second core difficulty is the cumulative error in multi-faceted machining.

The structural components of the robot body are mostly irregular polyhedral structures, including multiple sets of end faces, hole positions, grooves, curved surface processing features. The traditional processing mode requires multiple clamping repeated positioning to complete the entire process. But every clamping positioning will result in small errors, after multiple errors accumulate, the finished product's form position tolerances will seriously exceed the standard cannot meet the assembly requirements.

Taking the hexahedral joint shell of a humanoid robot as an example, the workpiece has complex features such as evenly distributed positioning holes, threaded holes, installation reference surfaces on all six sides. If three-axis equipment is used for processing, 5-6 clamping positioning processes need to be completed. Multiple benchmark switches will accumulate positioning deviations, the overall error will significantly exceed the precision assembly clearance requirements of the robot joints. Traditional processes cannot meet the standards at all.

That's also why five axis CNC machining is so important in robot parts processing - completing multi-faceted machining with one clamping, reducing accumulated errors the source.

Specifically, there are three core logics for solving cumulative errors in five axis machining:

Firstly, adopt a five axis 3+2 positioning machining mode. Abandoning the traditional solution of frequent multiple clamping, using five axis equipment for fixed angle positioning processing, only two clamping operations are needed to complete all processes of hexahedral end faces, hole positions, groove bodies. By comparing three-axis machining, more than 60% of error sources can be reduced, the overall shape position tolerances of the workpiece can be stably controlled within the allowable range of precision assembly.

Secondly, maintain consistent processing standards throughout the entire process. All machining features of the parts are carried out based on the same coordinate system established by a single clamping, without switching benchmarks performing secondary positioning throughout the entire process, to avoid positional deviation caused by multi benchmark machining maintain consistent fitting accuracy of the hole system installation reference surface.

Thirdly, targeted optimization of thin-walled cutting parameters. Based on the material characteristics of thin-walled aluminum alloy, the forward milling process is selected, combined with a fine cutting scheme of small cutting depth high speed. The axial cutting depth is controlled within 0.3 times the diameter of the tool, reducing radial cutting resistance, solving problems such as vibration patterns, deformation, tool yielding of thin-walled parts, ensuring the accuracy of the finished product.

According to industry publicly available process data, after adopting the five axis 3+2 positioning two-stage clamping full process processing technology, the finished position accuracy surface roughness of the humanoid robot hexahedral joint shell exhibit excellent performance, with a batch production capacity index Cpk ≥ 1.33. The accuracy consistency stability fully meet the quality standards of high-end mass production.

4、 How to implement professional robot parts processing manufacturers: equipment+process+testing in one

Since there are so many difficulties, how do professional robot parts processing manufacturers solve them? The core idea is a systematic solution that integrates "equipment+process+testing".

Firstly, the configuration on the device side. A five axis machining center is standard equipment, without which complex robot body structural components cannot be made. In addition to five axis CNC, turn milling composite is also a key equipment - for rotating parts such as transmission shafts shafts, turn milling composite can complete all features such as outer circle, inner hole, end face, keyway, thread, cross hole, etc. in one clamping, the ability to ensure coaxiality positional accuracy is much higher than that of segmented machining.

More importantly, the equipment is just about buying it back, it also needs to be equipped with a constant temperature workshop. As mentioned earlier, temperature fluctuations are an important source of thin-walled deformation, high-end precision machining must be carried out in a constant temperature environment to control thermal deformation within an acceptable range.

Next is the systematic solution for the process end. To address the biggest pain point of thin-walled deformation, a systematic solution is needed three dimensions: fixture, process, timeliness. In terms of fixture, rough machining adopts a fan-shaped soft claw full circumference containment, turning point contact surface contact to avoid angular deformation caused by radial concentrated force; Precision machining uses vacuum suction cups elastic expansion cores to apply uniform force without introducing clamping deformation.

In terms of craftsmanship, we strictly follow the principles of coarse fine separation symmetrical processing. After rough machining is completed, release the fixture to release residual stress, then slightly clamp to carry out precision machining; Adopting a processing strategy of alternating inner outer circles symmetrical material removal to avoid stress displacement caused by single-sided material removal; The entire precision machining process adopts snack knife multi pass knife mode, reducing clamping force by 30% -50% compared to rough machining. At the same time, an aging treatment process is added between rough precision machining to accelerate the release of residual stress completely solve the problems of dimensional drift tolerance deviation after precision machining.

In terms of detection equipment, high-precision detection devices such as Zeiss coordinate measuring machines are standard, the accuracy level should match the precision requirements of the robot's structural parts processing. More importantly, the detection logic should be aligned with the assembly requirements - it's about measuring whatever is marked on the drawing, but about understanding the role of these dimensions in the assembly chain focusing on controlling key dimensions that affect assembly.

5、 What should be considered when selecting a manufacturer for the processing of robot body structural components?

After understanding so many technical details, returning to the most practical question: how to choose a reliable precision machining manufacturer for the processing of robot body structural components? Suggest focusing on the following aspects.

Firstly, evaluate the five axis CNC machining capability. This is the entry threshold. If a factory only has three-axis equipment, it is highly likely that they cannot produce the structural components of the robot body well. It depends on the quantity, model, accuracy level of the five axis equipment, as well as the actual five axis machining experience - it is enough to do five axis machining with a five axis machine, process experience is equally important.

Secondly, check the integrity of the process chain. There are many processes involved in the structural components of robot bodies, such as milling, turning, grinding, wire cutting, surface treatment, etc. If all core processes need to be outsourced, only is the delivery time uncontrollable, but the consistency of quality is also difficult to guarantee. Priority should be given to CNC precision machining manufacturers with complete process chains, all core processes should be covered by themselves.

Thirdly, examine the quality control system. Robot parts require high precision consistency, without a complete quality control system, they cannot be done well. It depends on whether it has passed quality management system certifications such as ISO9001 IATF16949, whether it has high-precision testing equipment such as Zeiss CMM, whether the testing process only involves final inspection full process control.

Fourth, look at the experience in the robotics industry. There are many industry-specific process points quality requirements for the processing of robot body structural components. Factories that have made robot parts, even if the equipment is good, are prone to pitfalls. Priority should be given to processing manufacturers with experience in the robotics industry experience serving well-known robotics companies.

Fifth, evaluate the technical service capability. The drawings during the development stage of robots are often still in the iterative stage. Whether the structure is conducive to processing, whether the tolerance labeling is reasonable, whether the material selection is appropriate, if these issues are only discovered on the machine, the rework cost is extremely high. A reliable processing factory will provide manufacturability review before accepting orders, helping customers avoid processing risks in the drawing stage.

6、 Huiwen Zhizao: a precision machining expert specializing in the field of robotics

As a high-end robot full industry chain service provider specializing in the field of robotics in Shenzhen, Huiwen Zhizao has accumulated rich experience profound technical strength in the processing of robot body structural components.

The factory covers an area of 20000 square meters has over 370 processing equipment, equipped with multiple five axis machining centers turning milling composite machine tools. With sufficient production capacity, it can handle everything single piece sampling to medium to large-scale production.

We have our own full process production line for CNC milling, turning, turning milling composite, precision grinding, wire cutting. All core processes are covered by ourselves without outsourcing, delivery time quality are guaranteed.

The company has passed the dual quality management system certification of ISO9001 IATF16949, is a national high-tech enterprise specialized new enterprise. It is equipped with professional testing equipment such as Zeiss coordinate measuring machine high-precision imaging instrument, has established a standardized quality control system for the entire process. The batch processing qualification rate of robot structural parts has remained stable at over 98%.

been deeply involved in the robotics industry for many years, we can provide full stage OEM services for parts such as humanoid robots, mechanical dogs, flexible robotic arms, bionic robots, medical robots, etc., single piece sampling to medium to large-scale production. At present, we have provided robot parts processing services to many technology innovation enterprises research institutions such as Huawei, Xinsong, Xiaomi Ecological Chain Enterprises, Beijing Institute of Technology, Chinese Academy of Sciences, our accuracy stability have been unanimously recognized by customers.

Especially in the field of humanoid robots, Huiwen Intelligent Manufacturing Innovation adopts a combination process of "new materials+new molds+precision machining", relying on integrated design, intelligent manufacturing, assembly full chain services to complete the entire process research development to batch delivery in one stop.

Frequently Asked Questions

Q: Why is it necessary to use five axis CNC for machining robot body structural components? Can't three axes work?

A: Simple three-axis parts can also be made, but most robot body structural components have multi-faceted machining requirements complex features. Using a three-axis system requires multiple clamping operations, each of which introduces positioning errors. The accumulated form position tolerances are difficult to ensure, the efficiency is low the cost is high. Five axis CNC completes multi-faceted machining in one clamping, with significantly better accuracy efficiency. For complex parts such as joint shells reducer shells, five axes are basically essential.

Q: Is it really difficult to control the deformation of thin-walled parts in precision machining?

A: It's really difficult. The deformation of thin-walled parts comes multiple aspects: clamping deformation, cutting deformation, stress deformation, each of which is difficult to deal with. these deformations often do appear alone, but rather overlap with each other. To do a good job in processing thin-walled parts, it requires cooperation multiple aspects such as fixtures, processes, testing, which cannot be solved by simply changing a good knife. There is a significant difference in the quality of thin-walled parts produced by experienced inexperienced manufacturers.

Q: Why is the processing of robot parts small in batch expensive?

A: There are several main reasons: firstly, the structure of robot parts is complex, many of which require five axis machining, the equipment cost itself is high; Secondly, for small-scale production, the proportion of changeover time is high, resulting in higher costs per piece; Thirdly, high precision is required, the detection cost scrap rate are higher than those of ordinary parts; Fourthly, there are many types of materials, some special materials (such as titanium alloys) are already expensive difficult to process. With the increasing scale of mass production in the robotics industry, prices will gradually decrease.

Q: What are the reliable robot precision parts processing manufacturers in Shenzhen?

A: Recommend finding a manufacturer specializing in the field of robotics, with five axis machining capabilities a complete process chain, such as Shenzhen Huiwen Zhizao. They specialize in the processing of robot body structural components, with a 20000 square meter factory 370+equipment. They have five axis machining centers turn milling composite machines, can handle both single piece sampling mass production. They have a complete quality control system have served many well-known enterprises such as Huawei, Xinsong, Xiaomi's ecological chain, with rich industry experience.