Chapter 1106 Floating Clamping Method

The most taboo thing in research is to have only a partial understanding.

Therefore, although he believed in his heart that Chang Haonan must have a solution, Yang Weihua still expressed his concerns.

In short, it’s just one sentence.

Is it a bit too complicated?

“It’s complicated.”

Chang Haonan did not deny the existence of the problem, but just nodded:

“So, we have to do it step by step… First, for workpieces that are not particularly large, the milling force is the most direct factor causing the elastic deformation of the thin wall, so the first step is to start with micro-milling force modeling…”

The reason for choosing this research path is not entirely based on the consideration of going from easy to difficult.

Another reason is that the fan blades of AE1500 just meet the requirement of "not being particularly large in size".

Therefore, after achieving results, we can immediately start verification.

At this time, Wei Yongming continued:

"If we only study the shearing effect, there is a ready-made mathematical model that can establish the mathematical relationship between the synthetic current and the shearing force under the second-order damping system... Even in the case of multi-axis linkage processing, we only need to add a coupling effect between the multi-directional feed axes to eliminate the influence of the motor on the measurement structure when providing speed-changing torque..."

"The basic idea is indeed correct, but... it's not that simple."

Chang Haonan turned around, picked up a marker, and drew a cylinder on the whiteboard behind him.

After so many years of training, his painting skills have improved by leaps and bounds compared to his early years.

At least, everyone can see that it is a cylinder...

"In micro-milling, the cutting force generated by the tool during the cutting process cannot be simply equated with shear force, but should actually include plowing force..."

As Chang Haonan spoke, he drew a force analysis on the part representing the tool path:

"So, the basic expression of the milling force model in any direction should be..."

【dFj=[Kts·hj(θ)+Ktp]dz】

"Where Kts and Ktp represent the shear force and plow shear force coefficients in the corresponding directions respectively..."

"..."

Although it is the first step, just considering the milling force itself and the tool eccentricity caused by the milling force and installation error has made the entire system very complicated.

In addition, Chang Haonan almost spoke with just a pen.

Yang Weihua, who comes from an engineering background, is already having a hard time keeping up with the pace.

However, this is not because Chang Haonan used some sophisticated theories at the beginning.

It’s just that the derivation process is indeed a bit too complicated.

Write it down and read it a few more times, and you will eventually be able to follow the train of thought.

Fortunately, Wei Yongming, who had a good theoretical foundation, quickly caught up with the idea:

"All sensors needed to measure milling force are available on the MS series machining centers... If the MS45T three-axis CNC machining center is used as the basis, it only needs to modify the machine tool system to control the cutting force through digital adaptive cutting parameters, thereby compensating for the interference generated by the tool end during the cutting process, preventing excessive wear, and maintaining a high chip removal rate..."

“But when it comes to the specific machining process…if you want to directly determine the machining error through the tool position deviation, you must ensure that the impact of the clamping process on the workpiece is negligible…”

This time, before Chang Haonan could speak, Yang Weihua, who had been writing furiously with his head down, suddenly raised his head:

"Regarding this problem, I have a relatively mature solution..."

Chang Haonan's original plan was to separate the deformation caused by clamping and control it using a deformation prediction method based on stress field construction, considering that the clamping deformation basically occurs within a short period of time after the fixture is released.

But when he suddenly heard someone say this, he immediately became interested.

"Tell me more carefully?"

As a technician with a certain reputation in the industry, the process that almost confused him was definitely not a good experience for Yang Weihua.

And now, it was finally time for him to excel.

"To put it simply, a pressure sensor is embedded in the clamping device to monitor the change in force between the workpiece and the clamping device caused by the change in residual stress in real time. When the clamping force reaches a certain threshold, the clamping is released to release the deformation of the workpiece..."

"..."

"For example, for workpieces such as blades, three fixed clamping units can be set in the middle to completely position the workpiece to ensure the processing benchmark, while the surrounding floating clamping units and auxiliary support units can ensure deformation release and re-clamping... In this way, on the one hand, the deformation amount can be minimized as much as possible, and on the other hand, the degree of deformation can be predicted to a certain extent."

As he spoke, he tore off a page from his notebook and drew a schematic diagram of his idea.

“I came up with this clamping method when developing the MS75T five-axis linkage machine tool. However, no customer had such stringent requirements at the time, and the improvement of a single fixture would not help control machining deformation if it was not combined with other technologies. So I ended up turning it into a technical reserve…”

Although the introduction was very complete, it did not completely convince Wei Yongming:

“You said that floating clamping processing can fully release deformation while ensuring the processing benchmark, but the current “N-2-1” positioning method requires that the position and shape of the part remain unchanged during the entire processing process. There is obviously a conflict between the two.”

"In addition, in order to maintain the stability of the workpiece, the traditional positioning method will set the distance between the positioning points as far as possible. For floating clamping processing, too far distance between the positioning points will limit the release of deformation, while too close distance between the positioning points will cause the part to become unstable. How do you plan to operate it specifically?"

Since Yang Weihua dared to say it, he had obviously considered this issue before:

“Just divide the workpiece into a fixed clamping area and a floating clamping area.”

"The fixed clamping area uses three fixed clamping units to limit the six degrees of freedom of the workpiece to ensure the processing benchmark. The rest of the area is a floating clamping area, which is assisted in positioning by multiple floating clamping units. After the workpiece is released from deformation, the floating clamping units are adjusted to adapt to the deformed posture of the workpiece and assist in positioning the workpiece again in the deformed state..."

"As for the calculation of the fixed clamping area, the center of mass of the workpiece in the intermediate state can be calculated based on the processing dynamic feature information model to ensure that the fixed clamping area can envelop the center of mass during the release deformation process."

The so-called processing dynamic feature information model is a database type service provided by Torch-CB Ferrari to the user end based on the digital simulation technology first provided by Chang Haonan.

Complex intermediate state geometry can be transformed into a superposition of multiple simple layers.

Combined with the full linear motor drive and honeycomb structure patent at the hardware level, it is extremely attractive to users whose products have relatively standard specifications (with clear grooves, ribs, holes and contours) but have higher precision requirements.

This is mainly reflected in the fact that the processing efficiency is almost several times ahead of competitors.

Of course, as Yang Weihua said, it can indeed play a role in the field of floating clamping.

“What if the product being processed is atypical and has a poorly concentrated center of mass distribution?”

As the actual person in charge of the industrial control system, Wei Yongming naturally had to consider it in advance, especially when he knew what his leader wanted to process:

"For example, the center of mass of a turbine fan blade varies greatly during the machining process. It is probably impossible to manually determine the fixed clamping area, right?"

This question really hit Yang Weihua's weakest point.

The latter was unable to answer for a moment.

Therefore, the tense atmosphere immediately cooled down.

"This problem...is not difficult to solve."

It was not until they heard these words that Wei Yongming and Yang Weihua remembered that Chang Haonan seemed to have not spoken for some time since then.

I originally thought I was listening to the argument between the two of them.

But now it seems... that is not the case.

"Comrade Wei Hua just said that three fixed clamping units can limit the six degrees of freedom of the workpiece. Then the optimization of the fixed clamping area is equivalent to enveloping as many dynamic centers of mass as possible within the smallest possible area... rather than just calculating an intermediate state, especially for special-shaped parts with large changes in the center of mass."

Chang Haonan slowly said:

"Therefore, for complex parts that cannot be analyzed manually, we can consider using some optimization algorithms to implement them. For example, we can discretize the boundary of the part into multiple points according to the arc length, and then set the span value of the fixed clamping area in the main deformation direction of the workpiece as a penalty item..."

"..."

"Of course, the existing basic algorithms may not be very suitable for this type of specific problem, but in short, they can be further optimized based on genetic algorithms or differential evolution algorithms..."

Before Wei Yongming could react, Yang Weihua, who was supposed to be encouraged, was dumbfounded.

I was the one who came up with this idea first, so why does Mr. Chang seem to be more familiar with it than I am?