Chapter 1106 Floating Clamping Method

When doing research, the most taboo thing is half-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 little too complicated?

"It's really complicated."

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

"So, we have to do it bit by bit... First of all, for workpieces that are not particularly large in size, milling force is the most direct factor causing elastic deformation of thin walls, so as a first step, we can start with micro milling force modeling …”

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

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

Therefore, after achieving results, you can immediately put them into verification.

Wei Yongming also continued at this time:

"If we only study the shear effect, there are ready-made mathematical models that can establish the mathematical relationship between the resultant current and the shear force under the second-order damping system... Even in the case of multi-axis simultaneous machining, It is only necessary to add a coupling between multi-directional feed axes to eliminate the impact 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 the oil-based pen, and drew a cylinder on the whiteboard behind him——

After so many years of practice, his painting skills have improved dramatically compared to his early years.

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

“In micro-milling, the cutting force generated by the tool during the cutting process cannot simply be equated to shearing force. In fact, it should also include plowing force..."

Chang Haonan said while drawing a force analysis on the place 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 talks with a pen.

Yang Weihua, who has an engineering background, can no longer keep up with the rhythm.

However, this is not because Chang Haonan used any profound theory at the beginning.

It's just that the derivation process is indeed too complicated.

Write it down and go back and read it a few more times, and you can still follow the train of thought.

Fortunately, Wei Yongming, who has good theoretical foundation, quickly picked up the idea:

"All the sensors needed to measure milling forces are available on the MS series machining center... If it is based on the MS45T three-axis CNC machining center, then only the machine tool system needs to be modified to achieve digital adaptive cutting parameter control. Cutting force, thereby compensating for the interference produced 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 processing volume error through the tool position deviation, you must ensure that the impact of the clamping process on the workpiece is so small that it can be ignored..."

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

"I have a relatively mature solution to this problem..."

Chang Haonan's original plan was to isolate the deformation caused by clamping and control it using a deformation prediction method based on the stress field, considering that the clamping deformation basically occurs within a short period of time after the clamp 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 of almost being confused just now was definitely not a good experience for Yang Weihua.

And now, it was finally time to get to the part he was good at.

“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 due to changes in residual stress in real time. When the clamping force reaches a certain threshold, the clamping is released and the workpiece is released. Transformation..."

"..."

“For example, for workpieces such as blades, three fixed clamping units can be set up 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 amount of deformation is reduced as much as possible, and on the other hand, the degree of deformation can be predicted to a certain extent.”

While talking, he tore out a page from his notebook and drew a diagram of his idea.

"This clamping method came to my mind during the development of the MS75T five-axis machine tool. However, no customers had such stringent requirements at the time, and the improvement of a single fixture would not be helpful in controlling machining deformation if not combined with other technologies. , so in the end it was transferred to technical reserves..."

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. Between the two There is clearly a conflict."

“In addition, traditional positioning methods will set the distance between positioning points as far as possible in order to maintain the stability of the workpiece. For floating clamping processing, too far between the positioning points will limit the release of deformation, and the distance between the positioning points will be limited. Too close will cause the parts to become unstable. How are you going to do this?"

Since Yang Weihua dares to speak out, he has obviously already considered this issue:

“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. Multiple floating clamping units are used to assist positioning. The float is adjusted after the workpiece is released and deformed. The clamping unit adapts to the deformed posture of the workpiece and assists in positioning the workpiece again in the deformed state..."

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

The so-called machining dynamic feature information model is a database type service provided by Torch-C.B. Ferrari for users based on the digital simulation technology first provided by Chang Haonan.

Complex intermediate state geometries can be transformed into the superposition of multiple simple layers.

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

Mainly reflected in the fact that the processing efficiency is almost double that of competitors.

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

"What if the processing object is atypical and the center of mass distribution is not concentrated enough?"

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 boss wanted to process:

"Just like turbine fan blades, the center of mass changes greatly during the machining process. Determining the fixed clamping area manually...is probably impossible?"

This question really targeted Yang Weihua's weakest part.

The latter couldn't answer for a while.

Therefore, the atmosphere that was still very anxious just now cooled down immediately.

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

It wasn't until they heard this sentence that Wei Yongming and Yang Weihua remembered that Chang Haonan hadn't made a sound for a while since just now.

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

But now...it doesn't seem to be the case.

"Comrade Wei Hua also said just now 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 much as possible in the smallest possible area. The dynamic center of mass... rather than just calculating an intermediate state, especially for special-shaped parts with large changes in the center of mass.”

Chang Haonan slowly said:

“So, for complex parts that cannot be analyzed manually, you can consider using some optimization algorithms to achieve it, such as discretizing the boundary of the part into multiple points according to the arc length, and then setting the span of the fixed clamping area in the main deformation direction of the workpiece. Worth as a penalty..."

"..."

"Of course, the existing basic algorithms may not be very suitable for this kind of specific problems, but in short, we can continue to optimize based on genetic algorithms or differential evolution algorithms..."

Before Wei Yongming could react, Yang Weihua, who was originally encouraged, was dumbfounded——

Why do the ideas that I came up with first always seem more familiar to me than myself?