Chapter 1106 Floating Clamping Method
The most taboo thing when doing research 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 is indeed 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, Generally speaking, milling force is the most direct factor causing elastic deformation of thin walls, so as the first step, we can start with microscopic milling force modeling..."
The reason why we chose this research path is that It's all about going from easy to difficult.
Part of the reason is that the fan blades of the AE1500 just meet the requirement of "not 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 synthetic current under the second-order damping system. The mathematical relationship between the shear force and the The influence..."
"The basic idea is indeed correct, but...it's not that simple."
Chang Haonan turned around, picked up the oil-based pen, and put it on the whiteboard behind him. A cylinder is drawn on it——
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 the shear force. In fact, It should also include the plowing force..."
Chang Haonan said while drawing a force analysis on the place representing the tool path:
"So, the milling force model is in any The basic expression in direction should be..."
[dFj=[Kts·hj(θ)+Ktp]dz]
“Where Kts and Ktp represent the shear force and plowing 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 keep up with the idea.
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 pass the tool The position deviation directly determines the error of the processing volume, so it must be ensured 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, he had just kept his head down and writing rapidly. Yang Weihua suddenly raised his head:
“Regarding this problem, I have a relatively mature solution...”
Chang Haonan’s original plan was to take into account the basic deformation of the clamping. It occurs within a short period of time after the clamp is released, so the deformation caused by the clamping is isolated and controlled using a deformation prediction method based on the stress field.
But when he suddenly heard someone say this, he immediately became interested.
“Tell me more carefully?”
As a well-known technician in the industry, the process of almost being confused just now was definitely not a good experience for Yang Weihua.
Now, it’s finally time for the part he’s good at.
“Simply speaking, it is to embed a pressure sensor 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 force will be loosened. Open the clamp and release the workpiece deformation...""..."
“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-clamp... This way, on the one hand, the amount of deformation can be reduced as much as possible, and on the other hand, the degree of deformation can be predicted to a certain extent."
While speaking, he also tore off a page from his notebook. I drew a schematic diagram of my own idea.
“This clamping method came to my mind during the development of the MS75T five-axis machine tool. However, at that time, no customer put forward such stringent requirements, and the improvement of a single clamp could not be achieved if it was not combined with other technologies. It did not help control processing deformation, so in the end it was turned 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 obviously a conflict. ”
“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, the distance between the positioning points is too far. It will limit the release of deformation, and the distance between the positioning points will cause the part to become unstable. How are you going to do it?”
Since Yang Weihua dares to speak out, he has obviously already considered this problem:
“Just divide the workpiece into a fixed clamping area and a floating clamping area.”
“The fixed clamping area limits the 6 degrees of freedom of the workpiece through three fixed clamping units. To ensure the processing benchmark, the remaining areas are floating clamping areas. Multiple floating clamping units are used to assist positioning. After the workpiece is released and deformed, the floating clamping units are adjusted to adapt to the deformed posture of the workpiece and assist positioning again in the deformed state. Artifact..."
"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 dynamics The feature information model is a database type service provided by Torch-C.B. Ferrari to the user based on the digital simulation technology first provided by Chang Haonan.
Can transform complex intermediate state geometry into the superposition of multiple simple layers.
Combining the full linear motor driver and honeycomb structure patent at the hardware level, it is extremely useful for users who have relatively standard product specifications (with clear grooves, ribs, holes and contours) but have higher precision requirements. High attractiveness.
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 distribution of the center of mass is not concentrated enough?”
As the actual person in charge of the industrial control system, Wei Yongming, especially when he knew exactly what his leader wanted to process In this case, it is natural to consider it in advance:
“For example, the center of mass of a turbine fan blade changes greatly during the processing. It is probably impossible to manually determine the fixed clamping area... ?”
This question really targeted Yang Weihua’s weakest part.
The latter couldn't answer for a while.
As a result, the atmosphere that was still very anxious just now suddenly cooled down.
"This problem... is not difficult to solve."
Until they heard this sentence, Wei Yongming and Yang Weihua remembered that Chang Haonan had not spoken for a while since just now. Too loud.
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 6 degrees of freedom of the workpiece, so the optimization of the fixed clamping area is equivalent to optimizing the area as small as possible. Envelope as many dynamic centers of mass as possible... instead of just calculating an intermediate state, especially for special-shaped parts with large changes in the center of mass."
Chang Haonan said slowly:
“So, for complex parts that cannot be analyzed by manual means, 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 a fixed clamping area in the main deformation of the workpiece. The span value of the direction is used as a penalty term..."
"..."
"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 on the basis of genetic algorithms or differential evolution algorithms..."
Not waiting for Wei Yongming to make a decision Yang Weihua, who was originally encouraged by the reaction, was a little dumbfounded——
Why did Mr. Chang seem to be more familiar with the idea he proposed first than himself?
(End of this chapter)