Summary of design of oblique draw structure of mold

Time:2024-10-28 08:37:45 / Popularity: / Source:

design of oblique draw structure of mold 
In mold demoulding mechanism, processing of inclined shrinkage is more difficult than inclined lifter. How to overcome this difficulty is very meaningful.
Our goal: using existing processing methods, inclined mechanism is required to move smoothly and steadily, product has no flash and good wear resistance, and mold life is long (up to millions of times).
To this end, we must meet following requirements:
1. Mold structure design and process design are reasonable
2. Find correct measurement method to make compensation corrections when workpiece is not disassembled from machine to ensure that size of each part is within tolerance
3. There is a backup plan, when cumulative error causes assembly problems, it can be eliminated more conveniently, instead of grinding guide parts smaller and loosening them
Based on past experience, we have following difficulties:
Difficulty in process: Due to inconsideration, there may be defects in benchmark setting, fixtures, dimensional tolerance, process route, etc.
Difficulty in processing: Due to large workpiece and deep inclined hole, existing equipment and tools have certain difficulties in this regard. Processing may also require multiple departments to cooperate with each other, a few repeated back and forth will delay progress.
Difficulty in measurement: Due to large workpiece and deep hole, existing calibration table or CMM cannot be used, and it is difficult to check whether processing results meet dimensional tolerance requirements. Often, helpless move of grinding small and loose is adopted. Especially when construction period is urgent, measurement work is ignored.
Difficulty in assembly: Due to position error and angle error after inclined hole is processed, it will eventually lead to assembly failure or even failure to slide. If some workpieces do not leave a margin in advance, adjustment method is to deliberately loosen moving parts, which will bury hidden dangers.

Mold design

For circular bevels, design diameter should be as close as possible to ATP standard plug gauge series to facilitate use of existing plug gauges.
When designing mold, the measurement reference and clamping position required for processing deeper bevel holes should be considered and should not be omitted.
Sometimes, it is necessary to design some special fixtures (as shown in figure)
Design some inspection tools (such as plug gauges) or auxiliary inspection tools (such as balance blocks with magnetic attraction)
To reduce friction, angle between T-slot and bevel should be smaller while ensuring demoulding stroke.
design of oblique draw structure of mold 

Process design (I)

Reference number should be reasonable
For wire cutting that requires an angle, a reference number should be set
design of oblique draw structure of mold 

Process design (II)

In addition to position tolerance, angle tolerance and balance tolerance of inclined hole are more important and should be marked on drawing
It is best to indicate detection method, and a table can be prepared as needed to facilitate filling in detection data
Other instructions should be as detailed as possible
design of oblique draw structure of mold 

Precision requirements (I)

Matching tolerance of shrinkage and inner mold and mold plate is in accordance with APT standard, and sliding matching tolerance clearance is required to be 0.01~0.045
Surface roughness of all matching positions is RA0.4
Error requirement for the longest end due to angle deviation after shrinkage assembly is ±0.05
Hole tolerance is 0.01~+0.025 (Figure 1)
Outer dimension tolerance of shrinkage is required to be 0~-0.02 (also tolerance after two sides of resistant plate are assembled)
design of oblique draw structure of mold 

Precision requirements (II)

T position is a sliding fit, and fit clearance is 0.01~0.045
T position fit position on UV03 is shaft, and tolerance is 0~-0.02
Sliding fit position on UT01 is a hole, and tolerance is +0.01~+0.025
Surface roughness is RA0.2 (grinding machine or precision cutting)
Position tolerance requirement ±0.01
Due to angle deviation, the longest end has an error requirement of ±0.02
mold demoulding mechanism 

Margin Setting

After comprehensive analysis, it is determined that a 0.2 margin is reserved on the top surface of UV03, and adjustments will be made according to actual needs after the overall assembly.
mold demoulding mechanism 

Avoidance of inclined holes

Effective sliding surface of inclined hole generally does not use red surface shown in figure. In order to avoid its influence on assembly, avoidance treatment should be done.
If you choose to cut inclined hole by wire cutting, you can use CNC to rough it in advance to avoid air gaps.
mold demoulding mechanism 

Selection of processing methods (regardless of round or square holes)

CNC precision machining (or EDM for supplementary cooperation). Conditions: 1. Space inside inclined hole is large enough, and depth does not exceed 4 times tool diameter; 2. It is within processing range of machine tool.
Wire cutting. Conditions: Workpiece can be placed so that inclined hole is in a vertical state but does not exceed processing range of machine tool (if it cannot be vertical, it should not exceed 15 degrees).
Wire cutting is preferred because accuracy of wire cutting is more guaranteed.
mold demoulding mechanism 

Requirements for CNC programming

Horizontal CNC is preferred
Check whether workpiece contact number reference surface is reasonable and whether additional reference surfaces are needed
Reference surface should be precise and if there are omissions in process, process personnel should be informed proactively
Deep hole processing will inevitably have deviations due to tool reasons, so it is particularly important to choose tools reasonably
Always be prepared to add compensation tool path programs based on measurement results after processing, and programming department must give priority to it

Preparation before deep inclined hole processing

Check whether processing surface of previous process is in place as much as possible. If necessary, check whether workpiece is deformed and whether reference surfaces are vertical.
Check whether reference surfaces or clamping positions required for this process meet tolerance requirements. Influence of clamping position accuracy on workpiece placement angle cannot be ignored.
Check whether fixtures required for this process are in place, whether plug gauge is ready (plug gauges must be prepared for round hole processing), and whether dimensional tolerance is correct
Check accuracy of machine tool used if necessary.
Clamping and testing of horizontal CNC precision gong inclined holes (I)
For holes that are inclined in only one direction:
Align workpiece on machine tool table according to programming requirements, use a calibration table to check its verticality, and mark it after it meets requirements. Rotate machine tool platform according to angle of workpiece inclined hole (Figure 1) to make inclined hole direction consistent with tool drop direction.
Use a calibration table or a touch bar to take points on workpiece reference surface, and calculate to check whether current angle meets requirements. If there is a discrepancy, fine-tune it according to actual situation until it meets requirements.
mold demoulding mechanism 
Clamping and inspection of horizontal CNC precision gong inclined holes (Part 2)
For holes that are inclined in both directions:
Put workpiece on machine tool workbench according to programming requirements, use "auxiliary sine rule fixture" to pad workpiece and tilt it (Figure 1), first use calibration table to check verticality of workpiece, then take a point on workpiece reference surface, and check whether current angle meets requirements through calculation, then make fine adjustments until it meets requirements, and make sure it is in place.
Rotate machine tool platform according to other angle of workpiece inclined hole (Figure 2) to make direction of inclined hole consistent with direction of tool falling.
Use a calibration table or a touch bar to take a point on workpiece reference surface, and check whether current angle meets requirements through calculation. If there is a discrepancy, make fine adjustments according to actual situation until it meets requirements.
mold demoulding mechanism 

CNC machining of inclined holes (square holes) of workpieces

First, perform rough machining according to programming sheet. After machining, use calibration table to re-check whether verticality and bevel angle of workpiece installation have changed. If there is a change, adjust it to appropriate level.
First, perform fine machining (reserving 0.05~0.1 margin) on two sides of inclined hole (as shown in figure) according to programming sheet, and use collision counting software (programmer design program) to measure whether hole edge position meets requirements of drawing (see A value and L value in figure, and margin cannot be ignored). If there is a problem, find out cause and correct it.
mold demoulding mechanism 

CNC machining of inclined holes of workpieces (square holes)

After position tolerance meets requirements, a balance block with magnetic attraction is inserted into hole and sucked on inclined surface. By detecting balance block, angle deviation value of inclined hole of workpiece can be calculated. If angle error meets requirements, newly machined surface is continued to be fine-machined according to drawing. If angle error does not meet requirements, programmer will add a compensation tool path formula to correct it. This may need to be repeated many times until angle error is qualified.
Machining of remaining surfaces also uses a similar method to determine its position error, but balance between surfaces is best detected with a plug gauge.
When EDM is needed as a supplement for the position that cannot be machined by CNC, a special collision number drawing should be issued for process. After workpiece is angled on EDM machine, it should be based on plane that has been machined by CNC and connected smoothly.
mold demoulding mechanism 

CNC machining of oblique holes of workpieces (round holes)

Perform rough machining according to programming sheet. After machining, use calibration table to re-check whether verticality and bevel angle of workpiece have changed. If there is any change, adjust it to appropriate level.
According to programming sheet, finish mouth of oblique hole (reserve 0.05~0.1 margin) to a depth of about 50, use a plug gauge or a three-jaw micrometer to check hole size, and use collision software (programming design program) to measure whether center position of hole meets requirements of drawing (see L value in drawing).
Put plug gauge in hole without loosening, and use calibration table to check part of plug gauge outside hole to calculate whether center line angle of round hole meets requirements of drawing. If there is a problem, find out cause and correct it.
After above adjustments are accurate, continue to finish machining to depth. Use a plug gauge or a three-jaw micrometer to check hole size. If hole diameter is found to be too small, programming department needs to add a tool path compensation program to correct it until the entire plug gauge can pass smoothly, but not too loose.
Before disassembly after processing is completed, recheck aperture tolerance, position tolerance, and angle tolerance. Disassembly is allowed only after they are qualified.
mold demoulding mechanism 
Wire cutting of oblique holes in workpieces (method is same for square holes and round holes)
Preparation work before processing is same as CNC processing (see "Preparation before deep oblique hole processing")
Clamping and inspection: Worktable of wire cutting machine tool cannot rotate. Although machine head can rotate, angle with vertical line should not exceed 15 degrees, so it is more necessary to install fixture. After workpiece is tilted and placed according to angle requirements, it is necessary to use a calibration table to take points on workpiece reference surface. Through calculation, it can be checked whether current angle meets requirements. If there is a discrepancy, fine-tune it according to actual situation until it meets requirements, and wire angle can also be adjusted to match
Wire cutting processing: After workpiece is placed at a fixed angle, it can be wire cut. Number of cuts is done as usual. After cutting, it must be disassembled after passing inspection. Detection method mainly uses a calibration table, or a plug gauge or a magnetic balance block can be used.
mold demoulding mechanism 

Assembly sequence

When inclined hole is processed, install wear plate and use a plug gauge or a calibration table to detect assembly size tolerance and parallelism tolerance
When inclined hole is processed, install wear plate and use conventional gauges to detect assembly size tolerance and parallelism tolerance
Install inclined hole assembly into inclined hole, install T-head after matching, measure angle between sliding direction of T-head and vertical line in mold closing state, and then compare it with angle of T-slot guide slider
If angle comparison is not much different, you can try to install T-slot guide slider on T-head to measure whether its top surface is horizontal. This surface has a 0.2 margin for adjustment, and fine-tuning is performed according to actual needs during assembly. If angle comparison is large, you should check where problem is, find cause and take appropriate measures to solve it.
Finally..
Mold shrinkage design and processing flow
mold demoulding mechanism 

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