CNC turret punch has been widely used in sheet metal processing industry because of its fast speed, high precision, strong universality of mold and suitable for small batch and multi variety product production.
It has very high requirements for die precision and quality, so the selection and maintenance of turret punch tooling is very important.
How to select turret punch tooling
Select the best die clearance
Die clearance refers to the difference in size between the edge of punch and die.
It is related to plate thickness, material and process.
Selecting appropriate die clearance can ensure good punching quality, reduce burr and collapse, ensure plate flatness, effectively prevent material carrying and prolong die life.
If the gap is too large, the burr of the produced workpiece is relatively large.
If the clearance is too small, the punching quality is poor, and the die wear is serious, the service life of the die will be greatly reduced.
Therefore, selecting reasonable die clearance is conducive to improving product quality, prolonging die service life and reducing processing cost.
Usually, we will select the corresponding die clearance according to the product drawing provided by the customer and compared with table 1
Table 1 Selection of die clearance
|Material Science||Minimum clearance||Best clearance||Maximum clearance|
Note: if the plate thickness t exceeds 3.5mm, the maximum clearance is recommended; The plate thickness t is less than 1.0mm, and the minimum clearance is recommended
Select reasonable die size and station
(1) The die station is usually selected according to the standard die punching size range shown in Table 2.
Table 2 selection of punching size and die station
|Station||Size range / mm|
(2) Special punches are required for punching holes in the range of φ0.8 ~ 1.6mm.
(3) The minimum dimension of the cutting edge of the die punch shall be greater than twice the thickness of the processed plate as far as possible.
(4) For the edge part of punch, the ratio of minimum race to length is generally not less than 1:10. For example, for rectangular punch, the edge length is 80mm, and the edge width is more than or equal to 8mm.
(5) The cutting edge of the die for processing thick plates shall not have sharp corners or collapse angles that are easy to wear, and the sharp corners shall be replaced by rounded corners greater than 1 / 4 of the plate thickness as far as possible.
(6) When the processing plate is made of high chromium materials (such as 1Cr13 stainless steel and hot rolled plate, imported high-speed tool steel is selected as the die material.
(7) When processing thick plates, when the die size is close to the limit size of the station, the station shall be replaced with a higher station to ensure sufficient return force. For example, when processing the materials shown in Table 3, it is recommended to select a station one level larger than the corresponding station of the processing aperture.
Table 3 Selection of materials to be processed and die station
|Material||Plate thickness / mm||Aperture / mm|
Arrange reasonable blanking process
The blanking process of CNC turret punch directly affects the production efficiency. Unreasonable blanking process may lead to the scrapping of processed workpieces and even damage to molds and equipment.
Therefore, in the process of arranging the blanking process at ordinary times, the following points should be paid attention to:
(1) When the workpiece needs to be processed many times, the holes with the same process property shall be processed in the same programming program as far as possible to avoid position offset and burr surface of the holes with the same process property caused by workpiece displacement change during processing.
(2) When programming tool arrangement, the general principle of “small before large, round before, common mold before special mold” should be followed.
The number of tools selected in the same program shall be as small as possible.
Select the cutter with large size as far as possible to ensure that the total length of trimming is not less than 1.5 times the length of the selected cutter.
This is conducive to improve production efficiency and prolong the service life of the die.
3) If the same workpiece has different types of forming processing, special attention should be paid to adjusting the tool path in programming, so that different forming tools can be cross processed when necessary;
When machining workpieces with special tools, pay attention to the distance between two adjacent holes to avoid mutual damage caused by forming.
The center distance between two adjacent holes shall be greater than or equal to the sum of the radius of the tool die sleeve and the radius of the formed hole machined first.
For example, the diameter of the upper die sleeve of type a hole is 26mm and the outer diameter of the lower die is 25.4mm; The diameter of the upper die sleeve of type B hole is 47.8mm, and the overall diameter of the lower die is 47.6mm.
Among them, if the first formed hole is formed upward, the size of the above die sleeve is the standard calculation; if it is formed downward, the overall size of the following die is the standard calculation, so as to avoid interference when processing two adjacent holes
(4) During hole processing, pay attention to placing the mesh processing program before blanking and after other general holes to avoid plate deformation caused by mesh processing and dislocation of other holes.
In addition, if there is a line pressing process and there are other punching processes around the line pressing, the line shall be processed first and then other hole positions, so as to avoid extrusion and deformation of other holes during line pressing.
When blanking the profile, the tool in the X direction shall be placed on the surface, and the machining path shall be clamped close to the clamp along the Y axis
(5 Pay attention not to leave waste materials on the table during tool arrangement, and use full blanking or micro connection to maintain connection.
(6) There is a rectangular hole or square hole structure in the workpiece. When arranging the cutter, pay attention to avoid single cutting edge.
When the SQ knife is limited by the process, the opposite edge of the rectangular hole can be punched with OB knife or re knife, and then the appropriate sq knife or re knife can be selected to punch the remaining part in the middle.
At this time, we must pay attention to punching the edge first and then the middle, so that the contact can be reduced and the wear of the tool can be reduced through reasonable tool selection.
(7) During blanking processing, the workpiece must pay attention to the reserved material. The reserved material shall be selected appropriately according to the material thickness and workpiece size. Generally, it is four connection points with a size of 0.20.3mm.
When there are special cutting tools or chamfers, pay attention to increase the reserved material, the general size is 03 ~ 0.4mm, and the connection point can also be added
(8) Note that the width of the selected tool should be greater than the material thickness.
During continuous punching, the center distance between adjacent tools should be greater than half of the tool length.
When the same straight edge needs to be arranged in sections during machining, pay attention to the selection of the same type of tool to avoid uneven guiding edge and step form due to the difference between the upper and lower die clearance of the tool.
(9) The tool with fixed tool position in the tool table shall not be modified as far as possible, and it shall be edited if necessary.
When the tool with fixed tool position needs to be installed at different angles, it shall be edited on the original tool position, and it is not necessary to reinstall the tool in the empty tool position.
(10) When processing salad holes, the forming knife shall be processed immediately after the pre punching to ensure concentricity.
Because the forming cutter will squeeze and deform the sheet metal during machining, pay attention to placing the forming cutter before other cutters in the machining area.
When machining a circle or arc with large size and there is no suitable tool for single punching, the square cutter with smaller specification can be selected for step punching. Pay attention to manually adjust the spacing to set it in an appropriate range
(11) When the whole sheet of material is produced in batch for typesetting (nesting processing), most of them are processed by CO trimming with zero material.
In case of small quantity production (i.e. one workpiece is less than the whole sheet metal), priority shall be given to full row in Y direction.
(12) When there are upward forming tools in special tools, that is, the lower die is a punch, other tools shall be installed around the tool position as far as possible.
Pay attention to the use of special tools, such as stiffener tools. When arranging the tools, select the line punching command to arrange the tools, select the manual mode to set the gap, and set the gap parameter to a certain value.
At the same time, because the lower die of the tool is a punch, it is much higher than that of other tools, resulting in the scratch of the sheet due to collision during the processing.
Therefore, the stiffener shall be arranged for final processing or separately listed as one program processing.
When selecting special tools, attention should be paid to the processing direction.
Among the existing special forming tools, only tooth extraction and center punch can be processed in the upper and lower directions, salad holes, bumps and crimping can be processed downward, and stiffeners, louvers and clamping slots can only be formed upward.
Maintenance of turret punch tooling
Timely grinding can effectively prolong the service life of the die
If the workpiece has excessive burrs or abnormal noise during blanking, the die may be passivated.
Check the punch and lower die.
When the edge forms an arc with a radius of about 0.1mm, it is necessary to grind.
Practice has proved that frequent micro grinding rather than grinding when it is necessary will not only maintain good workpiece quality and reduce blanking force, but also prolong the service life of the die by more than twice.
Eliminate and reduce sticking
Due to the pressure and heat during blanking, the fine particles of sheet metal will be bonded to the punch surface, resulting in poor punching quality.
The adhesive can be removed by grinding with a fine oilstone, and the grinding direction shall be consistent with the movement direction of the punch, so that the grinding will avoid the further generation of adhesive.
It is not suitable to polish with coarse gauze, so as to avoid the rougher surface of the punch and easier to produce sticking materials.
Reasonable die clearance, good blanking process and necessary sheet lubrication will reduce the generation of sticking materials.
To prevent overheating, lubrication is generally used, which will reduce friction.