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A method to improve drilling accuracy

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Update time : 2019-09-19 15:07:24
First, the basic concept of drilling

Generally, drilling is a method of drilling holes on the surface of a product with a drill bit.Generally speaking, when drilling products on the drilling machine, the drill bit should complete two movements simultaneously:

(1) the main movement, namely the bit around the axis of rotation (cutting movement);

(2) secondary movement, namely the bit along the axis direction toward the workpiece linear movement (feed movement).

When drilling, because there are defects in the structure of the drill bit, the mark will be left on the place where the product has been processed, affecting the quality of the workpiece processing, and the processing accuracy is generally below IT10 level, the surface roughness is about Ra12.5 microns, belonging to the rough processing category.

Operation flow of drilling

1, marking: before drilling, the first understanding of the requirements of the drawing, according to the basic standard requirements of drilling, using tools to draw out the hole location of the center line, the center line must be clear and accurate, and the thinner the better, after drawing the line to use vernier caliper or steel plate ruler for measurement.

2. Check box or check circle: after the line is drawn and qualified, the check box or check circle with the center line of the hole as the symmetrical center should be marked as the check line during the test drilling, so as to check and correct the drilling direction during the drilling.

3, proofing punch: draw the corresponding check box or check the circle should be careful proofing punch.First hit a small point, in the different directions of the cross center line for many times, to see whether the punch is really played in the cross center line of the intersection, and then the sample punch force is hit, hit a circle, hit big, so as to accurately centering the knife.

4, clamping: wipe clean machine table, fixture surface, workpiece datum surface, and then the workpiece clamping, according to the requirements of clamping flat, solid, and convenient for inquiry and measurement at any time.Need to pay attention to the workpiece clamping method, in case of workpiece deformation due to clamping.

5, test drilling: before formal drilling must first test drilling: drill bit transverse edge on the hole center sample punching hole drilled a shallow hole, and then visually detect whether the shallow hole azimuth is correct, also need to constantly correct deviation, so that the shallow hole and the inspection circle coaxial.If the violation is minor, the workpiece can be pushed to the opposite direction of the violation with force at the beginning of the drill until it is checked step by step.

6. Drilling: machine drilling is generally based on manual feeding operation. When the bearing accuracy of test drilling is required, drilling can be carried out.Manual feeding, feeding force should not make the drill bit bending phenomenon, to avoid the hole axis skew.

Third, the drilling precision is higher method

1, grinding the drill is the beginning of everything

The corresponding drill bit should be choosed for grinding before drilling.In addition to maintaining the correct top Angle, back Angle and bevel Angle of the cutting edge are accurate, the length of the two main cutting edges are equal and symmetrical with the center line of the drill bit, and the two main cutting edges are smooth. In order to facilitate centering and reduce the roughness of the hole wall, the cutting edge and the main cutting edge should also be properly polished (it is better to rough grind on the grinder first, and then finish polishing on the oilstone).

2, accurate line is the basis

With the height of the ruler of accurate marking, the first should maintain the standard of accuracy, marking the needle Angle and the workpiece between the surface of the scribing 40 ~ 60 degrees of included Angle (along the scribing direction), so that the line is clear and uniform.To pay attention to the selection of the marking datum, datum to be processed accurately, to ensure their own flatness and perpendicular to the adjacent surface.After the hole position cross line is drawn out, in order to ensure the drilling is easy to find the right, using the center of the cross line rushed out of the center point (the requirements of the punching point to be small, azimuth must be accurate).

3, the correct clamping is the key

Under normal circumstances, about the diameter of less than 6mm hole, if the accuracy is not high, can be used to clamp the workpiece drilling;For the hole of 6 ~ 10mm, if the workpiece rule is flat, the clamp can be used, but the surface of the workpiece should be perpendicular to the spindle of the drilling machine.When drilling holes with larger diameter, the flat jaw pliers must be fixed with bolt platen.When the diameter of the drilling hole is more than 10mm for larger workpiece, the method of pressing plate clamping is used for drilling.

4.Accurate search is the key

Workpiece clamping end, do not rush to drop the drill, should be the first alignment.Alignment has static alignment and dynamic alignment.The so-called static alignment means that the alignment is carried out before the drilling machine is launched to align the intersection point of the spindle centerline and the workpiece cross line. This method is convenient for beginners and easy to grasp. However, due to not considering uncertain factors such as the swing of the drill spindle, drilling accuracy is relatively low.Dynamic alignment is carried out after the drilling machine is started. In alignment alignment, some uncertain factors are taken into account and the accuracy is relatively high.

5. Careful testing is indispensable

The detection can accurately and timely find the accuracy of the hole, so as to take necessary measures to compensate.For the hole with higher drilling accuracy, we generally adopt the process of drilling, reaming and reaming.After the first step to drill holes with a caliper testing center of the bottom hole to the datum of fault offset, checked by actual measured conversion direction of the center of the bottom hole and ambition, if the fault is greater than 0.10 mm, can be in reaming, appropriate increase bit apex Angle, weaken the self-centering effect, to borrow the positive direction appropriate push artifacts, gradually increasing the diameter of the drill point method to compensate.If the amount of fault is greater than 0.10mm, a mixed round file can be used to finish the two side walls of the bottom hole. The finishing part should be connected with the circular arc smooth transition of the bottom hole.
https://www.infignos.com/templates/updatelistingnow.cfm?email=ryanlee901213@gmail.comShenzhen Kangda Precision Manufacturing Co.,Ltd.,Machining Manufacturer,Shenzhen,FL