无锡亚博兰机械设备有限公司
Wuxi Ybolan Machinery & Equipment CO.,LTD
Home > Knowledge > Content
Aluminum alloy parts deformation and surface processing of black
Dec 27, 2017

Aluminum alloy material thin-walled parts, due to large aluminum alloy parts material coefficient of thermal expansion, thin wall easily in the process of machining deformation.

Especially in using free forging blank, machining allowance is large, the deformation problem is more outstanding.

 

The reason why the machining deformation

 

The deformation of aluminum alloy parts processing for many reasons, shape and materials, parts, production conditions, the performance of the cutting fluid, etc.

Basically has the following several aspects: the blank internal stress caused by deformation, cutting force, cutting heat caused by the deformation, deformation caused by clamping force.

 

Second, the technological measures to reduce the machining deformation

 

1, To reduce the internal stress of blank

 

USES the natural or artificial aging and vibration processing, can eliminate the internal stress of blank parts.

 

Processing in advance is effective method.

For the large parts, cause the large margin, yet after machining deformation is easier. If advance processing spare part of the blank, narrow margin of each part, not only can reduce the machining deformation after working procedure, and advance processing place after a period of time, can also be a part of the internal stress release.

 

2, improve tool cutting ability

 

Cutting tool materials, geometric parameters have important influence on cutting force, cutting heat, correct selection of the cutting tool, is very important to reduce the deformation of parts processing.

 

(1) choose reasonable tool geometric parameters.

Angle: before the Angle under the condition of keep the blade strength, anterior horn appropriately selected a few bigger, can grind the sharp edge on one hand, also can reduce the cutting deformation, smooth chip removal, and reduces the cutting force and cutting temperature, avoid by all means use negative rake Angle cutter

 

Angle: after angular size of cutters wear and the processing surface quality has a direct impact.

After cutting thickness is to choose the Angle of the important conditions.

Rough milling, the cutting load heavy,, because of the large feed calorific value is big, good requirements tool cooling conditions, therefore, the Angle should be chosen.

Finish-milling, sharp edge, reduce friction on the surface of the surface and processing after the knife, reduce the elastic deformation, therefore, the Angle should choose a few bigger.

 

Spiral Angle, in order to make the milling smooth, reduce milling force and spiral Angle should choose as far as possible.

 

Lord Angle: appropriate primary Angle can improve the cooling condition, bring down the average temperature in the processing zones.

 

(2) improving the structure of the cutting tool.

 

Reduce milling cutter teeth, increase capacity chip space.

Due to large plastic aluminum alloy materials, processing of cutting deformation is bigger, need larger chip volume space, so should the chip groove bottom radius should be larger, less milling cutter teeth as well.

Phi, for example, 20 mm below the cutter using two blade;

From 30 to 60 mm cutter adopts three blade is better, in order to avoid the deformation of thin-walled aluminum alloy parts caused by blocked chip.

 

Fine grinding teeth: cutter tooth cutting edge roughness values less than Ra = 0.4 um.

Before using the new knife, should use the fine grinding oil-stone behind, in front of the blade gently a few times, in order to eliminate grinding blade residual burrs and slightly zigzag lines.

In this way, not only can reduce the cutting heat and cutting deformation is small.

 

Strict control of tool wear standard: after the tool wear, workpiece surface roughness value increases, the cutting temperature rise, workpiece deformation increases.

Therefore, in addition to choose to wear good cutting tool material, tool wear standard should not be greater than 0.2 mm, otherwise prone to devolop tumor.

When cutting, do not over 100 , the temperature of the workpiece in order to prevent deformation.

 

(3) improve the workpiece clamp method.

 

For poor rigidity of thin-wall aluminium alloy workpiece, can adopt the following clip loading method, in order to reduce deformation:

 

For thin wall bushing parts, if the use of three jaw self centering chuck or collet chuck from radial clamping, once let go, after processing the workpiece must be out of shape.

At this point, should use rigid good axial end face compaction method.

Inner hole location in parts, homemade wear a threaded spindle, set into the inner hole of the parts, with a cover plate on its compression face using nuts back down again.

Machining cylindrical can avoid clamping deformation, and satisfactory machining accuracy is obtained.

 

Was carried out on the thin sheet workpiece processing, had better choose the vacuum suction cups, to obtain a uniform distribution of clamping force, and then processing by the smaller cutting parameter, is a good way to prevent deformation.

 

In addition, you can also use the tamping.

To increase the thin-walled workpiece process rigid, but inside the workpiece fill medium, in order to reduce the clamping and cutting process of workpiece deformation.

For example, to get to the workpiece urea melt containing 3% - 3% of potassium nitrate, after processing, the workpiece immersed in water or alcohol, can dissolve the filler poured out.

 

(4) the reasonable arrangement of process.

 

High speed cutting, and intermittent cutting because of the large machining allowance, so the milling process tend to vibrate, affect the machining accuracy and surface roughness.

So, CNC high speed machining process can be divided into general;

Roughing and semi-finishing - qing Angle processing - finishing processes, etc.

For the high precision requirement of parts, sometimes need to undertake secondary semi-finishing, then finish machining.

After rough machining, parts can be eliminated with natural cooling, rough machining of internal stress, reduce the deformation.

Leave after rough machining allowance should be greater than deformation, generally for 1-2 mm.

Finishing, parts finishing surface to maintain uniform machining allowance, is 0.2 0.5 mm, the cutting tool in machining process is in steady state, can greatly reduce the cutting deformation, good surface finish quality, ensure the accuracy of the product.

 

Three, operation skills

 

Aluminum alloy material in the process of machining deformation of parts, in addition to the above reasons, in the actual operation, the operation method is also very important.

 

For finishing allowance of parts, in order to make the better heat dissipation in the process of machining conditions, to avoid heat concentration, processing, appropriate USES symmetric processing.

If there is a 90 mm thick sheet metal needs processing to 60 mm, if the other side milling immediately after good side milling, a processing to the final size, the flatness of 5 mm;

If used repeatedly feed processing, each side two processing to the final size, can guarantee the flatness is 0.3 mm.

 

If there are multiple cavity in sheet parts, machining, unfavorable use a sequence of a mold cavity machining method, such easy to cause uneven parts stress and deformation.

Using hierarchical processing for many times, each layer as far as possible at the same time processing to all of the cavity, and then processing the next level, make the parts even stress, reduce the deformation.

 

By changing the cutting parameter to reduce the cutting force, cutting heat.

In the three elements of cutting parameter, turning back to the influence of the cutting force is very large.

If the machining allowance is too large, a feed cutting force is too big, not only can make the part deformation, but also affects the spindle rigidity, to reduce the tool durability.

If decrease turning operations, and can make the production efficiency.

However, in the numerical control processing is high speed milling, can overcome the difficulty.

In cutting back turning at the same time, as long as increased feed, improve the speed of the machine tool, cutting force can be reduced, at the same time guarantee the machining efficiency.

 

Feeding order also want to pay attention to.

Rough machining emphasis is to improve the machining efficiency, the pursuit of the removal rate of per unit time, usually can use conventional milling.

Namely, with the fastest speed, the shortest possible time to remove excess material on the surface of the blank, the basic formation of finishing the required geometry.

And the emphasis of finishing is high precision, high quality, appropriate USES down milling.

Because when climb milling cutter tooth cutting thickness from the biggest decline gradually to zero, work hardening to reduce greatly, reduce the deformation rate of the parts at the same time.

 

Thin walled workpiece when machining due to the clamping deformation, even finishing is also hard to avoid.

To make to minimize the deformation of workpiece, can before finishing soon to be a final size, put pressure tight a loose, free to return to original state of components, and then a slight pressure, will be subject to just can clamp the workpiece (completely by hand), so that we can get the ideal processing effect.

Anyhow, clamping force point on the bearing, best clamping force should be role in workpiece rigid good direction, on the premise of guarantee the workpiece is not loose, clamping force as small as possible.

 

When machining parts with cavity, the cavity machining try not to let the cutter like a drill down into the parts directly, cause cutter chip space is not enough, chip removal is not smooth, overheating, inflation and collapse caused parts knife, cutting knife, etc. Bad phenomenon.

To use first with cutter size or a bigger size of the drill hole under the knife, reoccupy milling cutter.

Or, you can use a CAM software production under the screw knife program.

 

 

 

Four, the workpiece surface

 

Aluminum oxide processing of aluminum alloy casting are generally made of metal mold casting, metal aluminium and aluminium alloy has good liquidity and plasticity, but in the use process is easy to turn black, reason is:

 

1, the process design is not reasonable.

Aluminum alloy die casting in clean or improper pressure detection post-processing, create conditions for aluminum alloy die casting mold black, accelerate the generation of mildew.

 

2, storage management does not reach the designated position.

Will be the height of the aluminum alloy die casting in different warehouse, the mold condition is different also.

 

3, the internal factors of aluminum alloy.

Many manufacturers in the die casting aluminum alloy die casting, machining process, don't do any cleaning, or simple water, can't do a thorough clean, die-casting aluminum surface residual release agent, cutting fluid, saponification liquid, such as corrosive materials and other stains, these stains accelerated the speed of the aluminum alloy die casting mould some black.

 

4, aluminum alloy, the external environment factors.

Aluminum is the active metal, in a certain temperature and humidity conditions extremely easy oxidation blackening or mold, this is the nature of the aluminum itself.

 

5, use cleaner may not when.

Selection of cleaning agent has strong corrosive, die-casting aluminum oxidation corrosion.

http://www.alucncmachining.com/