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Injection Molding MIM Common Degreasing Abnormalities and Solutions
In the production and manufacturing process of powder metallurgy parts, due to problems in the production process, cracks are easily produced.
powder metallurgy parts production and manufacturing
Common defects of metal powder injection molded parts are as follows：
1, under-injection: under-injection refers to the lack of pressure from the injection molding machine used or the poor fluidity of the injection material used and other factors caused by the material failed to fill the entire cavity of the mold so that the injected products appear incomplete. The reasons for under-injection of poor material fluidity, wall thickness of the product is too small, the mold temperature is too low and the injection time is too short, can be taken accordingly to improve the fluidity of the material or to replace the material, increase the wall thickness, enhance the mold temperature, increase the injection pressure and prolong the injection time and other measures to solve the problem.
2, fusion marks: material in the injection process in the cavity into a number of streams and then converge together, the convergence may appear line-like traces, that is, fusion marks, affecting the appearance of the quality of the product and even mechanical strength. The reasons for the formation of fusion marks for the injection pressure is too low, the injection speed is too slow, the material and the mold temperature is too low and the material flow too many strands, can be taken accordingly to increase the injection pressure, speed up the injection speed, improve the material and the mold temperature and reduce the shunt and other measures to solve the problem.
3, air pockets. In the injection process, the air in the mold cavity can not be discharged in time, the material is wrapped with or compressed to the mold wall to form air pockets, resulting in the surface of the product is not injected, affecting the quality of the appearance of the product and even mechanical strength. Formation of air pockets in the original Gang for the exhaust bad, inappropriate location of the gate, the injection speed is too fast and the thickness of the product is too large changes can be taken accordingly to add exhaust holes or deepen the exhaust holes, change the location of the gate, slow down the injection speed, extend the holding time and avoid sharp changes in the thickness of the product and other measures to solve.
4, deformation. Deformation refers to the molding products after cooling, bending or twisting, directly affecting the appearance of the product size accuracy, and even cause products scrapped. The causes of deformation for uneven cooling of products, products too hot and premature top, products too thin and unreasonable structure and products within the residual stress, can be taken accordingly mold waterway uniform cooling, extend the holding time and timely top out of the product, improve the product wall thickness and structural design and improve the molding conditions and other measures to solve.
To introduce to you the reasons for cracking of powder metallurgy parts, there are mainly the following aspects:
Common degreasing abnormalities and solutions in injection molding MIM
1, Linting. There are four reasons.
a. POM splitting too fast, usually just need to reduce the temperature, reduce the amount of acid and increase the degreasing time can be
b. Feeding paraffin content is too much, this is to replace the raw material
c. Mold, need to modify the mold structure
d. Injection temperature is too high, need to reduce the temperature
2. Cracking or fracture. The following 4 reasons should be checked to see if there is any problem
a. Workpiece placement, if there is a problem, please place it correctly.
b. The same POM splitting too fast, the solution is the same as above.
c. vibration, such as found in the vibration need to find the source of vibration and solve the problem
d. Density and weight of the workpiece does not meet the standard, need to change the injection process.
3, uneven degreasing in the furnace
a. Product placement, need to adjust the placement
b. Check the temperature difference between the furnace, need to test the temperature
c. There are dead corners in the furnace, need to increase the speed of circulating wind.
4、Discoloration of degreasing
a. The temperature is too high, need to reduce the temperature
b. Nitrogen flow rate is insufficient, need to increase the flow rate
c. Feed the high wax content, need to adjust the feed
5，Degreasing can not be completed
a. Process setting, need to change the process
b. Degreasing time is short, need to increase the degreasing time
c. Nitric acid concentration is low, to check and replace
6, degreasing stratification
a. degreasing temperature is too high, need to reduce the degreasing temperature
b. Degreasing rate is not enough, need to increase the amount of acid feed
The causes of cracking of powder metallurgy parts are analyzed.
1. Density uniformity of the side product ratio: in the side product ratio is more complex billet, due to the loading of powder is easy to be uniform, while the side product is relatively large, easy to billet surface shaped like cracks, especially due to the loading of powder is easy to be uniform, while the side product is relatively small and caused by the billet surface density difference;.
2. the shape of the inner hole of the negative mold along the demolding to the size change: processing inverted cone, the shape of the Department of abrasion, the mouth burr, etc. Jiezhu billet half easy to crack, the reason is that the end of the density of the higher elasticity increases so that the demolding taper increases and cause cracks;.
3. Poor powder compression: poor powder compression filling affects the shape of the billet poor powder particles combined with the low strength of the billet ejection rate, etc. prone to cracking.
4. press table flat, die head perpendicular parallelism super poor or billet pressure and die head setting deviation are so that the billet force uniform and die head force is greater when the billet lateral force is greater when the billet lateral force is greater when the billet lateral force is greater when the billet lateral force is greater because of proper billet between the two dies of the stamping stress difference caused by the pressure changes to make billet more bending stress is greater.
5. Powder lubricant content is less and uniformity: powder lubricant content is less or lubricant uniformity create local lubricant content is low increase compression blank demolding resistance demolding resistance three easy to make the powder body production slip three easy to make the compression blank produce elastic powder lubricant content or lubricant uniformity create local lubricant content surface weakening the compression blank between the body bonding force of the two kinds of powder body production easy to make the powder body production slip three kinds of powder body production easy to make the compression blank produce elasticity.
Harber Industrial's Press Molding Division (PM) specializes in the production of powder metallurgy products such as high-precision, low-noise oily bearings and high-performance mechanical structural parts. Injection Molding Division (MIM) specializes in the production of complex structure, high strength, high precision parts, experienced and green. The main products are copper-based, iron-based, iron-copper-based oily bearings, gears, cams, stainless steel parts and other types of mechanical parts, as well as a variety of shaped structural parts. Widely used in household appliances, automobiles, motorcycles, power tools, office equipment, textile machinery, food machinery, locks, furniture, toys and other industries.
