Why die casting parts is always oversized, let me tell you the reasons
Die casting parts have many defects such as cold flowers, shrinkage, bubbles, flash, etc. There is also another defect is oversize, because in production, oversize tolerance accounts for a significant portion of the scrap rate.
Now, for the size tolerance problem, let me tell you the reason which the oversize are caused? How to improve it?
1. Alloy chemical composition deviation, resulting in shrinkage deviation
Reason: Misuse of materials, mixed with excessive impurities
Improve: replace the correct material, adjust the shrinkage rate
2. Temperature (mold temperature, alloy temperature)
Reason: die casting parts in the mold cavity temperature is inconsistent, inconsistent wall thickness leads to inconsistent contraction
Improvement: Improve the structure of die casting parts, appropriately increase the size of cooling water of stiffener, position adjustment; release agent concentration, spraying time, position adjustment.
3. Process parameters unreasonable (such as flying material)
Reason: die casting machine chooses the tonnage or the choice of hammerhead is too small, mold or ejection time, the top pressure
Improve: replace the machine or replace the hammer, adjust the mold opening time, eject time, pressure
4. Surface material or lack of material
Reasons: mold manufacturing problems (multiple repair, welding or their own manufacturing poor), die-casting process unreasonable (mucosa, lack of material, etc.)
Improvement: Check the mold cavity look, adjust the process, according to the actual processing conditions
5. Open mold, core pulling, the stability of the top of the place (affected by the draft tilt), sub-surface dislocation
Reason: Poor mold stability (instability in place of the slider, mold wear, mold strength, precision, etc.), the top plate deformation, leading to the top deformation
Improve: Modify the mold, adjust the draft and so on, adjust the thimble parallelism, adjust the plunger position
6. Mold wear, cracking
Reason: die by metal liquid erosion serious
Improvement: repair the mold
7. Machining, polishing and other processing
Reasons: excessive machining allowance, or excessive deformation of the polishing force (when the die-casting temperature is easier to deformation)
Improvement: Control of machining allowance, automatic polishing
8. Plating and other surface treatment
Reason: the location of the hanging and die-casting parts in the corresponding position of the legs, hanging deformation of die-casting deformation, plating thickness is too large
Improvement: Change the hanger or change the hanger position on the product.