Never seen that before.
Could be several things causing it: bad part design, bad mold design or wrong material selection.
Could also be wrong processing conditions.
Needs further investigation.
Paul Kuklych
http://www.improve-your-injection-molding.com
The cavity block is located to the mould plate using 2 dowel pins. Its very simple to make.
If you look at the 4 cavity mould video in the link below, all 4 cavities & cores are directly bolted to the plates with dowel pins present on the cavity side...
Mike suggestion is good-individual mold bases are cheap.
If you still want to use aluminium cavity inserts then my question is why are you concerned about the mold plates cracking due to thermal expansion?
This suggests to me the inserts will be in pockets of the mold plates.
If designed...
It looks like surface finish on the mould.
Take a look at the mould cavities, if it looks the same then that is your answer.
Paul Kuklych
http://www.improve-your-injection-molding.com
First step is to do do die setting for a period of time.
The second step is learn how to process.
In other words, get hands on experience learning how to setup and start moulds. You will soon notice the faults on these moulds so you will learn how not to design.
Paul Kuklych...
There will be a weld line next to the screw hole where the 2 flow fronts meet during filling. This is normal but you will need to improve the strength of it by increasing injection speed or adding more pack pressure or study the screw fit - maybe too much interference with the part.
Paul...
Variation is not always a bad thing.
For example, its normal to have variation in the injection pressure so that fill time can be maintained. Slight changes in material viscosity or temp can cause the machine to use a different injection pressure in order to maintain injection speed and...
Also, did you find any variation in the process from shot to shot? For example does the fill time remaining constant over a 24 hour period? If it has variation how much is the variation?
Paul Kuklych
http://www.improve-your-injection-molding.com
Along with the suggestions above, do a short shot test eg 25%,50% and 75% full part.
Test for cavity balance and flow hesitation thru the hinge. Flow hesitation can cause quality issues. Post pics.
By the way, gate positions can be changed in hot runners its just at matter of cost & mould...
Since you are having a number of hinge breakages that means the rest of them are good parts. Correct?
Sounds like you are having variation in the process.
I suggest keep records of the process parameters such as injection time, hold time, pressures, material and mould temp for every shift...
Demon3 has the right idea stamping from flat sheet. Another option is to machine the disks from a length of 2" diameter rod.
Paul Kuklych
http://www.improve-your-injection-molding.com
If a third of them are coming out warped then that means 2 thirds are flat right?
You have variation in the molding process. Check for material changes such as the addition of recycled material. Also check process parameters for yourself. A small change in fill time will change in molded stress...
Sharp corners are a disaster waiting to happen. Part & mould failure (cracking) can occur due to lack of rads.
I put rads everywhere possible. Just breaking a sharp corner with a R0.1mm makes a huge difference to mould ejection and also adds strength to the part.
Some parts will need bigger...
How did you increase the diameter on the nylon part ? Did you change the mould or machine the part?
Did you run both materials thru the one mould to see the difference shrinkage? That will give a relationship.
Paul Kuklych
http://www.improve-your-injection-molding.com
Have you considered purchasing the 4 tool chests and doing product failure testing on them? That way you can see which latch will suit your application.
The blue latch has a manufacturing advantage in that it is just one piece the other have 2 pieces.
Hope this helps.
Paul Kuklych...
In addition to the above, you might encounter quality issues such as white stress marks caused during ejection from the tool.
Paul Kuklych
http://www.improve-your-injection-molding.com
Yes it can be done with zero draft with open close mould. Zero draft will probably leave scratches in the slot though. Is it a clear part?
Paul Kuklych
http://www.improve-your-injection-molding.com
