Help : Overheat Mold - Toolmaker vs Molder

[kenneykoay]

Hi,

I am a product designer and currently have problem with the toolmaker & molder.

When we were running pre-production, the molder did not put on the cooling channel.
After ~ 600 pcs of shot, the mold start to have dragging marks on part.
And have to send the mold to repair and incur cost.

Now, the toolmaker accuse the molder did not fit the cooling channel, thus causing the mold to overheat.
The molder defend themselves that running parts at 600 pcs will not cause overheat.

So I am not sure if any face similar problem. Will be helpful if you can share some limelight.

Extra Information

Part size : Approx 193mm x 176 mm x 60 mm
Material : ABS
Part Weight : ~ 220 gram

Tooling : 3 plate mold
Material : ASSAB 718HH (P20 equiv)

[Brent G.]

Kenny,

I would love to share some limelight. YES, some molds can experience galling in as little as 600 shots without cooling. A lot depends on mold fit,construction, steels and hardnesses, and complexity such as side actions. I am assuming the damage is galling, but maybe you can be a bit more specific. If it is galling, what are the hardnesses of the offending steels? I have seen molds run for multiple shifts without a problem also.

It could be due to water or lack of it, but there could be other problems. Where are you located?aybe I can come and look at it?

Is this a Chinese mold?


brent

[Al Hall]

If that was a sample run I would get a different molder. The mold will heat up as the run continues and the parts will change dimensionally and the mold is subject to damage. If he's to lazy to hook up the water get rid of him.

[kenneykoay]

Hi Brent,

Thank you for your offer. I am located in Malaysia (Probably I am at the other end of the globe).
You are right, i googled in the web for meaning of 'galling' and found the exact description to my current problem. There are some 'pimples' or 'asperity' on the the mold, which I believed resulting from rubbing of 2 steels.

The mold construction was quite complicated: 2 slides from the side. And the galling happened the mating surface of these 2 sliders. The steel hardness is 340-370 HB. ( http://assab-hk.com/ASPAC_718_Hi_Hard_EN.pdf ). Based on the tool drawing, I believed that both sliders and core cavity side is made from same steel.

The mold was made locally in Malaysia. (Not China mold).

Al,

Indeed we have sent the mold for repairs and move to another molder.
At the moment, it all about who is going to bear the cost.

Thank you once again. I really appreciate you guys help.

Regards,
Kenney Koay

[rickbatey]

The steels should be of different hardness or you will continue to have galling issues. I have heard the rule of thumb is 10 points differance between the two mating parts or they will always transfer material. Rick.

[kenneykoay]

Thank you Gentlemen.

I have learn something new and useful.

I believed the best way now is to confront both parties to settle it.

[qualicas]

Kenny
I agreed with all the above. I would suspect that the molder didn't grease the slides before starting either.
Was it only one cooling circuit that wasn't hooked up or did he not hook any cooling up? I can't imagine running 600 shots without cooling. I would think after about 20 shots there will be problems. Sounds like you can blame the moldmaker a bit for using the same steel on sliding surfaces and mostly the molder for being incompetent.
I'm a molder and I think it works better for the customer if they come to me and I arrange the mold build. That way if something isn't right the customer only has me to blame. I get to work it out with the moldmaker. None of this molder blaming the moldmaker and vice versa.