Unsolved ınjection problems

[yangozugur]

we have some problems as you see from addition.

ı give info about plastic injection machine, raw material, parameters which we used.

Plastic injection machine: Max Pressure:184Mpa , Raw diameter: 60mm( Haitan sa 2800 , B)

Raw metarial: LG ABS HI121H

Injection parameters:

Starting Position Pressure Velocity
155 80 90
100 80 90
80 80 90
60 80 90
45 80 90
30

Hold Parameters:

Pressure Velocity Tİme
80 60 12

ıf you need any info, please write and ı am going to answer for you.

[yangozugur]

ı want to add info

ı think this pressure and velocity values are too high.
ı said to machine operator reduce that values and he said ıf we reduce it will be incomplated filling.
than ı said ; after reduce this values you must increase receiving plastic material to complate filling succesfully.

however he didnt respect to me.

maybe ı was wrong.

your opinions so importand to effect machine oparator.

[rickbatey]

Water temperature ? Barrel temperatures ? Mold temperatures ? Screw recovery time and back pressure? Valve gate settings? Hot runner brand and style? Mold venting? Drier settings? Barrel residence time? Is resin UV or FR resistant?
Rick

[yangozugur]

thanks for your interest mr.Rick

ı dont understand which Some parameters you want so ı cant give any info.
ı am sorry.

ı add 2 images for temperatures(Barrel and nozzle temperatures)

water temperature:40C
Mold Temperature:50C

Screw recovery time: I checked my machine and ı guess it has not this parameter ı am sorry.
Back pressure: Back pressure parameter is in the receiving raw material parameters. Value is 30.
Hot runner: Internally Heated, Brand is Hatsys.
Mold venting:None
drier settings:80C, 2-3 hours
Barrel residence time: I cant see any parameters for that. I am sorry
Resin resistant is UV.
Nozzle temperature:250C
Injection time:3sn
Hold time:12sn
Cooling time:60sn
Mold open-close time:5sn


I hope these information help you to solve my problems.

[JayDub]

The defect looks to me like shear splay. If the location is random and not close to the gates, then it is coming from the material in the barrel. Try slowing down the screw recovery speed (lower screw RPM). If you need to add cooling time to reduce recovery time enough to get rid of the defect, then the machine does not have enough plasticating capacity for the part.

[Charles G]

I would be keen to hear how this was resolved - if at all?

If not - could it be insufficient drying? I would try a quality drier e.g. dehumidifying type. And ensure drying time is sufficient - a high throughput could result in too short drying time.

Could it be overheating - maybe in hot runner? I would look at reducing temp to see if this helps.

Could it be oxidation due to too much suck back after plasticising? Air sucked in will cause a burn mark (splay).

Could it be inhomogeneity? How is black colour achieved? Maybe colour masterbach not ideal?

Could the absence of venting play a role? i would look at short shots to understand fill pattern and ensure air vents are at appropriate locations.

[Pilot]

Hi,
acc me, the splays comes from material flow and some air (locked somewhere) which pop up on the surface.... please ty to do a new practical mould flow study, the injection speed profile can be not perfect now....

[rickbatey]

I suspect your barrel settings are too high for UV package in resin. Hence to odd locations. Need to reduce the barrel sertings, screw rpm and back pressure.
Rick