Variation in Temperature flow front

[mahanteshknot3305]

Hello All,

Hope all are doing well,

I have a question on flow front temperature, the part image i have attached.
Q: Why is the difference in flow front temperature at end of fill, what it means exactly.
Is parts surface quality would be good? Which result drives the surface quality ?
Thnaks in advance,

MRK

Edited by: mahanteshknot3305 on Mar 9, 2010 10:41 AM Edited by: mahanteshknot3305 on Mar 9, 2010 10:43 AM

[jean.uemura]

It would be a difference of mesh, edge lenght or thickness.
The not symmetry would be another reason.

I believe that it is not a concern, because the temperature difference is just 2-3 degree C (1,1%).

The weldline will be visible and brittle if the flow front temp is higher.

[madhukeshwart]

when materila is flowing through narrow side , there is rise in temeprature is observed
(may be due to shear heating )

and when materila is flowing through wider side , there is drop in temeprature is observed


i.e If these temperature difference is more than 5 deg C, then both the flow fronts may not fuse preperly &
may result in weaker weldline (in strength )

[mahanteshknot3305]

Many thanks Jean and madhukeshwar for your time on this and reply.


Jean :The mesh is done in hypermesh with high quality.
as you said the temperature should not be high at the weld-line, Should i try with 3 or 4 gates to get it down to recommended temp(260°C).
because the defference in temp at weld line is <1°C. do you think weld will be visible?

Madhukeshwar: Even i am thinking the same, when the material travel from narrow region it heats up due to shear, because this is glass filled material, but my concern is will the weld line be of good quality? (because this is the austhetic part).

Best Regards,
MRK

[GoncaloRodrigues]

Hello,

I agree with Jean & Madhukeshwar but could be other reasons for the temperature drops.

I think that you should try to translate one of the gates, if possible with tool construction, to have a ballanced fill. One of the part extremities is filled before the other one (side where you have temperature dropsis the last one to be filled). If you have a ballanced fill, it is possible that the temperature at flow front does not drop too much in the narrow region. Besides that, if you do not have ballanced fill, the pressure distribution inside the cavity will not be uniform and it can provoke flash.

I hope this can help you.

Best regards,

Engº.Gonçalo Rodrigues
MOLIPOREX,S.A.
Portugal

[mahanteshknot3305]

Hello Gonçalo Rodrigues

I have tried with shifting the gates and adding the gates and there is no sucess. but there is much improvement in 4 gates instead of 2 or 3 gates and all the gate sequences are balance and checked. The pressure required to fill this part is nearly 100MPa for single gate, 75MPa for 2 gates, 65Mpa for 3 gates and 52Mpa for 4 gates ( the hot runner is also modelled to know the exact pressure) and weld lines are the more concern for this part, i am trying to eliminate wel-lines completely. If we push the end flow at corners the flow is more uniform than at the central areas.

So any one has come across the similar part/ situation( part is uniform with 2.00mm thickness). How many gates do you prefer for this kind of part?

Best Regards,
MRK

[jean.uemura]

Which matrix polymer do you use? PA66, PP?
How many glass fiber on composite? 20%, 30%?

The difference in temp at weldline <1ºC probably will not be visible. It depend of the polymer, for semi-crystaline 5-10ºC is limit and for amorphos less than 10-15ºC.

[mahanteshknot3305]

Jean,

I am simulating with two materials, ABS+PA6 (crystaline) 8% and 20%.

[GoncaloRodrigues]

Hello,

I don't know how many gates you need to fill the part well.
You should confirm the flow lenght for the material you are using and then with the part dimensions you will check if 2 gates are enough to fill the part. The flow lenght main depends of the material and the part thickness (in this case 2mm).

However, like someone already answer is probable that you will not have problems with that weld line due to the low temperature differential (<1ºC).

You also should confirm with your client where is possible to have weld line because the part will have a weld line for sure.
The thing is that weld line could be visible or not.
So, where are the areas with minor risk of break?

EngºGonçalo Rodrigues
MOLIPOREX,S.A.
Portugal

[mahanteshknot3305]

Hello,

Many thanks for your suggetions, thanks all for your time and replies, this discussion was really usefull for me to get confidence on deciding the right thing fo this part. FYI i managed to get all the results optimized and relaxed molding window is developed. this part is recommended for 3gates.The weld-lines can be almost eliminated or converted in to meld-lines by uniform flow patterns at 3-corners with acceptable temperatures and pressures.


Thnaks once again all,

Best Regards,
MRK

[jean.uemura]

mahanteshknot3305,

Based on my background, ABS will have less visible weldline than PA6, and less fiber is better to visual aspect. It mean that your product must be painted, because the problem is the fiber orientation at weldline.

Regards,
Jean

[nohbyeongsu]

Hi.
It will be appear the weld line in this area.
I had been experance. If front temperature was not different, It can be appeared. because of feature.
Anyway.
Drop of front temperature may be due to the feature at the area of flow path.
feature of two flow path is not symmetry.
So, flow front temperature through the narrow feature will be shear heating.
But, flow of other path is more wide than narrow path. I think It shell be drop in this area.
You have to check the fill pattern or velocity at the near of this area.