Hi
I have this small part for plastic injection moulding. I have split the part right across the middle, but I wonder if it's wrong.
If the parting line was across the middle, the slots behind near the arch would need to be drafted separately, right? If so, does that mean another split/parting line is needed at the top of the slots?
I've attached the model here to help clarify the situation (v. 2015).
Thanks
John,
It is not necessarily wrong, you just need to evaluate the pros and cons of each potential location.
Most mold builders would probably not split this part right down the middle, most likely follow the outer radii profile to some extent.
The questions you need to ask are;
How much miss-match can you live with in the magenta area, with this parting line location?
The orange area has a 1mm wide blade of standing steel which would be fragile and exposed. How much draft can you live with in this area? You will need some draft to have good slide by shut-off surfaces.
Observation;
You will have a buried slide to pull the 2.5 mm core which will cause issues with parting the Ø7.5 mm feature.
Hope this helps.
Alan
Hi Alan,
Thanks for your analysis. I shall try having the parting line around the outer radii and study the part.
The magenta area is for clipping onto a 1mm thick wood. Indeed, having the parting line round the radii would help.
Re. the orange area, what do you mean by 'exposed'? Would that give rise to problems? I think I can live with at most 1.5 degrees. Perhaps, it'd be a good idea to shorten the orange area?
How come the Ø7.5 mm will cause issues? Would the 2.5mm core not fit?
Thanks
John
John,
If the parting line is in the middle as your first question the core to form that feature would stand up from the parting line.
The Ø7.5 could lend itself to be pulled during mold opening, if the wrap around under cut is eliminated, but the Ø2.5 mm core would require pulling before parting line split. This can be accomplished using hydraulic core pulls prior to mold opening, or mechanically holding the parting line closed while the mechanism operates to pull the core.
Alan
Alan,
If the parting line is in the middle as your first question the core to form that feature would stand up from the parting line.
Indeed - will there be issues if the core stands up above the parting line?
Thanks
John
Not necessarily, the part will usually dictate how the mold can be built, often there is no choice what can be done.
Alan
Hi Alan,
You mentioned that the orange area has a 1mm wide blade of standing steel which would be fragile. Isn't the blade for the orange area supposed to be joint with the core that makes the arch behind it? If joined up, the blade should be not so fragile - right?
Thanks
John,
The shape and orientaton of the model defines the split.
This part needs draft and seal-off angle whereever it is applicable
These are my suggestions (after the split)
Hi John,
Thanks so much for the detailed walk through!
I'm trying to follow each of your advices. Re thin core blades, could the 'arch' be flushed with the thin blades instead? In the part, the opening under the arch is connected to the two slots. I'm probably missing something, so please correct me.
Thanks
Yes, That's also possible.
Once you have all the release drafts and seal-off angles, your split may change
I would suggest to create the split into core & cavity, then you will have a better visual understanding
John,
The shape and orientaton of the model defines the split.
This part needs draft and seal-off angle whereever it is applicable
These are my suggestions (after the split)