Mechanical Design of Injection Moulded Products for 'Consumer Electronics' 3

[Sicilian Engineer]

Hi Engineers,

I am a recent-ish graduate working in a super varied role doing product design. A lot of these products require injection moulded enclosures I have read the bayer guide for df injection moulding but am looking for other tips and general good practice to consider In my work going forward. Generally these cases often need to be water proof, have tons of features, and be impossibly small. I'm going okay with gasket design but often struggle with selecting electrical connectors and other peripherals, as well as good cable routing design.

If anyone has experience in the above area any insights or general tips would be super helpful.

Below I have some more specific problems I was wondering if someone understood best practice for.

In my attached IMG green shows the planned route for a roughly known quantity of ribbon and other cables. I want to put heat-serts in the red and screw in cable clips (already have a bunch from something else). The blue circled 'scallops' I took out of the ribs to allow the cables to pass through as well as guide them somewhat. Essentially I'd like to know if what I am doing is sensible here or if I need to really rethink how and why I'm doing these things.

Anyway thanks anyone for your response or for even reading this mess, any help is appreciated. If anyone is interested in some quid pro quo I am most useful in the world of FFF and SLA printing alongside decent knowledge of machining processes.

Kind Regards,
Chris

 

[Mech1595]

Just from the perspective of an injection molder, a few of the general common ones I see regarding part design:

- The more draft, the better. Shorter features may require a higher draft angle to prevent sticking/dragging on eject. If you're working with appearance parts w/ a grained/textured surface, make sure to apply the draft (if applicable) recommended by the texture shop for that particular spec.
- Try to keep as much of the design in the core-half of the tool as possible, to help prevent potential issues with parts sticking to the cavity. Ribs, bosses, etc. Otherwise cavity-side ejection may be required. Not the end of the world, just adds to the cost/complexity of the tool & potential insert lines in visual areas. Or may require the addition of undercuts on the core.
- Radius sharp intersections to reduce stress risers and eliminate potential sticking points. This helps with appearance too, as the shear induced at the sharp transitions can show up in the part surface.
- Consistent wall thickness is ideal, just rarely feasible in a lot of design. Just be mindful and try to avoid extreme thickness changes, otherwise be sure to discuss with your molder/tool designer for potential quality issues.
- Apply realistic quality controls & requirements based on the part size, geometry, material, and application. Injection Molding is fairly precise & repeatable, but some customers seem to think these large complex plastic parts can maintain the same tolerances as a precision machined piece of metal....

 

[Sicilian Engineer]

Thanks Mech1595, I appreciate it.

 

[SWComposites]

Get an experienced mold designer and injection molding company involved early. Will save you a lot of headaches and expensive redesigns.

 

[Sicilian Engineer]

Cheers SWC, I do have a company for this but they are based in a different time zone so can be difficult to work together effectively.

 

[ShataCastings]

Its workable for your cable routing design, just need to pay attention to the cable bending radius in below area.

Regarding your details of 3D dwg, I can introduce you to my injection partner if you are interested. They have many customers who provide concept dwgs worse than this version, and their mold engineers provide techinical support to customers to make dwgs injectable.

Bella Liu
Markting Manager
Hebei Shata Casthings Co., Ltd.
Shi Jiazhuang, Hebei Province, China

http://www.shatacastings.com

 

[Sicilian Engineer]

Thanks Bella, I appreciate you taking the time to respond. We are still in early prototyping but depending on client wishes I may get back to you.

Thanks again

 

[MintJulep]

Threaded inserts for cable retention clips seems rather luxurious. Take apart most consumer electronics and you'll find self-tapping screws or push-on clips over a molded pin.

 

[ShataCastings]

Two options, one with thread inserts for small holes to ensure strength and easy to inject, another for larger holes with threads injected directly.
Cost of thread inserts will not be much higher than 2nd one, if quantity is not less than 1000 thread inserts, because thread insert can be produced from turning and milling composite machines, faster and cheaper.

Bella Liu
Markting Manager
Hebei Shata Casthings Co., Ltd.
Shi Jiazhuang, Hebei Province, China

http://www.shatacastings.com