Telephone project

[plastics-studen]

planar locks, hm... tried to find out a little more regarding them in the net, but it seems I am left up to buy snap-fit handbook

anyway there is a bit of light casted on the subject, two steps forward were made, great thx fot that.

I left surfacing for the while trying to set size constraints for major elements in the assembly like:

*battery(AAA type, there are a lot of specifiacation out there, good to me

)

*parting line position

*overall height and width conditions(this is what I would like to address in more detail later)

*PCB display holder

So this time I would like to discuss the most - I belive - boring issue one can consider tolerancing.

So there is display placed on PCB, joined with tape. I made special holder to mount it fasten, but came then to tolerancing issue.

this is how it looks already mounted with PCB






So, display, in the real example, is not fixed with snaps with the holder. It seems it is "fixed" by "tight" fitting, thus "tight tolerancing", am I right?



I have done following assumptions:

to fix display I made per three small ribs on the both sides. Now - the best - the width of the display is 34 mm. I made the ribs 0.3mm, so in general there is 0.3 mm gap between holder walls and display.

Is it right way to mount components tight each other? Or should I introduce extra gap between those small ribs and display, let say 0.2 mm which in the end is the tol. for plastics?

The sam problem I encountered with snaps, which mount holder on PCB. The question is - should hooks touch PCB or should be min. offset i.e 0.2 mm in the hook and "leg" area?

 

[plastics-studen]

I stucked with tolerancing componets assembled each other.

I`ve got a feeling I could insert every where the ordianry clearance 0.3(where +/-0.2 mm seems to be basic tol regarding plastics), but it would not be accurate for all issues.

In example - I think 0.3 mm is enough for the connectors and its "gates - windows".

However there are some componets, they seem to be fit tight one vs another. What are the fititng method here?

I feel like I have been lost in deep forest. I serached net through and found couple of great books, unrortunately very expaensive...

<h1 ="parseasinTitle">Designing Plastic Parts for Assembly - ca. 90$</h1><h1 ="parseasinTitle">The Complete Part Design Handbook: For Injection Molding Of Thermoplastics - ca 240$</h1><h1 ="parseasinTitle">The First Snap-fit Handbook: Creating And Managing Attachments for Plastic Parts - ca 100$</h1><h1 ="parseasinTitle">Designing with Plastics - ca 140$</h1>Question is - Who can afford this(regardin all of them)?