Manufacturing advice needed

[MohammadN]

Hi,

I am in the process of designing a transparent (plastic) dome that has stars on it (the stars are transparent, the rest of the dome is opaque, single color) but am not sure how to go about it.

Couple of thoughts I had were:

1 - screen/pad print onto an ABS sheet (or another plastic) and then vacuum mould the sheet into the dome shape I need. Not sure if moulded post-printing will affect the quality of the stars as I want them to be quite sharp. I also want the dome to be off decent quality and not too thin - maybe 3-4mm

or

2 - CNC milling the stars onto the plastic sheet and the moulded it into shape? Again, not too sure if moulding it post-milling will affect the quality of the stars.

I would prefer the stars to be cut into the dome as the edges would be a lot shaper than printing as I want light to shine through them (like a projector night light).

Not sure what the best approach to take is but any advice would be greatly appreciated.

Many thanks in advance.

 

[pentel]

Print then form would need to be a clear material. Petg is probably the best choice. Print on the outside face. The print will distort so we usually distort the print so that it is correct after forming.

Form from opaque material and then cut out would need to be cut using a 5 axis router. Not something we do.

Cut first and then form, not a method that will work.

If lots needed injection moulding is the route to go, stars can be moulded in place, tooling is expensive but parts relatively inexpensive.

Hope that helps.

 

[MohammadN]

I don't mind outsourcing for the first few runs to ensure that the project is a success before investing in any machinery myself.

Just to clarify, are you saying cutting the stars in (using CNC milling) and then vacuum forming will not work?

Regarding injection moulding, I assume a CAD drawing will need to be provided and I can get someone to manufacture the dome with the stars or whatever cut into it?

 

[pentel]

Vacuum forming needs to have a sheet with an airtight seal both around the perimeter and over the whole of the sheet. Cutting holes through the sheets prevents the formation of the vacuum hence it will not work.

For injection moulding you will need a 3D file in a suitable format. ( solidworks, iges or step files are common format). The design will need to take into account things like draft, material thickness and flow path.

 

[Deleted member 315997]

Hi, you'd be better off having an injection mould of the dome with the stars cut out already in the mould, this would ensure the stars are crisp. You could then have a second mould to produce the clear stars and have them fixed into the dome, mechanically or glued as a secondary operation. Do the stars need to be a clear plastic or is it just the shape you need for the light to shine through?

3-4mm is quite thick, what sort of diameter would it be?

Regards Laurence