rigid polyurethane moulding

[Alberto.E]

Hello everyone,

I have always designed injection molds in abs, pc, pp etc. but now I have to design a particular rigid polyurethane.
It is a material that I have never faced and I would like to ask those who are more experienced what are the characteristics that must have the particular, for example minimum and maximum thicknesses, minimum yields and poppets or other.
in practice what are the maximum shortcomings to be followed for the molding of this material.

Thank you.

 

[SHIREN]

Hello everyone,

I have always designed injection molds in abs, pc, pp etc. but now I have to design a particular rigid polyurethane.
It is a material that I have never faced and I would like to ask those who are more experienced what are the characteristics that must have the particular, for example minimum and maximum thicknesses, minimum yields and poppets or other.
in practice what are the maximum shortcomings to be followed for the molding of this material.

Thank you.

Hi.
you already have a specific experience in injection molding
So you won't have any probes.
a mould for polyurethane and easy practical economic
all in aluminum more or less a 6060 is fine but also a cheaper paralluman
in wear areas you can put metal inserts
opening and closing with commercial hinges
being an expansion material the injection can take place with a fully apete mold
or closed with n system of a cone and relative cap with fast closing
the big prob and the formation of bava which then needs to be eliminated by hand
you have to study a bava size or perimeter closure of the geometry of the piece that does not allow the formation of bava
if the forms (half-forming closures of the mold) are complex you can try to reset the half-mills with electroerosion operation
electroerosion that you can use on alumina even in all those areas where you do not get in cnc
Thank you very much

 

[Alberto.E]

hi shiren, thank you for the explanation.
Is there any problems with polyurethane? what are the minimum thicknesses?
in the case of a particular thickness 6 mm, which maximum thickness should be kept for ribs or poppets to avoid
deformations?

Thank you.

 

[SHIREN]

hi shiren, thank you for the explanation.
Is there any problems with polyurethane? what are the minimum thicknesses?
in the case of a particular thickness 6 mm, which maximum thickness should be kept for ribs or poppets to avoid
deformations?

Thank you.

Hello tree
I tell you my experiences
and it can also be that other prog. succeed in minor thicknesses
But I have always struggled to go under less than 3 mm thicknesses
the whole can also cover the type of artefacts
for meatballs and ribs no prob
enough that gives the possibility to the material to expand
where you can keep wide

other speech are the suckers or air bubbles that inevitably create at the top of the mold
you have to decide which side of the piece once it is hidden
and therefore will be the top part of the mold
This does not mean that you cannot eliminate air bubbles that form
once the mold is built, it makes a significant test of 10-20 pieces and evaluates the bubbled areas
in the mould a series of holes from 0.7mm running through the mould
It is obvious that a 0.7 tip has a length of 30-40 mm
and suitable to download the areas where the thickness of the mould does not allow to drill
or if there are the holes 8-10 mm passing and insert the aluminium pins of the same diameter faceted on two sides
0.2-0.3 mm per side
It is useless to tell you that if you make a mold you have significant production numbers
and for experience only one mold extends your production time
so you need more molds maybe on a multi-position carousel
this to tell you that the first mold goes under the name of pilot mold
in the sense that after the first test you make all the changes that need
do the necessary tricks and try again
then proceed to the final execution of other molds
I can add that it is better than running a manual lapping of all surfaces
and wanting a superficial nickel
it is easy to find on the market special polyurethane foam that have undergone a retouching with a two-component polyester filler to repair the formation of bubbles
the components in poly.... can be stunned and painted
these are my experiences
I hope you've been helped
Thank you very much

 

[volaff]

Hello, everyone.
I write here in this old discussion to avoid opening a new post.

any of you have experience of polyurethane reinforced in terms of "last generation" materials?

I want to do an investigation and I don't know where to start.

thank you anyway.