Insert molding

[Insertexpert]

Hello, I need to make a plastic block for a metal insert to be in the center. The block needs to be 0.85" deep and at least 2.5" in length and width. The inserts needs to be molded in and at least two edges sides need to be paralell, the other sides can be any shape as long as they are stay 1.25" from the center. I am worried about the thickness since the part needs to be a solid piece. What is the preferred molding method for this? I would assume injection molding since I will be using ABS, Nylon, PP. Is this part possible?

Thanks for any help.

 

[patprimmer]

The part sounds possible if I interpret it correctly which in itself is not assured.

The best way to encapsulate a metal part deeply inside thick plastic is to cast from monomer. This can only be done with a few resins, the ones that spring to mind are epoxy, thermoset polyester, acrylic and some nylons. The trick is holding the metal part in place while the resin cures.

You can also injection mould by two different methods I am aware of.

One is to hold the metal by the mould closing on a small area of it, over mould part of it in one cavity, then change to a second cavity where the part is held by the mould closing on the plastic and a second shot encapsulates the remaining bare metal.

Another is to use retracting pins so that the metal is held by the pins until the melt front reaches the pins, they are then withdrawn and the melt front proceeds past the point. One issue is that if the projected surface area of one side of the insert is larger than the other when the pin is withdrawn then the insert will move.

Regards
Pat
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[Richar24]

Hello Insertexpert.

I am not exacly sure of your design from the description.

Can the metal plastic have small tapered holes through the plastic?
If it can, you can add tapered pins that support and locate the block during the molding process.

You can use a retactable core, or cores. You place the metal block inside a retractable core, once the plastic has partially surrounded the block you can hydraulicly retract the slide and the part will be completely encapsulated. The metal blocks will need to be very clean, free of oil etc, and be preheated befor installing them in the mold.

If you can show me more of a design concept I can offer more help

Their are a lot of different ways to do this, All can get trickey, and usually take some fine tuning. After that they usually run pretty trouble free

 

[Insertexpert]

Thank you for your help.
My biggest concern is the shrinking of the plastic and warp around the insert because of the thickness.
I attached a screenshot of the current design of the mold.