McMaster Sells Ejector Pins

A project log for Micro Injection Molding Machine

Building a tabletop injection molding machine.

jupdykejupdyke 02/12/2016 at 21:004 Comments

I was looking on mcmaster for a dowel pin for another project and noticed that they sell ejector pins too.

Not terribly surprising, but one more piece of the puzzle. They are about $5 for a 1/4 inch diameter hardened pin. I figured I could fine them somewhere and worst case I could machine my own. But these would be precision ground and hardened which will be great.


Alex Rich wrote 02/13/2016 at 13:53 point

I have used these before on a couple aluminum molds I have made.  They are really nice quality but the hardened steel is a bear to face on a lathe if you need to cut them to length.  I broke a few carbide tips in the process.  I think the professional way is to use a surface grinder or dedicated pin grinder.  In your case you have cosmetic faces on both sides of your part, you might consider an ejector boss made from aluminum so you can match the finish to the rest of your cavity.

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jupdyke wrote 02/13/2016 at 20:49 point

I plan on putting the ejector pins such that they push on the pin holders and not the actual parts. This way the force will spread out over the two pins inside the parts and there will not be any ejector pin marks on the parts.

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Alex Rich wrote 02/13/2016 at 22:46 point

nice, and no need for precise length

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Jan wrote 02/13/2016 at 08:30 point

Yeah, I have to do make or buy decisions every day (working in mechanical engineering). Most of the time you can´t compete with products and prices of companies who specialized in their field...

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