Injection mold or extrusion?

So I am working on a pencil-like product. It is essentially a pencil in size and shape (think long skinny hexagon). The material I am using is not a standard injection molding material, but the company that manufacturers is has molding parameters and claim it can be molded in and standard injection molding machine.

Now, my question is, since the shape is pretty basic, is it better to use injection molding or extrusion?

It’s really a question of part cost, tooling investment, quality issues, surface treatment, etc that will answer that for you.

Injection molding will have certain draft requirements which may require tweaks to your existing design if the design is truly a pure extrusion. But, that result may be just as good for what you need.

You’d need to really speak with your manufacturer and understand what they are looking to do and what material you are using - it’s too hard to give specific answers without knowing all the details (material, design, cost target, CMF, etc)

Another factor may be how you finish the ends.

If you extrude the shape you will have to cut the ends to get the correct length for the final product- and depending on your material properties this may result in burrs or cracks. With an injection mold your part should come out “finished”.

As Cyberdemon has suggested - arm yourself with as much information as possible and then talk to your manufacturer to directly understand their recommendations.

Does your vendor have the machines and tooling for both or could the recommendation be influenced by what they can provide???

mo-i

A deep-core for a part like this could be more trouble than it is worth if an extrusion is a legitimate option. Manufacturers of pens, mechanical pencils, and markers have volume on their side to get around the cost of clearing this obstacle.

If you go with extrusion, you can probably get a decent edge and a decent throughput if you have a lathe with a stock feeder to do all your trimming.

Lay out a decision matrix with all your factors:

  • cost
  • finishing needs
  • tooling investment
  • material moldability
  • material extrudability
  • part finish
  • quantity
  • speed of assembly