Machining, 3D Printing, and Injection Molding: Which is right for your prototype?

In the medical device industry, before a product is realized, there are generally multiple prototypes made.  This can get very expensive.  With the technology of 3D printing becoming more and more available how do you know if that's what you want to use for your prototype?  Should you have it machined?  What about injection molding?  What’s the most cost effective?  What will get to you faster?  Today I will discuss the pros and cons of all 3 methods.

First of all let’s look at 3D printing.  3D printing is explained as such: “The creation of a 3D printed object is achieved using additive processes. In an additive process an object is created by laying down successive layers of material until the entire object is created. Each of these layers can be seen as a thinly sliced horizontal cross-section of the eventual object.”.  There are obvious pros to this.  Making only a couple of pieces is relatively cheap.  You don’t have tooling for machines, you don’t have to pay for the manpower to run a CNC machine, you don’t have to pay thousands for a mold to be made either.  You are also removing human error from the picture which takes away material loss, time wasted, etc.  Last of all, but most definitely not least, is the time factor.  You can get your components made within hours or days rather than weeks or even months.  That is definitely a lot of pros.  What about the cons of 3D printing though?  Once the prototype process is done and you go into production will you then have to have a program created or a mold created?  In some cases it would be like starting over.  You have to find out what can and can't be machined or molded.  What if you need your prototype to be made from a specific material so that you can test it?    What if it has to be stainless or even copper?  Then this won’t work for you.

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Next we have Injection Molding.  With this method of manufacturing a prototype there is a high initial cost for the mold to be made, but once that is done it is quite a bit more cost effective if you need to turn out a lot of pieces. You get a high production with a low overhead cost.  There isn’t much work to be done to churn out parts after the making of the mold.  There isn’t very much human error involved either.  The component will come out exactly the same, every time.  Also, there is a lot less waste with injection molding.  Whatever material isn’t used can be melted back down for later use.  So you have low production cost, lower material cost, quick production (once the mold is finished that is), and less handling by human hands.  There are disadvantages to this though.  The cost for a molding machine is very high and the machines are huge.  We’re talking anywhere from $10,000-$400,000 and a machine the size of your living room.  This can be extremely difficult for a start-up or even a smaller shop.  Also, if your prototype is very intricate or uses materials not handled by these machines then you’re out of luck.

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Finally, let’s discus CNC Machining as a viable option for your prototype.  As with the other 2 options, there are highs and lows to this method also.  CrossWind Machining uses CNC Swiss Screw Machines to create our components.  Probably the best thing about having machined parts is the ability to make extremely precise pieces.  I’m talking thousandths of an inch.  A human hair is approximately 3 thousandths of an inch (.003”).  At CrossWind we routinely make parts within +/- .001” tolerance.  You can’t get those kinds of strict tolerances with 3D printing or injection molding.  Another major pro for machining is that your prototype can be made out of whatever material your finished product must be made out of so that you can put it through what testing must be done for approval.  Machines are programmable, can hold multiple tools, and have multiple axis so quite a bit can be done. Now for the cons to machining.  First of all is the wait time.  Machine shops that are slow on work can possibly have your prototype to you in a couple of weeks.  If they are busy though, it could take a couple of months.  Also, there is the problem of human error.  Even when a program is created and perfect components have been machined problems can still arise.  Tools on the machine can break or wear out and have to be replaced.  There can be problems with the material that is being used.  Often the product have to be deburred or a 2^nd operation must be done to them manually or on a separate machine.  They then may need special cleaning or plating done to them.  All of these processes require them to pass through more hands.  The more hands on a part, the more chances there are for mistakes to be made.  The parts are put through a thorough inspection process, but sometimes there are mistakes that aren't caught right away.

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All in all there are justifications for all 3 methods.  They ALL have some very poignant pros and some frustrating cons.  In the end, it all comes down to what you need to have and what you can do without.

   Injection Molded Sample

    CNC Machined Sample

          3D Printed Sample