Less Wasted Material

On average, even with the extra connection pieces (runner), injection molding produces less wasted materials than CNC machining. This is because CNC machining starts with a solid block of material and then the part is cut out from the block. On very small production runs this cost maybe negligible. On larger production runs, and with more expensive material, this waste can add up to significant cost.

Less Production Time

CNC machining doesn’t require any upfront tooling. Once a CAD file has been finalized, it can be sent to production. CNC machining shines when there is a small production run. Once you get to a certain amount of parts in a run (this is determined by part size and complexity), it becomes quicker to produce parts with injection molding.

The biggest time sink for plastic injection molding is the creation of the production mold. Once the production mold has been created and properly set up, it takes only a few seconds to produce a part. The larger quantity of parts in a production run, the larger the time savings over CNC machining.

Lower Cost On Higher Production Runs

For CNC machines, each part has to be manually placed in and removed from the machine, so the cost per part is fairly static over production runs.  For plastic injection molding, the production mold is by far the most expensive item. After the mold is created, the parts are fairly inexpensive and fast to produce. Since plastic injection molding is fast and doesn’t require human interaction once the production mold has been setup, the cost per piece decreases as quantity increases. Depending on the complexity of the part, it can be cheaper to use plastic injection molding for as few as a couple hundred parts.