match: cnc machining vs stereolithographie

Today, we decided to compare the characteristics of two prototyping technologies: stereolithography (an additive technology similar to 3D printing) and CNC machining, a more traditional technology. Here is our test.

Mechanical properties: CNC machining

To evaluate the mechanical properties of a part, it must be made of the same material used during the industrialization phase. The mechanical properties can combine resistance to heat, a certain traction, the density and flexibility of the part, etc. Based on this principle, CNC machining offers a clear advantage by allowing the use of the “right material” (used in series production), while in stereolithography, the prototype is made of epoxy resin. CNC 1 machining – 0 Stereolithography.

Manufacturability indicator: Draw

Thanks to the stereolithography, it is possible to produce complex parts with undercuts. This can also be produced with CNC machining under certain conditions (5-axis machine, part manufactured in several pieces, etc.). Some of these parts will therefore not be “injectable” because their architecture does not allow demolding. CNC 2 machining – 1 Stereolithography

Production time: Stereolithography

The absence of human intervention allows stereolithography to offer fast production times (a few hours), unlike CNC machining which requires more work. CNC 2 machining – 2 Stereolithography

Aging of the part: CNC machining

In stereolithography, the aging of the parts is mediocre: the yellowed part must not be exposed to light. In CNC machining, the part is made of the right material and is durable over time (as in the case of injection molding). CNC 3 machining – 2 Stereolithography

Precision: Stereolithography

The precision of the parts made by stereolithography is generally +/- 0.1 mm, while it is +/- 0.2 mm in CNC machining. CNC 3 machining – 3 Stereolithography

Choice of material: CNC machining

CNC machining allows the use of the right material, the range of materials available will be wide and will match that injected during the industrialization phase, unlike stereolithography which only offers epoxy resin. CNC 4 machining – 3 Stereolithography

Finish: CNC machining

The appearance of the part is better with CNC machining than stereolithography on both the visual and touch levels. Machining offers many finishes: shiny, soft touch, mirror polishing etc. CNC machining 5 – 3 Stereolithography

Cost: Draw

The cost of production will be calculated based on three criteria: the need for labor, the type of material used and the quantity of material required. Labor: stereolithography does not require human intervention during the production phase, unlike CNC machining. Cost of materials: epoxy resin is cheaper than the right material used in CNC. Quantity of material required: With CNC, machining is done in a block, which leads to waste, in contrast to stereolithography which is a so-called additive technology. However, being based in China, we are able to offer very competitive prices with CNC machining. In fact, creating a large ABS part with Prototech turns out to be 30 to 40% cheaper than doing stereolithography in France. It is also the case for parts requiring a good finish. CNC 6 machining – 4 Stereolithography

Result: 6 – 4 for CNC machining

If you want a prototype close to the parts injected in series (functional and visual validation), we recommend CNC machining. If you only want a prototype to confirm the dimensions of your parts, stereolithography may suffice.