CMF stands for Colour, Material, Finish, which describes how a product looks, feels and behaves based on those characteristics. In product development, CMF is a widely used term, with designers and manufacturers going to great lengths to achieve optimal results - 'the perfect CMF', as it is known.
The Colour, Material, and Finish of a product determines its specifications and those specifications must be clearly communicated with the manufacturer for the perfect CMF to be achieved. In 3D printing, the concept of CMF can be used to fabricate retail-grade models for user testing and to develop prototypes that look, feel and behave like the final production model would.
Finding Opportunities for 3D Printing
Product design teams are using 3D printing right now to make product prototypes and assist small series production runs due to its ability to make products in a wide range of colours with a wide range of mechanical properties and characteristics. For example, there are materials that mimic rubber and materials with the transparency of glass.
In particular, SLA (stereolithography) is favoured for product design because of its ability to fabricate products with complex geometries, overhangs, and intricate details that would be impossible with a traditional manufacturing process like CNC machining.
These printers use resin photopolymers and a laser to cure and build up models one layer at a time. After each layer is printed, the printer’s tank moves in order to peel the newly printed layer off the surface of the resin tank and then the build platform is raised to allow fresh resin to flow under the build platform. It's a neat process to watch.
For the colour aspect of CMF, SLA is perfect. Resins are relatively easy to pigment without loss of quality and that applies to all of them, flexible, tough and all. With the Form 2, Formlabs do the Formlabs Colour Kit, which lets you make solid coloured parts straight from the printer.
The most common colour system used is the RAL colour chart and in the United Kingdom also the British Standard Colour Chart. These are 'stock' colours available in a form compatible with SLA resins. This allows for the fabrication of true-to-colour models with a 3D printer. It also ensures the manufacturer can get the colour of the final product spot on when basing it from a 3D print.
SLA prints also take paint very well. These can be applied by brush or spray to achieve the desired look. For a factory finish, spraying is the best application and only a few simple steps are required to prepare parts.
The material specification of a product plays the biggest role in how it feels and behaves. For example, a plastic bottle is strong and light and somewhat flexible because it is made from polyethylene terephthalate (PET). A road tyre is soft and sticky because it is made from rubber. A wax jewellery cast can melt and run away with little smoke because it burns cleanly.
Because photopolymer resins can be formulated to have a wide range of mechanical properties, they offer a much better solution for achieving the ideal CMF than regular thermoplastics which are extruded by FFF printers. Formlabs resins, for example, are used to simulate materials like silicone rubber, polypropylene, ABS, and glass-filled plastics, as well as natural wax and even ceramics.
This is a huge bonus for CMF because it means design teams can 3D print models that feel and look like real, final production materials and perform in the same way too. For instance, Tough Resin can be used to make consumer packaging, bushings and bearings, live hinges and snap fits because of its high elongation and low modulus.
In final production, finish standards are specific to manufacturing processes or classes of materials. For example, ISO is widely used, as is SPI. These define how the surface of a part should look and feel depending on what material it is made from. The specifications vary between standards, but all hold a material to a strict spec. In most applications, surface finish is important for functionality and durability, and 3D printing - specifically SLA - enables design teams to fabricate models that meet these specifications.
SLA 3D printing produces parts that perfectly mimic materials like PET, PP and silicones and rubbers. For plastic tooling, SLA printers like the Form 2 can produce very fine detail like grain patterns. Surface finish can be taken to another level by spraying and dip coating models, or even electroplating them for a metallic finish.
When it comes to achieving an optimal Colour, Material, and Finish on 3D printed models, design teams have the benefit of being able to quickly redesign models in CAD and send them to print, or quickly change out the resin for something different to study the differences between materials. This capability is why product designers around the world are using SLA printers like the Form 2 to advance their own production capability.
3D Printer: Formlabs Form 2.
This information is derived from an article by Formlabs.
If you enjoyed this article, you might find our article covering how to prepare your SLA model for 3D printing interesting.