The course content is designed to facilitate a working knowledge of the processes and steps on production of prototypes, from the inception of the concept, through modelling and all the way to the production of the physical model.
Intent and Purpose:
- CNC Milling Machine
- CAD Software
- STL Conversion or Stereolithography enabled software
- Manual design and process flows.
The purpose of this assignment was to get acquaint one’s self with the use of machinery such as the CNC milling machine. The idea was to produce a decorative tile all the way from the concept design stages, through the 3d modelling and finally to realization of the tile by milling it in the CNC Milling Machine.
The main challenge in making an iconic piece of art is of course the inspiration. You either have it or you don’t and if you don’t, you have to get creative with the solutions. Looking through analogous works be a colossal waste of time if one does not get inspired. So sometimes, it helps to just get started with the sketching and see where that leads. Considering adequate knowledge in all aspects prior to milling, I decided to focus on the milling, with elaboration on a few technical insights that could determine success or failure with regards to achieving required results. This is especially true for novices. Therefore a section on the milling process is also appended (Appendix -1)
The resulting Tile was an ergonomic piece of art and like most art, it would be east to mistake it for a trinket
without function. however, even then one would still find themselves reflecting on what the purpose is, what it could mean, what was the intent, and therein lies the true purpose of art, to drive the mind forward, stretch the limits of the imagination.
Appendix 1 – The Choices of End mills:
For a start, there are various lengths of end mills each of which would be suited to specific purposes. Whereas it would always be preferred that the end mills be as short as possible (to reduce chatter and for rigidity), there are a whole range of other factors to consider in choosing the end mills, depending on the material being worked on as well as the material of the end mills themselves.
End Mill materials:
- Cobalt Steel Alloy (High Speed Steel/HSS) – for softer materials
- Tungsten Carbide in a lattice of Cobalt (Carbide) – for harder/more abrasive materials such as Titanium
Geometry of the Flute:
- HSS end mills will wear out faster than Carbide ones – Carbide is a lot harder as a material.
- Carbide is more brittle than HSS and therefore requires more rigidity to avoid tool failure tool alignment is critical.
- Ability of carbide to withstand extreme heat allows for high cutting speeds.
- Up cut Spiral – tends to pull workpiece up. Preferred for cutting metal
- Down cut Spiral – Presses workpiece down. can affect chip ejection
- Straight Spiral – Ejects chips well.
- Flat end mill – Best for cutting flat areas with no scalloping
- Ball end mill – For non flat surfaces.
- Corner Radius end mill – Specialized for milling corners.
For softer materials, one can use a single flute end mill since it can handle larger chip loads, however it must be considered that the higher the flute number, the better the finish, however, the chip is ejected with increased difficulty. Therefore in multi flute end mills, the feed rate is increased to prevent burning and dulling of the end mill.
Whereas HSS end mills seem cost effective, the lower tool life, especially in comparison to the carbide ones, can in some instances incur excess costs. It is advised that for heavy workloads, cost saving can be achieved by reducing changeover time and investing in tooling. For this carbide may be recommended when one intends to run faster and accommodate higher feed rates.
On the other hand, when working with softer materials, HSS is recommended as this will reduce costs especially if the operation is not large in scale and duration.