What are my options for manufacturing a clear part? We look at CNC machining.
To demonstrate the different manufacturing options for producing a clear part, we have taken a simple two part ‘housing’ and produced it using cnc machining.
CNC Machining in polycarbonate and acrylic
We used two materials – polycarbonate (PC) and acrylic (PMMA).
Photograph 1 (PMMA) and photograph 2 (PC) show the parts in a ‘smooth’ condition. The term we use to designate ‘as machined’ plus a quick rub over, but not polished. The parts are both translucent and there is little to differentiate them apart from the PC being slightly greyer to the eye.
Photographs 3 (PMMA) and photograph 4 (PC) show the same part polished to a clear finish. Again the visual difference is limited to the slightly grey tint in the PC material.
The design deliberately included a large radius on the upper surface of the housing (photo’s 1 and 3), which the process has produced without any visible stepping. Thus making the polishing a relatively easy task with minimum material removal.
PC has a high impact resistance
From a properties standpoint, the PMMA is harder and as a consequence it is more brittle than the PC. In contrast the PC has a high impact resistance.
High clarity polished finish with PMMA
From a prototyping perspective the preferred option for high clarity is the PMMA as this is seen as easier to polish.
Leadtimes on parts of this type would usually be circa 7 – 8 working days in the polished state.
Larger parts can be machined quite easily subject to the material stock being available. (PC and PMMA are available up to 100mm thick). It is possible to fabricate components where access is impossible or material is unavailable. For fabrication, clear adhesives are available that produce striking results, so this should not be seen as a major problem.
Other examples of parts produced this way can be seen here and here.
You can compare the results with the results we achieved producing the same part using the Polyjet process in this FAQ.
