積層製造技術又被稱之為三維列印，這是一種將數位模型直接製造而成的新穎方式之一。由於此新穎的技術可應用在各種不同的領域上，因此近年來引起了廣泛的注意。然而，三維列印技術卻難以在單一模型上進行多色或者是多種材料列印。目前有很多問題已經有了解決方案，有的是用特別的方法研發出新機台；有的是設計出附加機構可以被安裝在單一噴嘴上。雖然市售上有一些桌上型三維列印機台已經可以進行多色列印，但是它仍然面臨到一些具有挑戰性的問題，如:線材滲漏、機台材料成本昂貴或者機台的操作複雜等。 本研究將設計出一種可以在一個複雜幾何形狀的模型上列印多種顏色的熔融沉積成型的三維列印機台。目前市面的多色三維列印機台通常需要搭配多個噴嘴提供給不同顏色的線材使用，而每個擠出噴頭都需要一個獨立的步進馬達來將線材推入噴嘴加熱，讓線材成為熔融的狀態。本研究提出一種線材轉換的新穎機構，此機構僅使用一個步進馬達來驅動多種不同顏色的線材的切換。其驅動原理與傳統的單色列印機台相同，使用步進馬達傳力動力到齒輪傳動系統，使滾齒螺栓夾住線材，使線材可以轉動向下。然而，由於齒輪傳動裝置上有一個特殊球型移動裝置，當步進馬達轉動時，只讓一個滾齒螺栓可以轉動線材。球型移動機構具有將軸與正齒輪之間有聯結或分離的運動功能。為了可以變換線材，有一個直流馬達帶動凸輪盤來釋放或按壓推桿來定位球型移動機構上的球。在本研究中，多色線材變換機構被設計成一個模組化的設備來添加到市售的三維列印機台上。此外，本研究開發之多色三維列印機台的噴嘴將設計成5進1出的噴嘴型式，此噴嘴型式可以分別將導入直徑為1.75mm的5種不同顏色線材，讓線材在噴嘴機構內進行加熱後，在0.4mm的噴嘴孔徑產生熔融狀態的細絲。這樣的機構型式也可以應用在多個噴嘴的三維列印機台上。 本研究所開發之多色三維列印機其控制器主要是修改Ramp1.4電路板與開放軟體Marlin，因此此多色三維列印機台可以使用G碼並且與Ulitmaker Cura兼容。最後，本研究進行多色模型的列印製造與測試。透過實驗結果顯示，球型移動機構可以順利將線材進行切換。雖然透過本研究所開發之機台列印之模型，其準確性仍受到一些技術問題的影響，但列印的模型結果是可以被接受的，其表面品質仍可以與市售三維機台進行競爭 ;Three-dimensional (3D) printing or Additive Manufacturing (AM) is one of the novel method of manufacturing parts directly from digital models. It has attracted a massive attention in recent years due to its potential use in various applications. However, one obstacle is the difficulty printing physical objects in several colors and materials. Many different solutions have been addressed, some have gone into developing a new printer with special methods; others have developed add-ons devices that can be integrated into the single color printer. Although a few of desktop multicolor 3D printers have been introduced and commercialized in the market, it is still facing extremely challenging issues such as oozing, expensive material or complex operation. The aim of this project is to design a multicolor Fused Deposition Model (FDM)/Fused Filament Fabrication (FFF) printer that can create complex geometry objects with multiple colors. Most of multicolor 3D printers are generally equipped multiple extruders to drive different color filaments. Each extruder requires an individual stepper motor to push the filament into the hot-end for melting. This study proposes a novel filament shifting mechanism that uses only one stepper motors to drive multiple filaments of different colors. As same as other single color 3D printing extruders, the stepper motor power is transmitted through a gear system to the hobbed bolts that bite into the filaments to force it downward. However, only one of the hobbed bolts could be rotated for feeding one filament when the stepper motor turns due to the special design of ball shifting mechanisms of the gear transmission. The ball shifting mechanisms have the function of coupling or decoupling the motion between the shafts and the spur gears. In order to change the filament, there is a cam disk that is driven by a Direct Current (DC) motor to release or press pushing rods for positioning balls of the ball shifting mechanism. In this research, this multicolor filament shifting mechanism is designed as a modular device that is added to a commercial 3D printer. Also, its nozzle is replaced by a Diamond “5 in 1 out” nozzle that has five filament inputs for 1.75mm filament and a common 0.4mm nozzle orifice. This implementation could be also integrated into multiple nozzles 3D printer. The controller of this multicolor printer was also developed by modifying Ramp 1.4 board schematic and Marlin open source firmware so that it is compatible to a free G-code generation software, Ultimaker Cura. Finally, the proposed multicolor printer was manufactured and tested by printing a number of real multicolor products. The experiments show that the filament switching mechanism works perfectly without major problems. Although the accuracy of the final printed objects is still affected by some technical issues, these results are acceptable as they can compete with other commercial 3D printers in terms of accuracy
