DIY CNC: A REVIEW. dhaval.patel1@git.org.in , ani_kyadaauto@yahoo.co.in. Abstract

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1 DIY CNC: A REVIEW Dhaval B. Patel 1 *, Aniruddh R. Kyada 2. 1 *Assistant Professor, Gandhinagar Institute of Technology, Gandhinagar , dhaval.patel1@git.org.in 2 Assistant Professor, Silver Oak College of Engineering& Technology Ahmedabad , ani_kyadaauto@yahoo.co.in Abstract The CNC machines are there from many years, but mostly they are unreachable to vast community specially students. Another disadvantages with them is that they are bulky and expensive. Why can t we make a CNC like printer? Why can t we make a CNC for small jobs with low capacity? There is lake of low cost CNC in market which can teach and also work. All CNC are general in terms of controlling (you just have to control three axis just that) but it produce more complexity when they came in existence. They produce different output i.e. drilling, milling, turning etc. In this paper we are showing that how you can build up CNC using open source hardware and software? What are the basic requirement for building a CNC and how to control them? Keywords: DIY CNC, CNC, 1. Introduction There were times when products were produced in mass quantity and hence the prices were lower. But they lack the personalization. Henry Ford was offering his Model-T in only one colour. As things get progressed the variety is increased, but today each and every customer wants their own personalized items. Which is the reason Android is more popular than ios. Nowadays more and more machines are being converted in CNC machines due to their high accuracy, high precision, less setting time and greater repeatability. One aspect of using CNC is that you can use unskilled or semi-skilled labours. The invention of CNC was for batch production and not for mass production though the cost is high. The basic controlling of a CNC is same as the printer. The reason is they are bigger and also stronger but not good for home environment rather they are mostly suited to workshops. The invention of 3D printer and more and more use of plastic now changing this scenario and it is becoming like home appliance (TV, Refrigerator, AC etc ). So why we can t minimise The CNC which have very small working area and working on softer materials like wood, plastic, aluminium etc... Currently in market there are many solutions are available which are reviewed in this paper. Figure 1 Basic components of a CNC CNC Components The main focus of this paper is to build up the CNC using open source hardware and software as much as possible. To initialize a CNC building company it requires lots of funding and brains. But, due to crowd funding website like Kickstarter, Indiegogo and many more it is possible to fund your projects. Also as open Mechanical Electrical Frame Drive System Carriage Controller Driver Actuator (Motor) Power Supply Acuator Guide For Drive For cutting 587-1

2 DIY CNC: A REVIEW source community grows it helps in terms of software and way to build up the controllers which is very useful and low cost than using Siemens or Fanuc. Any CNC machine (Router, Turning centre, milling centre, 3D printer or even simple 2D Printer) has two types of component Mechanical and Electrical (which consist electronics also). 2. Mechanical Components 2.1 Frame The structure which supports the whole machine is called frame. It can be made of various materials like wood, aluminium etc Generally for lighter work wood will be preferred as it is easy to work with it, aluminium give higher stiffness compare to wood but it requires machine tools to build up the frame. Generally box like structures are preferred and they made using above material. 2.2 Drive System It is the most important part of any CNC machine after the controller as it would carry your tool (pencil, paint brush, printing head, Dremel, cutting tool etc ) to desired position as per command provided by controller. The general drive system specified on basis of accuracy and load capacity as all the load working on tool is transferred to frame via this drive system. Figure 2 Rope drive with pulley ( (b) Timing belt drive Provide the benefits of rope drive as less expensive than ball screw and eliminate the disadvantages of rope drive as provide high accuracy. The timing belts are belt with profiled grove which also fits in same cavity made on timing pulley. It helps to reduce the slippage and also maintain constant velocity ratio between electric motor and drive. The GT2 belts and pulley are mostly used in all DIY CNC. There is other standard also like T5, T2.5, MXL it requires some times ideal pulley to increase the tension in belt. A standard GT2 belt and pulley is shown in figure 3. It is made of two parts actuator and guide system, the main purpose of actuator is to transfer the controlled motion of electric motor to carriage. Guides are used for proper guiding of the carriage and also it s reduce the friction hence increasing the response time and accuracy of the machine Actuators (a) Rope drive (thread drive) The drive with lowest capacity as it would just guide the tool but in case of forced feed it would be unusable. The most desirable condition for its use when tool and work surface are barely in contact i.e. painting with paint brush or drawing with pencil. It would develop very less friction and hence this drive would be suffice to operate the machine. It is required a pulley to attached with motor shaft to connect the rope with actuator. It also requires bearing in the path of the rope otherwise friction between rope and guide will increase too much to for rope. The benefits of rope drive is oblivious one its cost it also not required expensive helical coupling or timing pulley. Figure 3 GT2 belt with timing pulley( cfm) (c) Bolt and Nut drive Most sturdy and stiffen drive, capable of transforming the higher power with higher velocity. It consist a threaded bolt and matching nut. It provide higher accuracy as there is no slippage between nut and bolt. It is cheaper than ball screw but suffice for our DIY purpose. It is mostly used drive system like router. The mostly used standard is M5, M8 and M10. In most of the DIY CNC it used for Z drive as it is very compact than belt or rope drive. It requires a helical coupling (beam coupling) to connect with motor. Both are shown in figure

3 Figure 4 Threaded bolt with helical coupling Guide system (a) Simple groove It would be cheapest of all method just put a grove with corresponding male member attached with guide. It is mostly used with rope drive system and virtually having zero cost. The guiding of the drive is more depend on tension of rope drive rather than accuracy of the groove. (b) Slider drive These are basically telescopic channel made of generally steel and used in furniture purpose. They provide high accuracy comparatively to rope drive and also with stand against higher load but the friction between their inner components is high. Figure 6 Maker slide ( lide) 2.3 Carriage Carriage or tool holder is used for holding the tool. If the tool is passive it just hold the tool and if the tool is active it also holds the DC motor which rotates the tool D machine In two dimensional CNC the tooling system are generally passive so they are holding dead too only. They are connected with two drives which is moving them in x or y direction and also hold it. Figure 5 Telescopic channel (courtesy ofmetro wire products) (c)maker Slide Maker slide is an open source linear bearing for CNC equipment that is low cost and extremely easy to integrate into your design. It is an aluminium extrusion with two special V-shaped rails for wheels to roll on. This component is interesting for people designing CNC machines because it acts as both the structural support and the linear bearing system. The biggest design, cost and fabrication hurdles in a new CNC machine design are the linear bearings. With the help of some Delrin wheel and some side plates you can easily build up the drive system for your CNC. As it using rollers for guiding it has very low friction and higher accuracy due v-rail guide system. Figure 5 Carriage for 2D Machine ( D machine In three dimensional machine carriage is generally mounted on z axis. Most 3D machine are having active tools so DC motor which is driving the tool is 587-3

4 DIY CNC: A REVIEW mounted on carriage and tool is attached with this DC motor. controlling power is required Arduino Mega 2560 board is used. The GRBL controller which converts the G code in to machine language is flashed on microcontroller (ATmega328 in case of UNO and ATmega2560 in case of Mega 2560) of the board. Figure 6 Carriage with rotary tool ( D printing machine In 3D printing system generally plastic wires are used for printing. The head consist of plastic melting component along with wire feed mechanism and also a cooling fan. Wire feed mechanism is used to feed the plastic wire forward as it consumed. A thermistor or ceramic heater is used as heating element which melts the plastic (ABS or PLA). Figure 8 Arduino UNO ( 3.2 Motor Driver The Arduino board are operating on 5V and motor are operating on high voltage ranging from 12 V to 36 V. So there is need of driver which can take command from controller and drive the motor. There are many motor driver IC are available in market (i.e. A4988, L293D, DRV8825, DRV8824 and DRV 8834 etc...) Figure 7 3D printing head ( 3 Electrical components 3.1Controller The controller is used for converting the G-code into machine language. The most widely used and low cost controller is Ardunio. It is a microcontroller based board which have wide application and can be programmed for multipurpose use. It can drive servo and stepper motor along with DC motor. For controlling 3 stepper motor Arduino UNO will sufficient. But for 3D printing machine were more Figure 9 A4988 Stepper Motor Driver ( Table 1 Comparison between different stepper motor drivers Sr. Voltage Continuous Max Driver No. Range (V) current Current 1 DRV A 2 A 2 DRV A 1.2 A 3 DRV A 2.2 A 4 A A 2 A 5 A4988 black A 2 A 587-4

5 3.3 Actuator Stepper motor Actuators are nothing but the electric motor which drive the machine. In most of the DIY CNC stepper motors are used as it is good combination of accuracy and cost. Stepper motor are ruining in steps usually of 1.8 O or 3.6 O.Generally stepper motor with 100 steps per revolution are used which can be reduce by micro steeping of the motor. The facility if micro stepping is available on motor driver. Both bipolar and unipolar stepper motors are used for machine which is couple with drive system using pulley or helical coupling based on the drive chosen. The standard motor are NEMA 17 or for more power NEMA DC Motor DC motor are used for operating the spindle of the machine. It is present only in metal removing machine. Dc motor having 24V or higher are used for spindle and the cutting tool is directly attached with the shaft of the motor. 4. References (1) (2) (3) -3d-carving-cnc-mill-kit-shapeoko-2 (4) (4) (5) (6) (7) (8) ide Figure 10 Stepper motor Sr. No. Table 2 Comparison between well-known DIY Routers, Shapeoko and Othermill 1 2 Detail Shapeoko Othermill Work volume Drive Motor 3 Controller 298X301X54 mm NEMA17 Arduino with GRBL 140X114X32 mm NEMA17 Arduino with GRBL 4 Spindle tool size 1/8 1/8 5 Accuracy 0.01 mm 0.02 mm 587-5