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My first CNC Pantograph

Premessa

Questo post vuole essere un semplice tutorial, indirizzato a chi come me comincia a muovere i primi passi nel mondo delle Macchine a Controllo Numerico (CNC), scritto da un neofita per i neofiti. L'intento è quello di offrire una veloce panoramica senza addentrarsi però troppo nei vari argomenti, qualcosa da leggere velocemente per farsi subito un'idea. Questo articolo non ha quindi la pretesa di trattare tutte le problematiche, nè tanto meno la teoria legata alla costruzione di una macchina fresatrice a controllo numerico. Nell'articolo verranno descritte e illustrate, a titolo puramete indicativo, alcune fasi dell'assemblaggio del mio primo pantografo a controllo numerico.

(I miei primi lavori)

Breve introduzione al mondo CNC

Iniziamo subito con lo spiegare molto sinteticamente cosa è una macchina numerically controlled (NC). The abbreviation CNC stands for Computer Numerical Control, which then translated into Italian indicates any machine tool controlled by a computer. There are different types of machine tools such as lathes, milling machines, copying machines, customized machines or mixed. The main feature of a CNC machine is to work the material in a completely autonomous, without the operator is to move the pulleys and other machinery.
The production process begins with designing the object to be constructed by drawing with CAD programs. The design can also be 3D is then processed by a CAM software for the calculation of tool path, and finally a last control software CNC machines will manage ignition, speed of rotation of the drill and movements that will make the engines.
The above translates into practical terms in speed, repeatability and precision in the production of any PROJECT! With a good car and a good package CNC CAD / CAM software, you can design and produce an unimaginable variety of objects using various types of material.

How is made a CNC machine

E 'can outline blocks in a CNC machine to better understand its formation. We can then divide the system into the following parts:

- La parte meccanica a sua volta suddivisibile in:

• Il telaio di supporto e di movimento meccanico che consente la lavorazione in svariati modi dei materiali di diversa tipologia, muovendo l'utensile, o spostando il pezzo da lavorare su diversi piani e quindi nelle 3 dimensioni.
• La parte utensile che, a seconda della lavorazione da eseguire, può essere un fresa, un laser, una testa a taglio al plasma, un cutter per il taglio dei tessuti o altri materiali teneri. Molte di queste parti utensili possono, ma non necessariamente, essere controllate in modo automatico dal software, come la velocità o direzione di rotazione di una fresa, oppure l'accensione and off a laser or plasma.

- Part Electromechanics used for the movement and positioning in space of the tool itself can be composed as follows:

• stepper motors (stepping)
• brushless motors
• Servo Drives
• type tires on / off

- The electronics in turn divided into:

• Some pilot normally call that driver is dedicated to providing the right power to the various types of actuators.
• A control part consists of devices that are interposed between the control (computer science) and the pilot. E' molto utilizzata in questo campo la vecchia porta parallela per i sistemi più semplici ed ultimamente sta prendendo piede la porta USB nei sistemi più avanzati.

- La parte informatica o di comando costituita da:

• Un semplice e modesto PC o un controller dedicato specifico per macchine a controllo numerico in grado di interpretare ed elaborare quello che si chiama linguaggio g-code utilizzato per l'invio dei comandi di movimento alla macchina.
• Una parte di visualizzazione che consente all'operatore di conoscere in tempo reale la posizione e lo stato in cui si trova l'utensile. Per questo scopo vengono utilizzati dei comuni monitor per PC, oppure dei visualizzatori di quote a LED o in molti both cases.

addition to the above items, you can also add other parties to streamline and simplify the use of CNC machines while improving performance and safety. These are for example:

• The proximity sensors that send a signal to electronic control not just one of the axes is exceeding the physical limit of the shift. The control electronics will stop the car so that it can be damaged.
  
• proximity sensors with high accuracy (about 0.002 mm) and in conjunction with the electronics and computer science can be perfectly positioned (homing) of the tool in the workspace.
• The Automatic Tool Changer (automatic tool change) allows for precisely the automatic tool change, without operator intervention, and therefore without interrupting your work, thus maintaining a higher speed and precision machining. The ATC may also, but not necessarily, use the stylus to reset the Z (see below)
  
• The probe used to reposition the Z axis at the exact position after a tool change. Or even more profiqua can be used to search for the center of a hole to resume a process, the alignment of the axes X and Y to the piece to have references to "zero" piece, to scan a particular sia in 2D che in 3D nel Reverse Engineering .
• Sistemi di raffreddamento della fresa per le lavorazioni su metallo che possono essere ad aria compressa, a olio da taglio o a emulsioni di acqua e olio da taglio.
• Naturalmente sarà possibile aggiungere qualsiasi altro gadget sulla macchina CNC come ad esempio luci o webcam per la registrazione della lavorazione o il telecontrollo.
  

La parte elettronica

Nelle immagini seguenti è mostrata la parte elettronica da me assemblata utilizzando anche molto materiale recuperato da vecchie apparecchiature elettroniche dismesse. L'elettronica gestisce i segnali provenienti from the computer through the parallel port (the old port where it was once connected printers). E 'can drive up to 4 stepper motors (stepping motors) 3A, and operates the ignition and the electric signals from 3 switches / sensors for homing.
following images depicts the block diagram of the electronics box. The two schemes are as one represents the high voltage (220V AC) and a low voltage power (24V DC).

Starting from the board of low voltage side , identifichiamo nella scheda di controllo (in verde) il cuore del sistema. Questa scheda gestisce i segnali inviati dal PC tramite la porta parallela e li converte in corrente da inviare ai motori (X,Y, Z, A) che quindi si muoveranno gli assi nella direzione, con la velocità e con l'esatta misura contenuta nel G-code ricevuto. Ha la possibilità di controllare lo stato di 3 finecorsa, utilizzati per evitare che gli assi si muovano oltre il limite fisico della macchina, e 3 sensori di homing per referenziare a zero la macchina (origine degli assi X, Y, Z). E' presente inoltre sul pannello frontale un interruttore di emergenza a fungo (E-STOP) che permette il blocco immediato degli assi e del mandrino nel caso in cui vi fossero problemi of any kind. We are also always a relay controlled via the PC software, which is connected to three voltage 220V AC, and one of them is connected on the machine, the discovery on and off the drill are automated. The ignition relay is monitored by an LED on the left side of the BOX. The board and the motors are powered by a switching power supply with 24V DC and current up to 14 Amps. The power supply provides power even with 2 fans (Fan Fan BT and AT) 24V on the back which extract air, and a fan (Fan Profile) 24V always installed directly over the end of the card. To top it all have been installed on a front panel digital voltmeter (right side) that constantly monitors the voltage provided by the power and a digital thermometer (left side) which monitors, via an external probe, the temperature of the card. The

the high voltage side is much simpler. Starting from the electrical outlet (220V AC), the diagram shows that the input current is divided in two. A portion (right) meets with General un'interruttore place on the back of the box, the current at this point passes over a 5A fuse and then it is again controlled by a switch located on the industrial front. At this point there are 3 pole switches respectively monitored by an LED, allowing the activation or deactivation of any equipment you want to attest to the corresponding socket (in the diagram in red Exit 1,2,3). Here I expected to control a light in the future for the pantograph take rather than a suction system, or a refrigeration system. The other part of the 220V AC mains, always passes by a safety switch on the back of the box, through a 3A fuse and then enters a relay controlled by the board of the drives and managed by software from your PC. There are thus attested to the relay took third (green Exit 1,2,3), one of which is occupied by the cutter (Kress) so as to control the switching on and off directly from PC or G-code . As mentioned above, the activation of the relay is monitored by an LED on the left side of the box.

the electromechanical part

The mechanical part (See also photos at top) is a Valmec Dragon 500 I modified by adding walkways aluminum cable chains to mount. I then proceeded to the assembly of only three engines of the 3 axes, 3 of 3 proximity sensors and switches, wiring and connessione di tutti i cavi. Purtroppo, dopo il montaggio delle passerelle per le catene passacavo, ho dovuto rinunciare ai bellissimi carterini forniti a corredo che si vedono in foto sul sito del fornitore.

Le caratteristiche meccaniche del pantografo sono di seguito elencate:

• Area di lavoro: 500x360x100
• Max altezza Z: 100mm
• Dimensioni tavola: 600x360mm
• Max velocità: 0-3000mm/min
• Max. Velocità Lavorazione: 0-2000mm/min
• Precisione: 0,03
• Ripetibilità: 0,03

Di seguito vengono mostrate e commentate alcune foto che mostrano le parti aggiuntive che ho provveduto personalmente a montare sulla Mechanical Valmec.

axis X. Sensor Limit / homing inductive cylindrical thread M8x1, NPN-NC Normally closed, 10-30VDC 6-36VDC admitted, 2mm sensing, switching current 150mA max, total length 55mm, IP67.

Y-Axis Sensor Limit / homing inductive cylindrical thread M8x1, NPN-NC Normally closed, 10-30VDC 6-36VDC admitted, 2mm sensing, switching current 150mA max, total length 55mm, IP67.

axis Z. Sensor Limit / homing inductive cylindrical thread M8x1, NPN-NC Normally closed, 10-30VDC 6-36VDC admitted, 2mm sensing, switching current 150mA max, total length 55mm, IP67. In the picture you can see the motor coupling without backlash.

The picture below shows the mechanical sensor (switching) switches used in the axis of X. The same tipoligia sensor is mounted on the Y axis as well

If you want to mount the cable chains in order to improve the safe and orderly throughout the installation, I had to build bridges to their seats using the commonest of aluminum profiles found in all the DIY stores and DIY. The photos below show the catwalk with aluminum chains already mounted and the wires already in the past.

In the following photos shows some details of the cabinet that I made to support all devices. It 'made of steel profile and MDF. The photos below show from left, the rack housing the keyboard and mouse and the left side of the cabinet.

In order to seek to maintain the whole installation as orderly as possible, I added a power strip, which then distributes power to all devices. Through the switch in this strip, you can then remove power to the system with a single gesture, when not in use.

Using the same pantograph I then milled a table (in the photo is the part in yellow) where the cutters are gathered and placed in use, the number of clamps for ' Kress spindle. Then there is storage for the other tools. Everything is then protected from dust by means of a polycarbonate cover.

Finally, here are some photos showing two LED light bars mounted on both sides hot shorts of the pantograph. Bars, as well as their supports are easily removable if necessary.

The computer part or control

The computer part of my pantograph consists of a simple computer systems from Dell, Optiplex 745 model bought second hand on ebay. Not needed to control a CNC processing capacity high. According ArtSoft Mach3, one of the control software for CNC machines best known, the minimum configuration is as follows:

• Desktop (using the parallel port)
• 32-bit version of Windows 2000, Windows XP, Windows Vista , now Windows 7 Operating System (64-bit will not work)
• 1Ghz CPU 512MB RAM
• Non-integrated Video Card with 32MB RAM

The computer will then optimized according to the recommendations in this visible link , and must be devoted to driving virtually the pantograph. E 'strongly recommended the installation of other software than those strictly necessary for avoid any service running in the background could negatively affect the natural functioning of Mach3. Needless to say at this point that during work should not be used in other programs. Failure to meet the above tips can lead to loss of steps in the stepper motors and thereby ruining hours of work!