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How CNC machines Work

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koolguy

Active Member
Hello,
How CNC machines Work?
there are lot of machine based on it like vinyl cutter, routers, wood ,acrylic, steel, rods, etc etc.
 
I was a CNC retro fitter for years using Fanuc, Mitsubishi and PC based self designed systems.
There are many technologies/discipline's used in a CNC machine, but the basis is to control the various axis of motion trajectory using a servo or stepper motors, or even hydraulic servo valves using computer control.
The computer takes the G-code program entered by the operator, calculates the trajectory and rate of motion.
Max.
 
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Well, that's great too !

However, there's a very good Forum on the net .. ..called Electro Tech Online .. .. .. don't know if you've heard of it .. .. .. but it affords members the means to communicate meaningfully, without the need for face to face contact .. .. :p

S
 
Hi Max

You won't be impressed .. .. Chinese Import 3040T .. .. .. picture attached
Going to run it from Mach3 on a lab computer I found and rebuilt. Given all I really want it to etch/engrave PCBs and cut the odd slot in an enclosure .. ..

I've also got a self build I started based on a Sable machine with some modifications .. .. I've built the Y axis which is a platen on linear bearings running on 20mm supported chrome rails ... I need to replenish the budget and then get some gantry sides machined.

A huge learning curve but should be a good challenge and great fun !

S
 

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One weakness I have observed from some of the Chinese machines is the wiring and earth/grounding methods.
Also seen on sites such as CNCzone many DIY machines fail in this area also, hence some of the spurious noise issues, especially when using a PC and Mach etc.
Max.
 
And they are right !

There is earth from the incoming IEC to a tab bolted to the case which is powder coated. I looked for continuity with a DMM and was horrified to find nothing at all ! I've ground the coating away and made a good connection .. .. there is also a similar issue with the 3 Bulgin connectors that feed the stepper motors .. .. . they all have a screening strand clipped to the case .. but powder coating is in the way .. yet to do, but a similar remedy needs to happen.

I think this control box has a limited life span anyway, not least because it offers no PWM spindle speed control for Mach3. There is a 4pin connector on the control board and similar on the spindle board but the CNC forums suggest that the control chip may or may not be programmed to respond to the signal .. .. .. with my luck it won't be ! The only speed control is a potentiometer on the front case marked with a series of ever decreasing circles and not very reliable at that. I'm working on a little circuit to put a IR driven tachometer on the spindle with an LCD display on the control box so I've at least got some control.

I'm working on the control computer at the moment .. .. when I've completed that I'll go to work on the control box.

As I said ... a big learning curve :)

S
 
The water cooled H.S. 3ph spindles are also popular, many are fitted with a 4 pin socket to take the 3ph and GND, but in some cases it has been found the Gnd pin is not actually connected to frame ground!
Max.
 
Well this is all single phase, as you might expect, and the spindle is DC powered ( 41 vdc I think ) separately .. .. .. having said that the only Gnd is via the case. I'm going to add a Gnd strap from the carrier to the base.

Great to have a conversation, Thanks Max
 
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