Saturday, July 25, 2009

Re-Tinker CNC

A quick Google and we have more then a few pages on home build CNC machines of all sort...

There are 4 major components that make up a CNC machine
1) The tool head
2) The linear motion
3) The Motor drive
4) The controller

The tool head is what one decide to use the machine to achieve, be it lathe, milling, punching, grinding... etc. The criteria has not changed much since the industrial revolution and I do not foresee much changes in the near future. The new comers are water jet, plasma cutter, laser cutting, EDM or even 3D printing. These had revolutionized how many things are done and I will expect more to come.

Linear motion used to mean linear motion in X, Y and Z axis, but today, it does include rotational movements around the axis, which are called "DoF" Degree of Freedom. The design considerations involves size & material of work piece, speed, accuracy required, finishing requirements. is how the tool and work piece move with respect to each other.
Fix toolhead with moving work piece? Fixed workpiece with moving tool head? or move both partially?
Tranmission & motion conversion from rotation to linear motion,use mechanism such as lead screw & nut, belt & gear, rack & pinion, gear on chain...
Rail guides to ensure transverse in straight line using linear bearing on rod guide, roller on rail... etc

No drastic changes from what I learn in my school days...
I think I'm still pretty up-to-date in this area.

The greatest different were the controller and the motor driver development and availability.

The drive system, for stepper system, it consist of the stepper motor and driver; for the servo system, it consist of the servo motor, encoder and the motor driver.

Today, micro-stepping driver are available at an affortable price, I think this is the main reason for the CNC boom in recent year. Well within hobbyist pocket size.

Servo system too has become much more affortable, but still has room to go.

Only a few years ago, 'serious' CNC machine are built with a customized controller console with its own computing capacity and PC based controllers are in their infancy.

The controller takes in G-code, A.K.A. command list and send control signal to the driver which consequently operate the stepper motor.

What is G-Code? Its a code that the controller take in for processing and the code normally starts with 'G'. Serious... eg, G 00 means stop, G 19 is move to... etc

There are software that convert .dxf files from most CAD programs to G-code, or one can write the G-code manually. I'm still looking into such programs presently.

Currently, there are many affordable, pseudo-free & free PC based controller software, they all have active supporting forums, the two that cough my attention are Mach3 and EMC2.

Mach3 is a window based controller software, it is free until you decide to "go commercial" with it. USD150 will buy you a pop.

EMC2 is a Linux based open-source controller software under GNU license. This thing runs real time kernal, all the bells and whistle and more...

I think I've reach my typing limit for the day... blurry vision...tired finger joints...

How I Got Myself Into This Mess

Lately, I'm feeling the effect of aging working against... Soldering differed due blurry vision, workshop progress halted as my back ache...

Without much to do, I stared at the monitor and decided to retrace how I get myself into this mess.

I started in metalworking,
I learn welding and machining in my polytechnics days.
Woodworking is a hobby.
Electrical came naturally.
Fabrication is a big part of my day job.
My engineering skill grew through work and play...
Self-thought practical electronics to fill in the blank.
Analytical skill & experience are symbiotic...

Discounting those dismembering alarm clock events and bicycle repairs, the first "serious" machine I built was in my polytechnics days.

Its a stepper motor driven X-Y table carrying a high speed spindle. We build the X-Y table with Acme-lead screw and linear-bearing running on surface hardened guide rails.

My part in the project is the Linear Motion portion of the project, i.e. X-Y table, the motor & the spindle. The challenges were to design and build a light and rigid X-Y table which carries a high speed spindle, this table will transverse accurately to the stepper motor rotation.

The designing was easy, we were given the required leadscrew pitch, x and y treavels, estimated loads and the desired tolerance/accuracy. Throw all these info in salad bowl and came out with a set of CAD drawings of the "ingenious" design. Even tried to model a finite element analysis but not complete due to time constrain.

As ball-screw was expensive then as now, we opt for to machine ACME screws in the workshop & the Anti-Backlash nut and holding blocks while were at it.

After gathering all the part, shower after shower of welding spatter and flying grinding sparks, we got everything assembled. The hardest part was to align and tune the finished assembly. I can still remember how much easily metal flex under load and the agony of getting everything line-up precisely... Till this day, I'm still puzzled how we pulled off the project in such short time... Nevertheless, that was great fun and my inauguration into machine building.

Maybe I should re-kinder with CNC machine for old time sake...


Tinkle and tools hoarding are symbiotic...,The more I tinkle, the complexity grew... Need for more tools... Or was it the other way round?

Ah.... those polished-shiny-blinking tools...
The growing tool collection and the size of my junk box are the physical evidence of my tinkering journey... or is it my impulsive shopping habit...

The tool collection growth irrespective of the current global economic outlook... When time is good, you buy cos you have the moola; When time is bad, you buy because you have plenty of time to play....

Thursday, July 9, 2009

What's New?

I made a quick listening to the 6DJ8 preamp. As most tube amp that I build, she sounded good. but not great. Usual tube sound characteristics are present. Clean, crisp, sexy mid range... I should further tinker with the component values to tune for "optimum" result but there are so much distraction in this materialistic world...

My new toy had arrived...

Dress in Red,
Comes with bottoms...
And Spikes....
Just the type I like...

Impossible to keep my hands away...

Downloaded the open source Arduino environment here

Plug in the USB port

Set the Dip switches

Load the scrip

Press the biggest keyboard key


Blink! Blink!! Blink!!!

I herein solemnly declare I'm Micro-Processor Enabled!!!!

Wah Ha HA HAAA!!!

These Came with the kit,

All the bells and whistle

That Says.....

More to come!!!!!