New member seeking advice

[Rob Wol]

Hi everyone, I'm a time served precision mechanical engineer with 11 years of engineering experience. I'm doing a night college course at the moment and was looking for a new project for when I'm finished. I stumbled upon a very interesting vid on you tube. It was a cnc router constructed from MDF, I found this machine amazing! I was instantly hooked and wanted to build one.

I started to do a bit of re-search and came across this forum. I'm ok with the mechanical design and build part of the machine. However I have no electronics experience so I've got no idea about motors, controllers or drivers. Also have no idea about the computer software that is required to run such a machine. I've used drawing packages such as auto cad and solidworks. Do u need to do a drawing on any of these and then import it to another type of software to allow the cnc to cut it?

I would be gratefull for any advice on electronics and software.

Thank you Rob.

[JAZZCNC]

Hi Rob and welcome.

Regards software it basicly goes like this. Parts are drawn in CAD then brought into CAM software which produces a file that gets loaded into the control software which drives the CNC machine.
CAM is where you define cutting stratagies called toolpaths, the paths are defined from your Cad drawing or model.
There are different stratagies depending on operation to be carried out IE: Profileing toolpaths, drilling, pocketing, roughing paths for quick stock removal, finishing paths etc. There are basicly 2 types of machineing 2D & 3D each with there own set of cutting stratagies(toolpaths) thou often you'll see 2.5D mentioned which is essentially multi level 2D using just 2 axis simultanously true 3D use's 3 or more Axis at same time.

You define toolpaths by selecting areas lines, holes etc or surfaces or full models if 3D from the CAD drawing then assign parameters such as cutting tool, speeds/feeds, direction of cut (climb milling etc) the options available will depend on type of stratagie selected.
Then the Cam software generates a G-Code file that you load into the control software which then follows the instructions.

The control software does nothing more than translate the G-code file into movement telling the motors how far and in which direction to travel and perform or monitor the actions of the machine using I/O's (inputs & ouput) signals.
These signals can be outputs to turn on external devices like spindles, vacuum, etc even the kettle if you so desire.!! Often outputs will be triggered using special codes contained within the G-code file but can easily be triggered by other actions like inputs, all this is configurable within the control software.
Typical inputs are E-stops, limit switchs, home switch's but again could be anything from a switch to a light sensor to a button again all setup and monitored within the control software.

Now regards CAD &CAM there is software that incorparates both CAD/CAM in one package which often helps makes things easier and gel better but it's not required just more conveniant.
To be honest CAD/CAM is a funny area and which software or package to use will depend greatly on what you intended to do with the machine.! Even then it's not always clear cut and you may find you end up using more than one package.?
I for instance use one package mainly for 2D stuff because it's quick and easy and another for 3D or V carving because that provides better cutting stratigies, both will do the same 2D/3D but one does some things better or easier than the other.
Often it's a personal thing as well because you just can't get on with it's interface or how it works.!!

Regards the motors, drives a basic run down goes like this.!

From the PC parallel port goes a signal cable to a Breakout board (BOB), this BOB takes the signals and redistributes them to defined pins, each pin then gets used as either an input or output thats becomes under the control softwares command.

Outputs are used for things like motor direction, step amount, as well as for controlling things like spindles etc. Same goes for inputs which are usually things like E-stop etc There are a limited amount of I/O's dictated by the parallel ports 25pins of which only 17 are available 12 outputs 5 inputs.

These I/O's are arranged on the BOB to perform different functions IE pin 2 & 3 will control the Step count and Direction for the X axis motor, 4 & 5 Y axis and so on upto the BOB's axis limit usualy 4 some times 5. Any spare are used for turning on spindles or what ever you assign it to do, often the BOB will have a relay connected to an output thats used to safely control high power devices like spindles.

From these output pins signal wires goto each drives signal terminal, 1 for step count 1 for direction, 1 drive per axis. There will also be a power cable from a separate PSU that goes to each drive, Each drive shares the same PSU and this will usually be sized to match the drives MAX voltage and Amp requirements.
Then from the drives come cables that go to the motors to power and perform the movements.

Also from on the BOB there are input connections that get connected to things like E-stops, limit switchs etc which the control software then monitors and if the pin state changes it performs an action IE: stopping the motors if E-stop condition is reported.

So basicly that's it in a nut shell.

You need:
BOB . . . . . . . . . . . . . to distribute signals
Drives (1 per axis) . . . to control motors
Motors. . . . . . . . . .. .to Errrr. . . move . .:)
PSU . . . . . . . . . .. . . to power drives which power motors
Small PSU. . . . . . . . . .to power BOB, some times can be taken form drive PSU depending on BOB

The size of motors/drives and PSU will depend on factors like machine size and mass it's going to move and best left untill you have arrived at a final machine design and decided on other components like type of linear rails, whether it will use ballscrews, timing belts ,threaded rod, Rack&pinion etc all of which play a role in motor/drive/PSU sizing and selection.

On this note can I strongly steer you away from building using MDF and if you do plan building look to stronger materials like steel and Aluminium. It will workout cheaper in the long run with far less stress belive me.!!

Anyway Rob I think that should give you enough to chew on and don't hesitate to ask if your unsure about anything. . . Enjoy.!!

[motoxy]

OH! So thats what its all about :) Rob welcome to the forum. I started off wanting to build the mdf m/c but someone I know built one and was very disappointed with the accuracy. As a precision engineer you may want to bear that in mind. You will get a lot of good advice here.

[JAZZCNC]

OH! So thats what its all about :)

Narr thats just for starters Moto there's far more to curdle his noodle but I left that for another day and my lickle pinky couldn't stand any more. .:lol:

[Rob Wol]

Wow! Thanks for that. Wasn't expecting someone to give me that much advice so quick. That's great!
Im going to be making a start on the project around April/may, so up until then I'm going to be keeping my eyes and ears open and probably asking lots of questions.

I will defo start to look at other materials for the build though as a lot of things I have read say the same about the MDF machiene's.

Just another quick question for now. What sort of price would I be looking at for a software package to get me started? As I know software can be really expensive.

Thanks Rob.

[motoxy]

Actually the software can be free. Have a look in the cad/cam section. The major costs are screws, rails and electrics.

Bruce

Aw listen to me, i sound like i have some idea whats going on:lmao:

[m.marino]

Rob,

The points that Jazz makes are very valid ones. Now some points to consider before you even get to the CAM/CNC side of things:

1) What do you plan on doing with the machine? Be detailed in your answer as that WILL greatly effect design/ build of the machine greatly

2) What are your resources? Not just money but also time (learning the hardware/software) and lastly space (which will again affect design)

Answering just those two questions for yourself and write them down so you have it fixed and set where you want to be going with this rather in depth project.

Then get a CAD program. There are free ones and some are okay. For low cost I would suggest ViaCAD2D3D (I own this program and use and I AM a beta tester for their up scale program called Shark FX). Then once you have the feel of that and working with folks on the design side of things, I would look at which controller you plan on using (Mach3, EMC, USBCNC) and get a copy and start reading on the set up and function (yes before you get the machine). Next I would seriously look for CAM program that is within budget and will do what you need (CAMBAM is a good one for 2.5D and there are others). From there you get into the build and the physical learning phase of using the machine and doing. There is a lot of good program to help as well as text books or working with others and learning by experience and finding what works and what doesn't.

I hope this does not turn the temp in the brain pan up to high but better to start on as solid a footing as you can.

Best of Luck and ask as you need to.

Michael

[Rob Wol]

Hi Michael.
Thanks for your reply.
I just see the machine as a learning experience and it will be just used for pleasure really. Therefore accuracy shouldnt be an issue. I won't be using it to make parts that need to be accurate. I will be just making thing things that look good and decorative parts really. As its just a personal project i'll have lots of time to learn the software and hardware and understand how these machines work. Money is not an issue as I see it as a long lasting, on-going thing, although I don't wanna go stupid on the money front. Would prefer to stay in the £100's rather than the £1000's! Got loads of space too. It's the software that worries me the most as I'm no good with computers. So your advice to learn the software before doing anything sounds like a plan. I've touched on CAD and also a CAD/CAM package at college but only very slightly, so if I get the software for myself to play about with and with the help of people on here I can get my head around it!

Thanks Rob.

[Tenson]

I've just started learning this stuff too and need to settle on a CAM package. I had a look at a few, LazyCAM, ArtCAM and Dolphin PartMaker. PartMaker looks good to me because there are lots of tutorials on the site. http://www.dolphincadcamusa.com/cad-...ideo-tutorials

[black5f]

One of the wise people above said, "what do you want to make on it?". A really important question to consider! I'm taking a break from coupling rods and templates for leather and had a go at art? But wish mine was larger ;-)

http://www.flickr.com/photos/4933236...in/photostream

Series of holes cut at different depths with a 60 degree cutter. Software for doing that is free? Lots of things you can do.

Welcome!
Tom