Let's Make Robots!

Mechnical engineering plotter .

So here is the thing.

On september I got on my local technical university (http://www.tuc.gr) on the department of product and managment engieneering 

this one may look like a more of managment school but its not , you actually get the diploma of a mechanical engineer and 

a product manager .But  this samester I had this course about linear sketching of mechanical engineered objects and we had to 

do the sketches by hand but this was so boring .So I had an idea for the next course of this one .My idea is to build a plotter 

but not a usual one . This one will get an stl file and generate gcode but still not a usual one .Different gcode generators generate gcode on many different ways but I need to do it on a very specific way .

When the programm that will work on the plotter gets the stl file I want the gcode generated in different chunks of gcode.

For example first do the outer lines of the object with a specific pencil when you are done stop and wait till the user changes 

the pencil.Then continue on the unseen levels lines ,then on the sizes lines and numbers of each side ,then on the helping for the sizes lines , then on the cuts and the thing goes on .I have a book that says how you have to draw everything ,with what pencil, what thickness and stuff like this .

And then have the plotter to draw the sketch for you .

So the question is how the f**k im going to do this one ,yes I have the idea but not sure how to do it .

So if anyone can help or has any suggestions im all ears .

Thanx for your time anyway .


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You are describing a something that is done very, very often. Your different pens and pencils are just "tools" and you simply need to make your machine do a "tool change".

I would suggest looking at Mach3 as a control system and CamBam as your cam software. Both are free with trial periods/ limits.

You run your STl into CamBam, tell the sofware what line goes to what tool, how fast you want it drawn, etc. then hit "make G-code" and it will spit out your G-code (complete with tool changes).

When this code is run on Mach3, it will do whatever it is set-up to do. You can have it stop and wait for you, you can change the "bit" and have it auto-zero before it keeps going, you could even build an auto-changer and then include a tool-change macro in Mach to switch between pens.


The thing is are the helping axes,lines  I will use on the sketch be printed too?Does the gcode generator even counts them as lines or not ?

Different cam software works in different ways. If nothing else, when you are laying out your "cut" in the cam software, you simply tell it not to "cut" (draw) whatever lines you don't want it to draw.

I would say your biggest issue now is hardware. We can talk about cam software all day, but if no steppers are stepping...

Ok here is what i have at the moment.

I have 4 unipolar stepper motor from rscomponents  bought them on ebay on a bargain .

Their actuall model number is : 332-947 , 7,5 degrees step angle 12v dc 4 phase stepper motor size 1 .

Yes they may smaller for what I want them to do ,but check them out and tell me.

I also have an arduino duemilanove on which I can propably run the firmware for the gcode .

I have a big red button ,safety switch maybe (what a pencil can do to you?nothing just sayin).

I have lots of  nust and bolts many sizes .

I can find wood plates, to use them as the base of the machine ,easily.

I also have some alumunium foils.

Tools now .


I have a dremmel 300, a jigsaw , 2-3 drills and bit for the drills many of them ,

my weller soldering iron ,my hot glue gun,my 3d printer doesnt counts since its out of order at the moment .

I also have a small place that its full of wrenches and all sorts and kind of tools havent check on what exactly  I keep in there .

So thats what I have at the moment .



Alrighty, once you have the G-code, you are going to need to get it to your machine somehow. Now, Mach3 does this, and you can also set-up an Arduino to recieve G-code via Serial (the arduino running GRBL or 3d printer firmware). However, mach3 uses a parallel port connection and a parallel port breakout board, where as your arduino will use a USB serial connection and some kind of "g-code feeder" --probably written in Processing or VB or the like.

The issue you are going to run into (either way, Mach or Arduino) is that they are all set up to use bipolar steppers and drivers. Basically, your steppers will not work. I mean, I suppose you could get them to work, but it is going to be a mess trying to do so.

Mach 3, all the 3d printers, Arduino and GRBL, they all use Step/Dir style drivers, not the "4-pin and common" steppers you have now.

I would look at proper steppers, probably an all-in-one driver board (parallel port and drivers all on one board), Mach3 to run the thing, LM12UU bearings and 12mm rods for glides and XL belts for drive.

Steppers are good, a little small, but will probably work.

The parallel board is also good, but you would need to add drivers to it. I have used these all-in-ones and they work really well.


This is the same parallel port breakout you are showing, but also has 4 3A stepper drivers attached. Don't get the one I am showing, it is just an example --there are cheapers ones out there. Also, be sure to get a board one-axis-more than you need. If you have a 3-axix machine, buy a 4 axis board. This way you can blow a driver and the whole board is not dead (you have an extra).

Bearings are what you want, but look around --they have the same bearing with a big aluminum block around it that is drilled and tapped --might be easier for mounting. Also, look at other machines --you may not need a full 12mm rod for all your axis, you may want to go with 8mm or 10mm. I dunno.

There is nothing wrong with those belts, but you are probably going to get the drill rod you need from McMaster Carr --they have your belts too, and every differernt size you could need. I would get your rods and belts from McMaster.