My 3-axis foam milling machine

[Rhino3Master]

Hi guys , this is my first CNC build and I just finished it yesterday (still trying to learn the Mach3 software). I don't know if I post in the proper section as my 3-axis CNC-machine is specially designed for foam art with milling cutter. However, I'm going to upgrade it with bolt-on removable hot wire that will attach to the Z-axis gantry and act like a vertical hot wire cutter through YZ-axis and XZ-axis (it will be able to rotate manually by 90 degrees around Z-axis). This should make it something like a hybrid CNC to meet my requirements.

First, I would like to thank Ahren Johnson (ahren) who was kind enough to collect and send me the necessary parts from USA as they were not available here, nor I was able to purchase them through Internet. He also completed the wiring of the stepper motors and provided me with some helpful advices about the initial setup. I greatly appreciate his help and recommend him to anyone who is going to build its own CNC-machine.

I will need some help with configuring my limit/home switches properly , so I will describe my problem at the bottom of my post. Any suggestions from you guys are welcome as I tried everything and still can't solve the problem by myself.

Now some words about my build. I almost rejected it several months ago after I had a serious injure on the right arm (electric shock and temporary immobilized arm caused by accidentally broken electric cable of chinese mobile lamp), plus sinusitis and duodenal ulcer that came one after another. Luckily, I was blessed to restore my arm in short period and finish my CNC build more than half year after I started the planning and 3d design. This also added lots of unexpected expenses to my build (mainly the rent of my workshop that I was not able to use for that period). But the life would be deadly dull if we always know what will happen in the future. Anyway...

The working area of my CNC-milling machine is 1400 x 1050 x 550 mm (x/y/z) and I chose that size because the local stores sell foam blocks of 1000 x 600 x 500 mm; couple of these glued together are just slightly smaller than the max cutting area of my machine - 1200 x 1000 x 500 mm.

The gantry itself is made entirely from general purpose square and rectangular steel profiles, because I was not able to locate good aluminum extrusions in my country (actually I found few companies but their products were extremely over-prized). Although it's heavier than the aluminum analogues (roughly 280-300 kg without the parts), it's very strong and my NEMA34 640 oz-in stepper motors handle it quite well. I think I made it too strong for a foam cutter, but I always prefer to be double safe.

Speaking about the motors, my original plan was to couple them with 4 custom made lead screws and Polyamide /PA6 + MoS2/ backflash nuts (two sets for the Y-axis and one for X- and Z-axis). There were some problems with taking them from a local custom shop on schedule, so later I decided to use static chain design where both chain ends are screw-adjustable for precision control of the tension force. Since the X- and Y-axis chains are not movable (only the Z-axis uses closed chain and small tensioner gear) and lays directly on the rails, there is virtually zero backflash; not to mention the cheap maintenance cost in comparison with the lead screw design I originally planned.

The Z-axis weights nearly 8.5 kg including the spindle motor, so I added an off-board counterweight of 7.4 kg (simple steel block) through 1.5 mm thick "mountain bike" steel wire inside a spring wire shield (I don't know if this is the correct English term for this stuff). This is definitely better than the on-board counterweight designs used in some DIY CNC-machines, because the weight is transferred outside the moving gantry and also eliminates the inertial forces.

In general:
* Working area = 1400 x 1050 x 550 mm
* Total weight = approximately 300-320 kg
* Total cost = over 6.000 Euro (incl. rent)
* Time to build (incl. my unexpected "pause") ~ 7.5 months
* Gantry type: 3-axis, driven by chain and cogwheels
* NEMA34 640 oz-in stepper motors
* Keling S-350-48 power supply & Geckodrive G540 motor drive
* USB Gamepad for manual jog

Below is a simple diagram showing the difference between the on-board and off-board counterweight, plus a comparison between the open and closed chain designs. I still don't have photos and videos of my completed CNC-machine, but I will post a few once I get touch to my GF's camera. However, I also attach some pictures of the 3d model of my CNC.

http://img199.imageshack.us/img199/1...nterweight.png
http://img3.imageshack.us/img3/1319/chainsystem.png

http://img3.imageshack.us/img3/1750/cncgantry14.png
http://img269.imageshack.us/img269/6...drivingbox.png
http://img193.imageshack.us/img193/5055/cncgantry9.png
http://img269.imageshack.us/img269/5395/cncgantry11.png
http://img193.imageshack.us/img193/5998/cncgantry13.png



With regards to my problem... I have installed the G540 XML file at the Mach3 file folder and it was quite easy to learn the setup of the other things after watching the official Mach3 video tutorials, but I'm a bit confused with the step-by-step configuring of the limit/home switches and also setting the working coordinates (max travel) of my gantry. Everything was just perfect until I touched the REF ALL HOME button . Then either my home/limit switches "forget" their location after I restart Mach 3 or even refuse to act like switches and I was forced to press the E-stop quickly to prevent a potential damage of my gantry.
The most serious problem is that my Y-axis is not working properly, because my Y and A motors (A is set slave to Y) don't move together after I press REF ALL HOME (they always move one at a time). They are perfectly synchronized when I jog them manually or press the GOTO Z button, but seems that the REF ALL HOME button makes some hidden changes in the settings that I still can't figure out...

Here are my current settings:

http://img99.imageshack.us/img99/311...enshot2354.png
http://img199.imageshack.us/img199/2...enshot2355.png
http://img198.imageshack.us/img198/8...enshot2356.png
http://img5.imageshack.us/img5/2203/screenshot2357.png
http://img99.imageshack.us/img99/965...enshot2358.png
http://img99.imageshack.us/img99/112...enshot2359.png
http://img3.imageshack.us/img3/1585/screenshot2360.png
http://img99.imageshack.us/img99/300...enshot2361.png
http://img3.imageshack.us/img3/733/screenshot2362r.png
(below: test of my switches - when pressed, they all work at the Diagnostics page)
http://img200.imageshack.us/img200/7...enshot2363.png
http://img99.imageshack.us/img99/360...enshot2369.png
http://img99.imageshack.us/img99/485...enshot2370.png
http://img99.imageshack.us/img99/849...enshot2371.png
http://img200.imageshack.us/img200/9...enshot2372.png
http://img99.imageshack.us/img99/646...enshot2373.png
(below: Auto LimitOverRide activated)
http://img245.imageshack.us/img245/6...enshot2374.png
(below: when I press Machine Coord's the Z-axis value changes to 29 and so... ,I can't fix that)
http://img8.imageshack.us/img8/9610/screenshot2375.png

I'm still green in this field, so I really don't know how to set the software limits from the Soft Limits button, also don't know what's the purpose of the other buttons there (OFFLINE and To Go). Only GOTO Z is easy to understand and works without any undesired results.

I also have some other questions:

- When activate GOTO Z, the Z-axis moves to home position AFTER X- and Y-axis. Is there any way to move the Z-axis to the home (top) position first?

- How to speed-up/slow down the cutting speed (movement)? Maybe by pressing the FEED RATE + and - ???

- How to add a keyboard shortcut to some specific commands?

- How to activate Mach3's hardware (USB gamepad) functionality? Currently I use a keyboard emulator called "JoyToKey".


I add a simple diagram of my setup because sometimes a single picture says thousands of words:
http://img7.imageshack.us/img7/8245/setupfi.png

Here is Gechodrive G50's documentation showing a basic wiring setup:
http://img245.imageshack.us/img245/7...enshot2376.png
http://img269.imageshack.us/img269/8...enshot2377.png

Thanks!

[Rhino3Master]

Oops, I almost forgot - here is a 3d file (Rhino4 *.3dm and SolidWorks *.IGES) with accurate 3d NURBS models of NEMA34 640 oz-in stepper motor together with Lovejoy spider coupling that I have measured and modeled from my existing parts. The 3d scene is set to millimeters and the IGES file can be imported into SolidWorks and many other CAD programs...

[Rhino3Master]

Well, I finally did the proper settings at the Mach3 and my new CNC-baby works just as expected The software limits of the program made my day; I had so many problems with the settings of the hardware switches in the last few days... I also have 3 working separate (hardware) home switches for each axis.
The effective working area/travel of my gantry/ is actually 1065 x 1400 x 580 mm It was 1050 x 1400 x 550 mm before I move the limit switches a bit further to the end of the rails. I even can increase the X-axis up to 1200 mm if I relocate the switches, but I won't bother for this thing.

Tomorrow I will try to generate my own G-gode and see what will happen. Here is a photo of the machine, although it still needs some protection pipes for the cables and wooden working table (and cleaning up of the workshop as there are too many tools and garbage anywhere ):

[biggerbigben]

Wow! What a nice setup you have, have you been able to sort the problem and test it? That is exactly the sort of thing that I need to build! If you had your time again would you go for ali instead of steel though?

Any more pics of the finished item?

Ben

[rcpilot82]

Cool!

[Rhino3Master]

Hi guys, thank you for the comments! I have solved the problem 3 weeks ago and my CNC-milling machine already carved several foam pieces for car plugs. Too bad that the official video setup of Mach3 was not done more user-friendly.
The 580 mm Z travel is a great advantage as it saves me a lot of time by "eating" big portions of foam at once . The big foam blocks also saves money, because they are 10% cheaper than the same volume of thin foam sheets attached together, not to mention that I won't need to buy too much of the expensive polyurethane liquid foam to stick pieces together.
The spindle's 110 mm long steel base is able to drill up to 150 mm deep holes (with min diameter of 36 mm) when using my 40 mm long milling tool.
I also ordered a custom made milling tool that will allow me to go even deeper and reach up to 450 mm deep holes which is enough for any car part.

[biggerbigben]

Hi chap.. I sent you a PM yesterday but no idea if it worked. Would you be prepared to sell me the plans to your home made cnc?

Let me know,

Thanks
Ben

[Rhino3Master]

I received my new milling tool for roughing, 35 mm long and 50 mm diameter. There is some minor rust here and there, but I will remove it later. It works well with 500 RPM; my spindle can handle up to 33.000 RPM but I don't need more than 500 for foam cutting with this diameter and 12 cutting edges. However, I will use my 15 mm and 8 mm milling cutters set at 1000-2000 RPM for the finishing because the big one can't go into narrow areas.
http://img682.imageshack.us/img682/1...zerche50mm.png