Looking for CNC Mill Part I

[Zoltar]

Hello CNC-Group,

I wonder what I've been doing wrong all this time.......

Since about two years I've been fiddling arround with this hobby,
CNC stuff but I did not see a G-code in sight.......I did learn them once at school a time ago.............

And aslong as I am routing parts 2.5 D I leave the G-code alone and use HPGL.
This is the Hewlett Packard language to talk to their plotters. HPGL contains the 2D coordinates and the other half D is pen up / down (mill up mill down) and pen down.

Its really simple and works in combination with a file optimizer very well!

If you go to 3D, G-code or ISO is the language. As I am testing at
the moment some CNC work on 3D body's now G-code is needed. But still I did not find the need to alter G-code.

2.5 D -> Cad 2D->export to DXF->optimizer conversion to HPGL(Bonc)->PCNC(dos)->milling 2.5D

3 D -> Cad 3d->export to STL/3D dxf ->conversion (deskproto)into ISO/G-code->PCNC(dos)->milling 3D

Bonc is a fine working file-optimizer distributed free over the Web. Whitin this program you can do whatever is needed to prepare a file for routing parts.
PCNC(2,5/3D) is buyware, but at about 100 dollar its more then worth the investment. As this is a DOS program you can use a inexpensive PC
Deskproto is a expensive program, however distributed as a 30 day full working version. Time enough for some 3D experiment.....

Here a pic from a bottle with a simulation of milling paths arround it in Deskproto. The milling paths are written in G-code by the program. The setup takes place in Deskproto.

Greetings to all!

Chris

(www.rcmodels.net)

[crankorgan]

PanzyPoof,
The ICs are 7486. No body else spotted that! You can use the tablesaw to form a GIB or GUIDE. I went for a handmade machine. Feel free to change things. Del is DElrin 1/4" or thicker. You can get the 8ohm 20 watt resistors for the motor at Radio Shack. You can also put two 10ohms in parallel to make a 5ohm 20watt. Let me know what motors you have, current and voltage.

Cranky

[crankorgan]

Zoltar,
PLT files and GCode are both CNC. Feel free to use either. I run my machines in DOS mode. Lots of people want Windows. What ever gets the job done! Over here in the US very few people in CNC know what a PLT file is. They always want the latest even though they have no idea what they are doing.

Cranky

[DICKEYBIRD]

Originally posted by balsaman
I DL'ed Ace Converter but have not tried it yet.

I use Ace exclusively...try it you'll like it! I have drawn a "virtual worktable" in CAD that is exactly the same size as my work space. Once the CAD plan is finished, I copy/paste all the individual sheet parts I decide to CNC cut onto the "worktable" & move them around for best stock utilization. If there's a bunch of parts all cut from the same thickness stock, I glue 3" or 4" wide sheets together to make up 12"x12" blanks. This makes very efficient use of your stock and who cares if a rib or bulkhead has a glueline on it? You do have to watch grain/joint direction however.

Once all the parts are positioned, I assign each part a separate layer in the order that they are to be cut, making sure that any lightening cutouts have their own layer so that they are cut before the part outline is cut so they don't move around on you. Ace allows you to assign each layer a "Priority" number which is the order in which the parts are cut. You then set the Z-depth and release height (where the Z releases to between cuts) I use zero as my cutting depth, having preset the tool to just touch my sacrificial 14" foamboard worktable overlay, and 1/4" release height for most of my stock. You then click the "Convert" button and ZAAAP! You got yourself a beautiful G-Code. Unless I screw up the CAD work, it works EVERY time, and is FREE! (Hee, Hee!)

HTH,
Milton

[balsaman]

Ok, looking at ace converter I see it does a much better job doing the conversion then Kcam. I used Ace to convert a test drawing and used Kcam to view the resulting Gcode. The Gcode file looks good. Very useful program. Looking at the Gcode file I start to see how Gcode works. I can follow the colored lines based on the Gcode, altho I am not ready to write anything using just Gcode. I see that G01 is a straight cut move G00 is a straight tool up move, and G03 is an arc and the numbers following those are the coordinates that the moves end up at.

Where does tool offset come into play? Do I need to do that at the CAD stage? ie. draw the drawing with the offset built in? Is there a way to tell the software to do it automatically? Also, some tool offsets would need to be on the outside of a part, and others on the inside (eg. for weight relief).

Thanks again.

Oh and I forgot to include DICKEYBIRD and Zoltar whan I said thanks for sharing all your experience.

Eric

www.e-zflight.com

[crankorgan]

balsaman,
G00 calls up the fastest speed of your mill is set to in the software. This is where you can loose steps. If you jog your mill at 14 inches per minute you might not see a missed step. Putting F6 in the GCode will slow the mill to 6 inches per minute during cutting. But when a G00 comes along the mill jumps back to 14" for one move. G00s are put in when you convert from DXF to GCode. They are when the cutter moves to a new location. I change all G00 to G01. Some CNC programs run full out unless you put F numbers in the GCode.

Cranky

[DICKEYBIRD]

Originally posted by balsaman
Where does tool offset come into play? Do I need to do that at the CAD stage? ie. draw the drawing with the offset built in? Is there a way to tell the software to do it automatically?

My MaxNC control software doesn't support tool diameter compensation so I draw in the CNC path on a separate layer & color that's offset 1/2 the tool dia. to the inside or outside of the finished part as required.

I'm pretty sure that all tool dia. compensation is a feature included in the actual software that controls your machine, some do, some don't depending on the $$$. The actual command to activate it is added into your G-Code. Call me crazy but I get some kind of perverse pleasure from drawing it in myself. Of course if I decide to change the tool dia., I'd have to redraw all the paths again.

[crankorgan]

DICKEYBIRD,
Your not crazy! Being able to add amounts to a drawing in your head while you draw keeps your mind active. In programs like Kcam you can rescale a drawing. This can be used to make the part larger or smaller. For circuit boards, I figured out how big to make the pads and traces. The tool provides the width between the traces. I also draw the path so the tool goes around and overlaps where it starts. This get rid of nasty little burr shorts. Doing something the hard way usually has a reward somewhere.
Cranky

[balsaman]

Originally posted by crankorgan
balsaman,
G00 calls up the fastest speed of your mill is set to in the software. This is where you can loose steps. If you jog your mill at 14 inches per minute you might not see a missed step. Putting F6 in the GCode will slow the mill to 6 inches per minute during cutting. But when a G00 comes along the mill jumps back to 14" for one move. G00s are put in when you convert from DXF to GCode. They are when the cutter moves to a new location. I change all G00 to G01. Some CNC programs run full out unless you put F numbers in the GCode.

Cranky

So just set the max speed and the cut speed to a low enough number so it won't miss steps regardless of whether its cutting or jogging. Lots to learn. What would we do without the ezone!

Eric

www.e-zflight.com

[crankorgan]

balsaman,
In the software there is a Ramp Up and Ramp Down setting. This slowly starts and stops the motor. If this is set wrong you can also loose steps even if you run slow. Running a mill under Windows does not work well with the cheaper software. I won't name names. Drop Windows to DOS level and use TurboCNC for a starter. For $20 it works very well. There is also a conference for it! TurboCad-ACE-TurboCNC is a very cheap easy way to go. TurboCAD is FREE and so is ACE. TurboCNC asks for a $20 fee. It costs about $200 to complete a small CNC system for cutting wood parts. It would be nice to have a simple CAD-CAM program for cutting out parts. Mabe someday! I like this conference, there is no one here hawking their motor controllers and software.

Cranky

[balsaman]

Hey Cranky thanks for the Turbo CNC tip. I dl'ed it and it looks great! My laptop I am going to use is just a 486 so the Dos TurboCNC will be perfect! I was worried about whether the laptop would run the windows software. I think I will use Ace to convert, Kcam to get the WYSIWYG view of the resulting Gcode, and when all looks good, use TurboCNC to control the mill.

Now I just gotta build the darn thing. Got a lot of the tough parts made. I need to make room on my bench and start cutting some MDF.

Here are the bearing blocks and threaded nuts I made.

[crankorgan]

balsaman,
Looking good! You must have a good saw. I have a three wheel Black & Decker bandsaw with a dull blade in it a table saw that is a joke. My favorite tool is a Delta scrollsaw. The other tool I use is a bench mounted belt sander. I rebuilt my sears AA109 lathe, but so far I have had no use for it. I own a $89 drill press that the chuck come off if I put a large bit in it. Most of my parts are handmade. The rest are hardware store hardware. Not having or using expensive tools paid off!!! I found simple easy ways to make expensive CNC machines. What would NORM say? I like laying out a part and filing and sanding it in! I find it very relaxing.

Cranky

[balsaman]

The little lips you see on the parts was on the scraps of delrin I found at work, so I left them there. I just needed to cut them out and drill, tap etc. with a drill press. Your tools sound like my tools! I have nothing fancy. I do have access to a full machine shop and licenced machinists who love to help me at work. I like to make as many parts as I can myself as I don't like to keep asking them to make simple parts for me. I will have one of them make the threaded rod parts for me and some aluminum disks for the free end that I will make into manual cranks for the axis'. My design will use that 1/2-10 ACME rod which I will get turned down on the ends for motor couplings and disk/crank handles. I am very lucky to have access to the machine shop for the fancier parts. I know Cranky that they are not required for a mill, and that you have worked hard to make a design to be built with regular tools. Since I have access to the shop, I may as well use it.

Eric

[Zoltar]

Hello you all,

Personally I feel for 2.5D jobs, as we are mostly doing, why make it more complicated as the PLT languages can do the job without a problem, without having to learn G-Codes?

Are you using in the US -G-codes- only programs to drive your machines?

Greetingz

Chris

[balsaman]

So...does my driver board from Stepperworld.com understand a plt file? Do I just downlaod a HP plotter driver or how does it work? I could not find Bonc on the net...do you have a link?

Eric