Noob Question - How does my Software know what my machine can do?

[ahlbebuck]

Hi all

This is my first post after lurking here for months! I am ready to start building my CNC machine, but one issue still confuses me. How do I describe my machine geometry to the CAM software. I can imagine that straight XYZ is easy, but my machine will be different.

I will have a horizontal rotary table that is part of my main table that moves in the X direction. My spindle is on a Z axis (normal) that is on a fixed gantry that moves the head in the Y direction.

Perpendicular to, but in the X direction will be another rotary table and lastly, the whole spindle can rotate through 360 degrees. (imagine the spindle able to have a cutter on both ends, flip the spindle and another cutter is used)

Am I being ridiculous, or is this do-able?

regards from sunny South Africa!
Neil

[joecnc2006]

so its a 4 axis machine? any drawings, sounds kinda like a cnc lathe?

Set the peramiters in software.

Joe

[ahlbebuck]

I seem to count 5 axis. XYZ, Z also rotates aroun the X axis (like aircraft propeller) This will be 4th axis and then any of the 2 rotary tables will be the 5 axis - or have I got the whole axis thing cocked up?

I'll try and make a quick sketch of the machine layout. I see it as a milling machine, much like the moving gantry 3d router tables - only with some added abilities and in small, but heavy scale for acurate metal machining.

What CAM packages would suit this type of machine. I'm open as I've never worked with CAM software.

My day to day solid modeling is done in Rhino and Solidworks. I'm a civil engineer - our designs are a bit big to make on CNC machines LOL

As I said, I'm new to this, but the whole CNC "thing" sounds like a wonderful hobby (perhaps more!)

Neil

[joecnc2006]

I also am in the civil engineering and land surveying here in texas, CNC is a hobby now

[awerby]

Originally Posted by ahlbebuck Hi all This is my first post after lurking here for months! I am ready to start building my CNC machine, but one issue still confuses me. How do I describe my machine geometry to the CAM software. I can imagine that straight XYZ is easy, but my machine will be different. I will have a horizontal rotary table that is part of my main table that moves in the X direction. My spindle is on a Z axis (normal) that is on a fixed gantry that moves the head in the Y direction. Perpendicular to, but in the X direction will be another rotary table and lastly, the whole spindle can rotate through 360 degrees. (imagine the spindle able to have a cutter on both ends, flip the spindle and another cutter is used) Am I being ridiculous, or is this do-able? regards from sunny South Africa! Neil

[Everything is pretty standard for a 4-axis machine except for the second rotary table perpendicular to the first one. That one has me confused. Is it moving the whole X-axis stage, rotary table and all? If not, where does the workpiece go? A picture might help. To answer your question, there's usually a part in one's CAM program where one describes the machine, its dimensions, how many axes it has, whether there's a rotary table, what the toolchange command is (that's where you'd rotate your extra spindle rotary) and what post processor to use. What CAM software are you using?]

Andrew Werby
www.computersculpture.com

[ahlbebuck]

I'm sure your civil projects are more exciting than mine. After 20 years of trying to educate the masses on not using the same water for sewer / animals / washing and drinking, I'm ready for a new hobby / income generating pastime.

Neil

[ahlbebuck]

Andrew

Yes, both rotary tables are part of the moving table. Somewhat like a lathe running along the X axis, with a horizontal rotary flush with the table (like a record player)

Workpiece will either be flat on whole table, covering the horizontal rotary for router and engraving work or be mounted on the rotary for 4 axis 3d work or mounted on vertical rotary for lathe type milling / grinding of shafts, etc..

When used with either roatary tables, the whole spindle will also be able to rotate around an X axis, parallel to the Y axis. Eventually I would also like to be able to rotate the spindle around the Z axis in order to grind angled threads / augers with the vertical rotary table.

I'm trying to mock up a sketch quickly.

As I said, I do not have a CAM package yet, so I'm open to suggestions.

I intend this to be a prototyping machine, very accurate for any material up to mild steel. I'm prepared to spend some money on this project.

[ahlbebuck]

Hi

Here's a quick mock-up Hope the attachment works

Neil

[awerby]

Originally Posted by ahlbebuck Andrew Yes, both rotary tables are part of the moving table. Somewhat like a lathe running along the X axis, with a horizontal rotary flush with the table (like a record player) [The X and Y axes should be able to cut circles without the use of a horizontal rotary table. I'd make it simpler, and provide T-slots on the main bed, so that if you decide you really need a horizontal rotary, you can bolt one on at that point.] Workpiece will either be flat on whole table, covering the horizontal rotary for router and engraving work or be mounted on the rotary for 4 axis 3d work or mounted on vertical rotary for lathe type milling / grinding of shafts, etc.. [Grinding is hard on any machine with sliding parts. You might think about building a dedicated grinder if that's a big part of what you want to do, and take extra care in protecting the vulnerable ways and other exposed moving parts.] When used with either roatary tables, the whole spindle will also be able to rotate around an X axis, parallel to the Y axis. Eventually I would also like to be able to rotate the spindle around the Z axis in order to grind angled threads / augers with the vertical rotary table. [Thread-milling can be done without recourse to a horizontal rotary table, if your machine is tight and accurate. I'm trying to picture how the shaft is being held upright - does it go through the table?] I'm trying to mock up a sketch quickly. As I said, I do not have a CAM package yet, so I'm open to suggestions. [Take a look at VisualMill - it's a full-featured CAM program for a reasonable price.] I intend this to be a prototyping machine, very accurate for any material up to mild steel. I'm prepared to spend some money on this project.

[You'd better be. The rigidity required will probably necessitate some big castings; it's not the sort of thing that's usually done with gantry mills, although there are exceptions. (It's hard to tell from your sketch - does the gantry move in X, or is that a moving-table/fixed bridge design?) When you say "very accurate" what were you thinking about? Making a machine that's accurate to .001" would be challenging for most of us; something that can hold .0001" usually takes a pro, with a very well-equipped facility. Even that person would need to spend serious money on precision-ground preloaded ballscrews, etc.]

Andrew
www.computersculpture.com

[ahlbebuck]

Andrew

Its a moving table, fixed bridge. Shafts will be milled horizontally, between the upright rotary and the steady.

Total machine size X travel 24", Y=24", Z=12"max.

Plan to use servos, ballscrews with preloaded nuts, flat linear bearings, cast iron and steel construction, etc.

I was rather hoping on something a little better than 0.001" (0.025mm)!! Had in mind 0.01mm. Did not realise that such accuracy can be so difficult to achieve.

Where would the weak spots be? In the Bridge Y-axis / Z-axis area?

Neil

[oldjohn]

You will need to wright a hell of a postprocessor for thar machine.
John

[Roy...]

By Pre Processor do you mean a step controler?

I'm new at this, My Dabbling in robotics has lead me to build my own crude CNC, I carn't quite get a image from what you have built or have in mind.
I have build a preprocessor of my own design, simply to learn at the grass roots.
The axis you describe are they tied to a cube structure or based on a cone.
I'm thinking cone, like a Arm?

I have got a plan to build such a device just on a small scale, and yes the preprocess is a killer to program to wright, Pythogras is a good place to start if you are keen.

In a nut shell look at robotic software for your controls, Robotic Arms.

I'm keen to find out if its a cone or cube. Roy...