Newb needs some guidance.

[Biff]

I'm starting to look into making a router table. I've been looking at a few sites, namely buildyourcnc.com to see what goes into it. I feel I have the mechanics down at least as a whole though I'm sure there are some finer points I'm not yet aware of. I will most likely change his design to suit, and not use much (if any) MDF, instead use BB ply, steel and aluminum to make it more rigid.

The electronics/control side of it still has me a bit baffled. As I understand it I use autoCAD and save the file as a DXF, use another program to convert that to g-code then use (mach3 for instance) to use that g-code to control the operation.

Question 1.) What exactly am I drawing in CAD? The path I want the router to take? If so then do I use the z axis in the drawing to define the cut depth?

Question 2.) What if I need to change to a different bit? How is that represented on the drawing?

For the actual control as I understand it the computer communicates with a breakout board to pass commands onto the steppers. I've looked at the one linked to on buildyourcnc.com as well as others and there seems to be quite a variation. They all seem to have the same type of control, i.e. x-step and x-direction, etc. but the pinouts of one board doesn't always match a different board.

Question 3.) Do I need to manually change the wires in the parallel cable or can I define the pinouts in the software? Or is there a certain standard I need to adhere to?

Question 4.) Is there an advantage in having a separate breakout board and motor drivers or is an all-in-one board o.k.?

I know I have a lot more reading to do and you've probably answered these questions a hundred times for newbs but I'm hoping you guys can narrow down for me what I should be concentrating on.

Thanks for any help in advance!
Ryan

[Jesse B]

Originally Posted by Biff Question 1.) What exactly am I drawing in CAD? The path I want the router to take? If so then do I use the z axis in the drawing to define the cut depth? You just draw the piece that you would like made, and the g-code interpreter will take care of the rest. Model an object how you would normally. Question 2.) What if I need to change to a different bit? How is that represented on the drawing? I'm not 100% sure, but I'd assume there are options in the g-code software that will deal with that. Question 3.) Do I need to manually change the wires in the parallel cable or can I define the pinouts in the software? Or is there a certain standard I need to adhere to? http://pminmo.com/PMinMOwiki/index.p...warepinout.png That shows the role of each pin. Note that most control software will let you change the pin-out if your Break-out Board does not match said pin-out. Question 4.) Is there an advantage in having a separate breakout board and motor drivers or is an all-in-one board o.k.? While it does take up a bit more space, I prefer the modular approach. If you have an all-in-one controller, and one of the drivers goes bad, it's difficult to repair. If you're going modular, you can remove the faulty driver to repair, and the rest will not be affected. You can also run different drivers using this method, allowing you to use a multitude of different motors.

Answered the best I could in red. Hope I was helpful


- Jesse

[CarveOne]

Tool changes are defined as part of the gcode generation process. You will define the cutter sizes as Tool 1. Tool 2, etc. Each tool number is a specific size and/or type of cutter. You will need to manually adjust the cutter length to the correct height during the tool change before resuming the program. Automatic tool changers can do all of this for you in a production environment. Most home built machines don't have these, though some folks just gotta have one anyway.

CarveOne

[Biff]

hanks for the feedback!

I've been thinking for the electronics I'll probably just get a kit. I've seen the G540 mentioned many times so I'm assuming it's a popular and well accepted controller. At least that way I'll get a system known to work well together than spend a lot of time and effort to 'hopefully' get something that works well together to save maybe a $100 or so. For instance something like this.

Originally Posted by Jesse B You just draw the piece that you would like made, and the g-code interpreter will take care of the rest. Model an object how you would normally.

Geez that sounds almost too good to be true but I'm not sure if it clears any fog. Most of the stuff I design I use 3d solids modeling, but if I was drawing say a PCB I'd probably draw in 2d. Can the code interpret either? Sorry probably getting way ahead of myself here.

Originally Posted by CarveOne Tool changes are defined as part of the gcode generation process. You will define the cutter sizes as Tool 1. Tool 2, etc. Each tool number is a specific size and/or type of cutter. You will need to manually adjust the cutter length to the correct height during the tool change before resuming the program. Automatic tool changers can do all of this for you in a production environment. Most home built machines don't have these, though some folks just gotta have one anyway. CarveOne

It'll be manual bit changes, I'm just a hobbyist and not production. I'll have to play with this sort of thing when I get it up and running I guess. I'm just trying to avoid building the machine and then realizing I should have built it a different way or used different equipment because I don't have a feature I want. I'd rather be looking at, then looking for it.

Another newb question - I see 4 axis kits available. I can't think of what that 4th axis would be for. The only thing I can guess at is tilting the cutting head, but if you were going to do that wouldn't you want a 5 axis to be able to tilt the head in 2 directions?

Thanks again,
Ryan

[revwarguy]

Youre right! The 4th axis is (sometimes) to tilt the cutting head on one plane. Other axis can be to tile the cutting head on other planes.

However, there really isn't a standard for this - something becoming popular is to have a rotary table set up as the 4th axis - e.g., you put a long piece of wood in a setup that is very much like a lathe, but the wood material is rotated under the cutting head by a CNC stepper motor, and the cutter moves up and down and across the piece to carve up columns, etc.

[Jesse B]

Originally Posted by Biff Geez that sounds almost too good to be true but I'm not sure if it clears any fog. Most of the stuff I design I use 3d solids modeling, but if I was drawing say a PCB I'd probably draw in 2d. Can the code interpret either? Sorry probably getting way ahead of myself here.

As long as you export the file in the proper format, it does all the work for you I know *.DXF works for sure, but I'm not sure of what others do, but I'm fairly certain there are more.

As for PCBs, you obviously just design then in 2d. If you use Eagle (freesoft PCB layout and schematic software), there's a very easy-to-use plug-in available called PCB G-Code, which will automatically create the G-Code for isolation routing the PCB. You just set up the preferences, and it does the rest.

Originally Posted by Biff Another newb question - I see 4 axis kits available. I can't think of what that 4th axis would be for. The only thing I can guess at is tilting the cutting head, but if you were going to do that wouldn't you want a 5 axis to be able to tilt the head in 2 directions?

The 4th axis can do whatever you want it to! Most often I find it's used as a rotary table, so that you can rotate your piece and get true 3D objects. most 3-Axis routers are referred to as "2.5D", just because they can't get the back side of the object, not quite making them 3D. You can mount your piece in a 4th axis, similar to a lathe, that will rotate the stock, allowing you to get the top and the bottom. You can also rotate the cutting tool like you mentioned. Really it's just down to what you need it for, and you can run as many axes as needed, doing whatever you require of them.


- Jesse