Newbie Questions

[bryanrabb]

Humm, where to start? I guess I have 3 main questions. Let me start with where I want to go, and then I'll ask for some help getting there. I want a wood cnc router. Preferably 24 x 36 min. I have no CNC experience, yet, but I learn fast. I would like opinions on plans that are available rated by: 1) is it worth building, 2) are the plans worth it 3) would you make any changes or build it again.

Also, I have seen a lot of components that are available in liberty tool and Grainger. The problem I see is how to control the motors without building and boards, etc. (this area scares me off). I don't want to spend a fortune, I don't think it makes sense to build something you could buy at the same price. I am so ready to pull the trigger on this thing and could really use a mentor (or two, or three) in the Charlotte area.

Many thanks,

Bryan

[Ed_R]

Check the Xylotex three-axis kit . IT comes with the motors, board, power supply all for $345 bucks or so. And the 269-ounce motors are about as big as you can put on the xylotex board without getting into voltage issues.

[bryanrabb]

would that size motor be sufficient to use on a 24 x 36 table and a PC router? Also, one point I have yet to wrap my head around is how to set the tool? How does the software know where the tool is? In other words, when I put a new bit in, how to I let the software know what bit, etc. And how to you position the wood relative to the head?

[Ed_R]

Yeah, I think the kit will power a 24X36 table. I hope so, I'm running a 17X24 table with the same board and smaller motors
The tooling offsets and bit cpompensations and whatnot will be set in the CAM program you choose to use to help you write the G-Code. When you use the CAM program, you tell the program what bit you want to use and whether it's a standard cut ( bit rotation into the workpiece ) or a climb cut ( bit rotation out of the workpiece ) and where you want the tool to go, etc. It's a bit of fun let me tell you. TJHe challenge are many- you get to build a machine, then you get to learn how to draw in #-d programs, then you get to learn to use a CAM program, then you get to put it all together and do it all over again because of what your experience the first time taught you.
I'm looking forward to this process.

[ger21]

I'm not going to point you to any plans, but most people will tell you, especially on there first machine, that they'd do things differently. If you read enough posts here you'll see that almost everyone builds a "learning" machine, then gets the urge to build a better one. Faster, stronger, maybe bigger. Use the first one as a learning experience.

Like Ed says, the Xylotex, as well as the HobbyCNC drives, are you're best bet for good motor drives when you're on a budget.

As for how does the software know where the tool is? You tell it! There are a couple different ways. You can manually jog the machine into position, and zero the axis at that point. You can install home switches so the machine can zero itself. So you don't have to mount your wood relative to the router, you can set your router relative to the workpiece. Or you can use jigs or fixtures and do it the other way around. There are plenty of options. Start reading.

[bryanrabb]

Thanks. I have done a bit a reading, but it has mostly been on the mechanical side. I figured you could jog it into position. I have a Kongsberg 66 x 117 Cad table at work. It cuts out corrugated boxes and displays. I am very familiar with CAD design, etc. But the software we use is a seamless, and I have no visability of the G code. I was fired up when I found this website. Thanks for all the hard work.

[spalm]

Bryan, welcome to the Zone.

There is a lot to learn. I’ll try to have a whack at some of your questions. If you are talking a wooden based machine, I think I see where you are headed. The motors and motor controllers mentioned above are your best bet. These will be strong enough, and enough quality to last you through your adventure. You may be able to buy the motors a little bit cheaper through eBay, but that is an adventure in itself. Your call, but we can help if you want. Always ask before you buy. 24” X 40” or so seems like a good size to me; not too little and not too big.

As far as how does it all work? Like Gerry said, you position the router over your work piece (by jogging, which means using the arrow keys on your keyboard which spins the motors and moves the router) and then set this to be zero. Then press GO, and the machine does the rest.

This is really like printing, and is a three step process (although it is hidden from you sometimes). You create a source document in Word, Photoshop, Excel, etc. (this is the CAD program). Now you send it to the Print Driver where you select the paper size, rotation, color, margins, print preview, etc. (this is the CAM program). The output of this is Postscript or PCL, etc. which is sent to the printer (this is the CNC machine that you are building).

Remember that the printer has a processor in it that converts this final set of commands into paper movement and head motion commands. In our case, most of us use an old PC to convert our final set of commands (called G-code) into motor movement commands.

Good luck,
Steve

[bryanrabb]

Thanks Steve. I am going to build a wooden base machine like hacks, using 80/20. Knowing that it could easily be a POS if I am not accurate. (Not saying Hacks plans are a POS at all) I think that I will have a vendor burn the pieces out of maple on a laser used for corrugated cutting dies. That way everything is accurate. Should I be concerned about using ply v/s melamine or MDF? I know it is not as stable, but is should be more solid and accurate. I think.

[spalm]

Do you mean solid maple? The short answer is no. I can point you to many posts here warning against using solid woods. I have built several pieces of furniture and built-ins using solid wood. It is beautiful stuff to work with, but not here. Man-made compositions will work much better for machine design (Ply or MDF). If you are going with Hack’s design, the 80/20 will do most of the work for you. The only place I see as a potential problem is the gantry walls. These could easily be strengthened with vertical stiffeners if you see a problem when you are finished.

Some testing I have done has shown that MDF with thick plastic laminate glued on both sides yields a very strong structure. The melamine coated boards at the local Home Depot are not nearly as flex resistant.

Again, if you are going with Hack’s design, go with his design. The wood parts are the cheapest and easy to replace if for some reason you don’t like them.

Just a thought,
Steve

[bryanrabb]

Steve,
I am going to use 3/4 maple ply. It is the same wood we use for steel rule cutting dies. It has to be better than MDF. I thought about reinforcing the gantry walls with fiberglass. I don't know if it would help or not. I am mainly using maple because my die maker has it on hand and can burn it on the laser in about 10 minutes max. I am going to use Hack's design verbatim, I don't feel like reinventing the wheel right now. Thanks

[ger21]

Plywood will most likely start to warp before you even get a chance to assemble it, while MDF has a much better chance of remaining flat. Depends a little on the quality of the plywood, but just about all plywood will warp at least a little.

[jdholbrook]

While on the subject of Hack's design and the gantry walls.
Hack's design calls for 11.5 x 22.5" gantry walls.
I am contemplating using aluminum sheet in 3/8" thickness with some 1/2" braces.
Does anyone feel that is a bad idea?

Thanks