Wanting to build my first CNC machine...

eagletalontim

So, as the title says, I have been interested in building my own CNC machine, but have quite a few questions before I even get started. Basically to start things off.... What I will be cutting will mostly be either rubber (up to 1/2" thick), thin plastic (1/16" to 1/8"), and possibly some 1/32" tin if budget allows. What I am unsure of is where to find a cheap or free software / program to create 1D CNC plots? I am also unsure about the controllers for stepper motors. How do you connect a computer to a controller and it know how to control it correctly? I have seen some DIY stepper controllers, but how is a computer going to "print" to it? I figured there would be some drivers that need to be installed to correctly control the stepper motors. Last but not least, since I will be cutting up to 1/2" thick rubber, I am sure a router is not going to work due to friction of a bit. Any ideas on what I could use?

W9GFO

You need a program to draw your part first, in at least 2D, 1D would just be a line. There are many choices. SketchUp is free and easy to use, but anything that exports to DXF is good.

Then you need to convert the dxf into G-Code. Ace Converter is a free program that does, Mach 3 has the ability built into it.

Mach 3 is a popular choice for software to control the CNC, it will run 1000 lines of G-Code in demo mode but it is not expensive to buy the full version. TurboCNC is a free DOS based program that works well too.

Both Mach 3 and TurboCNC communicate with the stepper drivers via the parallel port. I have found Xylotex drives to work very well.

eagletalontim

So basically, there is not a free or cheap program that has all that built into one system? If I can get this built and working correctly, I would probably bring it up to my work where we hand cut gaskets out of all types of materials. The CNC would basically replaced alot of our hand cut gaskets and hopefully speed up production time. What about the cutting part of the CNC? I have heard of a saw blade type, but I can't seem to find a motor that can connect to a CNC?

W9GFO

There might be an all-in-one software solution, but I am not familiar with it.

The ways I know of to cut gaskets using a CNC;

Rotary tool - typical CNC router. Don't know how it would work with soft rubber - need to clamp material to work table.
Knife - a vinyl knife that rotates freely in it's holder to follow the cutting path. For thin materials only.
Laser - won't cut metal unless very high power ~ 400 watts to start for CO2, others very expensive.
Water Jet - cuts anything but very expensive.
CMC - CNC controlled matt cuter. Similar to the vinyl knife but the cutting blade is turned to follow the path by a fourth axis - about 3mm max thickness.

Except for the fact that it cannot cut tin, I think a laser would work the best. It has the considerable advantage that you do not need to worry about how to hold the material to the work table, and some lasers do come with all-in-one software.

T Chap

Rubber is sold in different durometers(basically a factor of how rigid it is). If the rubber is rigid enough, you could easily cut it with a plastic router bit. Look up Micro100, they sell cnc mills and have a plastic router in .125" and ,25", the model number starts with SFP ( single flute plastic ). If the rubber was thinner and flexible, you would need to rig up a hold down part that sat on top of the rubber while it was getting cut. For example, get some 1/4" Delrin, create the gasket shape in it, have some holes in the Delrin so it can mate with the base, put some bolts into the Delrin hold down part through the gasket into to the base. This way the hold down part puts pressure on the entire rubber sheet while it is getting cut. This method requires a bit more work as you have to create the base with tapped holes for the hold down to mount to, plus it needs some index marks or holes to re-align the end mill with. For thin rubber you could also try a 1/8' engraving end mill, which has a sharp point, also sold at Micro100. I use Mach3 and really like it. I have not seen a one software does all, maybe it exists. I use Bobcad for the CAD drawings and gcode output, but it is not free. I recommend Gecko drives, you can connect directly with a parallel port to the drives, then to the bipolar steppers. This requires configuration of port pins in the Mach3. Building stepper drivers can be done, but can also eat up a lot of time if things don't go smoothly. I recommend in the beginning stages to try to find as much ready made stuff as possible to get up and running right away, then work backwards from there if you want to get deeper into each aspect.

eagletalontim

Thanks for the info on the router bits. That is the way I want to go so I only have to go with a 3 axis setup and i don't have to buy extremely expensive parts just to cut the material. At the shop, there are several different things that are cut besides rubber, but rubber seems to be the hardest to keep from melting and binding when under a bit. I experimented with a simple dremel tool and a side cutting bit that was 1/8" in diameter. The rubber was able to be cut, but it constantly binding and melting pretty bad. I figure a thinner bit would be better since it would be cutting less surface area. The durometer of most of the rubber is ~60. Some is 40 which is the gum rubber. Other materials that we cut are basically like very thick paper or thin wood. The dremel does cut it, but it wants to walk to one side based on the direction of the blade rotation.

I have tinkered with Google Sketchup, but I have noticed that the circles are not quite circles. When you zoom into it, there are straight lines with edges to make up the circles. Some of the gaskets we cut need to be within 1/32" to fit inside pump seals. With straight lines, it may not work. Is there a way to change that?

W9GFO

Yes, in SketchUp, when you choose the circle tool you can type in a number that will be the number of segments in a circle. Same for the arc tool. A good rule of thumb for smooth circles is 1 segment per mm of circumference.

icepuck

some good info worth reading...
http://www.sherline.com/
http://www.sherline.com/emc/index.html
-dan

T Chap

If you have a tool that is cutting nicely, but you have a melting problem, just keep spraying at the tool while it is cutting. Some materials require constant temp control, a spray bottle would be the easiest. Another idea to hold down thin rubber is double sided adhesive. I just did a test with an engraving end mill that Micro100 makes. .125" soft rubber. I cut this in 2 passes, so it cut half way down first, then break it out on the second pass.

eagletalontim

Another question I have is how to tell the cutting device what depth to cut at? It would need to know the material thickness and the max depth it should go, but how is that determined from a drawing? I still have not been able to find how to change the number of segments in Sketchup

JasonDorie

Look into software like CamBam, or Cut2D. I started with Cut2D and was quite happy with it. CamBam has a free version that's a little older. Basically you use these programs to bring in a 2D drawing (or create it within them) and then tell them how you want to cut the drawing : on the line, inside or outside the lines, how large your bit is, what depth to cut to, how deep to cut per pass, how fast to move the bit, and so on. Those programs output GCode which you then load into a program like Mach3 (what I use) or EMC (free, linux based).

Mach3 / EMC actually interpret the GCode and control the machine. When setting up EMC or Mach3, you tell it how many steps each motor needs to move one inch, what your maximum speed is, which ports the various motors are connected to, and so on.

W9GFO

eagletalontim wrote: »

I still have not been able to find how to change the number of segments in Sketchup

Click on the circle tool. Type in a number. Hit enter. Proceed with drawing the circle.

Another question I have is how to tell the cutting device what depth to cut at? It would need to know the material thickness and the max depth it should go, but how is that determined from a drawing?:(

When you convert the drawing to G code you will enter the thickness of material, size of cutter and depth of pass.

You can also write the G code by hand, For simple shapes it is not at all difficult.

eagletalontim

Writing my own G-Code sounds interesting. I have been having some troubles figuring out a few things still. I have downloaded the CamBam software and have been tinkering with it. One thing I have found that would be hard to generate quickly for a waiting customer would be a standard round gasket with say 8 bolt holes in the face. Getting the bolt holes lined up correctly would be pretty difficult. I could get the bolt hole centers lined up easily, but not the distance apart. I guess I have a lot of learning to do!

One more question... The rod that the stepper motors drive to move the cutter around.... what is that called and where would be a good place to get some of those?

Edit * Figured out what the rods are. Lead Screws Now trying to find a good inexpensive vendor for them ..... any suggestions are welcome!

T Chap

Mcmaster.com precision lead screw is a cheap way to go, for a small machine 1/4" 16 tpi acme threads is fine, nema 23 bipolar is great for a bench top type machine.

Dumpstercnc.com is a good source of cheap antibacklash nuts. He makes some for 1/4" 16 acme.

eagletalontim

The dimensions I am wanting to go with are 6ft wide X 6ft long X 18in tall. The largest material that they get in at the shop are 60" X 120". Sometimes a gasket will span the entire width. Others that go over that have to be dove tailed together. I am hoping to build as much as I can from scrap parts I have along with cheaper and easier things to find at my local hardware store. I do have a welder which makes things a little easier

Brian_B

eagletalontim,
I have been experimenting with a gasket cutter myself ,I hacked apart a craft paper cutting maching for the paper ones. I use bobcad to draw with and have one lathe running mach3 and have a 23 year old milltronics mill that i have been disecting since I bought it and really want the gasket cutter propeller controlled.

The milltronics mill has one 80286 controlling the gcode-parser and displaying vga and watching inputs, it also has 3 8031 microcontrollers (one for each axis) controlling the movments. I have been convinced for sometime that the propeller could do the same job and more being that new drives only require step and direction to move.

I am thinking of starting a new thread for and open sorce propeller cnc controller ( I've seen a couple of 3d printer threads ,but they seem to run amuck after awhile),and like Ken Gracey says ,coolant,coolant and coolant (everything cuts better with coolant)


Brian

Jorge P

Don't forget about Caligari TrueSpace , it is currently free as of about 3 years ago. It has the following Import formats:

• BVH animation and motion capture
• DXF format (full layer support) compatibility
• 3D Formats: SCN, COB, SOB, WRL 1.0, GZ, WRZ, DXF, 3DS, ASC, PRJ, LWO, OBJ, LWB, IOB, GEO, STL
• 2D formats: BMP, TGA, AVI, FLC, JPG, DIB, AI, PS, EPS, PNG, DDS

And the following Export formats.

• Direct export to Virtual Earth (workspace)
• Improved X format (workspace)
• BVH animation and motion capture
• 3D formats: SCN, COB, CAN, WRL 1.0 & 2.0, DXF, ASC, 3DS, STL
• 2D formats: • BMP, TGA, AVI, JPG, TIFF, PNG, PSD

I've used it in the past and it can be quite intimidating for a new user, there are several helpful videos on their website. If I remember correctly, i think there are plugins that allow direct communication to an external device like a CNC machine. I could be wrong about that... I haven't used for quite some time now.

http://www.caligari.com