CNC Machine

[killdog]

Rite i have been wanting to make a Cnc Machine for along time but have no idea how to make one and everytime i look at ideas design and plans on cnc machines i get lost ( even tho i do product design Lol) So i was wondering would u guys be willing to help me as i go along and make this Mini Cnc machine becuz if i make this U are all getting Personal name tags for ur Keys Lol.

[treemty]

ok,. first off, you  will need to know how to program it,
then parts wise, you will need either metal or wood, as well as power tools such as a dremel or a different rotary tool, 3 stepper motors, a whole separate computer devoted to this cnc, this whole project will cost you a few $100

[killdog]

well i have a eee pc 900 that has student ds v2 and photoshop cs3 already so that should be ok programming may be a prob i never done it and get confuzed easy

[Jumbo]

You need a PC with a serial port.

Photoshop has NOTHING to do with CNC's....

ndrew is selling a kit in the Actions section for ~$500 comes with about everything including driver boards.

You might want to do more research on this though...

[Alien_X]

Everyone in this thread, desist from posting unless you know what you are talking about!

ok,. first off, you  will need to know how to program it,
then parts wise, you will need either metal or wood, as well as power tools such as a dremel or a different rotary tool, 3 stepper motors, a whole separate computer devoted to this cnc, this whole project will cost you a few $100

Since when do you need to hand code Gcode files with hobbyist cnc machines?
The rest of your information is either wrong or too vague.
Message to the OP - ignore the quoted post!

well i have a eee pc 900 that has student ds v2 and photoshop cs3 already so that should be ok programming may be a prob i never done it and get confuzed easy

You won't be able to use either of those.

You need a PC with a serial port.

Photoshop has NOTHING to do with CNC's....

ndrew is selling a kit in the Actions section for ~$500 comes with about everything including driver boards.

You might want to do more research on this though...

I haven't come across a single stepper driver pcb or CNC driversoftware which interfaces with the serial port, again get your facts straight it is a parallel port.

Ndrew's kit isn't really good for anything apart from the electronics section of the CNc build (The easiest part). The buildyourcnc machine had enormous amounts of flex due to its design (If it had a torsion box then I would be saying the complete opposite).

I am currently building (And have been for several months) a small cnc router, it is based off of the Rockcliff plans with a few modifications, it has run me upto about £400 - 600 so far, without the electronics and that is minus the software. The rockcliff design is good, however you do need a fair amount of tools and woodworking skill to build it (If you build it sloppy then it will cut sloppy).

The main thing you should think about is your choice of leadscrew and spindle. If either of those are bad then your whole machine will be a massive paperweight.

I also suggest you do alot more research (enough to realise that both Treemty and Jumbo do not have a clue about what they are saying) before you begin building. I have also been designing a bigger CNC machine for when I have finished my smaller one (4 X 2 foot cutting area):



(this machine has been since redesigned, but i don't have an up to date image).

[5th-axis]

This is a pretty involved process. To program the machine you will need a programming software package. I use Surfcam Velocity III. This is a full 5 axis software that costs $15,000. You can get the 3 axis version for much cheaper. There is also cheaper software. BobCAD/Cam is way cheaper and by all accounts works ok. You can also program without software but it is time consuming and the  more complex designs will be next to impossible to do. Now on to building the machine. A standard manual machine has standard leadscrews. A CNC machine has ball screws which are way more accurate. The positioning accuracy is handled with encoders or scales. The scale is the most accurate, although some machines use both and they need to be within a few counts of each other or the machine will throw an alarm. These machine use the Cartesian coordinate system to locate, and you can also throw in polar coordinates as well. You also need a spindle. I have seen home made machines that use a Dremel for the spindle. Keep in mind that this will work, but heavy cuts will not be possible due to the dremels low torque out put. They do have plenty of rpm though. Check out CNCzone.com. Those guys do all kinds of things, even pic programming for their stepper boards and everything. Look in the Controller & Computer Solutions forum. They also have a machine building forum too. You can do this, it will take time though. Study G and M code too. Good luck and welcome to the wonderful world of machining.

[5th-axis]

I like the gantry design Alien. That looks sweet. What software are you using to model in? Have you seen the design where the individual used an old plotter for his platform. It worked, but was obviously not rigid. I also like the linear rail setup. That will be extremely smooth. We retrofitted a grinder to the linear rail system and it was super smooth. Good work!

[Alien_X]

Hi

Thanks alot! I modelled it in solidworks, I have since redesigned it so that the X (long) axis rails are overhead, this should make it alot more stable with less flex. I also plan to dual drive it with Tr16 multistart leadscrews which should give it lots of power as well.
All of the critical pieces in my redesign are smaller than 330mmX 330mm so they can be milled on my current machine.
I also included a routed groove to help align the rails parallel, and the linear motion is (as you can see) a mix of skate bearings + ali angle and linear slides - my budget could only allow for one set of "proper" slides.

Are you a machinist?

[5th-axis]

Yes I am a machinist. I am currently working in motorsports where we are doing some multi axis stuff (cylinder heads etc) as well as various other pcs. Hooray for Solidworks! That is one powerful software package. I usually end up modeling everything in Surfcam though. I like the layers better than the design tree in Solidworks. Your design looks solid and keep up the good work.

[802Chives]

wow, Alien_X glad you came in here when u did nah, photoshop does have something to do with CNC if you use Vectors to make jewels like what most people are familiar with around here.

Parralel or usb or whatever, all depends on what you get/build. Looks like you guys clarified pretty well what is involved but if anyone knows me I must add my 2 cents

As with Most things, A CNC can be broken into 3 sections: Mechanical, Electrical, and Software.

Mechanical: as alien said, this is everything and it is the hardest part. this includes the XY table using some sort of linear type bearings to keep things square and true.   Usually ground rods are what one would use for the rails for the table to travel on, but all depends on how tight you want it to be. Z axis that is manual or automated may or may not be done the same way that the x and y axis are done.  Lead screws and lead nut are the next big issue cuz they will have to sourced according to your resolution requirements.  The motors need to be carefully selected with motor drive electronix, the motors need to be spec'd for torque exceeding what you want to cut, so err on the side of more is better since torque calculations suck to do. And with all that you have to keep very tight tolerances and make things very square.

Electronix: this is what drives the motor and interfaces with the PC. Should have provisons for an Emergency stop, and limit switches to prevent damaging your table.  It will consist of a power supply and drive electronix for the motors.  there are plenty of other features that are uselfull to have as well, like overcurrent shutdown if you accidentally take too deep a cut or run your cutter into your vice.  When sourcing drivers make sure you know what you are going to use for Interface software and that they are compatible.

Software: CAD, CAM and Interface software will round out what one needs in order to produce the files needed and run the drivers.  Interface software is something that should be chosen with your electronix in mind, or better yet they are known to be compatible.(Some interface software uses a card in one of your computer slots in addition to the drive electronix) The interface software is what reads the G-code and sends the appropriate signals to the drivers.  CAD and CAM programs can be one in the same, or two seperate programs in fact CAM and interface programs may be one in the same too, IDK if they exist or even if that is the norm. CAD is Computer Aided Drawing that will produce usually .dxf or step files that are then used by the CAM program (Computer Aided Manufacturing) in order to produce the G-code. 

There is one other note I want to touch on and that is there are several motor types that people use in CNC machines.  A unipolar stepper motor seems to be the most popular, but be aware there are other types of motors that will do the job, like bipolar steppers, and even DC motors. Obviously the type of motor has a huge effect on type of driver you will get.

I have never built my own CNC, but I am familiar with how they work, and I use a small 3-axis one on a regular basis.  So I wont be too much help on specifics, like Alien and 5th-Axis might be, but I can always take a look and tell you what I think

[5th-axis]

Good breakdown 802Chives. We could go even further with metrology and kinematics but I belive that is beyond the scope of this post. As far as software goes, I use Surfcam Velocity III which has the Cad/Cam integrated. I can do solid modeling and full 5 axis simultaneous machining. Alien modeled his drawing on Solidworks, which is extremely powerful software. It can do assemblies and animation and FEA with the right CosmosWorks plugins. I dont think Solidworks has a CAM package. I could be wrong. Alien can probably clarify this. The .dxf extension is referring to Autocad, which is highly popular in the CAD business. Each developer has their own extensions usually. Their is a standard called .iges or .igs. If Alien wanted me to machine a surface for him, he could save his file as a .iges file. I could then open it up on my pc and carry out the necessary operations. But not all software will open up another companies extension. What gets me is the cost of software. BobCad/cam i think is around $800.00. My Surfcam is around 15,000. The last I heard, Unigraphics is around 40 or 50 grand. That sounds crazy to me, but an IT guy told me that and it could have been a corporate wide license.
 Again, good post 802Chives

[Alien_X]

There is a cam package for Solidworks called SolidCam - it is very nice to be able to calculate everything from within the standard Solidworks interface + it works out all the machining depths automatically!

Just a little info about emergency tops - while Electronics packages should have provisions for emergency stop, they generally don't - The requirements of an emergency stop (in the hobbyist community) are to shut down the spindle (Hardware) and alert mach 3 (software) that an emergency stop has been carried out (usually through the use of an input pin and an NC switch). Whilst it would be desirable to have the motors cut out via hardware during an Emergency Stop, this cannot be done as shutting off the power while the motors are running causes damage to the drivers (So the motors have to be controlled via Mach 3's software Emergency Stop).

Stepper motors (The decent ones) are usually wired in either unipolar or bipolar, and I have never heard of a plain DC motor being used on a CNC machine (at least at hobbyist level), only servos.

[802Chives]

Home made cnc router without stepper motor(with dc motors)
didnt watch the whole thing, however I think he made a "suedo servo" using a dc motor with an encoder.  Eitherway I thinks whoever made that vid is a bit of an evil genious.

Thanks for the kudos 5th-axis, I could talk cnc and machining all day long.  Your right about the kinematics being the hardest thing involved, torques and speeds and pitches are not a lot of fun and most of the time involve a lot of handwaving at the hobby level.  That stuff is best left to whoever puts together a kit that you buy with the lead screw and lead nut prematched to whatever resolution you are looking for.

.dxf is pretty universal, I dont use autoCAD at all yet I always use .dxf for my most basic mechanical needs, whether it be PCB design or CNC programming.  It stands for Drawing eXchange Format and I am not familiar with any mainstream CAD programs that dont recognize it.  It does however lack some pretty crucial detail information like depths in the form of a third dimension that make it unpractical in a higher level CNC manufacturing environment.

The art of building a CNC and the Art of running one also vary quite immensly.  There is the concept of speeds and feeds that must be understood just like when using a manual mill (RPMs and FPS all depend on material and cutter spec's)

There is so much to talk about with CNCs it would be difficult to sum up with a couple long winded posts  

Alien: in you vast research on the topic of hobby CNC mills, what CAD/CAM packages did you notice as being popular and reletively inexpensive <$200?

[Alien_X]

Hehe "vast"   

There are quite a few decent packages around for roughly that price - cut2d, cambam, sheetcam, cut3d - and one other, which I can't quite remember the name of! - possibly artcam

[5th-axis]

CNCZone.com has many software forums. Give it a look when you get the chance. 802Chives, I could talk machining all day long too. It is an extremely rewarding craft to learn. Im also glad  you mentioned speeds and feeds. There are so many facets to machining it never gets boring. I wish I could post up pictures of some of my work, but Im afraid I would get in a little hot water. We all know how secretive motorsports can be. I am working on an idea for my old Sixaxis controller I can post up when it is completed. That shouldnt get me in trouble! And also, I think Artcam is a Del-Cam product and is more expensive than 200.00. Our software dealer showed us a sample piece. It was a portrait of lady. When held up to the light, you could see light pass through the material (Delrin), and it gave it a 3D look. It would be awesome for the guys doing the 360 case mods.

[Hazer]

OT: You can cut power to the motor with an E-STOP, you just need to cut the drive enable signal first, and then a timed cut to the motor power. This way the drive can brake the motor just before power is removed.

NFPA 70E Category 1 Emergency Stop.

Well beyond the scope of this project, but info is free.