Author Topic: Side note on terminology  (Read 2530 times)

Offline Wade@WEBFoot

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Side note on terminology
« on: September 11, 2014, 02:23:32 PM »
Thought Id mention this, as its something that kind of creates some confusion when trying to answer questions, and in many cases, it adds some confusion and requires more questions before one can answer.

CNC - Stands for Computer Numeric Control.  You can have just about anything CNC - CNC sewing machines, Lathes, vacuum cleaners (iRobot) etc...  heck... a printer is CNC as is a laser engraver.  So, keep in mind that a CNC is only a method of control.

A Mill - the spindle turns the tool, and the tool cuts on stationary material (as in not spinning).  A router is also in the same family.  One would use a mill or router to do things like cutting sound boards, engravings, making pockets (like in a box call), drilling patters, and making non-cylindrical parts.  Generally the hobby machines are referred to as "CNC Mills" and when you get to the professional/industrial machines, they will usually be called Vertical Machining Centers (VMC's).

A Lathe - well, you know what a wood lathe does... the tool is stationary and the spindle spins the material.  With a CNC lathe, its usually based on the premise of a metal lathe.  The difference from a wood lathe most are familiar with is quite big.  Even if you leave out the computer control part, they are different.  With a wood lathe, you hold the tool, and can position the tool how ever you want as youre using it.  On a metal lathe (and CNC), the tool is hard mounted to the machine, and can not be repositioned while in use.  The tool moves in two axi (Z - towards and away from the face spindle axially, aka length, and X which is towards and away from the spindle radially, aka diameter) but you cant rotate the tool to get into a little nook or cranny - its hard mounted.  So each feature has to be either planned around the tooling, or add tooling to come at one feature in multiple ways to make it possible.  Generally the hobby machines again are referred to as "CNC Lathes", but in contrast, so are the professional/industrial machines... but youll also find the industrial machines referred to as Turning Centers.

So in the process of "CNC'ing" an entire AR or RF style duck call (at least as far as Im familiar with them)you would use both a CNC Lathe and a CNC Mill.  The CNC lathe would turn the parts, both barrel and keg (insert).  The CNC mill would cut the sound board.

Of course there are always exceptions to the rule... and ingenuity is the only limiting factor. ( I know guys that make calls on a CNC mill - its a slower process but completely doable).  But generally speaking - to make an entire call, yould need both.

Also, a common misconception is that a 'CNC' is something you stick a piece of material in, press a button, and magically have a call.  Which is not true.   You have to tell the machine specifically what to do, when, the order, how fast, etc...  So just like any other computer - Garbage in, Garbage out.  One of the ways I look at it is...  A VMC and CNC Lathe is to a call maker - as - a Computer and printer is to an Author.  Nothing happens without someone at the controls.  One can create unique works of art or mass produce something of their own design/idea with them or they can plagiarize another and put their name on it.  So, like so many other things... its the "man behind the curtain".  I know not everyone thinks its magic... but without knowing more about it, it can sure look that way.  SO I thought Id mention that for those that dont know anything about it.

Hope that give you a little more info on the types of machines. 

Cheers
Wade


 

   
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Offline Gary Campbell

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Re: Side note on terminology
« Reply #1 on: September 11, 2014, 09:05:21 PM »
Wade...
Extremely well done!.  I wholeheartedly agree with all the points that you made and want to especially commend you on the last paragraph concerning the "common misconception".  IF you don't mind, I would like to take this a step or two farther.

Possibly the largest number of CNC machines in the US are flat bed routers, aka "Router Tables" or "CNC Routers".  Operationally they are similar to a 3 axis mill, but are usually much lighter in design and have a fixed table with a moving carriage or gantry with a cutting head attached.  Cutting action is provided by a common handheld Router or a "Spindle", which in this case is a 3 phase high frequency, high rpm (18-24000 or more) motor with a collet system for tool holding.  The higher rpm is desired for wood, plastic and will work on non ferrous metals.  They come commercially in sizes from about a foot square cutting area up to 8' by 24' in various price and quality ranges.  The 5 major producers have sold over 25,000 units, with minors adding another 10,000 and it is estimated that DIY machine numbers equal that of the commercial.

Most of the commercial brands offer an optional 4th axis.  As you might expect, they also vary in size and power.  What they are is an indexing axis.  Simply a CNC version of an index plate or shaft similar to what is often on a wood lathe.  But instead of 5 or 10 or 15 degree increments they are usually capable of 1/10th degree movement.  What they are not is a lathe, especially as Wade accurately describes them above.  Motion is provided in most cases by a stepper motor, which by design will not spin independently at true "turning" rpms to allow lathe type cutting.

They will, depending on design software capabilities allow the user to cut or machine virtually anything that can be accomplished on a 4 axis machine with the 4th axis perpendicular to the Z (cutting axis).  Design software ranges from a few hundred to mid 4 figures, depending on desired capabilities.  The 3 companies that I have contacts in have sold over 3000 combined 4th axis options.  The CNC forums are loaded with on line pics of their results.  Many are much more complex than the projects most would desire to do.  Like Wade says, there is no one button press or magic,  it takes a little learning.

The machines (CNC Routers) operating systems have evolved to the point where they are very easy to learn. Most manufacturers have training classes that cover machine operation, design, toolpath strategy and machine setup.  These 2-3 day classes go a long way towards getting a new user up and running with a new and totally foreign machine.  They are not, however, any more than a start in the right direction.  Like learning to play an instrument, you must spend time to become proficient.  Below is an excerpt from one of my classes concerning the effort required to gain proficiency:

The following is a timeline of average usage hours to attain noticeable skill levels:
Machine operation: 40 hrs - adequate, 100 hrs - good, 200 hrs - very good
2.5D CAD/CAM: 100 hrs - adequate, 200 hrs - good, 3-400 hrs - very good
High end specialty softwares (cabinet, graphic, machining, 3D modeling & design) 3-400 hrs - good, 1000 hrs -very good

As you can see, there is no easy button, but it is a very rewarding craft, and has allowed many that have put in the time to elevate both their skill and product levels to a much higher level than could be attained without CNC.
« Last Edit: September 11, 2014, 09:08:40 PM by Gary Campbell »
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Offline Steel Rain Calls

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Re: Side note on terminology
« Reply #2 on: September 12, 2014, 08:13:02 AM »
I know this is very technical but I am very interested in learning how to properly set-up and operate both types. I find it very very interesting
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Offline Wade@WEBFoot

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Re: Side note on terminology
« Reply #3 on: September 17, 2014, 06:44:13 PM »
Gonna try posting in smaller blurbs.
Reply was written on 9/12/14

Part 1
Probably the best thing to do, to get an idea of things, is to download the free version of Mach3 (I think it still exists - may be a newer version now?)
Anyway, its a windows based controller for actually running a machine, but it should still run in a training or demo mode...  then start reading the manual for it.  That will get you the jist of things.

THere are books on programming, and work holding/fixturing, and so on out there too - though I only got one book on programming, and it didnt help me at all as it was basically for a Fanuc control, and at the time I had an Okuma which is much different.  So it was little help.  I ended up teaching myself Gcode going straight from the manual that came with the Okuma lathe.  From there, I hand wrote all of my programs.
TBC...
« Last Edit: September 18, 2014, 05:17:53 PM by Wade@WEBFoot »
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Offline Wade@WEBFoot

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Re: Side note on terminology
« Reply #4 on: September 18, 2014, 05:18:22 PM »
Part 2

Keep in mind, there are some machine specific and control specific differences, and no way to know what they are til you know what machine and what control. (especially if you get into the industrial machines).

Generally speaking... in terms of setup - and this is over simplified, but I think youll find it does hold true...  You just have to do things logically.  The part needs to be firmly held - whether lathe or mill.  But you use different things to accomplish it on each machine.  And in the end - it comes down to (just like call making) money or ingenuity.  The main battle youll have with work holding is physics and clearance. 

High speed rotating objects, centrifugal force can had an affect on things.... including the chuck - especially lathe chucks.

Vises or hold down clamps... the machine needs to be able to clear them or drama ensues.
TBC...
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Offline Wade@WEBFoot

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Re: Side note on terminology
« Reply #5 on: September 18, 2014, 05:19:36 PM »
Part 3
In terms of programming - you have to command everything... from coolant on and off, spindle on after a tool change, offsets so the control know where the tool is and its diameter, movements - including the movement to tool change location, where the end of the program is, if its to start over or remain at that point in the program, or automatically repeat, RPMs, feed rates, and on and on.

Id say the one part that will either take the most time, or cost a notable amount, is getting an opject turned into data points, that then can be turned into the geometry of the part to be programmed.  It will either take time, cause youll have to graph it by hand, then covert to the appropriate coordinates, then hand write the program - or it will cost money to get a CAD program, and a CAM program to convert the CAD into code for the machine.
Ive farted with a lot of the free stuff out there over the years and not had much luck.  Especially for 3D stuff for the VMC... maybe things are different now, but a few years ago... the pickings were slim in terms of shareware/freeware and limited at best.

TBC...
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Offline Wade@WEBFoot

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Re: Side note on terminology
« Reply #6 on: September 18, 2014, 05:20:09 PM »
Part 4 - final chunk

Id say the best thing would be to treat it just like you do call making... find a forum or two and or books etc... and start reading, ask some questions, and so forth.  See if Mach3 still has the free demo to play with and just tinker.  Since its not connected to a machine, you cant break anything.  But it too is much like call making... a lot of things are hard to teach without hand on experience or being at a machine, one on one.  Id probably go as far as to say, its probably easier to teach yourself, by yourself from books and manuals, with a working machine in front of you, than it is to have an experienced person try and teach someone who doesnt have a machine at all or machining experience.  (not picking on anyone - just the way I see it, having tried to have someone explain stuff to me prior to having a machine, and then teaching myself from the manual once I got one).

Cheers
Wade

edit - YAY it all made it up.  But it didnt like when I posted part 3 and 4 together so broke those two down.
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Offline Butch1

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Re: Side note on terminology
« Reply #7 on: September 19, 2014, 03:03:31 AM »
Finally back to work after my shoulder surgery and blood clot lots of overtime in the plant  but here's my  :2:. Mach3 is still available it is downloadable for free the user manuals are also available for download. The mach 3 will be fully functional until you install the drivers for the axis motors, at that time it will install a 500 line limit of code per program and limit other functionality such as threading. The license is only 175 to 200$. I have a copy loaded on a laptop (windows 7) that I write my code on and simulate on it if it looks good i load on a thumb drive and then load to a desktop connected to the mill or lathe and dry run it with the spindle off, mach recommends  xp and a desk top to control the tool ..laptops have a different architecture  on their boards which make them slower(higher latency) than desktops according to the linux or emc2 manual another free or open source cnc software but it has a bigger learning curve.Also mach needs a db25 printer port to control the machine. The mach manuals are very informative they will explain the difference between open loop steppers, closed loop feedback servo motors, screw pitch  axis speed  and inertia calculations etc. There is a list of gcodes and mcodes with the rules that apply to them such as g02 and g03 "used to cut arcs" mach has to be within  .0002 2tenthousandths of an inch from the start of the arc to the end  in your code or it will flag a fault. I would recomend anyone interested just load the software and manual read it "many times in my case" write some code run the simulator if all goes well find a machine to connect to it. Cnc zone is a forum and guys there are as eager to help as here  , it's late another 12 hr day tommorow maybe Wade or Garry will add to this I will try to add to this later .

Offline Gary Campbell

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Re: Side note on terminology
« Reply #8 on: September 22, 2014, 01:34:54 PM »
To add to Wade's post about trials of CNC control software....  All of the PC based controls have a free or trial version that you can "try before you buy".  This applies to LinuxCNC, ShopBot, Mach and WinCNC.  OF course there are price variations for working versions, and as you might expect, you get what you pay for, so it is a good idea to look them all over.  In each case, the hardware requirements are different, and at different costs.  Each of these control brands have a very supportive user base that can provide assistance when you need it.  WinCNC and ShopBot have brick and mortar tech support with published phone lines and support email address's for purchasers of their hardware.

Most all of CNC router mfgr's offer training pertinent to their machines operation.  At CAMaster (my day job) we offer a 2 day class that covers machine operation, maintenance, bit selection, toolpath strategies and numerous hold down methods.  One day of this is taught by myself and our tech support ace.  The second day is taught by a rep from one of the major CAD/CAM suites covering design on 2D, 3D and rotary (4th axis) along with machining strategies for each.  CAD/CAM has developed to the point where todays new users will seldom, if ever, have to actually input any GCode from the keyboard.  Of course, the ones that can will have an advantage, but the cost of going back to the CAM module with new parameters is nowhere near the time penalty it was a decade ago.
« Last Edit: September 22, 2014, 01:36:27 PM by Gary Campbell »
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