CAD/CAM Machine tools

[MKi12]

Hello everyone. I am just wondering what the relationship is between the controllers we use to control Machine tools and CAD/CAM? I am very new to the field .

 

[mcgyvr]

CAD = a software program that creates a graphical 3d model (or 2D)
CAM = takes that graphical model and creates the program to send to machine tools/CNC centers,etc.. This program includes the tools needed and the paths they need to move in. This is typically G-Code or other similar numerical control file

https://en.wikipedia.org/wiki/Numerical_control

 

[MKi12]

Thank you Mcgyvr, are there any other ways to program CNC machines other than the CAD?

 

[mcgyvr]

ironic that I'm currently reading an article about how many Engineers have no concept of how parts are actually made and how sadly that education is not taught in college at all.
DFM (design for manufacturability) has become a big buzz word in the last 10 years and it makes me sick when I hear it..
The day I design a part and don't have a 99%+ grasp on exactly how its going to be manufactured and the problems that may be encountered is the day I need to retire. To me that has always been an Engineers job from the start.. But I guess thats a benefit of working for a small company where there isn't another manufacturing team taking it from design to manufacturing and many times back to design again.. I'm a 1 stop shop and damn glad about it..

 

[mcgyvr]

Thank you Mcgyvr, are there any other ways to program CNC machines other than the CAD?

Sure.. By hand sitting down and creating the code from scratch either in a computer or directly at the machines terminal..

Our CNC operator (just passed away a last year) would take my 2d drawings and create the program line for line on his computer in a text editor..
Just before he passed I got a proper CAM package hoping he would learn it to save on programming time..
We had a race.. What took him 5-6 hours to program by hand took me about 6 minutes in my CAD/CAM program.

So basically you need to know where the tool paths need to be.. Working directly from a 3D model is the BEST way to do that

 

[MKi12]

Thank you mcgyvr. can we talk a bit about the available approaches to control the machine tools ? I know there are different ways such manual, CNC and PLC that are used in industry. how to choose between them? Do you know any other approaches apart from these 3?

 

[mcgyvr]

Besides manual control everything else is "computer/electrically controlled" in one form or another.

Could be as simple as mechanical relay control all the way up to complex computer systems..
The machine may incorporate a PLC for some aspects of it but also may have its own dedicated machine controller utilizing microprocessors,etc.. or a system of controllers all communicating together
VFD's may be used for spindle/motor control and everything from servo motors to stepper motors each with their own controller..
pneumatics/hydraulics,etc..

You choose based on the needs/required functionality of the machine.

 

[MKi12]

Thank you again mcgyvr. do you know what situations and needs require incorporating a PLC? so Generally speaking, one can divide the way to control machine tools into two methods, manual and computer controlled? what else can we add to this if someone wants to generally know what we control machine tools? thank you for your help dude.

 

[BillPSU]

You also need to know what tooling is required to do the job and depends on what type of programming you are doing.

Machining: Roughing end mills, finishing end mills, reach problems using long length end mills, material issues cast austenitic stainless versus aluminum, ETD 150, hardness of part requiring ceramic machining, deep hole drilling with through the spindle coolant or coolant inducer, fast spiral polished flute taps for aluminum, reaming allowance, back spot facers, screw machine length drills, jobber length drills,
taper length drills, extended length drill, cutter compensation, climb cutting versus conventional cutting, grinding allowance, heat treatment shrink or growth, reaming and roller burnishing, cutting taps versus cold forming taps, spiral point tap, taper tap, bottoming tap, interrupted thread tap, honing allowance, live tooling on a CNC lathe.

Punching: clearance between punch and die, louver punch and die, tonnage limitation, high shear punch, bevel angle for plasma cutting, cut direction differences with plasma, piercing issues with plasma or laser, following error of slides,

Turning: Limiting max spindle speed, decreasing pitch threads.

These are some of the issues I have faced in my career. CNC programming can be very challenging depending on what you are doing. Understanding what you are making and knowing what tools to use is the most important skills.

Good Luck
Bill

 

[MKi12]

Thank you Bill, It is always great to learn from someone who actually uses these systems. if one asks how a machine tool is controlled,.. how would you answer that?

 

[MKi12]

Bill, do you know when or under what conditions and circumstances operators normally include PLCs in their control schemes when control machine tools?

 

[BillPSU]

All CNC equipment have PLC's doing the mundane things on machine tools. Turning pumps on, monitoring limit switches, cycling way lube, ball screw lube, indexing turrets many functions to many to mention. Most of these are not controlled by the operator but by the machine tool builder. If fixtures have auxiliary functions then usually a PLC is utilized to activate the functions. We have welding fixtures which have PLC controlled clamping which are sequenced and clamped and unclamped under control. We actually have material handling robots which move the part from fixture to fixture. These are programmed by our weld tech's with help from a electrical engineer. The average operator on a welding robot usually loads parts into fixtures and follow step by step processes prior to launching the welding robot and adding parts as required during the welding process. Automation requires a certain level of production where it is economically feasible to justify the expense.

You've got a lot to learn and hopefully you have some good mentors at your company. I happened to work for a company making parts with tight tolerances and parts for military applications with some high volumes. Never quit reading and gaining knowledge. Learn from the tool makers and machine operators what works best and be open to suggestions.

Good Luck
Bill

 

[MKi12]

Thank you Bill. I thought some machine tools can reply on CNC to achieve effective control performance without the need to incorporate PLCs?
Can the CNC deliver the functions such as Turning pumps on, monitoring limit switches etc without the need for PLC?

 

[berkshire]

Within CNC commands functions like turning pumps on and of are sometimes handled by M codes. A lot depends on the builder of the machine.
B.E.

You are judged not by what you know, but by what you can do.

 

[BillPSU]

Typically the control manufacturer is not the machine tool manufacturer. An example is Fanuc controls are used on many different configuration machine tools and the primary interface to machine is the servo drives and auxiliary systems. The servo drives are glorified PLC's and the auxiliary systems are PLC's. PLC's are a necessity due to the amount of computing required and response time and the amount of power required to drive these subsystems. Spindle drives can be in excess of several 100 horsepower for a large lathe vertical boring mill. Designing machining systems are mostly modular and sized for the necessary requirements. I do not envision any machining system except for some very small systems eliminating the use of PLC for the above reasons.

Bill