CNC Machining and Precision Lathe Machining
You are being redirected to http://www.milspec-mfg.com.au, if the page does not load after 5 seconds Click Here Many of Milspec’s key activities require CNC Machining and Precision Lathe Machining :
We do:
- Precision Machining and Engeneering
- CNC Machining and Precision Lathe Machining of Mild Steel and
- Stainless Steel
- Brass and Aluminium
- Titanium and most forms of Plastics
CNC precision machining on the Milspec Mitsui Seiki multi-tool and multi-task machine.
So what is CNC and what does CNC stand for?
The abbreviation CNC stands for Computer Numerical Control, and refers specifically to a computer "controller" that reads G-code instructions and drives the machine tool, a powered mechanical device typically used to fabricate metal components by the selective removal of metal. CNC does numerically directed interpolation of a cutting tool in the work envelope of a machine. The operating parameters of the CNC can be altered via software loaded programs.
A short History of CNC
NC was developed in the late 1940s and early 1950s. NC (Numerically Controlled) machines, which were hard wired and their operating parameters could not be changed. The first CNC systems used NC style hardware, and the computer was used for the tool compensation calculations and sometimes for editing.
Punched tape continued to be used as a medium for transferring G-codes into the controller for many decades after 1950, until it was eventually superseded by RS232 cables, floppy disks, and finally standard computer network cables. The files containing the G-codes to be interpreted by the controller are usually saved under the .NC extension. Most shops have their own saving format that matches their certification requirements.
The introduction of CNC machines radically changed the manufacturing industry. Curves are as easy to cut as straight lines, complex 3-D structures are relatively easy to produce, and the number of machining steps that required human action and assistance have been dramatically reduced.
With the increased automation of manufacturing processes with CNC machining, considerable improvements in consistency and quality have been achieved. CNC automation reduced the frequency of errors and provided CNC operators with time to perform additional tasks. CNC automation also allows for more flexibility in the way parts are held in the manufacturing process and the time required to change the machine to produce different components.
Just like the domestic scanners and copiers (they are small CNC machines) the larger CNC machines have come down in price, allowing for ever increasing new and more complex applications.
In a production environment, a series of CNC machines may be combined into one station, commonly called a "cell", to progressively machine a part requiring several operations.
CNC machines today are controlled directly from files created by CAM software packages, so that a part or assembly can go directly from design to manufacturing without the need of producing a drafted paper drawing of the manufactured component. In a sense, the CNC machines represent a special segment of industrial robot systems, as they are programmable to perform many kinds of operations (within their designed physical limits, like other robotic systems).
CNC machines can run over night and over weekends without operator intervention. Error detection features have been developed, giving CNC machines the ability to call the operator's mobile phone if it detects that a tool has broken. While the machine is awaiting replacement on the tool, it would run other parts it is already loaded with up to that tool and wait for the operator.
The ever changing intelligence of CNC controllers has dramatically increased job shop cell production. Some machines might even make 1000+ parts on a weekend with no operator.
CNC machined aluminium instrument housings ready for conformal treatment in our paint shop.
Types of CNC instructions used
A line in a G-codes file can instruct the machine tool to do one of several things.
Movements
The most basic motion for a controller is to move the machine tool along a linear path from one point to another. Some machine tools can only do this in XY, and have to accept changes in Z separately. Some have two further axes of rotation to control the orientation of the cutter, and can move them simultaneously with the XYZ motion. Lately 4, and 5 axis machines have become popular. The 2 additional axies allow for the work surface or medium to be rotated around X and Y. For example, a 4-axis machine can move the tool head in XY and Z directions, and also rotate the medium around the X or Y axis, similar to a lathe. This is called the A or B axis in most cases.
All motions can be built from linear motions if they are short and there are enough of them. But most controllers can interpolate horizontal circular arcs in XY.
Another aspect of precision CNC machining at Milspec
Tool changes
Originally there would be a G-code instruction telling the machine tool to stop so that a human operator could remove the cutting tool from the chuck and insert a new one. Modern machine tools have a magazine of different tools which they can change themselves pneumatically, hydraulically, and or electromechanically.
Drilling
A tool can be used to drill holes by pecking to let the swarf out. Using a special tapping tool and the ability to control the exact rotational position of the tool with the depth of cut, it can be used to cut screw threads.
Drilling cycles
A drilling cycle is used to repeat drilling or tapping operations on a workpiece. The drilling cycle accepts a list of parameters about the operation, such as depth and feed rate. To begin drilling any number of holes to the specifications configured in the cycle, the only input required is a set of coordinates for hole location. The cycle takes care of depth, feed rate, retraction, and other parameters that appear in more complex cycles. After the holes are completed, the machine is given another command to cancel the cycle, and resumes operation.
An action example of CNC assisted drilling
Parametric programming
A more recent advancement in CNC interpreters is support of logical commands, known as parametric programming. Parametric programs incorporate both G-code and these logical constructs to create a programming language and syntax similar to BASIC.
Various manufacturers refer to parametric programming in brand-specific ways. For instance, Milspec’s Okuma refers to it as User Task 2. The programmer can make if/then/else statements, loops, subprogram calls, perform various arithmetic and manipulate variables to create a large degree of freedom within one program.
An entire product line of different sizes can be programmed using logic and simple math to create and scale an entire range of parts, or create a stock part that can be scaled to any size a customer demands.
Parametric programming also enables custom machining cycles, such as fixture creation and bolt circles. If a user wishes to create additional fixture locations on a work holding device, the machine can be manually guided to the new location and the fixture subroutine called. The machine will then drill and form the patterns required mounting additional vices or clamps at that location.
Parametric programs are also used to shorten long programs with incremental or stepped passes.
A loop can be created with variables for step values and other parameters, and in doing so remove a large amount of repetition in the program body.
Because of these features, a parametric program is more efficient than using CAD/CAM software for large part runs. The brevity of the program allows the CNC programmer to rapidly make performance adjustments to looped commands, and tailor the program to the machine it is running on. Tool wear, breakage, and other system parameters can be accessed and changed directly in the program, allowing extensions and modifications to the functionality of a machine beyond what a manufacturer envisioned.
Examples of machines and tools with CNC variants
Drills, EDM’s, Lathes, Milling machines, Wood routers, Sheet metal works, Hot-wire foam cutters, Plasma cutting, Water jet cutters, Laser cutting, Oxy-fuel cutting, Sheet metal punching, CNC assisted folding and cutting machines.
Milspec and CNC
With the assistance of CNC machining and skilled manual operators Milspec is able to do some outstanding CNC machining, precision lathe machining, milling, punching and folding of complex parts in a large variety of materials.
Can you guess how many CNC machines Milspec has?
Here's the list. 2x Okuma MC-5VA - Vertical Spindle, 4-axis
1x Mitsui Seiki 5B - Horizontal Spindle, 5-axis
1x CNC Lathe Okuma LR-25 Model C-2S x 850
1x Strippit CNC sheet metal punching machine
2x Mazak CNC sheet metal punching machines
2x Comatel and a Megabol CNC assisted folding presses
Also a CNC rotary pocketing, multi-face machining, thread milling and a cnc engraving machine.
CNC Machining requires precision
and you only get precision when you have correctly calibrated tools.
The Milspec calibration and metrology Satation
At Milspec we do the calibrations with the aid of a computer assisted program able to track the 500+ precision measuring devices and jigs we have in the constantly expanding database. It is an ongiong process as each item comes up for calibration every 12 or 24 months. Items beyond our capabilities, necessitating special processes, are sent to specialist calibration companies.
Our CMM is an essential part of CNC machining.
The Sheffield Coordinate Measuring Machine has recently been upgraded with a modern PC based CMM-Manager program.
What could Milspec do for you?
Contact us now using the form below
|
