Construction of VMC machine - Reverse Engineering

 Construction of CNC Machine

          A Vertical Machining Center, commonly known as a VMC machine, is a type of CNC machine used for milling and metal-cutting operations across various industries such as automotive, aerospace, and many more. Building a VMC machine is more challenging than other CNC machines because it must meet critical parameters like high accuracy, rigidity, and overall structural strength. In this article, we’ll discuss the construction and structural design of a VMC machine, along with the benefits it offers for different metal-cutting applications.

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Based on No of column and his movement, There is three types of structure design seen in VMC machine as mentioned below:

1. Single column/ C frame VMC machine 
2. Double column
3. Gantry milling

Single column/ C frame VMC machine

Structure of Single column VMC machine

• Normally VMC machine are appear in C frame structure and this Design universally followed by manufacturer. For certain bed (worktable/work area) range this structure is best then the other VMC structure, but for large bed size this structure is not suitable because of large space required, balancing and design of column and base become critical task.
• In single column VMC machine constructed jn such way that single verticle column is fixed on base of machine, this fixed column spindle head move updown and other two axes are mounted on base. Namely this 2 axis are X and Y directly mounted on Base and Z axis are move along and mounted on verticle column.
• Critical jobs like turbine blade, aero space small components, automobile engines, mold and die, surgical components, defence parts are manufactured by this types of machines.

Advantages of Single column VMC machine:

• Design and manufacturing benefits of this structure are less components assembly,  standard used by most of manufacturer, Spindle head balancing possible 

Key components in single-column VMC machine:

• Rigid bed, worktable with 2 direction movement, verticle column and spindle head enabling Updown movement.

Double column structure/ Bridge type VMC machine 

• Famous for machining long and heavy components. Also known as "Bridge mills". Double column VMC machine is the one in which two vertical column fixed with base and manually parallel to each other support longitudinal axis on which spindle move updown and left right. If we discuss about axis then bed is mounted on Y axis so bed can move in one direction only and X, Z axis are combinly mounted on two columns as seen Image.
• Because of this arrangement space required is less compared to C frame (single column) structure. This design overall vibration is less, large machining area achieve, heavy and rigidwork possible in double column vmc machine.
• Double column cnc machine used for machining of aerospace and automobile long and heavy parts machining, railway components, die and mould machining, hardware part machining, heavy base of machines.

Major advantage of double column vmc machine:

• 2 rigid fixed verticle column reduce deflection and vibration which enabling fine machining and long life of machine.
• Heavy and Large parts possible to machining
• Reduce clamping time by enabling pallet changer 
• Enable 5 face machining by the help of multiple axes spindle

Major Disadvantage of double column vmc machine:

• Design and assembly of this machine is critical than other one due to following reason more parts mates with each other, chances of longitudinal beam bending, heavy weight of spindle head and his left right movement beam is transfer to base by the help of column.
• Generally this type of structure seen in big machinery and cost of double column vmc machine is high.

Key components in double-column VMC machine:

• Rigid bed, worktable with front back movement, two fixed verticle column(V rib reinforcement), spindle head and longitudinal beam for enabling left-right movement.

Gantry type vmc machine

• This type of structure less use as VMC structure because load of 2 axis with spindle arrangement are distributes to ground by moving axis, as youcan seen in image. In other structure of vmc, axis mounted directly to resting surface. Where in case of gantry movement horizontal axis which support verticle axis and spindle arrangement are under bending and transverse load.

Key components of gantry type vmc machine:

• Fixed base, two moveble vertical column, worktable, spidle head supporting beam and spindle head.

Major advantage of gantry type vmc machine:

• Heavy weight and long workpiece whose machining is less is easily machining by this types of vmc machine.
• Manufacturing Cost is less compared to other structure  and majority this type of structure seen in wood router,  cnc laser cutting and small size vmc in which machining's MRM ( material removal rate) is less.

Two different design are seen in VMC machine with gantry structure :

You can easily different structure by below images.

• The first images is universally accepted as gantry type structure by manufacturer in which work table is fixed in bed and in some cases there is no worktable, work piece mounted directly on base. This type of cnc structure commonly seen in diy machine, cnc laser cutting, cnc wood cutting,  cnc machining center, stone cutting, ceramic cutting router, engraving machines and measurements instrument like cmm. As we seen in double column structure, Spindle arrangement and Z axis mounted and move by horizontal X axis., X axis is horizontal axis which supported by two rigid verticle column in each end , hence axis load is transfer to ground via column and base. Same structure seen in gantry there is only one change is that instead of column fixed incase of double column, column incase of gantry movement two column is move front-back by the help of end linear motion mechanism and work piece which mounted on worktable is fixed with base, which is movebleincase of double column structure. 

Advantage of Gantry type CNC structure:

• The main advantage of gantry type structure has to carry heavy load and clamp long length workpiece in compact structure design because of workpieceis fixed and full structureis moveble from column. 

Disadvantage of Gantry type CNC structure:

• This structure is suitable for medium and soft machining operation and not suitable for heavy machining operation because of spindle head weight constraints in design. Column which moves on base by the help of horizontal beam has to carry weight of spindle head, horizontal beam and column itself and also because of bending issue of beam from center , when load of cutting is add structure stability is imbalance so chances of structure parts failure or vibration on workpiece. If heavy machining operation is performed. Hence recommend to use this type of structure for heavy load and long part with soft and medium machining.

In gantry movement there is another one design is recently trendy in VMC machines manufacturer in which problem mention in above gantry type structure is justified and machining operation fast and heavy. In this structure, worktable is fixed and all axis situated at one position but on single column and  this structure is suitable for small size less than 1 meter bed size.

First advantage is rapid of vmc  is high in this design, also workpiece weight constraints seen in other design is not occur in this design. Because worktable is fixed hence there is no movement of workpiece which mounted on worktable, hence heavier weight material can easily cut with high rapid, lead to reduce cycle time and machine electric consumption of axis motor.

Key components in Gantry type VMC machine:

• Rigid base, fixed worktable, moveble two verticle column, spindle head and longitudinal beam for enabling left-right movement.

How to diffrentiate VMC machine is single column or double column or gantry type

what is diffrence between single and double column VMC machine