Fabricating enormous components with tight tolerances, such as aircraft wings and engine blocks, can be a headache even for the most experienced manufacturers and engineers. However, with the right CNC milling machine, for instance, a bridge or gantry mill CNC machine, this fabrication process can be quite seamless and cost-efficient.
But which milling machine deserves a spot on your shelf or in your workshop? Read on to find out what differentiates bridge mills from gantry mills.
Gantry Mills Vs Bridge Mills at a Glance
Whilst bridge-type machining centers and gantry-type machining centers may look alike, they are quite dissimilar, and the table below pits these two machining centers against each other.
| Key Feature | Gantry Mill | Bridge Mill |
| Movement | Comprises a movable gantry and an immovable worktable. | Made up of a mobile worktable and a stationary bridge. |
| Workpiece Handling | The workpiece remains stationary during machining. | The workpiece is rotated during cutting or machining. |
| Floor-Space Requirements | Requires relatively less floor space due to its compact nature. | Requires comparatively more floor space due to its slightly larger configuration. |
| Weigh Limit | Perfect for relatively heavier workpieces. | Has a workpiece weight limit. |
| Precision | Quite precise. | Offers unrivalled precision. |
Key Differences Between Bridge Mills and Gantry Mills
· Machine Structure and Axis Movement
At a glance, bridge and gantry milling machines may look quite similar, but upon digging deeper, you will realize that they boast distinct structures. CNC gantry milling machines stand out thanks to their movable gantry structure coupled with an immovable workpiece holder or worktable.
This distinct configuration paves the way for machining relatively larger workpieces such as 50-foot-long aircraft wings. CNC bridge mills, in contrast, boast an immovable bridge and stationary worktable, allowing operators easier access to the workpiece being fabricated. This configuration, however, makes it impossible to machine relatively larger and heavier workpieces.
· Workpiece Handling and Table Configuration
Bridge mill machining centers come with a fixed and immovable worktable, meaning that the workpiece being fabricated remains stationary during the machining process. The machining tool is, however, supported by a moving bridge structure, which rotates the cutter as it engages with the stationary workpiece. This unique worktable configuration makes it possible for manufacturing engineers to achieve high tolerances, especially when machining medium-sized components.
Gantry machining centers, on the other hand, boast a movable spindle supported by a movable gantry. Their worktable is, however, fixed, meaning that the workpiece is machined while it stands stationary. This configuration suits comparatively bigger or bulky components such as shipbuilding parts better.
· Machining Envelope and Large-Part Capability
Gantry mill CNC machines come with a flexible gantry situated right above an immovable worktable. This allows for the machining of comparatively larger and wider components since the machining tool has more room for movement.
This creates a relatively bigger machining envelope, explaining the high regard in which gantry CNC mills are held amongst manufacturers producing gigantic components such as automotive and aerospace parts.
CNC bridge mills, in contrast, have a limited machining envelope, making them unsuitable for fabricating massive components. This is because their design features fixed columns, which limit the movement of the machining tool during machining. However, this confined machining envelope makes bridge milling centers ideal for producing high-precision medium-sized components such as medical implants.
· Rigidity and Machining Performance
Bridge mill CNC machines are designed for manufacturers, engineers, and workshop owners fabricating medium-sized components. As such, they are made from robust materials, but they are not as rigid as gantry CNC mills, which are tailored to fabricate gigantic workpieces.
Thanks to their relatively compact size, bridge mills thrive in machining high-precision components, such as medical implants, which require intricate cuts. Gantry mills, on the contrary, promise high precision when machining large components, but cannot match the precision offered by bridge mills.
· Floor Space and Installation Requirements
CNC gantry milling machines are made for industrial workshops and manufacturing facilities producing enormous components. As such, they are gigantic and bulky, meaning they require more floor space. Furthermore, their gigantic stature makes their installation comparatively more complex and demanding.
Bridge mill machining centers, in contrast, favor relatively smaller workpieces requiring higher tolerances. As such, they are not as gigantic as gantry mills, meaning they occupy less floor space. This makes them perfect for relatively smaller production facilities and workshops. They are also much easier to install and cost relatively less.
· Cost and Total Ownership Consideration
Gantry mills are not only bigger than bridge mills, but they are also bulkier and more complex, featuring multi-axis structures. This inevitably raises their upfront cost, with average prices ranging from $25,000 to over $1,000,000. They also occupy large floor spaces and consume more energy, taking their ownership cost a notch higher.
They, however, promise a lower per-part cost for gigantic components produced at a large scale. Bridge mills, conversely, are smaller, and this translates into relatively lower upfront capital cost. Furthermore, they occupy less floor space and are cheaper to maintain.
· Typical Manufacturing Applications
Whereas CNC gantry mills thrive in the mass production of relatively gigantic components and parts, bridge milling centers thrive in the fabrication of high-precision, medium-sized components.
Bridge mills are highly prominent in workshops and manufacturing facilities producing electronics, complex automotive parts, and mold-making cavities. Gantry mills, in contrast, are favored by industrial workshops producing heavy-duty components such as aircraft wings and shipbuilding parts.
Bridge Mills or Gantry Mills: Which Configuration Fits Your Application
- When to Choose Bridge Mills: CNC bridge milling centers are tailor-made for contract manufacturers and workshops fabricating parts with relatively more complex geometries. They prioritize precision over size and weight.
- When to Choose Gantry Mills: Gantry milling centers promise the most returns on investment when utilized to manufacture large or heavy-duty components at an industrial scale. Although they are not as precise as bridge mills, they guarantee a lower per-part cost of production.
For automotive components that require repeatable dimensions and complex milled features, automotive CNC machining can support both prototype development and small-batch production.
FAQs
Can bridge and gantry mills be configured for 5-axis machining?
Yes. The majority of bridge and gantry mills in circulation today support 5-axis machining, making it possible for machinists and part manufacturers to fabricate complex components with intricate details.
How does foundation design affect large bridge and gantry mills?
Enormous gantry or bridge mills installed on unstable or weak surfaces are more likely to experience rigorous vibrations, and this can lead to machining inaccuracy.
Can gantry mills be configured for unusually large workpieces?
Yes. Gantry mills are generally tailored to fabricate unusually gigantic workpieces such as 50-foot-long airplane wings. This is made possible by their distinct configuration, which creates a relatively larger machining envelope.
Can bridge and gantry mills be integrated with automated material handling?
Yes. Most modern CNC milling centers come fitted with automated material handling systems, making it easier for operators to load and unload gigantic workpieces.
Which CNC control systems are commonly available for bridge and gantry mills?
CNC bridge and gantry mills boast high precision and a greater throughput thanks to the computerized control systems integrated into their operation. They primarily rely on Programmable Logic Controllers (PLCs) and Human-Machine Interfaces (HMIs), allowing operators to initiate and conclude operations with the touch of a button.
Final Thoughts
CNC gantry and bridge milling centers not only make the production of large, intricate parts possible, but they also help lower production costs. However, each milling center is tailor-made for certain applications, and manufacturers must be methodical when choosing between the two to ensure optimal returns on investment.
For all your custom CNC machines, TSINFA is your trusted partner in China – Get a quote now.
