Turret Lathe or Gang Tooling for CNC? [ +Swiss Lathes ]

4 weeks by cncdivi

For further insights, please check the tool turret for cnc lathe.

This subject generates considerable debate and strong opinions among machinists. I personally delved into hundreds of online articles and discussions with our G-Wizard customers concerning this choice.

To give you a quick overview, here's a video that succinctly covers the key points:

For a more detailed exploration, continue reading.

Let’s commence with definitions and the primary conclusion I reached from extensive research and conversations, and then explore the various details.

Understanding Turret Lathes and Gang Tooling

On traditional manual lathes, a single tool is typically mounted on a Quick Change Toolpost (QCTP). While functional, CNC applications demand greater productivity. Although it's possible to attach a conventional manual lathe QCTP to a CNC lathe, this is usually only seen in Toolroom lathes.

For production-level machining, tools are generally mounted either on a gang plate or on a turret. Interestingly, the image above illustrates both formats in operation: every turret tool station is equipped with a gang plate, which increases the number of tools accessible from each turret position.

Gang tooling presents a straightforward option. In this approach, tools are arranged in a row on the lathe's cross slide. Engaging a tool involves retracting along the spindle's axis to avoid contact with the workpiece, sliding the X-axis to align the appropriate tool, and then moving along the Z-axis to initiate cutting.

A gang slide typically showcases this setup:

The video effectively demonstrates the swift motion for tool changes in gang setups. Note the two tooling formats: the rough turning tool takes a substantial cut and utilizes a typical square shank lathe tool holder. Meanwhile, the additional tools have a round shank with a flat design, more common in gang tooling. This compact configuration often features a single holder accommodating two inserts for varied tasks.

In contrast, here’s a turret lathe in action:

The machine in the video possesses two turrets, one of which mounts a clean live center tailstock to process that long, slender part. This provides a clear example of how turret lathes operate, akin to the rotary tool changers found in CNC mills.

Which Option Is Superior?

A thorough list of advantages and disadvantages exists for each option, but let's start with a high-level conclusion:

The decision between gang tooling and turrets for a CNC lathe primarily hinges on the type of parts being manufactured. Gang tooling excels for smaller diameter, short parts that do not require a tailstock, while turret lathes offer unparalleled versatility, particularly when a tailstock is necessary.

Throughout my research, I encountered machinists who desired to utilize their gang lathes universally but opted for turret lathes for parts that were too lengthy and slim to process with a gang lathe.

Exploring Swiss Lathes

This comparison suggests that the rivalry between gang lathes and turret machines may be somewhat misleading. A more appropriate rivalry might be gang lathes versus Swiss machines. Swiss machines employ a guide bushing and turn from the end towards the headstock, ensuring ample support with minimal overhang.

While Swiss machinery entails higher costs, increased complexity, and the necessity for pricier bar stock compatible with their bushing setup, it permits the machining of parts that would otherwise be too long and delicate for gang lathes.

Gang Tooling Advantage #1: Speed

Let's begin with the gang tooling community's perspective on their machines:

If a part can be manufactured on a gang lathe, it is typically completed faster and at a lower cost than on a turret lathe.

Keep in mind that some components cannot be fabricated on gang lathes due to the absence of a tailstock. The gang tooling may interfere with the workpiece if it cannot fully retract because the tailstock is obstructive. Certain gang lathes feature retractable tailstocks, but this limits a gang lathe's primary edge—swift tool changes.

The gang tool change process outperforms turret lathes in efficiency due to its sliding mechanism without turret indexing. Turret lathes require moving to a tool change position before rotating the correct tool into place. After positioning, the machine then moves back to the cutting state. In contrast, gang tools merely adjust to the position of the next tool and return swiftly.

Consequently, gang tools are generally faster, with machinists frequently stating that gang machines complete operations significantly quicker than turret counterparts.

Gang Tooling Advantage #2: Simplicity and Cost-Effectiveness

Turrets are sophisticated precision instruments, comprising numerous moving parts, while gang tooling is minimalist, consisting of a few blocks installed on the cross-slide, with all tool changes executed by the lathe's conventional axis servos.

This simplicity often renders gang lathes considerably less expensive compared to turret lathes. In certain scenarios, shops acquire two gang lathes for the price of a single advanced turret lathe, reaping substantial benefits.

For parts necessitating live tooling—such as machining wrench flats or drilling bolt circles—the cost with gang tooling is significantly less. Various types of spindles can be integrated if the lathe includes an indexable C-axis spindle. Conversely, motorizing a turret incurs additional expenses due to challenges in transmitting rotary power to turret tool positions.

Overall, gang tooling tends to be more cost-effective, whereas turret tooling can be pricier but offers robustness and larger-scale operations.

Gang Tooling Advantage #3: Quick Setup

Setup speed varies, but the ease of swapping out an entire block of tools with gang tooling generally leads to quicker methodology, especially since setups can occur offline or be organized as assembled blocks for specific tasks.

For further knowledge, please explore our website on the turret indexing mechanism.

Quickly replacing a block of gang tools consolidates all necessary tools for a particular part.

Alternatively, numerous gang operations can be accomplished with a foundational tool set, merely changing one block housing a specific twist drill size.

Gang Tooling Advantage #4: Precision

The simplicity of fewer moving parts minimizes tolerance accumulation and other inaccuracies, enhancing the tool's accuracy. Achieving the correct centerline position with the tool is vital. Once set, gang lathes tend to maintain accuracy better than turrets.

Another factor contributing to accuracy superiority is the limited distance gang lathes travel while machining.

Gang Tooling Advantage #5: Robustness

This benefit correlates closely to simplicity, indicating that gang lathes possess fewer points of failure compared to turrets. Turrets entail greater wear and tear, alongside potential costly repairs or alignment if a crash occurs.

Turret Lathes Advantage #1: Versatility

Nonetheless, we shouldn’t overlook turrets, which excel in flexibility. They support tailstocks, making it feasible to machine longer, slimmer components compared to gang lathes.

Turrets can also accommodate larger parts since gang tool setups require sufficient clearance to fit components between tools, limiting diameter and count. Turrets allow for larger diameters and greater flexibility.

Turret Lathes Advantage #2: Simplified Programming

While experienced users find gang lathe programming manageable, beginners often find turret programming more intuitive. Gang lathe users must account for part clearance during tool changes, posing risks for incorrect moves. In contrast, turret users generally use a single positive value, making programming straightforward.

Turret Lathe Advantage #3: Increased Tool Availability

The aforementioned image shows turret stations equipped with multiple gang tools. This scenario enhances programming complexity but allows for greater tooling capabilities. For instance, a 3-tool gang plate can replace 3/4” or 1” square shank holders.

Foxwood Machine designed this product for situations where a turret cannot accommodate sufficient tools or change tools quickly enough.

Turret Lathe Advantage #4: Expanded Operations and Complexity

This advantage links back to turrets' versatility, positioning them fittingly for intricate setups involving dual spindles or multiple axes without needing multiple setups.

Turret Lathe Advantage #5: Enhanced Hogging Efficiency

Turrets generally showcase superior hogging capacity, especially larger lathes. Dual turret machines can employ two cutting tools concurrently, effectively reducing cycle times.

Consider a scenario where each turret utilizes a tool for a 1/8” cut while aligned, enabling simultaneous 1/4” material removal—thereby countering any deflection caused by the parts.

Turret Lathes Can Also Employ Gang Tooling!

Picture each turret position housing a small gang plate comprising multiple tools. The possibilities become intriguing.

Nostalgia: Historic Manual Turret Lathes

Reflecting on earlier designs, manual turret lathes look notably different from modern CNC counterparts.

Conclusion: The Right Tool for the Job

Rather than pitting one option against the other, it becomes evident that, in this instance, it's ultimately about choosing the best tool for specific tasks. Evaluating the types of parts to be produced and understanding the advantages necessary for those components should guide your decision.

Should you face uncertainty about the parts you will produce or cannot accommodate the limitations of gang tooling for shorter, diminutive parts, opt for a turret. If straightforward programming and reduced learning curves are essential, a turret lathe is befitting. However, for minimizing cycle times and maximizing output from gang lathes on suitable parts, consider gang tooling.

See Also

Originally Posted by underthetire

Depends on the turret type as well. The old hydraulic motor turrets don't like being out of balance by a lot, so all heavy tools on one side and light stuff on the other can make those over/undershoot.

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