Abstract: Drilling and tapping machines are widely used for machining holes in batches of parts, and commonly come in three structures: rotary table, feeder table, and slide table. Samkoon Technology provides an integrated control solution based on PLC, servo, and HMI, supporting complex processes such as drilling, tapping, chamfering, integrated drilling and tapping, and multi-stage machining, and implementing torque detection to protect the taps. The solution balances program simplicity with on-site debugging flexibility, helping equipment manufacturers quickly deliver stable and reliable drilling and tapping equipment.
Project Introduction
In machining, drilling and tapping are the most basic and common processes. To improve efficiency, many manufacturers have begun using automated drilling and tapping machines instead of traditional manual bench drills or single-station machine tools. Based on the different loading and workpiece movement methods, these machines are mainly divided into three categories:
Rotary Drilling and Tapping Machines:The workpiece is mounted on a rotating worktable and passes through different processing stations sequentially as the turntable rotates. Suitable for small to medium-sized regular parts, capable of single-sided or double-sided drilling and tapping, and the number of stations can be increased or decreased according to process requirements.
Feed-type Drilling and Tapping Machines: Primarily for bar stock parts, an automatic feeding mechanism delivers the bar stock to a designated position, processes it, and then automatically unloads it. Common configurations include two-axis, seven-axis (with tool changer), and nine-axis, suitable for multi-process processing of batches of bar stock.
Slide-type Drilling and Tapping Machines: The workpiece is fixed on a slide, and the slide moves to align the workpiece with different machining spindles. Each spindle can be equipped with different tools (such as drilling spindles, tapping spindles, chamfering tools, etc.), and multiple processes can be completed in one round trip of the slide. Common models include one-sided, two-sided, and three-sided models.
Regardless of the structure, the core control requirements are similar: the spindle (which drives the tool to rotate) and the feed axis (which controls the forward and backward movement of the tool or workpiece) must be precisely coordinated, especially during tapping, where the feed axis must move a distance of one thread pitch for every revolution of the spindle. In addition, deep hole machining requires segmented feed and retraction for chip removal, and the ability to detect tap overload to prevent tap breakage.
Solution Configuration
Samkoon Technology’s standard control solution for drilling and tapping machines includes the following components:
Part 1
Controller: Utilizes a Samkoon PRO series PLC (specific model selected based on the number of axes, such as C16X16T+), responsible for logic control, motion command calculation, and communication.
Part 2
Human Machine Interface (HMI): SK series touchscreen (e.g., SK-102QS-G), used to set machining parameters (drilling depth, tapping pitch, segment length, feed/retract speed, etc.), and to display the current station status and torque value in real time.
Part 3
Servo Drive System: Matches an R8 series servo drive system based on the number of axes to control the feed axis, rotary table indexing axis, and slide movement axis. The spindle can use a frequency converter or servo drive, selecting constant speed mode or position/speed mode according to process requirements.
Part 4
Torque Detection: Real-time reading of the servo’s internal torque feedback value via Modbus communication (RS485) between the PLC and the servo drive. When the torque exceeds the set threshold, the PLC immediately alarms and stops machining to prevent tap damage.
Advantages of the Solution
1. Covers Multiple Machining Processes, Flexible and Adjustable Parameters
Our PLC program supports common modes such as drilling, multi-stage drilling, tapping, multi-stage tapping, chamfering (upper chamfer/lower chamfer/both chamfers), integrated drilling and tapping (drill first, then tap), and hollow multi-stage drilling. The depth, speed, and retraction method for each mode can be set individually, and operators can directly modify them on the touchscreen without modifying the program.
2. Precise and Synchronous Tapping, No Pitch Deviation
During tapping, the feed axis and spindle form a virtual electronic gear system. We directly convert the lead screw lead and tap pitch into pulse equivalents. After triggering the interpolation command, the two axes are strictly linked according to the pitch relationship, ensuring the tapped thread profile is complete and free of defects.
3. Multi-stage Drilling Balances Chip Removal and Efficiency
Deep hole machining is most vulnerable to chips clogging the hole wall. We offer two multi-segment drilling methods:
3.1 Fixed-length segmentation: Chips are removed after each segment is drilled, suitable for batch drilling of deep holes with consistent lengths.
3.2 Custom-length segmentation: For holes of varying depths, the feed depth for each segment can be set separately.
4. Torque detection effectively protects the tap and reduces wear.
RS485 communication directly reads the real-time torque value of the servo motor, eliminating the need for additional wiring. During normal machining, the torque value remains stable. If a blind hole, hard material spot, or tap wear is encountered, the torque will suddenly increase, and the system will immediately alarm and stop to prevent tap breakage. Customer debugging is simpler; only a torque threshold needs to be set, significantly reducing the maintenance threshold.
5. Clear program structure facilitates secondary development.
We have written different processes (drilling, tapping, chamfering, etc.) as independent subroutines, which are called by the main program according to the workstation flow. Although rotary, feed, and slide table types have different mechanical structures, the core machining subroutines can be reused. The touchscreen interface is also designed according to the “workstation + process” logic, making it easy for equipment manufacturers to get started.
6. Adaptable to multiple machine models, easy to replicate and promote
This solution has been used on various machine models, including two-axis bar drilling and tapping machines, seven-axis drilling and tapping machines with tool changers, and two-sided sliding table drilling and tapping machines. Whether it’s standard batch production of parts or multi-variety small-batch production, it can be adapted with only parameter adjustments and a few program changes, making it very suitable for equipment manufacturers to standardize shipments.
