Automatic Screw Tightening Machines

There are six common types: handheld, benchtop single-axis, benchtop XY multi-axis, multi-spindle simultaneous, robot-arm type and inline type. The choice mainly depends on three numbers: how many screws per workpiece, how long the allowed cycle time is, and how many changeovers per month. With few tightening points but frequent model changes, handheld or benchtop single-axis has the lowest total cost; with many tightening points and fixed models, XY multi-axis is the most cost-effective; when tightening from multiple sides or at 3D angles with frequent changeovers, a robot arm with a tightening module offers the most flexibility. Only when the cycle time is very tight do you need to consider multi-spindle simultaneous or an inline type integrated into the conveyor line.

It can be divided into five parts: the tightening spindle (outputs torque and judges the tightening result), the Z-axis feed mechanism (moves the tightening spindle down for thread engagement), the screw feeding (delivers loose screws one by one to the pick-up point), the positioning mechanism (moves the tightening spindle to each coordinate, such as an XY Table or robot arm), and control and data (stores tightening results and torque curves and connects to MES and ERP). Utrun-Tech provides the tightening spindle, Z-axis tightening module, screw feeding and tightening data; the machine enclosure, fixtures and positioning mechanism are usually designed by an equipment integrator or the customer. If your line already has a robot arm or XY Table, you usually do not need to buy a complete machine; adding a tightening module and screw feeder is enough to build an automatic tightening station.

Blow-feed (air blow) uses compressed air to blow screws from the feeder through a hose to the jaws on the tightening spindle; it is the fastest and suits small headed screws, but screws that are too long, too flat or have washers tend to jam in the tube. Suction-feed uses a vacuum nozzle to pick up screws from the pick-up point and can handle non-magnetic screws such as plastic, aluminum and stainless steel, as well as special head shapes; the nozzle must be changed when the screw specification changes. Magnetic pick-up relies on a magnetized bit to hold the screw directly; it has the simplest structure but works only with magnetic screws and is not suitable for products sensitive to residual magnetism. The screw itself decides which method to use: head type, length-to-diameter ratio, whether the material is magnetic, and whether the product can tolerate residual magnetism.

Listing the following items usually leads to a concrete solution: screw specification (head type, thread diameter and length, whether the material is magnetic, with or without washer) and the number of screws per workpiece; target torque and allowable tolerance; workpiece material (plastic self-tapping, tapped metal or screwing into nuts); the coordinate layout of tightening points and whether tightening from multiple sides is required; required cycle time and daily output; changeover frequency and number of models; and whether tightening data needs to be stored or uploaded to MES. Pre-installation selection evaluation, mechanism integration advice and post-installation technical support are all provided by Utrun-Tech in Taiwan. Please call +886-2-87975610 or email info@utrun.com.

First confirm the screw specification and workpiece material, then match the torque range. M0.6~M1.2 screws commonly used in precision electronics mostly fall within 10~45 mN·m, M1.2~M2.0 is about 50~180 mN·m, and M2.0~M3.0 about 200~700 mN·m; general 3C assembly is mostly 0.2~3 N·m; automotive, construction and similar applications can reach tens to thousands of N·m. When selecting a tool, we recommend that the actual working torque falls in the middle of the tool range rather than at its upper or lower limits, for better accuracy and service life.

The key is that the process is measured, not just the final torque. Models with a built-in torque sensor can control torque output in real time and record the tightening history and torque curve, and with upper and lower limits set, defective parts are judged on the spot. The PRO-FUSE uses closed-loop control with thread-search detection accuracy of 0~10 mN·m, torque rise detection time of 0.01~1.00 s, and allowable turns settings of 0~10 turns in each direction, identifying unengaged threads, insufficient turns and stripped threads. The HFC3000II uses reverse rotation combined with vibration-sensing thread engagement to reduce cross-threading and damage to threaded holes.

Yes. The MFC-S series controllers of the AFC3000 have an Ethernet port compliant with IEEE802.3 (100BASE-T), store up to 120,000 tightening results and 100 torque curves, and can be fitted with expansion units supporting fieldbuses such as CC-Link, DeviceNet, PROFIBUS, PROFINET, EtherNet/IP, CC-Link IE and EtherCAT. The HFC3000II stores 12,000 result records, 100 curves and 500 error records, and with the optional CF card slot on the controller, data can be stored on a memory card even without a PC connected.

A conventional automatic screw tightening machine controls the torque and speed of the rotating spindle, while the vertical direction is usually just a constant-speed pressing mechanism. The patented PRO-Z technology brings the motion speed and pressure of the vertical Z axis into synchronized control: after the user enters the screw specification and motion conditions, the system matches the tightening action and adjusts the pressing behavior, allowing it to handle variables that are difficult to control with conventional methods. In testing with M0.8 screws on the same workpiece, it performed more than 1200 consecutive tightening and loosening cycles, averaging 0.8 s/screw. The module can be integrated into a robot arm or XY Table via TCP commands from a Robot Controller.

It is generally recommended to verify it regularly according to your quality system requirements. A common practice is to check the actual output of critical stations with a torque meter before each daily line start, and schedule periodic calibration according to internal standards. The PRO-CHK torque meter has a measuring range of 20~5000 mN·m and accuracy of ±0.5%, with four measurement modes (peak, peak down, real-time output and track); upper and lower limits can be set for direct pass/fail judgment by indicator lights, and 800 measurements can be stored and output in ASCII format.