Weft changing on a rapier loom is achieved by controlling the movement of the weft picker. Newer rapier looms use computer-controlled electromagnets, which in turn drive the weft picker, enabling arbitrary weft mixing ratios. The PU130 rapier loom, however, mechanically drives two weft pickers, limiting it to 1:1 weft mixing ratio products. To meet market demand for multi-ratio weft mixing products, and considering the characteristics of the PU130 rapier loom, we have meticulously designed and actively researched and developed an automatic weft mixing system specifically tailored to its features. The system is pneumatically powered, with solenoid valves controlling cylinders, which in turn drive the weft picker according to process requirements. The solenoid valves are controlled by a PLC programmable controller, allowing for easy modification of the program to achieve multi-ratio automatic weft mixing. This system is simple, practical, stable, requires minimal investment, and yields quick results.
1. Problem Statement
The PU130 rapier loom, manufactured in Switzerland, dates back to the 1980s. When introduced in the early 1990s, this advanced machine primarily produced heavy, standard denim fabrics such as 7x6 and 7x7, consistently delivering high-quality products that satisfied customers and playing a vital role in production. It also brought new markets to the company, generating significant economic benefits. However, with continuous socio-economic development and increasing societal demands, denim fabric varieties have become increasingly diverse. The old model no longer meets these needs, replaced by new multi-component blended denim fabrics with varying weft counts, colors, and proportions. Moreover, demand for these new fabrics is growing rapidly, dominating the market. The PU130 rapier loom, limited to single-component blending, suffers from limited product variety, severely hindering new product development. Although the PU130 rapier loom has been upgraded, the new equipment's complex and expensive automatic weft changing system makes further upgrades impractical.
The PU130 rapier loom is one of the key pieces of equipment at the Second Cotton Mill Branch, accounting for a significant portion of the weaving workshop and having a crucial impact on the company's production and operations. However, with the continuous improvement in the automation level of new imported equipment, the shortcomings of this machine have become increasingly prominent. Furthermore, after more than ten years of use, the machine's components are aging, leading to an increased failure rate. In addition, this model of imported equipment has been upgraded, and spare parts are expensive and difficult to obtain, resulting in increased maintenance difficulty and costs, often affecting production and product quality. Adjustments to product varieties require lengthy modification times and increasingly larger investments. Therefore, achieving multi-ratio weft mixing on the PU130 rapier loom and continuing to fully utilize its capabilities has become a major challenge we face.
2. Determination of the research and development plan
The PU130 rapier loom has two weft selectors, each driving one weft yarn. They work sequentially, mechanically, to achieve a 1:1 weft blending ratio. To achieve an n:1 weft blending ratio, one weft selector must work continuously n times before the other begins, thus achieving multi-ratio weft blending. Through research, repeated studies, and demonstration, the following design concept was developed:
1. Powered by an air source, the weft selector operates. The air source is controlled by a solenoid valve, which in turn is controlled by a programmable controller, thereby controlling the weft selector's movement and achieving multi-proportion automatic weft mixing.
2. Complete the weft replacement work for parking, weft breakage, or other reasons caused by parking through a certain procedure.
3. The actions of the solenoid valves controlled by the programmable controller must be coordinated with (synchronized) with the movement of the loom.
Fourth, since the weft selector needs to complete 300 actions per minute, all selected components must be of stable quality and able to meet the requirements of high frequency and long-term operation.
3. System Composition and Working Principle
3.1 System Composition
Air compressor: Provides air to drive the cylinder, which in turn powers the weft selector; air pressure is 0.7-0.85 MPa. (The company already has one and is using it in production; no separate purchase is needed.)
Programmable Controller: The selected model is the Mitsubishi FX1n-MR24 from Japan, which features stable performance, reliable operation, and low price. The selected sensor is an NPN type with a frequency above 50Hz, and its operating voltage is consistent with the voltage provided by the selected programmable controller (24V).
Solenoid valve: The solenoid valve selected must meet the requirements of high operating frequency and fast response speed, and be powered by DC 12V or 24V power supply. After multiple tests, the Taiwanese-made solenoid valve model T180-4E1-PSL was finally selected.
Cylinders: Cylinders require high operating frequency, good lubrication, friction resistance, and low temperature rise, and are specially processed by specialized manufacturers. We have independently designed and manufactured a series of components such as dedicated connecting rod joints and bracket joints.
Weft selector: The one that comes with the original machine is used.
3.2 Working Principle: Powered by an air source, the weft selector operates according to process requirements, and multi-ratio automatic weft mixing is achieved through PLC control. System Working Process: Two valves entering the cylinder are controlled by solenoid valves. The air entering the cylinder drives the cylinder piston to move. The cylinder piston drives the weft selector through the connecting rod joint. The PLC programmable controller controls the solenoid valves according to the program, thereby controlling the weft selector to operate as required, achieving the purpose of weft mixing at different ratios.
4. System debugging and determination of operating parameters
4.1 Turn the programmable logic controller (PLC) switch to the running state, then short-circuit X2----COM to start the loom. At this time, it should operate according to the 2:1 weft ratio. Similarly, short-circuit X3---COM and start the loom; it should operate according to the 3:1 weft ratio. The sequence is as follows: X4 corresponds to a 4:1 weft ratio; X5 corresponds to a 5:1 weft ratio; X6 corresponds to a 6:1 weft ratio. 4.2 Run the loom in the 6:1 state. When it reaches a single weft position, stop the machine. The operator should remove the last weft yarn and then start the machine again. Alternatively, when reaching a single weft position, break the weft yarn (without removing it) and then start the machine. The fabric should not have any missing weft yarns for that unit.
4.3 To ensure the loom operates in a 6:1 ratio, and when weaving multiple wefts, stop the machine or break the weft yarn. The operator should remove the last weft before restarting the machine. The number of multiple wefts should be 6. When weaving multiple wefts, regardless of the reason for stopping, the programmable controller output Y0 should close. At this time, the solenoid valve will engage (working state), driving the cylinder to work.
4.4 Process Parameter Setting: D128 value is required for the process.
