In September 2021, we received an inquiry from Mr. Abdullah in Saudi Arabia regarding a continuous foaming machine. The client was planning to establish a PU foam factory to produce products for the local and Yemeni markets. He had some basic knowledge about machine usage and selection.

The client had no prior experience in foam production before, so he was particularly concerned about after-sales support and technical assistance.

We began by analyzing the client's target market (specific industry) and understanding the local product requirements (such as foam density, hardness, etc.) to confirm the client's production needs.

Through video conferences, we guided the client through our PU foam production process, providing the client with a concrete understanding of foam production and highlighting the convenience and efficiency advantages of our machines compared to those of other manufacturers.

Drawing upon our more than 20 years of experience in foam foaming, we shared insights with the client about using the machine and common challenges in the foam foaming process, addressing any technical concerns the client may have had.

We also provided the client with factory layout plans to expedite the setup of the entire foam production line while maximizing production efficiency.

Due to the client's high level of trust in our professional service, he ultimately chose us as his supplier for foam machinery and later made repeat purchases for a rebonded foam production line and foam cutting machines.

In December 2021, we received an inquiry from Mr. Hairun in Malaysia. Mr. Hairun is a mattress manufacturer in need of producing rebonded foam. He had limited knowledge about machine usage and selection and had no prior experience with the production process. Therefore, he required guidance from experts who could assist him from the ground up.

We systematically explained the principles of foam production to Mr. Hairun, along with the necessary materials and equipment. We also took him on a tour of our factory to provide a clear understanding of the entire production process.

After understanding Mr. Hairun's preferences for the rebonded foam, including density, softness, and market prices, we offered him the most suitable foam production solution. We also provided him with information on foam production costs and compared raw material prices for his reference.

Based on the client's needs, budget, and existing factory layout, we devised a cost-effective machine configuration and layout plan for his facility, including an assessment of startup costs.

Once the machines were successfully installed, our team of engineers provided Mr. Hairun with one-on-one foam production training. When he successfully produced the foam he desired for the first time, he called us and said, "I am happy with crying, thank you very much!" Afterward, he purchased a batch foam machine from us and continued to reorder foam chemical materials from our company.

For many small-scale enterprises, although the continuous production line of polyurethane flexible foam offers high output, the costs are also very high, and the target market may not require such large quantities. As a result, non-continuous production lines for polyurethane flexible foam have become their preferable choice. The following is an introduction to the non-continuous production line for polyurethane flexible foam:

1. Box Foaming Process Equipment

The box foaming process and equipment have been developed as a new technology to accommodate the needs of small-scale polyurethane foam production facilities. It builds upon laboratory and manual foam production techniques, essentially an upscaled version of laboratory foam methods. This process has gone through three development stages. Initially, all component materials were sequentially weighed and added to a larger container, followed by the addition of TDI. After rapid mixing, the mixture was immediately poured into a large box mold. This method had high labor intensity, emitted high concentrations of toxic gases, and posed significant health risks to operators. Additionally, the splattering of materials during pouring would entrain a large amount of air, leading to the formation of large air bubbles within the foam structure and even causing foam cracking. Furthermore, there was a significant amount of leftover waste, resulting in substantial material waste and high production costs. 

Later on, the process incorporated metering pumps to convey materials to a mixing barrel with an automatically opening bottom. After high-speed mixing, the bottom plate of the mixing barrel would open, and compressed air would swiftly expel the material into the mold for foam expansion. However, this approach suffered from uneven foam pore structures due to the rapid material flow, leading to swirling foam structures and quality issues like crescent-shaped cracks. The third stage of process improvement is the box foaming device that is mostly adopted today. Its fundamental foaming principle is illustrated in Picture

(a) Raw Material Metering and Mixing      (b) Foaming     (c) Foam Rises to Limit Height

1 - Elevatable Material Mixing Barrel; 2 - Assemblable Box Mold; 3 - Floating Box Top Plate; 4 - Foam Body

Picture 1: Schematic Diagram of Box Foaming Principle

The industrial production equipment for box foaming primarily consists of raw material tanks, metering pump units, elevatable mixing barrels, and assemblable wooden box molds. As depicted in the schematic diagram of the box foaming equipment manufactured by Hennecke (Picture 2), the foaming raw materials are stored in tanks and regulated by control devices to attain the required processing temperature range, typically maintained at 23°C ± 3°C. Sequentially, the metering pump injects polyether polyols, catalyst, surfactants, foaming agents, etc., into the mixing barrel for a stirring duration of 30 to 60 minutes. Next, according to the formulation, TDI is introduced, either directly or through an intermediate container with a bottom switch. Immediate mixing follows TDI addition. Depending on the materials and formulation, the stirring speed is usually controlled at 900 to 1000 revolutions per minute (r/min), with a stirring time of 3 to 8 seconds. After stirring, the mixing barrel is swiftly lifted. The lower part of the barrel lacks a bottom and is placed on the mold box's bottom plate upon lowering, utilizing a sealing ring at the barrel's bottom edge to prevent material leakage.

When lifted, the well-mixed slurry can be directly spread and dispersed on the bottom plate of the box mold, allowing natural foam rise. To prevent the formation of a domed surface on the upper part during foaming, an upper mold plate that matches the mold area and allows for upward limit movement is equipped. The mold box primarily comprises rigid wooden panels, with the bottom plate fixed on a movable mold transport carriage. All four side panels are assemblable, featuring quick-opening and closing locking mechanisms. The inner sides of the panels are coated with silicone-based release agents or lined with polyethylene film material to prevent adhesion. After 8 to 10 minutes of forced maturation within the box, the side panels of the mold box are opened, allowing the removal of block-shaped flexible foam. Following an additional 24 hours of maturation, these foam blocks can undergo cutting and other post-processing procedures.

1 - Raw Material Tank; 2 - Metering Pump Unit; 3 - Control Cabinet; 4 - Mixing Barrel with Elevating Device; 5 - Foaming Box; 6 - Foam Finished Product; 7 - Floating Plate

Picture 2: Box Foaming Equipment Manufactured by Hennecke (BFM100/BFM150)

Box foaming process and equipment exhibit characteristics such as simple operation, compact and straightforward equipment structure, low investment, small footprint, and convenient maintenance. These features make it particularly suitable for small enterprises engaged in intermittent production of low-density block foam. However, its drawbacks are also quite evident: lower production efficiency, less favorable production environment, high concentration of emitted toxic gases on-site, necessitating the use of highly effective exhaust and toxic gas purification systems.

To enhance mixing efficiency, some companies have added several vertical and equidistant baffles to the inner walls of the mixing barrel. These baffles, combined with high-speed spiral-type agitators, facilitate high-speed mixing. This approach can to a certain extent reduce laminar flow effects in the mixing liquid and improve mixing efficiency. An example of this is our product, the SAB-BF3302. For the product's appearance and technical specifications, please refer to Picture 3.

Picture 3: Fully Automatic Box Foaming Machine (Sabtech Technology Limited)

This production line comes with both fully automatic computer control and manual control modes. It's suitable for producing flexible polyurethane foam with densities ranging from 10 to 60 kg/cm. Maximum foam output: 180L. Foam height: 1200mm. Mixing power: 7.5kW. Total power: 35kW.

2. Equipment for Open-Cell Foam Preparation

Open-cell polyurethane foam is a functional foam product developed in the 1980s. It possesses a high porosity, a distinct network structure, softness, breathability, and good mechanical strength. It finds wide application as excellent filtration and shock-absorption material in transportation, instrumentation, medical material filtration membranes, and as catalyst carriers in the chemical industry. Filling it into aircraft fuel tanks can suppress oil agitation and reduce the risk of explosions. Impregnating it with ceramic slurry and high-temperature sintering results in a novel open-cell ceramic filter material used in the metallurgical industry.

The preparation of open-cell polyurethane foam involves methods such as steam hydrolysis, alkaline soaking, and explosion. In industrial production, the explosion method is predominantly used. Initially, polyurethane foam of a specific pore size is prepared using the box foaming process. Subsequently, it's placed in dedicated explosion network equipment, filled with explosive gas, and ignited after completely filling the foam body. By utilizing the impact energy and high-temperature heat generated by the explosion parameters, the cell walls of the polyurethane foam are ruptured and fused onto the cell walls, forming a distinct network structure, as shown in Picture 4.

Picture 4: Clearly Networked Open-Cell Foam

Methods like steam hydrolysis or alkaline soaking are used to prepare open-cell foam. However, there are issues of low efficiency, poor quality, and environmental pollution with these methods. They are mainly employed for small-scale production such as laboratory sample testing. Large-scale production primarily uses the explosion method.

ATL Schubs GmbH, a German company, specializes in the research and development of polyurethane reticulated foam and manufactures the ReticulatusTM foam explosion machinery. The explosion chamber of the reticulated foam explosion equipment comes in two forms: cylindrical and rectangular. The former is suitable for cylindrical foam, while the latter is more versatile. It can be used not only for square foam but also for processing reticulated foam from cylindrical foam, as shown in Picture 5. The explosion chamber is constructed from high-quality 100mm-thick steel plates. Operation is controlled by a computer modem, offering features like automatic opening and closing, automatic locking, automatic operation, and automatic alerts. Additionally, remote program design and modification can be facilitated through data transmission sensors.

Picture 5: Polyurethane Foam Reticulation Processing Equipment (ATL Schubs)

During production, foam bodies measuring 3 to 6 meters in length that are intended for reticulation are pushed into the explosion chamber. The chamber's door is closed hydraulically, and the air inside the chamber is evacuated using a vacuum pump. Under computer control, a precise proportion of oxygen and hydrogen gases is introduced, and the gas mixture's ratio is mechanically adjusted based on factors such as foam sample type and network size requirements. 

Sensors continuously monitor the process, ensuring that all process parameters are within the specified conditions before controlled detonation is initiated. The explosive force and flame intensity generated by the explosion penetrate through the entire foam body, creating a distinct network structure. After forming, the foam body is cooled, residual materials and waste gases are purged using nitrogen, and the pressure chamber can then be opened to retrieve the reticulated foam. The entire process takes approximately 8 to 10 minutes. The pore diameter of the reticulated foam falls within the range of 10 to 100 pores per inch (ppi) (Note: ppi refers to the number of pores within one inch).

The above provides some insight into the non-continuous production process of polyurethane flexible foam. I hope this information proves helpful to you.

PLC (Programmable Logic Controller)

It is an automatic control device with instruction memory, digital or analog I/O interfaces; primarily used for logical, sequential, timing, counting, and arithmetic operations with bit operations; used to control machines or production processes.

Variable Frequency Drive (VFD)

A VFD is a control device that transforms power frequency from one frequency to another using the on-off action of power semiconductor devices.

The main circuits of a VFD can generally be divided into two types:

- Voltage type: Converts DC voltage from a voltage source to AC in the VFD, with capacitor filtering in the DC circuit.

- Current type: Converts DC current from a current source to AC in the VFD, with inductor filtering in the DC circuit.

Photoelectric Switch

It utilizes the obstruction or reflection of an infrared light beam by a detected object, detected by the synchronous circuit, to determine the presence or absence of the object. It can detect any object that reflects light, not limited to metals.

A mirror-reflective photoelectric switch is used on the vacuum perforating machine.

Heat Exchanger System

Controls the temperature of raw materials in the system to meet requirements.

As the temperature of the raw material rises after passing through the heat exchanger, its viscosity increases. To ensure the normal operation of the high-pressure pump, a special feeding pump is required. Specific requirements are calculated based on flow rate and raw material viscosity.

The temperature control of the heat exchanger should be near the mixing head, correlating the raw material temperature with the switch of the cooling water to automatically control the flow of cooling water to cool the raw material.

Perforating Machine

There are roller perforating machines, vacuum perforating machines, and brush perforating machines, with roller machines having the best control effect, followed by vacuum perforating machines, and brush perforating machines being the worst. Currently, brush perforating machines are rarely used.

The purpose of perforating is to prevent product deformation.

The roller perforating machine controls the size of the gaps. If the gaps are too large, the perforating effect is not good; if the gaps are too small, there will be obvious pressure marks on the product.

There are two methods of perforating: 1. Chemical method - using perforating agents, 2. Mechanical method - using perforating machines.

Products must be perforated as soon as they come out of the mold. Some products may expand after being demolded, and at this time, they should be left for a period before perforating.

TPR

It can prevent product shrinkage and collapse of bubbles; its most basic function is effective perforating to facilitate demolding. However, it can also lead to fluctuations in ILD (Indentation Load Deflection); TPR directly affects the rise speed of the foam.

Loop Pressure Regulating Valve

It is crucial for balancing system pressure in the control system and should be placed as close to the nozzle as possible. If it is far from the nozzle, pressure fluctuations may occur, leading to system instability and unstable products.

How to properly control the tension of the upper thread?

When removing the thread, be sure to pass through the thread clamp on the upper thread clamp. The thread clamp cannot be adjusted too tight. When you need to adjust the tightness of the upper thread, you cannot pull the upper thread directly. You must control the tightness of the upper thread through the thread clamp on the control device; when adjusting, it should not be too tight or too loose, and there should be no jamming, otherwise it will cause jumpers. Or disconnected.

How to draw a pattern?

When drawing a pattern for a quilting machine, we can use professional pattern drawing software, but the exported format must be HFP. How to enlarge or reduce the size when drawing a floral pattern? In "Edit Pattern", open "Scale Entire Pattern", and based on our needs, click on the pop-up box's "millimeters" or "inches" option, then add the X and Y parameters according to our needs, and click "OK" after entering.

How to troubleshoot the cause of abnormal noise in a quilting machine?

First, check whether the frequently worn parts are lacking oil, and add some machine oil or grease to the dryer areas; then check whether there is any clearance in the bearings of various components; also carefully observe whether the accessories and wear parts are excessively worn, and replace them timely if discovered.