What Is Continuous Foaming Machine Price?

When using a batch foam machine for polyurethane soft foam foaming, have you encountered the following situations?

1.Uneven and numerous foam pores,

2. Rough foam texture.

3. Chaotic pore sizes across the entire foam surface, with slight signs of large pores.

Issues like these are quite common. The main reason for the first issue is that the distance between the mixing impeller of the foam machine and the bottom of the mixing barrel is too great; the second issue is that the mixing blades are too short and narrow: the third issue is that the angle of the mixing blades is too large.

Many manufacturers who design and produce foam machines only understand the principles during the design process, without understanding the significant relationship between a different design in foam production and product quality. A reasonable and perfect mechanical design can only be gradually improved in actual work, and only experienced foamers can achieve this.

Here are some experiences we have had with machine modifications and upgrades, hoping they will be helpful:

First, the installation position of the mixing wheel should be as low as possible, closer to the bottom of the mixing barrel is better. In general, the distance between the lowest point of the mixing blade and the bottom of the mixing barrel should be around two centimeters

Second, the shape of the mixing blade should be fan-shaped, with a moderately wide edge. The advantage of being wide is that it increases the contact area with the liquid material, providing sufficient power and also balances the liquid material.

Third, the length of the mixing blade should also be as long as possible, leaving about three to four centimeters from the baffle inside the mixing barrel.

Fourth, the two edges of the mixing blade should be sloped, with the angle of inclination based on the width of one end and two centimeters difference on both sides. After the mixing blade is modified, proper operation is also crucial, especially the mixing speed. Most batch foam machines nowadays are equipped with high-speed timing frequency conversion devices. However, in actual production, this device is often unnecessary. The operating speed mainly depends on the amount of material in the mixing barrel. If there is a lot of material, the speed should be appropriately faster, and if there is less material, then the speed should be lower.

Testing Conditions:

1. Fast foaming is taken from the center of the foam, while molded foam samples are taken from the central part or for whole sample testing.

2. Newly made foam should be matured for 72 hours in its natural state before sampling. Samples should be placed in a constant temperature and humidity environment (as per GB/T2918: 23±2℃, relative humidity 50±5%).

Density: Density = Mass (kg) / Volume (m3)

Hardness: Indentation Load Deflection (ILD), Compression Load Deflection (CLD)

The main difference between these two test methods is the loading area of the foam plastic. In the ILD test, the sample is subjected to a compressed area of 323 cm2, while in CLD the entire sample is compressed. Here, we will only discuss the ILD test method.

In the ILD test, the sample size is 38*38*50mm, with a test head diameter of 200mm (with a round corner of R=10 on the bottom edge), and a support plate with 6mm holes spaced 20mm apart. The test head loading speed is (100±20) mm/min. Initially, a pressure of 5N is applied as the zero point, then the sample is compressed to 70% of its thickness at the zero point, and unloaded at the same speed. This loading and unloading is repeated three times as pre-loading, then immediately compressed at the same speed. The compression thicknesses are 25±1% and 65±1%. After reaching the deformation, hold for 30±1s and record the relative indentation value. The recorded value is the indentation hardness at that compression level.

Additionally, 65% ILD / 25% ILD = Compression Ratio, which is a measure of foam comfort.

Tensile Strength, Elongation at Break: Refers to the maximum tensile stress applied during the tensile test until fracture, and the percentage elongation of the sample at fracture.

Tensile Strength = Load at Fracture / Original Cross-sectional Area of Sample

Elongation at Break = (Fracture Distance - Original Distance) / Original Distance * 100%

Tear Strength: Measures the material's resistance to tearing by applying specified tearing force on a sample of defined shape.

Sample size: 150*25*25mm (GB/T 10808), with the sample thickness direction as the foam rise direction. A 40mm long incision is made along the thickness direction (foam rise direction) at the center of one end of the sample. Measure the thickness along the sample thickness direction, then open the sample and clamp it in the test machine fixture. Apply load at a speed of 50-20mm/min, using a blade to cut the sample, keeping the blade at the center position. Record the maximum value when the sample breaks or tears at 50mm.

Tear Strength = Maximum Force Value (N) / Average Thickness of Sample (cm)

Usually, three samples are tested, and the arithmetic mean is taken.

Resilience: Measures the foam's rebound performance by allowing a given diameter, weight steel ball to freely fall onto the surface of the foam plastic sample from a specified height. The ratio of the rebound height to the steel ball's drop height indicates the foam's resilience.

Test Requirements: Sample size 100*100*50mm, the ball drop direction should be consistent with the foam usage direction. The steel ball size is ∮164mm, weight 16.3g, and it drops from a height of 460mm.

Resilience Rate = Steel Ball Rebound Height / Steel Ball Drop Height * 100%

Note: Samples should be horizontal, steel ball should be fixed before dropping (static), each sample is tested three times with 20s intervals, and the maximum value is recorded.

Compression Permanent Deformation: In a constant environment, the foam material sample is maintained under constant deformation for a certain period, then allowed to recover for a period of time, observing the effect of the deformation on the sample's thickness. The ratio of the difference between the initial thickness and final thickness of the sample to the initial thickness represents the foam plastic's permanent compression deformation.

Compression Permanent Deformation = (Initial Thickness of Sample - Final Thickness of Sample) / Initial Thickness of Sample * 100

Are you testing foam performance? Choosing the right foaming machine is crucial to your product quality!

We specialize in efficient and reliable polyurethane soft foam production equipment, including foaming, cutting, and lamination machines. Contact us now for a free solution and quote!

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.

The production of block-shaped soft foam typically utilizes the batch foam machine foaming process, a gap-type production method. This method evolved from manual foaming in laboratories. The process involves immediately pouring the mixed reaction materials into an open mold resembling a wooden or metal box, hence the name "boxed foam." The molds (boxes) for boxed foam can be rectangular or cylindrical. To prevent the foam block from forming a domed top, a floating cover plate can be placed on the top of the foam during foaming. The cover plate stays closely attached to the top of the foam and gradually moves upward as the foam rises.

The main equipment for boxed foam production includes: 1) Electric-mechanical stirrer, mixing barrel; 2) Mold box; 3) Weighing tools such as scales, platform scales, measuring cups, glass syringes, and other measuring devices; 4) Stopwatch for controlling mixing time. A small amount of mold release agent is applied to the inner walls of the box to facilitate easy removal of the foam.

The advantages of producing soft foam using the boxed foam method include: low equipment investment, small footprint, simple equipment structure, easy and convenient operation and maintenance, and flexible production. Some small and underfunded domestic and township enterprises use this method to produce polyurethane soft foam. Boxed foam molding is a non-continuous production method for soft foam, so the production efficiency is lower than continuous methods, and the equipment is mostly manually operated, resulting in higher labor intensity. Production capacity is limited, and there is a greater loss in cutting foam plastics. The process parameters for boxed foam should be controlled within a certain range because even with the same formula, the foam properties may not be the same when different process parameters are used. The raw material temperature should be controlled at (25±3) degrees Celsius, mixing speed at 900 to 1000r/min, and mixing time at 5 to 12 seconds. The mixing time of the polyether and additives mixture before adding TDI can be flexibly adjusted depending on the situation, and after adding TDI, a mixing time of 3 to 5 seconds is sufficient, with the key being thorough mixing after TDI addition.

During boxed foam molding, attention should be paid to the following aspects:

1) Prepare before production, including material temperature and machine equipment inspection;

2) Measure as accurately as possible;

3) Control the mixing time appropriately;

4) Pour the mixed material liquid quickly and steadily, avoiding excessive force;

5) Ensure the box is placed steadily, with the bottom paper flat, to avoid uneven material flow during pouring;

6) When the foam rises, gently press the cover to ensure the foam rises smoothly;

7) Additives should be used as specified, and pre-mixed materials should not be left for too long.

Three types of foam equipment have emerged in boxed foam molding. Initially, various raw materials were weighed into a container according to the formula, mixed with a high-speed mixer, and poured into the box mold for foaming and shaping. This method often resulted in residue in the mixing container. An improved method used a metering pump to transport the raw materials to the mixing barrel for uniform mixing. A mechanical device automatically closed the bottom of the barrel, and compressed air was used to press the material into the foaming box for shaping. Both of these methods could create eddies due to the rapid influx of materials into the box, which might cause defects or depressions in the foam products. The most reasonable boxed foam device is to place a bottomless mixing barrel directly in the center of the foaming box. A metering pump delivers the various raw materials needed for foaming into the mixing barrel. After mixing for a few seconds, the lifting device raises the mixing barrel out of the foaming box, allowing the foaming material to flow smoothly over the entire box bottom. This prevents foam cracking due to material eddies, and ensures relatively uniform height throughout the foam.

A pressure device can be added to the expanding foam material to produce flat-topped foam, reducing waste during cutting. This device is suitable for the production of polyether-type polyurethane soft foam and high rebound soft block foam. For polyvinyl acetate polyurethane blocks, this method cannot be used due to the high viscosity of the material, and continuous methods are generally employed.

Understanding the principles behind foam reactions is crucial. To master foaming, we must strive to establish a foam reaction model in our minds using the following four reaction equations. Through familiarity with the variations within the model, we cultivate sensitivity that allows us to comprehend the entire foam reaction process. This approach helps structure our knowledge base and professional skills in polyurethane foam. Whether actively studying foam reaction principles or passively exploring them during the foaming process, it serves as a vital means for us to deepen our understanding of formulations and enhance our skills.

Reaction 1

TDI + Polyether → Urethane

Reaction 2

TDI + Urethane → Isocyanurate

Reaction 3

TDI + Water → Urea + Carbon Dioxide

Reaction 4

TDI + Urea → Biuret (Polyurea)

01: Reactions 1 and 2 are chain-growth reactions, forming the main chain of the foam. Before the foam reaches two-thirds of its maximum height, the main chain rapidly elongates, with chain-growth reactions predominating inside the foam. At this stage, due to relatively low internal temperatures, reactions 3 and 4 are not prominent.

02: Reactions 3 and 4 are cross-linking reactions, forming the branches of the foam. Once the foam reaches two-thirds of its maximum height, the internal temperature rises, and reactions 3 and 4 intensify rapidly. During this stage, reactions 1 to 4 are vigorous, marking a critical period for the formation of foam properties. Reactions 3 and 4 provide stability and support to the foam system. Reaction 1 contributes to foam elasticity, while reactions 3 and 4 contribute to foam tensile strength and hardness.

03: Gas-producing reactions are termed foaming reactions. The generation of carbon dioxide is a foaming reaction and the primary exothermic reaction in polyurethane foam. In reaction systems containing methane, the vaporization of methane constitutes a foaming reaction and an endothermic process.

04: Reactions leading to the formation of foam constituents are known as gelation reactions, encompassing all reactions except for gas-producing reactions. This includes the formation of urethane, urea, isocyanurate, and biuret (polyurea) from reactions 1 to 4.