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Everything You Want to Know about J Box

Mar. 25, 2021

Chapter 1,What is J Box

Everything You Want to Know about J Box

Most people talked about J box in home improvement, but I don’t think most of you have researched junction box till now.

There is a simple explanation on Wikipedia, it says j box is an enclosure housing electrical connections. Junction boxes protect the electrical connections from the weather, as well as prevent people from accidental electric shocks.

In our opinion,this is a little bit written.The junction box is a sort of connector in the entire home power line, they just fix the wires and It keeps you away from electric shock.

It is worth mentioning that different regions have different names for the J box.

For example, in North America and most regions, it is called Junction Box or J Box, while Australia is called Portable Box.Even people called them Cabinet for used large item such as street furniture.They are all the same product except the size are different.

BTW,there are 2 different types on the market,the first one is a metal j box and the other one is a plastic (ABS or PVC ) junction box.We only talked about plastic one for this is our area.




Chapter 2,How About Internal Structure for J Box?

 Everything You Want to Know about J Box


It looks simple after we post the images for the internal structure.But we can still get lots of information.

(1)   Material Thickness

This is important for the product because too thin raw materials are not only easy to damage,but also most of J boxes are buried underground and you can not check them every day.So the plastics are embrittled faster and are more likely to be damaged,it will lead to dust or water entering the adaptable box for causing danger.

(2)   Terminal Block & Block Base

Most of them don’t care about this detail. If they applied too thin or recycle plastic,the fixed place will easily break and cause the terminal block to move in the J box over time. If there are still keep objects especially metal parts in the J box, It is easy to be dangerous.

(3)   Sealing Ring

In general, the sealing ring is made of a rubber-like car.But the biggest problem is the anti-aging and anti-flaming properties are not so good,especially the junction box outside used.

So we used specially formulated PVC soft rubber seals to improve the above properties.

BTW,all the 2-gang, 3-gang adaptable box you have seen on the market, they also need the extra sealing ring for holes,so the difference of the materials will also affect the performance and durability of the sealing rings.

(4)   Screws

In most cases,you need the screw to fix the J box but you do not care about this accessory unless it is missing.

Most of the screws on the market are made of iron with nickel plates.Because iron is easy to oxidize and rust, the electroplated layer can effectively alleviate the occurrence of rust.

But if we applied stainless steel to make screws, you are still worried about this?Actually,this is what we have done.

(5)   Cover

The cover is important too.It is sealing the whole adaptable box with a sealing ring for protecting the dust and water outside.

The thickness and structure design are key points property for the cover.We talked about the thickness and you must know the thicker of product,the better durable in general.But the structure design is important too,why?

Good product design will be got repeated drawing and testing during the design stage, and will generally simulate the real user environment for test purposes.

The best practice is to simulate actual user usage,test what problem is during used,and modify the design to prevent the problem happened.For example, plastic materials may deform invisible to the naked eye after being used for a period time, which may affect the overall sealing performance.Therefore,our designers will add structures that restrict movement in certain places in advance, which we call limit positions.Common practices include adding some extra stress points,or adding some extra accessories to prevent this happening.

Therefore, if the quality and thickness of the raw materials of the J box determine durability in daily used purpose.Then product design, especially the product prototype stage, has already laid a solid foundation for the quality of mass products.


Chapter 3, How to Made Qualified J box?

Briefly,the production of J box mainly includes the following processes

(1)   Mold Making

(2)   Materials Mixed

(3)   Baking Materials & Parameter Adjust of Injection Machine

(4)   Die Closing

(5)   Filling

(6)   Pressure Holding

(7)   Cooling

(8)   Mold Opening & Ejecting

(9)   Post-processing

(10) Quality Checking

(11) Loading & Shipment


⑴Mold Making

Everything You Want to Know about J Box

Mold design and manufacturing is a professional job,and most of the processes are involved and it takes 20-30 days in general.

Generally,the industry confirms and arranges the project through preliminary samples or drawings, and then reviews the possible problems in the mold manufacturing process.This is the first step.

The second step is to order raw materials and standard parts after confirmation,and then process the raw materials and accessories and assemble them.The last step is to test the mold after assembly.This is mainly to test whether the various parts of the mold can work well, and then whether the qualified products are manufactured according to the expected plan product.

Why did we claim this job professionally? Because the mold designer and maker not only be good at the mold design and the role of each structure,but also learned the working process of the injection machine and predict the possible problems.

However,the hardness enhancement and precision control of the mold itself in the manufacturing industry have reached a high level. The commonly used vacuum quenching to enhance the hardness,and the application of CNC numerical control machine to cut and engrave of the mold, the unit for calculating the internal tolerance of the mold is 0.01 ( Calculate by millimeters ),so that the products produced can guarantee the same quality.


⑵Materials Mixed

Everything You Want to Know about J Box

Per you understood that plastic products are produced with plastic raw materials,right?But the truth is these products need to be combined with toner or color masterbatches to dye color,because the general plastic material particles are only pure white.

Moreover, in the early stage of injection molding, it is necessary to match the toner or color masterbatch according to the proportion of the formula to be used normally.In addition, it is necessary to add additional additives,such as flame retardants.According to different products and end uses, which can increase the flame retardant coefficient of the product.

Because there are some subtle differences in the application of formulas in the industry, we will not detail explain here. This part is just letting readers understand that in the early stage of injection molding, it is not just simply preparing plastic raw materials.


⑶Baking Materials & Parameter Adjust of Injection Machine

Everything You Want to Know about J Box

Plastic raw materials need baking first in general,or it will cause water lines and other defects in the final product for water contained in the material,which will reduce the qualification rate of the product.

Different raw materials have different times and temperatures in the baking process.You must be paying more attention to excessive do.Or it will affect the performance of the plastic material.

We would like to talk about injection molding machines now.

Generally, the injection molding machine needs to debug the relevant parameters before pre or mass production.Such as inbound barrel temperature,injection pressure and speed, holding pressure time, and so on.

All parameters adjusted need considering different raw materials and product type,even the mold condition,and there is no standard data that can be used directly.So the personnel who need to debug have a clear understanding of the raw materials, the principle of the injection molding machine,and the products,then debugging can be completed in the shortest time and save waiting time for the machine.


⑷Die Closing

Die Closing is an action of the injection molding machine,but it is mentioned separately because this step is important for the whole production process.Because the opening and closing of the mold involve a lot of professional knowledge, such as clamping force. We just want to explain briefly here, so that everyone has a simple understanding of this process. When the mold is locked, the melted plastic will be injected mold cavity in the next step, so the role of this step is to prepare for the next one.

Therefore, the reader can simply understand that the mold is ready to be formed after the mold is closed.



As we mentioned above it calculates the pressure and time for the injection of the compound into the mold cavity,the injection molding machine in the industry commonly uses 3-stage even 4-stage segmented injection when it is injected into the cavity.Which will accurately control the amount of filling.

Therefore, if you need to adjust the time and pressure during injection molding, it is necessary to calculate the injection pressure and time based on the weight of the product and mold runner consumption numbers to ensure that the rubber is sufficient during the production.Or there will be a lack of plastic (It looks like the product has not been complete to injection.For example, the corners are still not complete).

In some cases,debugging the machine needs to slowly modify the parameters, using seconds and minutes to test the injection time,etc.The details are not explained here. This step is the key process of injection molding.It can be said that the success of this step is at least 50% related to product quality.


⑹Pressure Holding

The meaning of Pressure Holding is the duration of the pressure applied by the mold, which allows the plastic to gradually shape after being injected into the mold cavity.

When the plastic material is injected into the cavity,it is a hot liquid,so it takes time for it to gradually shape.The setting of time and pressure in this process is very important.For instance,the correct setting of time and pressure can allow the product to be fully shaped and compact every structure inside.On the contrary, the product will have problems such as uneven plastic materials in various parts and even adhesion to the mold.

The reader can simply understand this step as,After the rubber is injected, the shape and structure of the product are fixed with force to make the product structure compact.



Hot liquid and frequently open & closed actions will make mold temperature inevitably increased.The mold temperature must be keeping right value rang to ensure mass production, so the mold needs to be installed cooling system to make sure that the mold temperature is always kept at the optimal temperature around.

The cooling system has been considered at the beginning of mold manufacturing,. Therefore,lots of water channels will be designed on the mold to ensure that the water flow assists the mold to dissipate heat. Yes, the mold uses a water cooling device for cooling. There are 2 key points here.The first is that the design of the waterway must be reasonable to ensure that the mold can be cooled as a whole,or it can not guarantee the normal operation if it is only a partial cooling.The second is that the sealing and position of each water nozzle are very important.Tightness nozzle is to ensure that the mold will not leak water and cause accidents.The location is to ensure that it will not affect the normal operation of the mold and the convenience when connecting to the waterway.


⑻Mold Opening & Ejecting

Everything You Want to Know about J Box

You are almost there!

This is the last step of injection molding machine production. When the molding and cooling are completed,the mold needs to be opened.At this time,our injection molded products have been produced.At this time, the products need to be taken out within the in time when the mold is opened.

Theoretically,the opening and closing of the mold are controlled by computer. The computer will control the injection molding machine to open the mold when the time is set, so this step does not require much explanation.

What about ejecting?This step will encounter some problems.For example, when the mold is opened, we found the plastic part cannot be removed,and maybe partially stuck on it or other related problems. At this time, the technician needs to determine the cause according to the situation and debug again.The machine ensures the back to normal next time.

We supposed everything works well,there are generally two ways of operation to get the products.

The first is that workers take it directly by hand or fall naturally by gravity, and then we can prepare a plastic plate or box under the machine to catch it;The second is using a robot arm,you can set the parameters on the robot arm first after purchased.Oh,do not forget about installed on the injection molding machine.When the mold is opened, the robot arm will move to the middle of the mold, use a suction base or similar device to pick up the product, and then place it in our designated position,it looks like production automation.



Everything You Want to Know about J Box

The content of post-processing is generally to remove the plastic nozzle part,or take out the required product from the whole set of ‘products tree’.However,it is necessary to cut the nozzle to make the surface of the product flat without scraping hands.

At the same time,workers will check the quality issues during operation,and this step will be before the quality department.If they found any problems,the technical staff will be notified to check the status.Which ensures the smooth production of the product and eliminates the problem.

If there are no problems here,the worker will stack the product neatly in the packaging container following the ‘Working Guideline’ and waiting for inspection by the quality department.


⑽Quality Checking

Quality staff will detect all possible problems with the product at the production line.They will use professional tools to test whether the product has problems in strict accordance with the requirements of the internal document guidelines. If they cannot judge at present,they will be taking samples to the laboratory for related testing to finally confirmed the product is ok or not.

Common inspection projects include outer diameter length and width, inner diameter length and width,verticality,wall thickness and related chemical performance tests, such as aging test, UV test,and so on.

In short, the purpose of quality inspection is to find problems early, and not to send defective products to customers.


⑾Loading & Shipment

Everything You Want to Know about J Box

We talked about the 2 things that should be paid attention to when loading and shipment, you can click the link to view.

However we plan to make a PDF file to explains some precautions during loading and unloading of goods and transportation,and open download it to our readers. We will add a link here at that time.


That's it.


Chapter 4,How to Choose J Box?

We talked about tons of details in chapter 2 and named How About Internal Structure for J Box?You can review this chapter and got more information.We split adaptable box details for you.

Now,we would like to reveal more information here.


You can use your lighter burning the j box and see anti-flame first.If the flame goes out in 30 seconds,it looks like has a primary fire-proof performance.

You can also see the smoke is black or not.If the smoke is too dark, it means added too much recycled raw material in it,which will affect the performance of the material.



We are generally more subjective in terms of whether the appearance is qualified or not. So we list some visible parts for your reference.

Check for any deformation.Contains accessories such as J box main body cover,you can take a straight steel ruler for a simple comparison if available.

Check the size of the J box is acceptable.According to the purchased size, use the rough measurement just now to measure whether each size is qualified.

Check the surface of the adaptable box is scratched or not. Although these are some details, it reflects the manufacturer's focus on quality or not. If the details are not done well,the quality of the product will not be very good.

Check the seriously dirty inside. Similarly, if the basic cleaning is not done before shipping to the factory,it also means that the manufacturer does not pay more attention to the product.Of course, J box is an industrial product only,if you comparison with children's toy,this is unreasonable.

Check the appearance of the accessories.Check whether the accessories of the matching J box are normal in appearance and whether they are damaged or not.

Color checking.Check all J boxes for color uniformity. If there is a serious color difference in some areas with the entire box, it may prove that there may have been the quality issue or there may be problems with the raw material formula.


    IP Rate

Everything You Want to Know about J Box

You can simply test the IP rate of the adaptable box.Do not need a lab,do not need complex tools.

Generally, IP65 means that the dust-proof grade reaches level 6,which can completely protect the dust in.The latter number 5 means it has to prevent spray water from entering, the water flow rate needs to reach 12.5L/min, and the test time is 3 minutes.

As a consumer,you do not have such complete equipment,we only need to test the waterproof because the waterproof level can be achieved,then it is proved that there is no problem with the sealing performance, and the dust resistance can be achieved also.

The test method is so simple, just connect a water pipe in your yard, and then the nozzle is about 39-59 ft away from the J box, and spray it for 3 minutes. If there is no water inside,it is qualified.


    High & Low-Temperature Test

Everything You Want to Know about J Box

Preparing the same two adaptable boxes.The one place in a refrigerator at -20 or -45°C and the other one place electronic oven at 120°C. After 2 hours later, take them out, and then they will fall freely at 45° from a height of 4.9ft. If there is no break, it is qualified.


Congratulations,you must know how to choose a good J box now.


Chapter 5,FAQ

    What different types & size J box on the market?


By Materials, Metal and Non - metallic.

By Shape, Round, Square, Octagon, Pancake, Rectangular

By Connector, 2 to 4 gang


Considering most of the different sizes on the market,we list the size list for your ref only for home decoration purposes.

3.35 x 3.35 x 2.44 in ( L x W x H )

4.13 x 4.13 x 2.83 in

4.25 x 4.25 x 1.97 in

6.42 x 4.25 x 3.19 in

8.31 x 4.25 x 3.19 in

11.81 x 7.87 x 5.98 in

11.81 x 7.87 x 7.87 in


    J box or adaptable box can be used for Ethernet & Bluetooth purposes?

Exactly,most of DIYers used J box for these.You only pay more attention to the signal interference issue for 2.4GHz used by most of the home appliances(Bluetooth used 2.4Ghz also). And if you would like to place a Bluetooth transmitter,do not to bury the J box deep under the ground for the signal will be weak.(Not mentioned about the sealed J box will also block part of the signal)


    What is an outdoor electrical junction box?

In fact, the outdoor use J box needs to meet the following conditions.

1. IP Rate. The IP rating must be at least IP65 or above, and the current highest rating is IP68, which can block the ingress of dust and water;

2. Prevent the bad weather outdoor.For example, the sun shines for a long time, heavy rain and rest of bad weather conditions.So the adaptable box must be pass UV-related tests, flame-retardant tests, and compression tests etc.Now the J box can be used outdoors.


④ What's mean of explosion proof, dustproof,rustproof,waterproof,weatherproof?

Dust and waterproof,we explain on above,actually, this is involved in IP rate.For example,IP65 means 6 grades of dustproof with 5 grades waterproof.

Explosion-proof means The conduit will not explode when it encounters combustion or a large amount of pressure,so that it will not cause further danger.

According to industry experience, this item is generally tested in IEC60079,so you only need to buy products that comply with IEC60079 to avoid such problems.

Weatherproof we talked about above,it similar to the outdoor J box,so it needs to pass UV- tests, flame-retardant tests, and compression tests etc.

Rustproof for metal J box or accessories.IEC 60670 will be test related rate,and China published related papers named GB8923.1-2011 and list A,B,C,D grade for this.

But you are still don't know more details.For example,all iron products will be coated with a chemical coating to prevent rust before shipped from the factory.It looks good,right.

But this layer of anti-rust chemical coating will be failed over time.(We has not mentioned about the thickness and quality of the coating is ok or not)

The best metal raw material for rust prevention is stainless steel,which is why our J box uses stainless steel to make screws.


⑤IP code means what?

Most of the people confused about this IP code and we simply explain here.

We take IP65 as an example,

IP (Ingress Protection )   6 (Dust Protection Grade)    5 (Waterproof Grade)


As to the detail numbers meaning,you can check the list as below,


Dust protection level (from 0 to 6)

0. no protection

1. Prevent the intrusion of large solids

2. Prevent the intrusion of medium-sized solids

3. Prevent the intrusion of small solids

4. Prevent solids larger than 1mm from entering

5. Prevent the accumulation of harmful dust

6. completely prevent dust from entering


Waterproof Grade (From 0 to 8)

0. no protection

1. Water droplets into the shell have no effect

2. Water or rain dripping onto the shell from a 15-degree angle has no effect

3. Water or rain dripping onto the shell from a 60-degree angle has no effect

4. Water splashing from any angle has no effect

5. Low-pressure injection at any angle has no effect

6. High-pressure water jet has no effect

7. Resistance to water immersion in a short time (15cm-1m, within half an hour)

8. Long-term immersion in water under certain pressure


⑥What is a fiberglass electrical box?

Still an electrical box or J box / adaptable box but has different performance for different materials.It still has pros and cons,We list some for your ref.


Perfect chemical resistance.Compared with plastic products,the chemical resistance rate is better.It can work with general cleaning agents,carbon tetrachloride and toluene and will not corrode it,and it can even be used in the high salt area.Moreover, its flexibility is slightly better than that of plastic products.


Its cons are also obvious.The price is more expensive than plastic products.

In addition, you need to be more careful when processing because the glass fiber will spread out and may enter the eyes, so you need additional protective equipment to continue the operation.

Although it can be perfect to protect chemical corrosion,it does good protection against sunlight exposure.After long-term exposure,it will affect the structure and strength of the glass fiber,making them deformed or even scrapped.

In addition, the competitor mentioned they are easier to cut match with metal products,but we believe that this is not an advantage compared to plastic products. The processing of plastic products is simpler and does not require additional protection.

As for insulators, some competitors say that glass fiber is an insulator, and plastic is undoubtedly an insulator too, so this is not an pro also.


Fiberglass electrical boxes are used for special regions and environments.But for home decoration purposes,plastic products is the smart choice.

⑦How much does a junction box cost & Where to buy a junction box?

It hard to say because the price depends on size.

But for home decoration purpose J box / adaptable box,the detailer price range should be $5 to $20,the wholesales should be cheaper but you need to buy more.

Where to buy it?

Of course, you can choose an e-commerce company such as Amazon or Walmart to purchase if you just a consumer.But you can try to follow our suggestions to run a simple test after purchasing,then you can learn about the product quality before installation.

We highly recommend you can contact us now for getting more professional guidance if you are a wholesaler or brand merchant.

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