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I recently bought a barely used JBC JT6040 hot air station and also found a heavily used older JT6040 as a potential spares donor for the future. The JT6040 is a very nice piece of equipment but it’s design has lead to me looking at the different types of air pump/compressor used in hot air stations.
The newer model of JT6040 uses a Regenerative air compressor driven by a 240V Universal brushed motor. The Compressor motor RPM is controlled via a pretty standard ac motor speed controller. The older version of the JT6040 uses a different air pump design. The compressor is long and relatively small diameter and appears to be a multi stage turbine of some sort. The motor used to drive the compressor stages is a brushed DC type that is mounted in the air path within the compressor casing. This compressor is surprisingly noisy in operation and sounds like it has some form of gearbox within it. A small fan is visible at the rear of the tubular housing but this alone would not produce the required performance. I will add pictures of these two JBC air pumps to this post later.
Seeing these two different forms of air compressor got me thinking about the different technologies I have seen in my hot air rework stations. These are the ones that I have seen used in this application (including the JBC units mentioned above):
1. Dual diaphragm pump - similar in design to aquarium pumps and uses a pair of bellows connected to an inductively driven linear movement armature.
2. ‘Turbine’ blower - Pace have used what appears to be a variant of a centrifugal fan but they describe it as a “turbine”. It bears no resemblance to the multi stage turbine compressors used in aero engines though !
3. Centrifugal fan - Used in many recent models of hot air rework station. Mounted either in the station base unit or in the hot air handpiece. Usually driven by a brushed or brushless DC motor and associated speed controller.
4. Conventional piston compressor driven by a DC or AC motor - this compressor is relatively complex and expensive to manufacture but has been seen in high end hot air rework stations. In its simplified form it is still seen in a motor driven diaphragm variant for vacuum pickup tools.
5. Regenerative Compressor - Used in the JBC JT6040. Driven by a powerful 240V universal motor and ac speed controller
6. Multi stage turbine compressor ? - Believed to be used in the early JBC JT6040. Driven by a DC brushed Motor and dc speed controller
So why am I listing these different air pump/compressor/blower types ? Well I have discovered something interesting about their differences besides mechanical design. The diaphragm, motor driven piston and Regenerative compressors can produce decent air pressure at low air flow rates. The simple turbine and centrifugal ‘blowers’ are not normally capable of producing much air pressure at low air flow rates. Why does this matter ? Well in the case of a hot air rework station you do not want very high air flow that blows components off of the PCB yet you do want air pressure that is maintained even with highly restrictive small cross section air output nozzles.
So in theory, the diaphragm, motor driven piston and regenerative air compressors are ideal for hot air rework with different output nozzle sizes and lower air flow rates (below 40 l/m) but the centrifugal and turbine blowers are most unsuited to that deployment ! The centrifugal and turbine blowers are best suited to applications that require high volumes of air movement with little variance in back pressure through changes in output port cross sectional area. They are not normally considered appropriate to a interchangeable output nozzle size application as back pressure becomes an issue and these pumps are incapable of producing much pressure, especially at low air flow rates.
So with the above in mind, why are we seeing centrifugal and simple turbine type air blowers in hot air rework stations that, by their very nature present the blower with a less than ideal variable output port size, back pressure and a need for low flow rates ! I am surprised that the blowers even work properly. I can understand a centrifugal or turbine blower used in a hot air paint stripper, heat shrink gun or hair dryer as the output port size is reasonably large, but using such a blower for SMT rework just seems illogical if the air pump/blower manufacturers guidance is to be believed.
We all know that some cheap ‘in handle’ hot air stations that use a centrifugal blower do not shower themselves in glory for various reasons but we are seeing centrifugal air blowers in the recent high power Quick and even JBC hot air stations. For me this is an interesting development. Are those manufacturers just using ‘oversize’ blowers to overcome the pressure issues or is there another clever ‘trick’ being used I wonder ?
I am no expert on air pumps or compressors so welcome others thoughts on the matter. For information, I purchased a pair of very nice AMETEK Microjammer 3” BLDC powered blowers that are great quality. I was thinking of using them in my diaphragm pump based hot air stations, in a similar way that Quick use such a blower. Having read the AMETEK data sheets carefully and their guidance on such blowers..... they seem totally unsuited to the hot air station application. They are recommended for 700l/m unobstructed air flow, not <40l/m highly obstructed output air flow
Nice blowers though 
I will add some information on Air pump/blower selection from AMETEK shortly to this thread. I hope the topic is of interest to others as I have never really bothered to study air pump/blower technology, beyond using cooling fans and seeing various air pumps in equipment.
Fraser
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Quote
So in theory, the diaphragm, motor driven piston and regenerative air compressors are ideal for hot air rework with different output nozzle sizes and lower air flow rates (below 40 l/m)
In practice they are the worst type you can get. They produce highly fluctuating airflow. The result is that even with low airflow it's very easy to knock off components from PCB. -
The JBC JT6040 regenerative air pump. Low flow rate but relatively high pressure capability
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JBC early JT6040 possible multi stage turbine pump.
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The Pace 'turbine' pump
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The common Dual Diaphragm pump.....
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Small centrifugal blower - handle mounted .....
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Centrifugal fan used in the Quick series of hot air stations and now used in the JBC stations......
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AMETEK comment on air pump/blower selection:
From: https://www.ametekdfs.com/learningzone/ametek-dfs-blog/comparingregenerativeblowers
What is a Regenerative Blower?
A regenerative blower has impeller blades passing the inlet port to draw air or other gases into the blower.The impeller blades then, by centrifugal action, accelerates the air outward and forward. Here the regenerative principle takes effect as the air is turned back by the annular shaped housing to the base of the following blades where it is again hurled outward. Each regeneration imparts more pressure to the air. When the air reaches the stripper section at the outlet (the stripper is the part of the blower Located between the inlet and the outlet in which the annulus is reduced in size to fit closely to the sides and tips of the impeller blades) the air is stripped from theimpeller er and diverted out of the blower.The pressures or vacuums generated by the one or two spinning, non-contacting, oil-free impellers are equal to those obtained by many Larger multi-stage or positive displacement blowers.
What is a Positive Displacement/Rotary Lobe Blower?
Unlike the blower mentioned above, a positive displacement blower (also called a rotary Lobe or PD compressor) operates using the positive displacement principle, whereby two figure eight, precisely machined impellers are mounted on parallel shafts. These shafts are married together and turn in opposite directions.The shafts are held in synchronization by lubricated gears, mating the two shafts together. The gears need to be continually submerged in a bath of oil or other lubricants, and sealed from air flow. Rotary lobe/positive displacement blowers can be used in applications requiring constant flows and pressures of 4-15 PSI.
What is a Rotary Vane Blower?
Rotary vane blowers are similar to PD blowers, but they can provide variable pressure at a constant flow. Most popular units have a series of four or more sliding vanes fitted into a rotor. These vanes will capture free air as the offset rotor passes the inlet port. As the rotor turns the air is compressed by the decreasing space on the inlet. This compressed air is forced out of the pressure port.
What is a Centrifugal Blower?
A centrifugal blower is similar to a multi-stage centrifugal blower in that the flow will be variable while the pressure or vacuum remains constant. This design is normally found where a Large flow is required with Low pressure. Air enters the center of a rotary impeller in which there is a number of fixed vanes, using centrifugal force the air is directed outward where it is discharged.
What Performance is Available?
With all of these blowers, you must be thinking they have similar performance Levels, but this is not the case. In order to help you decide what blower is best for your application, it is helpful to know the approximate flow and pressure that you will need to have for your project. Don't forget to think about any system impedance that may change performance Levels. Let's discuss the different performance Levels for each type of blower.
Rotary vane blowers perform best for higher pressure Levels (IWG) and Low flow Levels (CFM). Rotary Lobe (positive displacement) blowers are best for high pressure Levels but can also handle a Large volume of air flow. When you are considering a blower that has high pressure Levels remember to also think about mufflers and noise reduction techniques to help combat the high noise Levels of these blowers. Adding silencers and mufflers may require you to readjust your needed performance Level. Many blower manufacturers sell these add-on accessories when you purchase a blower.
On the other hand, centrifugal blowers can provide high flow while maintaining Low pressure. They are great if your application requires a Large amount of air flow, rather than high pressure. To maintain flow Levels, these blowers run at top speed. As you can see in the performance Levels chart, centrifugal blowers can produce flows up to very Large volumes. Please keep in mind that different manufacturers have different rates of flow for their blowers, we're providing you with the most common flow and pressure for each type of blower discussed.
Finally, Regenerative blowers cover a wide range of performance Levels, due to their unique design. These blowers can efficiently and effectively work in most applications where you could use a rotary vane, PD, or centrifugal blower. They also provide performance Levels up to 250 IWG and up to 1800 CFM. These blowers also are available with accessories specially designed for the blower, in case you need noise reduction or filtration for your application.
The chart below shows the performance Levels for each type of blower discussed. As you can see, not all of the blowers operate in the majority of performance Levels
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Stanmech comment on Regenerative and Centrifugal types of air pump/blower
https://www.stanmech.com/articles/regenerative-versus-centrifugal-blowers-what-are-they-and-when-do-i-use-what
Both regenerative and centrifugal blowers are widely used in industrial processes. Superficially the two types of blowers can seem similar and it can be difficult to find good information on the differences between the two types of blowers and why one would be selected over the other.
First, we’ll discuss what the two types of blowers have in common. Both types move air using an impeller on a rotating shaft. The air comes in the inlet and is focused while traveling with the impeller before exhausted as linear flow at the outlet. This is where the similarities end.
How can you tell the difference?
The difference in construction between a centrifugal and regenerative blower make it easy to tell the two apart by sight. A centrifugal blower is configured so that the inlet and outlet are perpendicular, with the inlet feeding air into the centre of the impeller and the outlet tangential to the rotation of the impeller. In a regenerative blower the inlet and outlet are parallel with both positioned perpendicular to the rotation of the impeller
Blowers
What is the practical difference?
The impeller and impeller casing of the two types of blowers are designed for different end uses. In centrifugal blowers, air enters at the center of a rotating impeller on which there are a number of fixed vanes. As the name implies, centrifugal blowers move air through centrifugal action, air is forced to the periphery of the impeller and housing where it is discharged as a steady stream through the outlet. The negative pressure created at the centre hub, in turn, sucks in more air. The vanes basically act as paddles to push volumes of air to the outlet. No significant pressure is built up in this process but centrifugal blowers can be used to move large volumes of air.
In regenerative blowers, as the impeller pushes the air around the ring, centrifugal forces cause the air trapped between the rotating impeller vanes to move towards the blower casing. The air flow is then forced to the base of a following impeller vane for recirculation in the same manner. This circular flow in combination with the revolution of the impeller causes air to follow a spiral path through a regenerative blower (see picture); the result is air that is under constant acceleration. This "regeneration" of air with each revolution allow regenerative blowers to develop significant pressure.
As a general rule centrifugal blowers are considered low pressure, high flow blowers while regenerative blowers are high pressure, low flow blowers. These fundamental characteristics inform the types of applications to which they are suited.
Where to use what?
Centrifugal blowers work for applications such as heating a furnace with hot air where a large air volume is required to fill the space. Blow-off applications are generally better suited to centrifugal blowers because large volumes of air are required to get optimum air velocity out of air knives.
Regenerative blowers can produce enough pressure to overcome air flow constraints in a process system; for example, if a nozzle is required that constricts the air flow from a large cross section to a smaller cross section. If the air is required to travel a suboptimal path with sharp bends or a torturous route the pressure of a regenerative blower will be useful.
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The diaphragm, motor driven piston and Regenerative compressors can produce decent air pressure at low air flow rates. The simple turbine and centrifugal ‘blowers’ are not normally capable of producing much air pressure at low air flow rates. Why does this matter ? Well in the case of a hot air rework station you do not want very high air flow that blows components off of the PCB yet you do want air pressure that is maintained even with highly restrictive small cross section air output nozzles.
Seems to me that, as long as the restriction (i.e. the nozzle diameter) does not vary dynamically, the "pressure vs. flow rate" property of the air source is not too critical. Choose a nozzle diameter, then set the fan speed such that you get the desired air flow -- done. This should work with any old fan, and works well enough in practice, as witnessed by my cheap Chinese hot air station. -
Pneuvay Engineering comment on Centrigual vs Regenerative blowers.....
http://www.pneuvay.com.au/pneumatic-conveying/news/Centrifugal-blowers-vs-regenerative-blowers---The-BIG-difference/
CENTRIFUGAL BLOWERS VS REGENERATIVE BLOWERS - THE BIG DIFFERENCE
Centrifugal and regenerative blowers are widely used in industrial processes. Both can look very similar but there are many distinct differences you should know about these two blowers such as the following:
CONFIGURATION OF CENTRIFUGAL BLOWERS AND REGENERATIVE BLOWERS
Distinct differences are clearly seen in the configuration of these two blowers as explained below:
Centrifugal blowers are configured such as its inlet and outlet are perpendicular. The inlet feeds air into the centre of the impeller while the outlet stays in tangential to the rotation of the impeller as shown in the image below.
centrifugal blowers vs regenerative blowers
On the other hand, regenerative blowers have parallel inlets and outlets that are positioned perpendicular to the rotation of the impeller as illustrated above.
IMPELLERS AND IMPELLER CASING OF CENTRIFUGAL
BLOWERS AND REGENERATIVE BLOWERS
Centrifugal blowers allow air to enter at the centre of its rotating impeller where a number of fixed vanes acts as paddles that pushes volumes of air to the outlet. Through a centrifugal action, air is forced to the impeller and housing where it is discharged as steady steam through the outlet. This creates negative pressure at the centre hub that sucks in more air.
Centrifugal blower working principle
Unlike centrifugal blowers, regenerative blowers are fashioned in a different manner. It consists of an impeller that spins within a housing compartment, which contains both an inboard channel and an outboard channel; thus an alternate name given to it as side channel blowers. The moment the impeller spins past the intake import, air is drawn in and is trapped between its impeller blades. As it continues to spin, air is pushed both inward and outward through both of the channels. This continues until the impeller stops rotating. As a result, regenerative blowers can act either as a pressure blower or a vacuum blower.
Regenerative blower operating principle
MAINTENANCE OF CENTRIFUGAL BLOWERS
AND REGENERATIVE BLOWERS
In comparison, centrifugal blowers require more frequent maintenance compared to regenerative blowers because of certain parts that requires lubrication, particularly its bearings. Regenerative blowers are considered contact free machines thus it is virtually maintenance free and can operate up to 40,000 hours without the need of being serviced.
NOISE LEVELS OF CENTRIFUGAL AND
REGENERATIVE BLOWERS
Regenerative blowers showcase extremely low noise which make it a favourite for noise-sensitive applications. Talk to us to know more about our centrifugal blowers with low noise level for your specific requirement.
APPLICATION TO INDUSTRIES OF CENTRIFUGAL
BLOWERS AND REGENERATIVE BLOWERS
As a general rule centrifugal blowers are considered low pressure, high flow blowers while regenerative blowers are high pressure, low flow blowers. This makes it ideal for the following industry applications:
APPLICATIONS OF CENTRIFUGAL BLOWERS
Centrifugal blowers work for applications such as heating a furnace with hot air where a large air volume is required to fill the space. This includes:
Climate control
Cooling machinery
Dryers
Dust collectors
Exhausting gases and vapours
Filter installations
Food industries
Furnaces
Grain elevators
Printing machines
Hot air blowers
Household machines
Incinerators
Machinery for the food and beverage industries
Plastic extruders, laminators, film processing machines
Pneumatic transport
Pollution control equipment
Uniform temperature equipment
Textile machines
Woodworking machines
APPLICATIONS OF REGENERATIVE BLOWERS
Regenerative blowers are mostly used in flammable gas, hazardous duty, industrial air movement, water treatment, and heavy duty transportation applications such as:
Aquaculture/pond aeration
Chip removal for engraving equipment
Dust and smoke removal
Industrial vacuum systems
Packaging applications
Pneumatic conveying
Printing presses
Spas and dryers
Sewage aeration
Soil vapour extraction
Vacuum lifting
Vacuum packaging
Vacuum sintering and casting
Pneuvay Engineering distributes Spencer centrifugal blowers and regenerative blowers. Talk to us at 1300721458 to know how we can deliver these to your business.
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The Weller hot air station also uses a centrifugal blower.
https://www.eevblog.com/forum/reviews/weller-wha-900-hot-air-station-teardown/
So it would appear that centrifugal blowers can be made to work in a hot air station application. Interesting that they do not use the more appropriate regenerative pump/blower though. Could it be cost related or maybe marketing based on the high "litres per minute" of air that they can produce....... a daft characteristic to use where SMT reflow is involved though. High flow for shrinking heat shrink maybe, but when working on tiny SMT components it is just asking for trouble. As Alex on the NorthridgeFIX Youtube channel would say.... they would get blown into the 9th dimension !
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Could it be cost related or maybe marketing based on the high "litres per minute" of air that they can produce....... a daft characteristic to use where SMT reflow is involved though. High flow for shrinking heat shrink maybe, but when working on tiny SMT components it is just asking for trouble.
Quick works just fine within full 1-120 l/min range. Not to say with lower airflow there is a way less pressure to supply. -
Wraper,
120l/min is not that bad, as you say. My pace units maximum airflow is around 25 l/m and the JBC is 34 l/m. The AMETEK centrifugal fans I was looking at had figures of 700 l/m ! My little 3" AMETEK blowers are rated at 18cfm which is 500 l/m !
It would appear that the Quick blower, despite its relatively large size is not running at anything like its full output flow capability. That is why I was wondering whether manufacturers are using an 'oversize' centrifugal blower and just not running it hard in order to better cope with the variable output port dimensions. As I previously said, this is not a topic that I have studied so I am just curious.
I attach pictures of my diminutive 3" AMETEK centrifugal blower. They are usually scary expensive at around $500 each but I bought them new for £25 each. Very nicely made 6Vdc to 14Vdc units. The BLDC motors have a built in controller that uses supply voltage to set shaft RPM. Even if I do not use them for the hot air station upgrades, I feel sure they will come in useful. Sadly mini regenerative blowers are anything but common and those I found were also around $500 !
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I'm not a fan of universal motors, they're noisy and maintenance intensive. Personally if I were designing something like this, I think I'd look at a centrifugal compressor as used in automotive turbochargers, and drive it with a brushless motor. Some aircraft engines use centrifugal compressors, many early jet engines did but you see them in more modern turboshaft and turboprop engines too. They look similar to a centrifugal fan but have a somewhat different operating principal.
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Quick does not use usual centrifugal fan, it's quite a bit different. Also it operates at high RPM. IIRC BLDC motor in 861DS/DW is rated for 28k or 25k RPM.
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Seems that older quick used two stage turbine.
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Since caption is food for thought , I am wondering if bottle of nitrogen with pressure regulator can be used instead of blower?
It is bulky but it should be cheap and noiseless. Flow metering and regulation tools are already on the market.
One bottle will not last long at 500l/min but in daily jobs probably 10l/min is more than enough.
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CPAP machines use similar blowers. I took apart an older one and found it had a centrifugal compressor driven by a BLDC motor. I don't know what speed it runs but it was in rubber mounts and was very quiet since it's designed to be used while sleeping.
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Wrapper,
Many thanks for showing the inside of the fan. I was wondering what it’s impeller looked like, but could not find any pictures.
That looks similar to the impeller that is used in vacuum cleaners ?
I will see what I can find out about that design. I have heard of “Nautilus” blowers (as in nautilus shell), maybe it is that design ?
Fraser -
Ace1903,
You can use any source of pressurised gas to drive a hot air rework handpiece, provided the gas is inert and compatible with the application. The regulator could set the required flow but it would be an expensive solution to run. Conventional Air compressors are also useable if a suitable flow regulator and diffusion nozzle is used. In electronics it is just more convenient to use a relatively simple air compressor or blower. They can be relatively quiet if well designed.
Fraser -
From initial checks, the Quick blower is actually a conventional centrifugal blower that is commonly found in vacuum cleaners
Interesting article on forward and backward curved impeller designs is here......
https://www.rs-online.com/designspark/fan-types-why-choose-a-forward-curved-centrifugal-fan
Fraser
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Interesting YouTube video showing the building and testing of a blower with different styles of impeller. Nice build
https://youtu.be/YuEaP9kyiFc -
Another blower build by the same chap I love that he builds these units from wood rather than metal
Nice trick for checking impeller balance with a marble as well
https://youtube.com/playlist?list=RDCMUCckETVOT59aYw80B36aP9vw