Wave Solder Energy Saving

Due to the huge thermal inertia I would think the savings would be minimal and the probability of screwing up the production process huge.

You would probably save more by improving the insulation of the machine or providing extra insulation during 'off time'. After all ..if you allow it to cool, it will require extra energy to heat it back up...solve the problem, not the symptoms... Stop it cooling!

Del

Hard to calculate without some more parameters:

• Shape, Material, thickness of pot for both heat retention rate and cooling rate,
• Temperature of room?
• How is the pot heated and the efficiency of the process?
• How long does it take to heat the solder per degree Celsius?
• How full is the pot kept... What is the lowest level allowed?

Does 1 shift hour mean 1 hour usage in 8 hrs, 12 hrs, or 24 hrs?

Hi,

I am a production engineer in charge of an ERSA 330 solder wave machine installed at our plant and it has an inbuilt clock and calender which you can program for on/off periods. Our machine switches off all power to the solder bath at the switch off time and then monitors it's temperature as it gets colder. It then uses a mathmatical approximation to determine how long prior to the 7AM start time it needs to switch power back to the heating elements in order that the solder reaches the programmed process temperature by 7AM. I have also run it's inbuilt data logger and I can tell you that Tuesday to Saturday it gets down to below 100 C( I would need to check the log files again to get an exact temp. At some stage on a Sunday it cools right down to room temp.

One thing to be careful of however is that, if you are heating a tin-lead solder pot which is solidified, it will at some point, during liquification, spurt molten solder from the surface (We place a cover over our pot to prevent solder from splashing inside the machine). The funny thing is this phenomenon does not seem to happen when we use our lead-free pot.

Hope this helps.

Hi,

your answer from down-under is very interesting. It would be very helpful for me if you could provide some results from your datalogger.

many thanks

Schorschimi

Germany

Many thanks for your interesting reply.

After reaching the steady temperature the heater switches off.Did you register the exact time?

If you have also logged the cooling process this would provide enough information to make a calculation of the problem I raised. (although we use leadfree solder with a melting point of 227C).

Do you have heater on-off data during production and during idle periods? This data would be highly appreciated.

Schorschimi

Hi Schorschmi,

I have done some more investigation into this and here is the result:-

There are a total of 4 heating elements attached to our solder pot. A front pair of 3.1kW and a rear pair of 3.1kW. A pair of elements consists of a bottom element and a top element. The top element is supposedly a higher wattage than the bottom to ensure that the solder melts from the top down rather than the bottom up.

The machine's PLC uses 2 solid state relays with a common control input to control the power applied to these heating elements. From what I have observed by watching the LED indicators these relays are switched on continuously at the 04:35 start time. They remain on until the solder temperature is about 5 to 10 degrees from it's programmed value which is at approx 15 mins prior to the temperature reaching it's equilibrium. The relays then switch on and off at a frequency of 1 Hz and with a declining duty cycle until the temperature stabilizes. When this happened, I attached a multi-meter with a frequency and duty cycle measurement to the control input on the solid state relays. The frequency was 1 Hz and the duty cycle varied up and down a little but seemed to average at about 40%. This leads me to believe that the power needed to keep the solder pot at 250 C is 40% of 6.2kW or approx 2.5 kW. Thus our approximate saving calculations are as follows:-

Energy consumed to heat up from room temperature in a 2.5 hour time period =

(6.2kW X 2.25 hours) + (6.2kW X 70% X 0.25) = Approx 15kW hours

Energy consumed to heat up from 120 C in 2 hour time period =

(6.2kW X 1.75 hours) + (6.2kW X 70% X 0.25) = Approx 12 kW hours

NOTE for above : Duty cycle reduces from 100% to 40% in the final 15 minutes, therefore averaging 70%)

Power required to keep oven at 250 C = 6.2kW X 40% = 2.5kW per hour.

If we use our shift schedule as an example, we start at 7AM and finish at 4PM for 5 days per week, therefore energy consumed =

(9 X 2.5) + 12 = 34.5 kW hours per day

If we do not use the timed switch-off capability then our power usage =

24 X 2.5 = 60kW hours per day

Thus our daily saving is approx 25.5kW hours per day

On Saturday we work from 7AM till 12pm and consume (5 X 2.5) + 12 = 24.5 kW hours

Thus for the week we consume ( 5 X 34.5 ) + 24.5 = 197 kW hours.

If we leave machine on continuously we would consume in a week

( 7 X 24 X 2.5 ) = 420kW hours

Therefore, saving per week = 223 kW hours X 0.17Cents = NZ $37.91

Not a huge saving, but it still contributes to a greener planet :)

The rate at which heat is lost increases with temperature difference between the solder bath and the environment.

Therefore if you turn the bath off as soon as the shift is over, the rate of heat energy lost will decrease as the temperature gets less over time. Provided that the solder does not cool through a solidification point ( nor other non linearities), the savings will be (Power to keep at constant temp x Time between shifts), minus (Mass x SH x (Temp of bath during shift - Temp of bath reaches in cooling between shift) plus the Energy required to bring the bath back to working Temperature.

If that much energy shows significant savings to you, then you could calculate the latest time to switch the bath back on so that it it is ready by the beginning of the next shift.

I expect the saving will be marginal, and you would be better off to invest in insulation. That way you can assure yourself that the bath is ready for production all the time

If possible no guesswork, but numbers.

Sorry no numbers but 1 of the issues of the Wave Solder we used was if the solder solidified for some reason it took extra time to get it going again. You might check the latent heat of your solder to give you better numbers.

Brad

If you are using 63/37 (eutectic) solder it melts at 361.4ºF with no pasty range and you should be able to lower the pot to around 400º with a quick recover time.

A better idea is a production plan to schedule machine usage such as m/w/f 6 hrs. this may take a little getting used to but also gives your operators a deadline they have to meet.

A stainless or titanium cover over the pot will help maintain pot temp. but most of your power is consumed on start up.

Sounds like you are running Sn100 (99.3Sn, 0.7Cu). I don't have any solid numbers for you, I would only recommend that you leave your pot on, and just turn off your conveyor and preheaters when not in use. Heating up a cold pot is where you will use most of your energy. If you are not working on weekends, then turn the pot off on a Friday evening. Some machines have timers so you can set your pot to heat back up on say Sunday evening so that it will be ready to go again Monday morning.