LS1 Solder Reflow Oven（看看外国人怎么改的）

liyf

I just did a nice conversion of an Oster oven to make a high quality solder reflow oven.  I wanted to PM Bart and ask if there should be a new build category created for "Non-CNC related DIY projects", but it appears he blocks PM now.  Anyway, I'm uploading a video now and I would like to describe to you all how to build one by making a buildlog here.                                                

Let me start over by saying that I have done this before.  Two years ago I bought the Black & Decker toaster oven and the TechFX USB reflow controller.
It works, but I am at the point now where I can afford to put a bit of money on something better, but the divide between DIY and Commercial is huge.  

There must be some middle ground.

I have looked at the new Chinese units sold on ebay and they look nice, but I have come across some reviews that say they have very bad problems with hot and cold spots.
The T962 ($272 delivered), with only 800W cannot bring the boards up fast enough for a good profile.
The T-962A ($555 delivered) has 1500W, but according to some is a fire trap waiting to happen and has really bad hot and cold spots.
This is a shame, because I was really ready to puchase that unit.

So now I'm back to DIY.  I decided I would invest in a nice oven that will be a solid foundation for conversion.  I decided on the Oster TSSTTVDGO1 being sold at Target for $85.
Even if I find the heating elements to be lacking, the oven is large enough and solid enough to give me room for conversions.  
                             
                               



Clearly, there is potential here, even if I find I need to add additional heater elements or move elements so they are all on the top.  

The convection fan can be a blessing for even heat distribution, but also a curse because when it is running it increases the heat loss via conduction of the side walls.
I believe in the end I will run the convection fan for initial warm up to soak temperature, but I will cut if off for the reflow period, and then restart it for cooldown.


The electronics control package was easily removed.              
                 
                               
                               


Then a new aluminum plate was fabricated that allows mounting of the ramp/soak controller, on/off switch, and the solid state relay for the heater.               
               


I will speak more about this ramp/soak controller in a future post.  At this point it may or may not be the final controller used in this build.

Now let me speak for a moment about cooling.  Most others on the web simply open their door during the cooldown phase.  
A very few have added a cooling fan and some very strange contraptions to block open and close vents.  Here is my solution thus far:

The rear of the oven has a bulging metal piece as shown below:               
               


I found that the roaster pan that comes with this oven fits this bulge perfectly and only needs to be trimmed at one end.

I have a nice Pabst metal blade fan that I will use for forced air cooling.         
                     


In the image below you can see where I have drilled air inlet ports in the rear panel, and air exit ports in the bottom of the unit.  
Since hot air rises, these ports in the lower end of the oven do not "leak" heat from the oven.  They remain relatively passive until made active through forced fan air movement.              
                 


The next step is a trimming of the roaster pan to fit over the rear and direct the fan output through the new inlet ports.
"CAUTION" "sharp edges" "there will be blood"            
                  


Once trimmed and the fan is mounted, I simply routed the power cord of the (115V) fan back into the controls section.   
                            


In this image below, you can see how the addition of a solid aluminum front panel allowed a solid mounting of the controller, the switch, and the solid state relay.
All wiring is complete and the unit is ready to close up for initial testing.            
                  


Future posts will be made as the testing and evaluation progresses.I have been evaluating the quartz heaters in this oven.  The oven total is 1440W, with 820 in the top and 620 in the bottom.  This has room for growth.  I can easily bring it up to 2KW and not blow my 20amp breaker or heat any wiring feeding my workshop outlets.  

So you are asking yourself "how can you change the power from a quartz heater?".  It's actually quite simple.  The heaters are built for standard kitchen use and have a life expectancy of about 10,000 hours.  In order to acheive this life, they have put about a large safety margin on their heaters.  
Some calculations.  1440W up to 2000W is an increase of 40%.  The two heaters on top are 820W (410W each) and will grow to 1148W (574W each).  This is only asking for 164W more from each heater.  This is well within the capabilites of the tungsten heater and quartz.  The bottom heaters will also increase by 40% going from 620W up to 868W.   An increase of 124W per heater.

The top heaters are removed.

               
heaters removed from oven               


They are marked as 410W at 60V.  This makes sense.  Since they are in series, they will split the 120V, so each will have 60V.  They are measured at 8.7 ohoms each.  This also fits E*E/R to give 410W (413 to be exact).  Next I calculate the resistance they need to be to produce 574W.  Answer is 6.3 ohms.

The quartz is removed and the filiment exposted.            
                  


Meter is used to find the point on the filiment that has 6.3 ohms.            
                  



Filiment is cut at 6.3 ohms and the remaining coil is stretched to widen spacing between coil windings.  This is important for distributing the higher wattage over a larger area.         
                     


Finally, the quartz tube is placed back over the heater coil and the straightened out portion of the coil is passed through the ceramic end piece.  I then use inline crimp splices to attach the high temperature wire directly to the tungsten wire.

               
Finished heaters now 574W each               


Same process repeated for the lower heaters.  
I now have a 2KW oven and it works perfectly.

robter

这个很好，学习了，多谢楼主