[Eclipze]

How did you control the temperature (traic? relay on/off?).
Did you use temperature feedback?

I liked the toaster oven idea, cheap, but concerned the thermal response would be very slow or not hot enough.

[ciccio]

inertia of the system makes it slow.
In my opinion there is no need for feedback.
It starts, goes to setted temp, then stops
and "beeps" to remember to open the door to cool .
Elektor oven has feedback and very fine software.
I started with triacs, but now I use relay.
It works, no problems, and it is good for me.
Why do'nt you try elektor oven?
paolo

[Eclipze]

I don't really like working with high voltage, but also concerned that these ovens would limit the ability to fine tune the process.

I really want to following a reflow soldering profile, and also ensure the board heats uniformly. Not sure if this is possible with a small toater oven.

[ciccio]

If you need an oven for professional use: buy it
If you need an oven fore some SMD board: elektor oven ( or similar)
If you want to test, try a 20 Euro oven , you can have good result even without electronic ( just to see what happens)
There are good inexpensive toaster oven with a fan
You can buy TWO low cost ovens, take heaters from one oven and double heathers on the other.
If you do not like mains voltage, please ask for help from an experienced technician.
Paolo

[Eclipze]

I would really like to follow a reflow curve, and know that it is in fact performing accurately. I can't risk having even prototype boards "well done" and have potential problems. I have done trials with a heat gun and multimeter thermocouple, and was quite successful with reflowing double sided boards. However I did find it difficult to control the temperature manually. The first attempt I made I accidentally went well over 300'C. Hence, prefer to have it automated.

The small/cheap toaster oven I looked at had a top and bottom element, with a metal slotted shield around it. Simple mechanical timer, with option to have top, bottom or both element on. I'm not sure if it contained a fan for convection.

What wattage oven have you used?

[ciccio]

I would really like to follow a reflow curve, and know that it is in fact performing accurately. I can't risk having even prototype boards "well done" and have potential problems. I have done trials with a heat gun and multimeter thermocouple, and was quite successful with reflowing double sided boards. However I did find it difficult to control the temperature manually. The first attempt I made I accidentally went well over 300'C. Hence, prefer to have it automated.

The small/cheap toaster oven I looked at had a top and bottom element, with a metal slotted shield around it. Simple mechanical timer, with option to have top, bottom or both element on. I'm not sure if it contained a fan for convection.

What wattage oven have you used?

here is my SMD oven
I think it was +- 1200W

[Eclipze]

Very nice!

I was reading up on this thread...
http://www.elektor-electronics.co.uk...pic&postid=697
Lots of people have mentioned trouble getting peak temperatures.
But I might buy the Jan06 article for some background material before making a decision about using an oven vs trying nichrome wire.

[ciccio]

You can buy two low-cost toaster and add heathers from
one oven inside the other you convert to SMD oven.
This is difficult for home-made SMD ovens here in Italy, because we have only 2.700W ! So 1500W for oven, 500W
for PC, two lamps, solder iron....
I can have enough temperature without problems, time seems OK. Not tested with RHOS compliant solder paste.
But I can buy another oven (20 euro) and build my 40 euro -2400W smd oven. Where can I send you a file?

[ciccio]

Here are temp:
1' 00 100 C°
1' 30 135 C°
1' 45 155 C°
2' 00 170 C°
2' 15 185 C°
2' 30 197 C°
3' 00 222 C°
3' 15 230 C°
3' 30 245 C°
3' 45 252 C°

[Eclipze]

I would like to acheive a system that can peak to 270'C for 10 second, though from practical experience I've found that 250'C to be sufficient.

The profile I would like to be able to acheive is...
0 25
60 150
120 200
150 260
160 260
220 50


I plotted this against your results, and believe it to be favourable.
Are your results from maximum heat, or have you controlled the rate of heat rise?

[ciccio]

.

The profile I would like to be able to acheive is...
..........
150 260



.
Are your results from maximum heat, or have you controlled the rate of heat rise?

Yes, max power, relay always ON
I think you need a lot of power, at least a better toaster than mine!
please see post on your address
Paolo

[Eclipze]

I should add, I haven't had convincing results using the nichrome wire yet. I have been able to reflow solder, however using a 15V power supply at 3A is barely enough to power for a 20x20mm area at 5mm of height. I really need to setup a pre-heater under the board to assist.

[phomann]

You can buy two low-cost toaster and add heathers from
one oven inside the other you convert to SMD oven.
This is difficult for home-made SMD ovens here in Italy, because we have only 2.700W ! So 1500W for oven, 500W
for PC, two lamps, solder iron....
I can have enough temperature without problems, time seems OK. Not tested with RHOS compliant solder paste.
But I can buy another oven (20 euro) and build my 40 euro -2400W smd oven. Where can I send you a file?

Below is a link to an artile on the SMT oven I built.


http://http://www.homanndesigns.com/...enProject.html

IT may give you a few tips.

Cheers,

Peter.

[Eclipze]

The link re-directed to something a little more x-rated than expected haha... but found it via the main page ;-)

http://www.homanndesigns.com/SMDToasterOvenProject.html

Had a good look through the report, very interesting thankyou!

I'm going to continue with the nichrome wire for now. With further tests, I believe a proper reflective metal enclosure and a decent transformer will provide the power needed for small boards. Will need a slight airflow and also a resistor bank to assist and help with pre-heat, but the temperature control has a good response.

[ppBuilder]

Hi guys,
Any progress with your P&P machines?
I'm also thinking of building one later this year, must get the mill modified and running in cnc 'mode' first.

About the P&P...I can't really decide how to drive the XY axes. I'd prefere to have the servos drive the axes by timingbelts, 'rack&pinion' style.
For better accuracy and repeatability the servo's encoder could be replaced with a linear scale placed along the axis...expencive, messy, and potential problems with servo stability/hunting

Yet another other option is to use ballscrews, either direct drive, or geared down with timing belts. Screws would have to be fairly high lead, probably 10mm or so, and this will obviously require preloaded ballnuts. All in all an expencive solution.


Anyone got far enough with your machines to advice for or against any of the above solutions ?

[Eclipze]

Well... my small reflow oven works FANTASTICALLY!!!!

Forget the toaster ovens. Too big, too hard to control. Small reflow box running nichrome wire from a 20A 13.8V power supply and some CPU fan/heatsinks. Works really well. Be using it for production work. In a basic comparision, a board that took 29mins with the soldering stick took 18mins with the paste and reflow oven. But when I build multiple boards at once it feels more like double. The first "build for hours" session I built twice the number of board I ever have!

I did have to implement a PID control loop to get really good temperature profile tracking. The nichrome wire needed to be of a specific length to match the power source and the windings need to be varied to even the heat (otherwise centre gets too hot). In addition, and very importantly, you mush have airflow to get consistent reflow. Otherwise, stratisifcation becomes evident.

For the pick'n'place... now that I have the reflow working, the pick'n'place with solder paste dispenser becomes very realistic!

I'm using DC motors geared from worm, to pinion to belt pulley. I tried steppers, but it was constantly a problem to get the resolution, torque and speed. The trade off is alway causing a problem. The DC motor however doesn't have that problem. Will have to implement a PID control loop to get fast performance, as well as an optical encoder coming from the worm drive for precision.

For the PnP head... I'm actually using remote car servos! Mechanism is far more precise, and I can easily use a servo saver to prevent the needle from pressing too hard. They push/pull on linear bearings. I have a dual head arrangement, one for components, one for solder paste dispenser.

I'm up to design revision 16 on the CAD model. I have tried LOTS of different configuration, linear sliders, bearings, screws etc etc... But I'm very happy with revision 16, it's looking a realistic solution!

Now I just need to get my time machine to work so I can make it!

[phomann]

Well... my small reflow oven works FANTASTICALLY!!!!

For the PnP head... I'm actually using remote car servos! Mechanism is far more precise, and I can easily use a servo saver to prevent the needle from pressing too hard. They push/pull on linear bearings. I have a dual head arrangement, one for components, one for solder paste dispenser.

I'm up to design revision 16 on the CAD model. I have tried LOTS of different configuration, linear sliders, bearings, screws etc etc... But I'm very happy with revision 16, it's looking a realistic solution!

Now I just need to get my time machine to work so I can make it!

Hi,

I've been really keen to build a P&P machine that in in end I purchased one. It's a 17 year old Yamaha 84. (Philips 84CSM). Works well, but is very expensive for what it is.

I just couldn't afford the time to design and build a beast. I am still interested in building one, as they still apear overpriced for what they are.

Cheers,

Peter.

[Eclipze]

Hi,

I've been really keen to build a P&P machine that in in end I purchased one. It's a 17 year old Yamaha 84. (Philips 84CSM). Works well, but is very expensive for what it is.

I just couldn't afford the time to design and build a beast. I am still interested in building one, as they still apear overpriced for what they are.

Cheers,

Peter.

OMG!!! Homann Designs.... (looking at website) in Highett. That's less than 10 minutes away from me I'm in Parkdale!

I am slowing optimising the design so that it uses 3mm sheet aluminium and L shaped extrusions. This is in an effort to obtain the best assembly accuracy. It does take a lot of work to figure out exactly how everything assembles, including provision for the bolts. Dimensionally, the model is accuately very accurate. I hope when the design is finished, I can have the necessary components CNC'd.

Before anyone starts blabbing at me for certain blacklash error, servo inaccuracy and bearing slop, please don't. Everything is going to work with feedback control! Besides... if you look closely at the design you should be able to pick out certain concepts I have applied to obtain accuracy. Such as the precision of the servo is greatest at it's extent of travel (when closer to the PCB). The servo actuates in 0.2 sec for full swing, but its velocity is slower as it approaches the board.

I have gone through a lot of design approaches. This is revision 16... aka, the 16th design approach I have taken. It will be quite fast, but made for the hobby level assembly.

I tried concepts for tape feeders, but just too complex and expensive. So I will be placing a tape strip manually, and the system will pickup components in sequence until the tape is empty. Realistically, this is the most flexible and fastest way to getting this operational.

The system is so light weight, the best design kept coming back to using a big solid single X axis. One with a carriage that has adjustability for tracking. Dual rails was always a nightmare! The X-axis is long, to accommodate a decent length of component pickup area. The Y-axis is kept as short as possible, to minimise error. The rail used is quite solid though.

I've used a worm drive from DC motor, as I believe it has the lowest backlash error and provides a high rotation area to provide the optical sensor pickup. I can also change the counter gear to suit the tradeoff between speed and precision. This setup by far has been much easier to deal with than 1.8 degree steppers driving the pully direct. The torque with micro stepping just doesn't allow the speed, and I'm far more happy with optical positional feedback.

Only trouble I have at present is getting the vacuum line to the needle head, while providing the flexibility for rotation.

[phomann]

OMG!!! Homann Designs.... (looking at website) in Highett. That's less than 10 minutes away from me I'm in Parkdale!

If you give me a bit of warning, I'll set up a viewing of the machine operation. It will give you a lot of ideas. I'm just off Nepean Hwy.

A couple of points though.

1. Run the Y axis out the other side so you can have feeders on both sides. You WILL need them.

2. Consider having 2 X rails, one on either side of the PCB. If you don't want this, then at least have a dolly wheel to support the cantilevered weight.

3. Not sure why you want to make the machine light. The machine I have is 600+ kgs. The weight helps with the accuracy of the machine.

4. Condider making the Z axis a Pneumatic slide. Or at the very least, have the servo only lift the axis to stop it dropping down. Allow it to go down via gravity or a weak spring. THat way you won't RAM it into the PCB by mistake. Another thing is that my maching only has about 8mm of travel in the y-axis.

5. The head only needs to rotate +/- 180 degs, so you can use a small universal pneumatic coupler for the air to the read.

6. Not sure how you are planning to do the feeder advanchment. For what it is worth, my machine has a plunger mouned to the side of the head, so that when it lowers the head to pick up a part, the plunger pushes down on the feeder advance mechanism. As the read raises up of the feeder, the feeder advanches to get the next part ready.

Just a bit of brain food. Keep up the good work.

Cheers,

Peter.

[ciccio]

Peter,
please help us with detailed pictures!
You know what we need.
Detailed pictures, dimensions, ideas for Z axis from
your P&P: everything can be useful!
Thank you
ciccio