Reply with QuoteHow's it going Eclipse?
I thought at the speedy rate this was progressing that it would be finished by now.
Nice video.
I don't believe that a taper is necessary on the nozzle. It should be accurate enough without.
I agree that it is not necessary to have a good seal. My Yamaha P&P "leaks" (by design) all over the place.
As to the nozzles and magnets. You need to make sure that the nozzle tip is not magnetised. Otherwise the chip components will tick to the nozzle.
Cheers,
Peter.
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Homann Designs - http://www.homanndesigns.com
How's it going Eclipse?
I thought at the speedy rate this was progressing that it would be finished by now.
I got sucked into this project too much... spent too many hours on it all at once. I got a couple of big orders, and given I was way behind to start with, it was serious catch up time there for a while.
I have spent a little bit of time on the P&P lately, but I've also been working on getting my larger CNC up and running at the same time... as I'II need it once I've finished the head assembly.
See here
This CNC has been time consuming to get ready to use, and not quite there yet. One of the steppers is skipping, and it's either power supply, interconnects or stepper driver. It's electrical, but just haven't spent the time on it yet.
As for the P&P, I've been working on a new design for both the pick up head, so it can later support a tool change function, as well as a new approach for the solder paste dispensing.
I'm now using a linear stepper and half a syringe for the paste. Designed so the syringe can be removed easily (put in fridge, refilled, replaced) by two screws. Also with adjustment to accommodate syringe length. The plunger is coupled to the stopper by a magnetic connection, which was an important part to being able to disconnect the syringe... without the stopper haven't to move. Don't want to remove the stopper, as I don't want any air in the syringe. I also want to fill it through the syringe tip (without nozzle attached). I have built it, but haven't cut a syringe to exact length and loaded with paste to give it a try yet. The main concern is whether the shaft will turn (it's a non-captive shaft).
I have drilled/tapped set screws in the solder paste Z-Axis carriage too, so it's a snug fit on the rail now :-) Machined the servo cam, but haven't fit to the servo disc.
The X-Axis stepper coupler got too difficult, due to the depth of the coupler I wanted to machine. Achieving the desired tolerance was going to be difficult. In addition, the pulley have a poor run out, which made it more difficult. So I had a mate machine down the stepper shaft in a lathe, and then bore out the pulley to a high degree of accuracy. Press fit and glued, it's absolutely perfect! Better solution than the coupler. I wish I had a lathe and knew how to use it.
So it's still a work in progress... albeit at a pace that won't bite me in the ass again :-)
Don't worry about that shaft too much. It won't rotate in this particular setting as long as there is some minimal amount of lubricant on it.Originally Posted by Eclipze
Excellent update Eclipze, thanks for that.
It looks like that head assembly is getting heavy, I take it you will add a second main rail to basically have a moving gantry? Or with that small X travel of 160mm will you just balance the weight of the head against the X stepper motor weight and hope the sag is not too great?
Nice thread on modding your CNC router too.
The linear stepper shaft is rotating on the suck back stroke and some of the downward stroke. I was hoping it wasn't going to. However the motor doesn't have enough grunt to push the paste without skipping steps anyway. So I plunge, pause and retract, skipping steps during the plunge anyway, however it has consistency of travel. Running the linear stepper at 12V too, not 5V as it's rated.
I had to go to a plastic tapered nozzle to reduce the resistance, as the metal pin type was just too much for the stepper to dispense through. I attached four 1/4W resistors around the plastic tip and run some current through, to warm the paste in the hope it was more compliant. Didn't actually make much of a difference.
I could get an amount to eject consistently (without drooling too) if the amount was large enough, but it was a bit much for an 0805 pad.
I think the paste is too dry for small spots and not sticky enough to adhere to the board. Perhaps I need to mix with some thinner. I am using paste from the jar, which I normally use for stenciling. The jar is recent and refrigerated, but the syringe I made up has been sitting on the bench for a couple of weeks now. I was considering buying another pre-filled syringe to see if that paste is thinner. Comparing to the youtube videos of paste dispensing, like the Taig mill one, there paste is very wet and I'd expect much better success with this.
Having trouble with the file upload function again, so here is a link to the picture instead...
http://www.eclipze.com.au/pnp/paste_dispenser_02.jpg
BTW... the meltage on the tip was from heatshrinking the resistors in place <oops>, not from the heat the resistors were pumping out.
Few things I can do... try paste from a purchased syringe. Find out from the manufacturer what I can use as a thinner. Also, move to a thinner syringe vessel, which will reduce the resistance and give finer precision.
I don't want to go to a larger linear stepper, due to the weight and physical size. I have been very careful with keeping the weight low on the head assembly. Not concerned about the X and Y steppers... they zip along faster and with more acceleration than practical hahaa... Currently, the weight distribution with the head assembly fully extended is giving a weight loading of ~330g. It won't be until I have the X rail bolted to the base board than I'II be able to see what level of flex/movement this produces under acceleration. Until I see the effect, I'm not going to rush out and buy a support rail. I have the provision for it, as it may need it, but not the evidence to justify adding it to the design yet ;-)
There are two types of solder pastes, one for stenciling with higher viscosity and close to 90% metal content and one for dispensing with 80-83% of metal content and much lower viscosity. Those are the "by weight" numbers, not the volume, so the actual difference is much greater than 10% due to the weight of the metals. Try to get the paste designed for dispensing paying attention to this "metal content" parameter.
What gage size needles and tips are you trying to use?
On the motor. Are you using microstepping or full step mode? What current? That motor can take 0.5A or higher intermittently.
On a side note. Have you considered making some parts out of Delrin or other engineering plastics? It would help with weight reduction and wont compromise the rigidity. You are already using plastic in the most critical spot - the bearings, why not use it elsewhere? That would possibly allow you to put a bigger motor on the dispenser.
-scsi
Solder Paste Dispensing
I'm not sure if I posted my dispensing videos here. I'm using custom auger valve mechanism in both, but the first video with 0.5mm dots is nothing special. Believe it can be done with the motor driven piston or regular pulsed air without much trouble. Dispensing paste type-3 with 83% metal content is used here, not the regular stenciling type.
"http://www.youtube.com/watch?v=tPjFQ15Zdp0"]YouTube- Solder paste dispensing with auger valve - test #1 22GA 400x 0.5mm dots
The second video shows mixed results in a first attempt of depositing 10 mil dots (0.25mm). Thinner paste and smaller nozzle would help and I'm still working on it. Don't try this at home!
"http://www.youtube.com/watch?v=4EGH5xG-wSc"]YouTube- Solder paste dispensing with auger valve - 0.25mm dots 0.5mm pitch
I've had really good success with the 63/37 solder paste from zeph at http://www.zeph.com/zephpaste.htm . I use it in a solder paste dispenser very similar to yours with a linear actuator pushing down on the plunger of a syringe. The paste is really sticky and sticks to the board very well. I also tried using regular stencil paste in a syringe and the results were that it would not stick to the board reliably. I have a tube of the Kester R276 dispensing paste that I haven't tried yet, but I'm hoping it works as good as the zeph paste since it is cheaper.
I was using a 0.8mm nozzle. Stepper was driven with full step. It is a 2.7W 5V stepper, which I was driving at 12V. After a dispension sequence, the driving board de-activates all driver phases to avoid it getting too hot. The paste I was using is a Tin-Lead, particle size T3, T4, T5 with 88.5% metal loading.
The supplier I use, AIM, also have solder paste for the MyData MY500 Jet Printer. That is a machine that uses an auger and solenoid to shoot paste dots. It comes in 30cc syringes too. There is a good animation of this half way through this video...
"http://www.youtube.com/watch?v=f70nZQFDEhs"]YouTube- Solder paste application using Inkjet technology
I've had thoughts of considering an auger valve approach.
I have considered delrin before as a friend uses it often, however most of the weight is in the motors, the rails and bearings. The aluminium used is a only a minor contributor.
I'm guessing this system would be a tad expensive
"http://www.youtube.com/watch?v=jp0mwlgnr8g"]YouTube- Jet dispensing with an EFD PicoDot(TM) system
Yes, EFD's PicoDot is nice and all, but I'm not convinced that it can handle solder pastes because of high viscosity. Costs an arm and a leg too.http://www.efd-inc.com/Valves/Jet/
One thing I like about jets is that you don't have to worry about the Z-gap and don't need to move the Z up and down at all.
The mydata's system in your previous post can handle solder alright but you have to sacrifice some more expensive organs for it. It costs like a decent Lamborghini. Looks like it inside too with all that carbon fiber, gold and stuff
-scsi
I have finished dreaming and drooling for now :-)
Seeing how well your system works has given me a bit of perspective. I'd always considered the paste side of this machine as purely for the occasional prototyping. Normally for small production runs I make a stencil, but I could see how a good mechanism could save quite a lot of my time in avoiding this messy step. I don't mind transferring that workload to machine time.
You need to use paste designed for a syringe. The viscosity of stencile paste is too high.
Cheers,
Peter.
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Homann Designs - http://www.homanndesigns.com
Just a suggestion have you ever thought of using a pneumatic paste dispenser? it runs on compressed air, and does a small pullback after dispensing. you can buy the used units cheaply on ebay. it uses a syringe but only needs a small light nylon hose to work. would make the head lighter at least.
These are fine for manual work, but after 50 or so cycles, the syringe body gets quite warm and you need to reduce the duration. I need to constantly change the duration timer when using it.
An auger driven despenser will bethe way to go.
Cheer,
Peter.
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Homann Designs - http://www.homanndesigns.com
Nice design eclipze. From my point of view, it´s maybe only a personal preference,
the possibility of adding a jedec tray (14x34cm) is missing, as uplooking camera too.
Possible improvements: Add fotocells near the pick-up point on the X axis and at least
one on the Y axis. This allow you to check, if for some reason you misses some steps
and correct the problem as soon as possible, because you microcontroller can check the
position without problems at each component pickup on the X axis and sometimes on the
Y axis too. The same and more important is a sensor on the Z axis, that tell you if the
component is hitting the pcb, nice/bad for pickup, this mean wrong Z axis size or wrong component, and more badly on the placing location, because for some types of components, the solder paste is compressed, bridges and a lot of trouble.
For the rc servos, there exist a possibility to add quadrature encoding internally, in order to don´t relay anymore on the inaffidable trimmer.
For the vacuum system, if you use glass syringe, the o-ring don´t wear out, if you have
problem with it. I have used it sucessfull on a vacuum table.
Cheers Chris
Thanks for your comments Chris!
With the Jedec tray, I'm going to make the left/right loading banks removable. So when I have components supplied on tray, I can simply load the whole tray in one of the banks. Could even leave one bank off and have longer placement area.
I have photo sensors at the limits of both the X and the Y. But have not given consideration to having one for continuous calibration. I have run CNC's for hours in open loop mode, not having any encoder feedback or alignment, and not noticed any loss of position. I believe if the acceleration and trajectory parameters are set appropriately for the motors/mass/friction, this should not be an issue. Ideally I would like an up facing camera that can detect the position of the pickup head needle and paste needle.
I am not planning to have Z axis position feedback at this stage. Some complexity needs to be left off, otherwise I will never get to the stage of having something running. However I have given consideration to how this may be achieved. When the Z-Axis actuates too far, and the component is compressed on the board, the servo bearing will stop touching the surface that rests on the bearing (under gravity). I could use this as a contact sensor, so it would be detectable if it went too far, as well as provide a reference for calibrating the component height.
Glass syringe would be a nice addition, although I'm quite stubborn when it comes to introducing any weight :-)
Do you already have the driver. If not, can you pls. pass the info about the motors used.
This, if you want use my SW / HW appliance for running it.
I have a Gecko G540 to drive the bipolar X, Y and C axis (head rotation). The two Z-axis and additional tape index probe I have been planning to design a Modbus board to drive them, as well as anything else that needed specific control (paste dispension etc...). My intention has been to look as customising Mach3 to suit the application, as I haven't found any other software I could use. Which software do you use Chris?
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