Flippersplace Pick And Place Machine MK1

[flippersplace]

I have a working DIY pick place machine

State as at July 2011:

http://www.youtube.com/watch?v=4DFtt7RTR2k]DIY Homemade PCB SMT Pick Place machine 2011 July - YouTube

I'm fairly active with incremental improvements

I keep track of the details of the machine are on my own webpages at Home made pick place SMT machine

This thread is for any discussion re this machine

[flippersplace]

This change is the first attempt at converting from recycled DVD drive heads stepper mechanisms to pneumatic actuation

Goal is to reduce complexity, and vibration (DVD steppers are half stepped and are a bit 'clicky' contributing to parts moving around during up / down strokes of pickup heads )

Also, I now have cool as 'pssst' sounds from pneumatic solenoid exhausts

Details here Changes 20110829

Before & after pics below, as well as rear of machine after a bit of rearranging to make room for the pneumatic valves etc

Video to come soon

[James Newton]

wow... Questions that pop to mind: What sort of steppers and drivers are moving that? You program pic's and live in NZ? I know several people who fit that description, do I know you? How about 4 alignment boxes so the parts on all 4 heads can be aligned at once (assuming they are the same size parts)? Other random queries will certainly follow...

[RomanLini]

Good to see your build thread up! It didn't take you long to get those air pistons in there.

How expensive does it work out for the pistons and also air solenoids to control them? I was lucky already having a nice fast 12v air solenoid in the junk box, and I've been dreading buying more solenoids although a multi-pickup tool like yours looks real tempting!

[flippersplace]

@James
No we do not know each other

The steppers are generic Chinese Nema 23 76mm driven through a generic Chinese TB6560-3V2 via parallel port

Screws originally were 1605 but due to warp the bottom one has been replaced with a 1/2" 10tpi thread as that's what I had spare

Re 4 bump pits, I do have 4 for each head but they are not quite aligned to the space between the heads. Well, actually, I have 2 per head, one large & one small.

I wasn't too worried about getting them precisely spaced to match the heads as even my heads are not precisely identical, (I can't fabricate things ie brackets etc to that level of precision)


@Roman, I bought 20 sets of more or less identical pneumatic assemblys which gave me the premanufactured pneumatic actuator including linear slide, festo cylinder, 4 way valves, SMC speed controllers etc etc. When I saw them initially I could see how easily I could use them for this purpose.

A lot of parts for NZ$65 each, shame I had to buy so many though. I figure I'll sell off some of the spare bits as I now have 20 x 4 way Festo 24V valve assemblies, 80 SMC AS1000 speed controls, 20 SMC rodless cylinders etc etc etc

I was amazed with the precision of the micro linear slide shown

Photos are:
- Pneumatic assembly as purchased
- Donor actuator from above
- Dissembled parts I reused
- A new head ready to bolt in

[flippersplace]

Today. second DVD head in 2 weeks that didn't retract

So I just bolted in & calibrated one of the heads removed a week a go from right side bank in the interim (took literally 5 mins as they are all interchangeable)

I had been considering upping DVD drives from 5V to 6-7.5V to try avoid the above. Had played a bit with that in the past and they get a bit warm at anything over 5V however my PIC firmware powers down a head pretty quickly after a move (in anticipation of the above voltage increase) so it was still an option

Instead I'm just gonna move ahead and convert the second bank of heads to pneumatic

I'd already made another 4 brackets 2 days ago and had almost finished modifying the linear slide brackets etc per the other set of 4 heads yesterday anyway, just a small bit of filing the plastic left

However, I am short a 4x Mosfet driver PCB for the second bank of 4 pneumatics valves. I have a new 4 x mosfet PCB (all SMD except jacks in the post at the moment from iteadstudio.com (US$9.90 + post for 10 50mm x 50mm PCB's, just like seeedstudio, probably the same company for all I know) and the relevant SMD optoisolator & Mosfets shipping from Mouser as well, but they might be days away for all I know

So reluctantly got out the laser printer / hot iron / toner transfer and made another of the above this morning old school like and will have all pneumatic heads Monday.. I did take the opportunity to use some bright component colours however (its good to find additional creative outlets)

Still tweaking supply pressure vs additional springs (is a one way festo cylinder) as occasionally, one of the new pneumatic heads will bounce adjacent parts out of the exposed tape.. but not too often. Its really important to pad a peeled tape underneath so there is no give to minimise this

Basically trying to balance down stroke speed/impact/downward pressure vs upward start abruptness/ speed / stop abruptness

Machine was placing the 0.5mm pitch SSOP IC's for the current PCB but not always accurately. Seems some issues to resolve with the alignment of each PCB origin.

When I first ran this machine I used the downward looking camera to align to the edge of the PCB at the PCB origin. However I noticed that the guillotining is really variable in the same batch (I am assuming each PCB is at least square...) so I changed to use the downward camera to visually align to the centre of a mounting hole (all my PCB's have mounting holes 4mm in from each corner) but either the SSOP footprint is not centered or the PCB layers are not aligned accurately enough. I'll investigate this over the next day or so as well

Regardless, I think I'll end up nominating a pad from each PCB and use that instead

I do have to align for each rotation at the moment but it's very quick, ie Click VB dialog move button, jog a bit, click set VB dialog button

I did buy some smaller steppers with the idea of bolting a new pneumatic head assembly to one each of these but between the trade off of additional mass on the gantry, extra control lines per head etc etc I still think any effort I put into that area will be rotating the PCB instead. I have a small order of various T5 belt and pulleys coming from the UK so I can perhaps experiment with options. Additionally my Excel to GCode generation is sequenced by rotation so it should fit nicely.

Long term if I one day get to a vision system for centering parts, whether I rotate the head or the PCB its pretty much the same maths anyway

Roman, in your own thread you mentioned about dropping the part into a shaped pit for centering, iI had tried that but I can't make the pits accurate enough. However at the time I thought this was an ideal time to rotate the part as well. Not gonna happen for me but maybe for someone else.

I did download a trial of RoboRealm last night but it looks too complex to spend time on right now

[RomanLini]

Roman, in your own thread you mentioned about dropping the part into a shaped pit for centering, iI had tried that but I can't make the pits accurate enough. However at the time I thought this was an ideal time to rotate the part as well. Not gonna happen for me but maybe for someone else.
...

I think I will still give that a go, for common sizes like 0805 and 1206 anyway. My CNC is pretty good for fine precision work although I need a 1mm diameter ball end mill, currently I only have 1mm dia straight end mills. If the smallest part of the pit is say 10% larger than the 0805 it should locate the part to within +/-5% which should be plenty accurate enough for 0805.

Thanks for sharing your work with the pneumatic heads, it is interesting hear about tuning the pressures and the parts tape bounce caused by overspeed etc. I'm still sticking with RC servos for head lowering because I have the servos and because I have some experience tuning them for speed and position in small robotics applications.

Regarding your PCB alignment, you really need to work with aligning to the top copper as all other layers (holes, silkscreen etc) may be out of place in the PCB manufacture. You might be able to get away with holes for alignment, although I have received PCBs back sometimes where the vias are drilled noticeably off centre (so all holes were) and that might be enough to upset a TSSOP alignment.

Can you give more info on your tape holders? Are they machined to hold the tapes snug to allow accurate blind pickup, as that is the system i was hoping to use. I generally use lots of 0805 and 1206 and hoped for good enough blind pickup and placement without really needing to bump align. That's the theory anyway!

[stewi]

Air activated component feeders used to be trouble.
Back in the time, we had successful assembly houses in US, I designed and patented a feeder concept. Apparatus for feeding electronic ... - Google Patents
At a low speed you are going with a single nozzle head, you would not require the fast acting air piston motion for the feeder. If you are worried that the components flip out of the tape pocket during advancement, you would need a component cover, which pulls back before component pick up.
However, this is an interesting thread. I started working on 4,000 component an hour placement machines and they do easily 40,000 now.

[RomanLini]

Thanks for the link to the patent Stewi. It doesn't look that much different from the feeders that were in commercial use since the 80's? What were the feature(s) original to yours that had never been done before?

[stewi]

There are a few things unique to other feeders.
The feeder has a base with one advance motor and several solenoids in order to engage only the required feeder. The feeder itself has only a few inexpensive plastic components and is meant to remain on a half empty tape, for minimal change over time. The cover tape is peeled off and than guided towards the empty tape. Empty tape is cut off by most of the placement machines and chip shooters.
The feeder base was meant to adapt to different machine vendors, such as Siemens, Universal and others.

[flippersplace]

Can you give more info on your tape holders? Are they machined to hold the tapes snug to allow accurate blind pickup, as that is the system i was hoping to use. I generally use lots of 0805 and 1206 and hoped for good enough blind pickup and placement without really needing to bump align. That's the theory anyway!

Hi

My holders are the generic chinese made things from Ebay like this one

1 set 5 way SMT SMD Feeder for DIY Prototype Pick Place | eBay

However, regardless,yes the tapes are held firmly, and if not I insert pins to ensure they are. I can calibrate each feeder using the downwards USB camera very quickly as I have a custom VB dialog just for that purpose

However the primary issue is that the fit of the parts in the tapes is such that the parts can move around. So the accuracy of your place is determined by this slop.

Picture is 0805R

Do a few R's or LED's in a row and it soon looks pretty untidy & unprofessional

[stewi]

If you look at the spec than tape width can deviate by +/- 0.1 mm. All automatic feeders advance the tape with pins in the perforation holes, because holes and component pockets are punched out together more accurately. Tape pockets are over sized to accommodate component size variations.
Together with the fact that the solder pads are larger and the re-flow process does some pulling as well, an automatic pick head with +/- 0.1 mm accuracy should be doing blind pick and place with 1206 and 0805's without optical or mechanical component alignment.