[Eclipze]

I've played around with quite a few designs for a small hobby desktop pick and place machine in the last 2 years. But I've finally come down to a solution I'm going to build :-) It's actually the 20th design model

There is of course many different approaches you can take. I've held a core theme for my design... small capacity desktop machine, light weight, support a flexible design for modifications and support fast movements.

It's not a design for full blown production, rather a design suitable for prototyping or a short pre-production run. I specifically want it to support placement for components with footprint around the size of 0805, SOT23 and fine pitch IC like TSSOPs. The option for two placement heads has also been of interest. This is either for two different pickup nozzles, or to have one setup for paste dispension. I tend to machine my own stencils for small runs anyway, so the paste head mechanism hasn't quite been finished yet.

Ultimately... this will never been anything like having a proper production machine. It's far more of a hobby... some people build ships in a bottle, others are happy to spend many late night procrastinating over a feather weight pick and place machine hahaa.....

I am concentrating on the basics. Not the end goal. Vision based alignment, auto head changing, automatic feeders are all future upgrades. If I spent too much time looking into all the extras, I'd never actually get the first model up and running. So please bare that in mind with any comments.


Basic design specs...
X Axis Travel is ~160mm
Y Axis Travel is ~440mm
Z Axis Travel is ~25mm
X & Y step resolution is 0.0125mm
C Axis step resolution is 0.14 degrees
PCB area is flexible, currently shown as 220x180mm

I really wanted the design to have a lightweight head, to enable fast acceleration and also to keep the cost down. I've looked at many approaches using double rails and ballscrews, which always add a significant amount of weight and cost. However the more I played with the idea of light weight, the more I realised I could achieve a rigid design with just 3 linear bearings, belt driven. I have the igus Drylin T Series rails for X, Y an Z, and 2.5mm pitch, 6mm wide belts.

The X and Y are using NEMA 17 motors, and the C is using a tiny 20x20x32mm stepper. All are bipolar 1.8 degree step. The Z axis are all controlled by RC servo motors. I sure a lot of people are going to choke on that one hahahaa.... I have picked servo motors for good reasons. They are light, very fast, inexpensive (consumable) and easy to drive with the electronics (no stepper drivers). They have a radial movement, which means their translated linear movement has variable precision. The way I have the mechanism set, I achieve the highest precision as the placement tip descends close to the board. In addition, if the tip over travels (tries to crush the part underneath), it can't. The only downward force the tip has is the weight of the carriage/head. Once touching the component, only this weight will be on the component, after which the servo bearing disengages from the mating surface. I'm hoping that although I may not have fantastic precision, I can safetly overdrive the placement without risk of any damage.

The head has a separate tape indexing pin to feed the tape with. Each strip of tape also has a square box where the component is picked up, so component alignment by bumping can be done at the point of pickup. Rather than traversing to a specific cavity to perform the function.

The C-Axis uses a rotary tube fitting, which is held in place by a large bearing. A gear is attached to the rotary tube fitting, whereby the stepper can rotate the bottom half of the tube fitting (which is connected to the pickup needle). The top isn't fixed, however the air tube will restrict it's movement anyway.

I'm using ribbon cable for passing all data/power. All the actuators are so small, that the power requirements are relatively low. I still use 16 wires for the Y Axis stepper (4 wires for each stepper wire) just to be sure. I really like the idea of using ribbon cable, as it tracks so nicely without any sort of guiding mechanism. It's so very light too. It should impeded movement like a track conduit system would, and it much lighter than having an overhead cable bundle.

I have an adjustable camera on the head, so placement can be watched via PC. Expanding to vision based feedback is something for future work.

I have tried to create a flexible mechanical design solution. The use of angle aluminium is the basis to achieve this. If something isn't performing as I'd like, or an upgrade is desired, it's likely that only a bracket needs to be changed or modified. I have used 7.6mm polycarb where where thicker material is needed. The baseboard and the component feeder bases will be made out of corrian. It's a nice hard/stiff material that machines well, and should be nice and rigid for this application. I'm just using freebie off cuts. The frame is inch square aluminium with plastic joints. This leads to future possibilities for what is mounted underneath.

Design Variations
The base board defines the basic layout, which I currently show with placement area in the middle and tape strip feeders on each side. Those tape strip feeders are 8mm tapes, 16 per side. But these can be variations of other tape widths and component trays. I hope to have standard trays with most used component values, then others to cater for more specific needs. If I have a short run to place, I should have enough feeders that I can double up on components that are used more, or swap trays in/out as needed. I've also got the idea to mount reels underneath... if it's worth going to that effort of course. Including upward facing vision for component alignment is quite possible... it's just a variation of the base board to provide the real estate to mount it.


I've spent a lot of time considering many different options. Input is welcome, however at this stage of the game I'm reluctant to make any significant modifications in order to get to first base - something that does the basics. I'm mostly into construction/build mode, modifying the design to suit build/machining requirement. Please keep in mind how small this machine is and it's intent. Aiming for design elegance, not design overkill :-)

I'II be machining the parts over the next couple of weeks, and will post some pictures as I go. Hope everyone finds it of interest!