View Full Version : JuKu's pick and place project

20-11-2012, 04:17 PM

This is my first foray to CNC world. Hi all! I'm an electronics designer and tinkerer. Recently I acquired SMD reflow capability to my lab. After some test runs, I built my first real board. It had 450 components on it, which I manually placed. No way I want to do that again! This, and because it will be a fun project, I'm also going to try a pick and place machine. My goals:

- The machine is targeted to a prototype lab, only a few or maybe just one board at a time. So, no real need for feeders at this point.
- Accuracy and speed must be significantly better than hand placement, but not more.
- Can place loose components. In fact, if the machine asks the user "put R13 (22k) on pickup spot", user does so and the machine then looks at the pickup spot and can pick up the part and put it where it really belongs, I'll be very happy! There would be very little setup needed for my one-offs.
- I'm limited in my machining capability and even more with tools. So, the more I can use off-the-shelf parts, the better.

I'm comfortable with software and electronics, but as noted, a real NOOB in machine building and CNC. Therefore, I would appreciate any feedback and improvement ideas. So, may I present for you to ridicule: JuKu's first CNC desing, the pick and place contraption. The attachment is a picture about what I have so far, the PDF is the same in zoomable and rotateable form. Btw, the PDF is much clearer by selecting solid outline viewing mode.

Starting from right, we have a belt-driven block on a 13mm steel bar that holds a stepper motor. On the same plate (2mm steel, drawn semi-transparent for clarity) there are holders for two other steel bars and a shaft (darker gray), that transfers driving force to the other side. Not shown is the same arrangement on the other end of the bars (sans the stepper, pulley and idler wheel). Sliding along the two bars is another (semi-transparent) steel plate. On top, there is a piece of aluminum profile and a stepper motor with a threaded shaft. (I said I'm limited in machining capability, I'm trying to avoid a need for bending or welding steel.) The threaded shaft motor rises and lowers the pick and place head, which goes between the yellow plates. The whole thing is mounted on two pieces of aluminum profile, oriented 90' to the first bar; the supports are mounted on top of the profile. The tube-like thing with an antenna-looking cable mockup is the camera.

Not shown in this proof-of-concept sketch:
- Bolts don't have washers or nuts. Some bolts are of wrong length.
- The mirror image of the other side carriage
- The pieces of the aluminum profile the whole thing is mounted on
- Belt anchors and tensioners
- electronics, cables, vacuum tubing and solenoid valve
- The actual pick and place head mechanism. I have not designed that yet, but I'm going for this Basic idea: Pick n Place Head Outguessing the machine (http://tim.cexx.org/?p=728), but improved: There will be a spring load, the motor should be mounted the other way around and I already have the camera.

So, what do you think? Where this contraption sucks the most? (Apart from the suction pipe, not shown.) What I like about this is that is is fun to design. So far, the parts are not very expensive, and most are available off-the-shelf. The custom parts are plates only, with no precision placed holes. In other words, even though I'm buying some laser cutting time for the prototype plates, I can make replacement from aluminum in my own workshop, should I need to.



20-11-2012, 08:50 PM
I look forward to following this thread with interest, JuKu. Haven't yet got my mind around the design, but will come back to it as it makes a pleasant change to the normal builds.

Btw, just looking at google maps to see where you live, makes me feel f-f-f-freezing cold... Lol


Robin Hewitt
23-11-2012, 01:44 AM
So, what do you think? Where this contraption sucks the most?

I think you may be making problems for yourself :whistle:

Valiant effort and all that, but could I make a few suggestions...

It's incredibly rigid where you don't need it and flexible where you do.

Why is the X axis motor mounted on the gantry with that convoluted belt drive? It's just extra weight to move, long cables, extra bearings and lots of things that can bend or be a tadge off centre. I suggest two belts go around driven pulleys at one end and sprung pulleys at t'other.

One linear bearing per shaft is enough for pick and place. I used 16mm for X and 10mm for Y and that was overkill.

Do you really want to screw drive the Z axis? It makes it heavy and if anything goes wrong it could drive the pickup nozzle down into a component. I suggest a cam to lift it and let it drop under it's own weight.

The simplest component feeder is a ready peeled 8mm tape sitting in a groove. If you have 2 tapes at 90 degrees you don't need to rotate the nozzle.

If you attach the pick-up nozzle to the head with a magnet then auto-changing is so simple there is no point not having it.

09-12-2012, 08:42 PM
Edit: Got a better design idea, a bad design removed.