Hi all,

I am considering to build a pick and place machine for my company. I have extensive experience in electronics circuits design, this is my company's area of activity for 15 years. I have some experience with mechanical engineering, I have some tools available, but I lack experience with the specifics of building mechanics of a CNC machine. So, if somebody can give me some advice, would be really helpful.
What I will use:
-software is available, Open PNP, looks fit for my purpose.
-some of control electronics, more specifically translator between openpnp/gcode and various signals for motors controllers, actuators, sensors, etc, I will build myself
What I want to obtain:
-a mechanical pick and place machine, preferably 1,5x1m size
-enough precision for 0201 components
-speed as high as possible
-head with around 10 nozzles
What I have in mind to use so far:
-400w servo motors for high inertia, panasonic, with matched controllers and with absolute linear encoder, in full closed loop configuration
-screw balls for driving head and gantry
-wide linear guides, with balls, for both x and y, to be able to sustain high inertia forces
-a thick aluminium base
-price of course does matter but is not the main selection criteria, the goal is performance, within resonable price limits.
What is not clear and where I need advice:
1. I think at 1x1.5m aluminium base, maybe 25mm thick, this will have around 100kg. I think it needs to be heavy to damp as much as possible from vibration generated by x/y movements. Am I right? Do I need heavier or 100kg is too much?
2. Considering 1,5x1m machine size, gantry with placing head will be on the long axis, 1.5m long, to allow easy access to feeders placed on the length. With all the items on it (10 nozzles head, cameras, valves, cables, etc. I do not see gantry weight under 20kg. That is a rough estimation. At this size/weight, is it wise to drive the gantry from one side only, even if using wide ball tracks (around 80mm wide, like this: http://isel.ro/images/mecanica/lfs83.pdf ). Or do I need to drive it from both sizes?
3. Considering I want to use full closed control with external absolute encoders, is the precision of the ball screw very important? Do I need C5 or better, ground screw, or a rolled will be ok?
4. I have not done load calculations (not good at them thou), but as a starting point, I considered a screw around 20-25mm diameter, lead around 20-25mm as well, as I think this is a good compromise between speed and precision. I am considering to buy them from TBI, the're more accessible in my area. Also available at aliexpress. What is your experience with ballscrews on ali? If the seller says it's TBI, is it really TBI?
Any other thought will be helpful as well.
Thank you.

Best regards,
3.

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