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Desktop Pick-&-Place Machine: An EETimes Community Project

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Aeroengineer
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Re: Trading speed for size and accuracy
Aeroengineer   6/23/2014 11:05:46 AM
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I think that this may be a good thing to do a poll on.  What do you think about that Max?

Max The Magnificent
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Re: Trading speed for size and accuracy
Max The Magnificent   6/23/2014 11:01:53 AM
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@Aeroengineer: What size work area are you thinking of Max?  It seems that we are talking as low as 4"x 6" up to 8"x 10".

Oooh -- that's a hard one -- obviously I would like to have the capability of going as big as possible -- on the other hand most of my boards would be quite small -- it would be rade indeed for me to be making an 8 x 10" board ... and then I think about making an 8x8x8 LED cube...

How about going up to 6" x 8"?

Aeroengineer
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Re: Counterweights ??
Aeroengineer   6/23/2014 10:48:38 AM
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I like the thoughts that you have going on this.  This is one of the reasons that I have not rules out stepper motors and a belt system either as with the belt system, it would be very easy to do the counter balance approach by mounting the weight right onto the belt.  I have not looked into the steel wire method, though doable, usually for higher load parts.

 

The dual heads moving in different directions could be an interesting idea, and could make it very useful in that you would not have to dock heads.  Have to give this one some thought on a general methodology to integrate it.

 

Aeroengineer
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Re: Acceleration and nozzles
Aeroengineer   6/23/2014 10:44:34 AM
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I see that you found more than my twitter page ;)  Yeah, I am an engineer because if I were anything else, I am not sure what I would do.  I love it. 

 

My back of the envelop crazy calcs are just that, crazy, trying to help me understand the absolute limits.  I did a quick calc with a whole sequence last night, including a trap accel.  The accel definitely will play into the time on this machine as the travel distance is so short.

 

The other thing that I need to look into is the PV capacity of the nuts.  Usually they are not just rated for a linear speed, but a value that is proportional to the load times the speed.  This will bring some more reality into this effort.

Aeroengineer
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Re: Motion solutions: motors- a mammoth post
Aeroengineer   6/23/2014 10:40:35 AM
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Good info. I will read this in more detail when I get back to the hotel tonight.  I will see what I can digest and then ask a few more questions.

Aeroengineer
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Re: Oversized I think
Aeroengineer   6/23/2014 10:39:07 AM
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Correct, this was the overall footprint of the device, not the build area.

Aeroengineer
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Re: Trading speed for size and accuracy
Aeroengineer   6/23/2014 10:38:22 AM
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What size work area are you thinking of Max?  It seems that we are talking as low as 4"x 6" up to 8"x 10".

Max The Magnificent
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Trading speed for size and accuracy
Max The Magnificent   6/23/2014 10:29:02 AM
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Personally, I'd be happy to trade speed for increased PCB size and increased placement accuracy.

FYI I've already cleared a corner of my desk in anticipation of this unit :-)

salbayeng
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Re: Oversized I think
salbayeng   6/23/2014 5:16:35 AM
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Hi antedeluvian  ,

I think the 11" x 17" refers to the size of the machine sitting on the desktop. 

The actual max pcb might only be 4" x 6" . (I think all the hobbyist proto shop sizes run in multiples of 50mm)

The amount of travel needed to get to the PCB and the parts, depends on how the parts are picked up , could be double the PCB area.

 

salbayeng
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Counterweights ??
salbayeng   6/23/2014 5:05:03 AM
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some crazy ideas with counterweights:

This only works on the Y axis: have a two head machine, going in opposite directions on either side of the gantry (could be a paste head one side, placing on the other) or camera on one side?, This probably needs a long "fast" counterbalanced Y axis and a slower X axis, so you would put components on a pickup grid above and below the PCB. Maybe 4"PCB + 4"grid top + 4"grid bottom = 12" Y travel, and 6" X travel = PCB width. 

Or you could go all out, and put the X motor underneath the workpiece (PCB+platen+parts+motor), have the heavy workpiece move sideways 1", while the light gantry moves 5" other way for 6" total . 

Also for the  Z axis , have you considered using bail bars (like the old fashioned pen lift on chart recorders) the "high position" has no accuracy requirement, while the "low position" will have a spring anyway, this would be adequate for placing, but might need better Z control for pasting.

You might consider making "double wishbone" suspensions for the placing nozzles from laser cut shim, this gives parallel motion and a soft spring (wouldn't be that hard to make it 4 nozzles spaced 1/2" apart  either) Need some thought how the component aligning fingers work with multi-head. 

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