Alternative mounting for Delta Smart Effector
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My home built delta printer is made out of machined bits of aluminum and Delrin and uses what I thought until recently was a pretty unique ball joint system. Seemecnc's injection molded ball joints are very similar to mine. I would like a better Z-probe setup and it isn't a very good option for me to use the Delta Smart Effector as intended with the mag-balls.
If the Delta Smart Effector is a sort of strain gauge, how much of the PCB needs to flex in order for it to work? I could modify my current aluminum effector to use the 6 mounting holes intended for the mag-balls, but I need to know if each of the holes would need to have its own spacer/standoff, or if I could attach each corner pair to just 3 larger spacers. I will need to machine out the center of my effector for clearance of the connectors and wires.
One option I might have would be to mount the Smart Effector above my current effector and have the nozzle tip extend just below the lower surface of my effector- this would give me quite a bit more Z-travel. This would make it harder to use the LED lighting.
A more straight forward mounting would be to place it under my current effector, and the 6 or 3 spacers I use could be short enough that I wouldn't lose much height. I drew this option with the larger spacers in each corner.
One more option would be to machine adapters to mount between the smart effector and the Delrin ball mounts I made. This would probably be the most work since I would have to make the new adapters, rather than just modify what I already have. This version also looks like it might be the hardest to get all the angles and spacing correct since I would only have the 2.9mm holes to use for mounting the adapters. My current arrangement uses dowel pins to ensure alignment. In the options above the alignment is less critical since none of the features on the PCB are used to determine the delta geometry. I am sure that the PCB hole spacing is at least as accurate as my machined parts, it would just be harder for me to use just those holes to maintain the geometry I already have. I could maybe use 2.9mm dowel pins, but I would have to come up with another way to fasten the adapters to the PCB. I will have to give this a little more thought. Does anyone know how thick the PCB is?
I guess my biggest question is whether the Smart Effector is going to work as intended if it isn't mounted as intended.
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The area with the strain gauge traces takes up the majority of the board. If you look at the drawing here:
https://duet3d.dozuki.com/Wiki/Smart_effector_and_carriage_adapters_for_delta_printer#Section_Strain_Effector_DimensionsYou should assume that everything inside the Electronics components needs to flex.
Looking at your proposed designs, all should work as they support the effector by the ball stud mounting holes and allow the nozzle touch to flex the smart effector PCB.
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One slight complication I can see is that the mounting pillars will tend to constrain the PCB so as to bend in an S shape instead of in a spherical shape. So there might be some loss of sensitivity. Other than that, it should work.
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Thanks for the responses. I am amazed at how easy it has been to get support here.
I am wondering if I would get a slightly better flex out of the effector if I only used 3 of the single-hole spacers:
It also just occured to me that maybe the spacers could be replaced with precision length die springs. The springs would allow the PCB to flex more naturally- the trick would be getting the right spring tension. The screw passing through the spring would maybe need to be a smaller diameter than an M3. I have a 4-40 on my desk that measures 2.78mm. That might work- though the springs might allow the nozzle tip to shift away from center a bit.
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I guess the ideal would be to have ball ends on the pillars that the smart effector mounting holes sit over, and springs holding the smart effector against them.
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While that looks like it would work, why not go with a FSR or pezio type z probe? I feel like it will overall be easier to set up, unless you're dead set on having the cable management aspect of the smart effector.
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I designed this effector (see second image) which incorporates piezo and raises the hotend up quite a bit:
https://www.thingiverse.com/thing:2775282 could easily be adapted to be a larger version.
