Dr Boo's Parameterised FSR Groove Effector for Delta Printers V3 by DrBoo

Last crawled date: 3 years, 1 month ago

27/Nov
VERSION 3
increased passage size for FSR tails. Printed and tested that they fit. Also tested FSR operation in assembled mechanism; it works!
added nut slots for rod connections. Each rod now has its own screw and nut, although there is still the option to use a single large screw if you wish (for each pair).
clamp and plunger now reduced in size, with the top of the E3D/jhead now inserted into the upper plate of the plunger. Plunger is now effectively flush with base of the effector, allowing a standard fan mount to be used on E3D.
17/Nov - This is going to need a bit of a re-think for attaching fan mounts, as they will need to be stationary with relationship to the J-head. Either mounts need to come off the top of the plunger, or the bottom. Probably the bottom...
16/Nov - I have added a WIP SCAD file called BooDeltaUpsideFSR which moves the FSR to the top (undersurface) of the plunger, and places a sloping channel for the FSR tails to exit inwards and up through the plunger, exiting around the pushfit. The reason for this change is that this allows the wiring of the FSR to be tight; the FSR now move with the plunger, which seems to make more sense. I haven't printed this one yet. Also I've been working at reducing the width of the arm connectors, so I'm not sure if the clearance is there for full movement. I may go for one bolt per arm... watch this space....
This is an effector/print head assembly with three embedded force-sensitive resistors (FSRs) set into an effector, with spring-loaded 'plunger' to enable z-depth testing using the hothead. It's gone through a few iterations now, and I don't anticipate major changes.
I have successfully printed this, as shown in the pictures, and the head-suspension spring mechanism works well. I'm still building the printer it's to be used on, so actual performance is unknown. I will say, however, that the print head is embedded very firmly into its mount and doesn't shift at all relative to its mount. Also, the 'plunger' is firmly held in place and it's only movement is the up/down axis when pressed on a firm surface. It works exactly as I expected. The mount clamps can be printed separately in ABS if required, as they are screwed on to the plunger.
The other bits and pieces are shown in one of the pictures. You need 3x 3mm diameter long screws (say, 44mm), 3x springs (I sacrificed 3 ballpoint pens for these), 3 x 3mm washers, 3x 3mm nuts. The black screws are M3, 25mm the longest I could find locally. They're almost perfect, and the nuts beside them were not needed. There was no drilling required; fresh off the printer I just screwed it all together. The screws simply screw in to the holes with a screwdriver and make their own threads. The hole fit is excellent.
Per the earlier comments, it may be true that a FSR should not be "always on" as it reduces lifespan. However, I don't know that for sure and this is a more elegant design than the alternatives I can think of. In any case, FSR embedded below print beds are also "always on" so clearly it's a reasonable thing to do.
If you have previously downloaded this, I suggest another download and grab the latest version because there have been some minor size and position changes of stuff.
I've recenlty (2/Nov/2014) updated the files with minor changes to hole sizes and placements. Specifically, the 'unused' holes are now positioned so that they have good clearance from everything, and the nut traps are correctly sized and flush with the effector base, so mounting anything underneath the effector won't have any obstacles.