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

by DrBoo Oct 29, 2014
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really nice job, just adapted your design to adapt my printer! nice job

where can I get fan duct like that?

Thanks to this your idea I realized my effector with the particularity of being able to extract the extruder from above by removing only the three screws holding together the two plans.
If you want to see and tell me what you think of my work I am sending the link

Hi, very nice work, I was suggested this link on the reprap forums after trying to come up with about the same idea for a corexy printer (decompressing instead of pressing onto, no visible movement for triggering).

Are you still developing this solution? What is the repeatability of the FSR solution? I find it one of the best solutions out there apart from a strain gauge that would be way more sensitive but again needs special board/etc. I've read that the repeatability of the FSR is arund 0.02mm (from the Kossel FSR Wiki) and also that the output of the FSR can go straight to the Z_MIN on the controller board.

I see below comments about another board to interface the FSR to the arduino. I believe that is not needed.

Again congrats and keep us updated.

Thanks for the nice comments. Unfortunately I have lost interest, for the while, in building my 3D printer - and as such I cannot really comment as to the repeatability. Though I designed and manufactured the unit, I have not continued to actual testing of the FSRs and completion of my printer. I can say that my tests with a multimeter did show that fairly small pressures were sufficient to trigger reasonable changes in the FSR resistance, and of course there's no perceptible movement in the mechanism/springs when this happens. That is, although the whole head CAN travel a significant distance, this doesn't actually happen in practise. The large travel does however give you good "head crash" survivability. I would love someone to continue with this design and run with it.

That's sad that you have lost interest, it's hard at times to keep fighting in this arena of pioneering struggle but it's most of the times rewarding. I hope you will resume your build and keep the flame open.

Was this ever updated?

As for the FSR's being always "On" I don't imagine its much worse than having the entire heat bed rest on them as is done in the under bed installation. I wouldn't worry too much about that. I think this is a much more elegant use of the FSR's. A nice addition might be mounting tabs for the JohnSL board if your entertaining suggestions.

You want to use the JohnSL FSR Endstop Controller, get it on Ebay pretty cheap, they even sell whole kits that include the 3 FSR's. This controller allows you to just wire the three FSR to the controller board and then have 2 wires going to the Z min endstop location as normal. No firmware changes or anything, the controller board takes the resistance readings from the FSR's and converts that to a High/Low signal for your printer controller. Pretty Slick! Happy Printing Everyone!!!

hey, nice work. Printed all parts, assembled with an E3D, fits perfect !
But, you don't say anything about any change to any firmware... I know, several versions are used out there, no doubt. I use marlin on my kossel/rostock and search for the point where to add or uncomment lins to activate it.
What firmware are you using, are using you other guys out there ?
What changes are needed for getting it working ?
Can you post some examples ?

I like this design but noticed that the FSR would be decompressed when the nozzle touched the build surface vs. most other designs where it is compressed. So this would make the resistance increase rather than decrease on contact, right? Would I have to change anything in the firmware to use this design?

I haven't got that far, but yes there would be a change in the firmware. You are looking for a very small change in resistance, by the way -- it will probably be fairly simple. I've taken a bit of a break from my 3D printer build. Let me know how it goes :)

2 layers of perimeter, 25% infill seems to work fine for me.

What infill and perimeters settings do you recommend for this?

I assembled my FSRs into the new design last night and did a test on how well the mechanism works. It seems to do OK. Where I expected the whole mechanism to travel significantly, in fact it has no visible movement before the FSRs detect a change. When static, I was seeing about 48k ohms resistance from the three FSRs wired in parallel. When I put a bit of downward pressure on one of the carriages (forcing the head to touch my glass bed), it didn't take much pressure at all for that resistance to change. Certainly way less than required for visible physical movement of the plunger mechanism. So it looks like it will work just fine.

Yep I'm still working on this. I have a new design which fixes the issue you mention. I have put a couple of slots on the underside of the effector body into which you slide the nuts, then you can use shorter screws on each side (one per rod) to firmly attach the rods. I will upload the newer design in a few hours when I have access to the files. There are a few other changes, too; specifically the slots for the tails of the FSRs are a bit too narrow to allow them to push through, and I've made the width of the distance between the rods on the effector exactly the same as the width between rods at the carriage end. The design here doesn't allow correct attachment of the rods; that is fixed in the new design with some conical mounting points that give sufficient clearance. Please watch for a new upload in a few hours.

l'm just getting back to this now. Are you still working on it? Anyway, I recommend adding a nut trap where the traxas joints attach to the rods. It seems like this design only allows you to thread the bolts into the plastic, which will eventually work itself loose. Alternatively, you could try to get a really long M3 screw but that will be somewhat hard to find. Any other suggestions?

Very nice work, I will print it and give it a try on my mini kossel since another similar design on here did not work as expected. What hot end is this designed for?

One suggestion- make the "knobs" that the rods screw into flat against the bed so it can print without an overhang. Most other effects do it like this. I will post a pic when I get it done.

I will refine it as suggestions/comments come in. One probable change is the mount holes for the arms; rather than one long mount hole for a pair of arms, I may change it to one per arm. Shorter screws are easier to find. Will also consider your suggestion about the mounts. I'm learning. It's an E3D hot-end compatible mount. Though, as noted, it's parameterised so should be easy enough to change things for other hot-ends.

The choice of springs makes a huge difference to the operation of this unit. You want them strong enough to keep the head stable, but loose enough so that you don't need too much downward pressure to affect the pressure on the FSRs. I'm still building my printer and waiting on parts, so would be keen to hear how this works for you, and make any changes required.

I'm interested in helping you test it. It is basically what I had envisioned for what I was going to build, but more bulky/ robust. I've got a mostly manually calibrated kossel that I can add it to. Might take me 1- 2 weeks to get back here with results.

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