New FSR Plate mounting system

By mhackney Thursday, February 9, 2017

I've posted quite a bit about FSR probing along with my previous mounting system. I've been using FSRs for probing for coming up on 3 years.
They are 100% reliable, very precise and result in excellent calibration results. I originally designed this system for a Max Metal delta printer but it worked so well that I used it on my Rostock MAX V3 and I'm going to retrofit my other deltas with it over the coming year. There are 2 significant aspects to this new mount.

1. The FSRs are now positioned outside the build plate perimeter as you can see in the renderings below. This minimizes the "teeter totter" effect when probing 1/2 way between FSRs. Moving the probing points out significantly decreases this effect.

2. The second improvement comes in the way the FSRs are mounted and how they are triggered. In my previous mounting system, a printed plunger moved inside a printed cylinder. This led to one of the two reasons folks had problems with FSRs (the other was that their bed is not stiff enough - this mostly applies to the Kossel Krowd™ that simply used glass with a Kaptan heater). The plunger system works reliably but only if you use high quality prints and prepare and lubricate them properly as I've described on multiple forums and here. Otherwise, they can bind ever so slightly, leading to inconsistent triggering. The good news is, this issue is easy to identify and correct. The better news is, this new system eliminates the problem altogether! Here's what it looks like:
With this new system I simply adhere the FSRs and rubber plungers with sticky tape so they are constrained in X-Y but free to move in Z. The FSR has a sticky back, just peal off the protective film and stick it to the top surface of the printer. The plungers that come with the Ultibots FSR kit also have a sticky back, so peal that and stick it to the top of the FSR sensor itself. Now you put a small dab of silicone seal on the top of the 3 rubber plungers (a SMALL dab) and press the FSR Plate onto them and allow to cure.

I actually don't bother with the silicone, I just have my plate resting on top of the plungers. I've never had an issue with the plate moving. I am working on a simple printable locator that will attach to the top printer plate that will keep the bed from shifting but since this has been working so well, I have not bothered.

Finally, you can see in rendering below a recent modification - the FSR Plate now has three ears. In my V3 photo at the start of this post I'm using big binding clips. I needed to add 3 additional rubber plungers under the FSRs to make room for those. But, by tweaking the FSR Plate with the ears I can remove those and use the ears to attach the Onyx/glass with the little blue (or other) holddowns. I do one other thing on my printer, I adhere the Onyx to the top of the FSR Plate with a disk of the 3M 468MP tape we use to attach PEI. This holds the Onyx perfectly flat while allowing it to expand and contract in the X-Y plane without buckling. It works quite well.

20 comments to ''New FSR Plate mounting system"

  1. Michael helped me setup this system on my max v3 last time he was in town and I got to say the fsr's are amazing.

  2. Awesome... What is the FSR Plate made of? Are they for sale or something you custom made?

  3. They are the same melamine that is used on the SeeMeCNC Rostock MAX printer. It is a a little more than 5/16" thick. is going to offer these but Brian just told me it will be about 6 weeks. I am going to post the DXF files too if you want to make your own.

  4. Thank you for this blog and all the posts you make on the forum. You've really improved my v2 and got me excited about printing again. Any chance the dxf files are posted yet? I just orderd the FSR kit.

    1. Thanks for the feedback and yes I have published the DXF:

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  6. Looking to convert my duet wifi v3 to FSR's soon enough but was curious if you used the same setup/Ultibot FSR kit from your previous FSR post( or did you add any new info or tweaks for the v3? Thanks

  7. Scott, yes, the Ultibots FSR kit is the way to go. He provides everything you need including pre-made connectors. Believe me, adding connectors to the naked FSRs is not fun!

    Trick Laser will be manufacturing the new FSR Plate. I got the first 2 prototypes on Saturday and they are good to go. I don't know what the date is but it should be soon.

  8. A) Do I understand correctly that from top to bottom, you see:
    1. glass buildplate
    2. heater pcb
    3. your new melamine plate (with plungers attached at the bottom)
    4?. no more black plastic heatspreader?

    B) I was also wondering if the fsr kit can be easily used with the rambo (they show up as simple endstop if I am correct?)

  9. Arne:

    A) you missed the PEI on the very top! Otherwise that is correct. The black plastic thing is NOT a heat spreader, it was a bed support (the injection molded 12" round piece that came with the V3). It is not needed, the melamine FSR Plate replaces it.

    B) Yes, FSRs are perfectly compatible with RAMBo and with all versions of firmware as the JohnSL board makes the FSRs look like a simple end stop switch to the controller and firmware.

  10. I'm thinking about getting a Duet Wifi and a set of FSR's because of bed leveling issue's I am having at the moment. I am hoping the new setup with Duet autocall will solve my struggles.
    I am also thinking about insulating the heated bed with aerogel sheets. Do you have any suggestions on where to put these in the fsr setup?

  11. Are you truly having bed leveling issues or delta calibration issues? Delta calibration includes "bed leveling" and bed leveling is a much easier/different issue to fix.

    You can simply put the aerogel on the bottom of the melamine plate if you think it necessary, but the melamine provides pretty good insulation. If you intend to reuse the black molded base plate, you can put triangular shaped pieces between the ribs - but then you are on your own to figure out how to place the FSR mounts.

  12. I am having trouble getting the nozzle at even heights around the buildplate.
    I would love to reuse the old black plastic but I have no mounting system.

  13. I have an R2 Onyx, which has PCB-mounted parts and surface-soldered wire ends where one of the tabs is (unless I'm missing something). Seems like I could change the design to have two hold down tabs on that side with a cutout in between for the parts/connections. Does that sound reasonable?

  14. There are actually slots to clear the electronics on the left and right of one of the ears. I checked this against my V1 Onyx and it worked. Should be the same as yours. But, in any case you certainly could modify the design or even drill/cut the part to get the clearances you need.

  15. Thanks for your reply. Even with the slots, that tab still covers the resistor and LED on the R2 Onyx, assuming those parts are mounted on the bottom, as recommended (Rostock MAX Assembly Guide, 2nd Edition, p117). I superimposed your DXF drawing over an image of the R2 Onyx to confirm this. Seems like this issue should be mentioned on the TrickLaser site for people considering purchasing the FSR plate. Anyway, I have my own laser and will modify your design to fit my Onyx.

    You mentioned using 3M 468MP to avoid buckling. Did you notice actual buckling when the Onyx was screwed down?
    Do you still use a heat spreader on your V1?
    And BTW, thanks so much for all of the great information you've shared!

  16. Yes, they must be mounted on the the bottom or they will interfere with the glass on top.

    I'll talk to Brian about adding that to the site.

    Absolutely, the Onyx buckles when only screwed down at the periphery by at least 5mm in the center. I do still use a heat spreader on ALL my printers, its the only way to ensure even heating across the bed surface. Even a couple of sheets of heavy duty aluminum foil works. But be careful with your Onyx and make sure that all leads & components are insulated (Kapton tape works well) to prevent a short circuit.

    And sorry about the blog design, I'm in the process of updating the template and there are a few kinks!

  17. Wow, 5mm!

    I cut a disc out of a sheet of 1/32" copper as a heat spreader. So it sounds like you must have three layers of 486MP, one between the FSR plate and the heating plate, one between the heating plate and the heat spreader, and one between the glass and the PEI.

    Yes, your blog is looking much more presentable now. The original default images makes one wonder who the theme author was targeting.

  18. I actually only have 2 layers of tape. I do not usually adhere the aluminum heat spreader to anything - it floats between the heated bed (Onyx) and glass/PEI.