FSR Mounts

by SublimeLayers, published

FSR Mounts by SublimeLayers Feb 11, 2016
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FSR Mounts by SublimeLayers is licensed under the Creative Commons - Attribution license.

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This is a simple, printable mounting system for FSR auto leveling (worse sensitive resistors). I've used these on Rostock Max, Kossel 250, Mini Kossel delta printers and also in a Taz 4 Cartesian printer. I highly recommend buying the FSR Kit from UltiBots - it comes with the JohnSL interface board, the wiring harnesses with preassembled connectors. They work perfectly with this mount.

UPDATE: I've added a second version that is designed for the Kossel 250 or similar printers. There are 2 mount parts, one is for a threaded insert, the other is plastic and can be threaded directly. This extra hole is for an M3 cap screw that fixes the Holddown part as shown in the attached photo.

Print Settings

Printer Brand:



Rostock MAX






.2mm layers, 4 perimeters




I print these in PLA but make sure your heated bed has insulation under it if you do. ABS makes good parts too.


Print 3 holders, 3 plungers and 1 of the JohnSL brackets. The TAZ bracket holds the board vertically, the other holds it flat - which is more suitable for delta printers like the Rostock Max.

It is critical that the plunger slides free - but without slop - in the mount. The plunger was designed with 3 points of contacts to make them easy to fit. First, clean out the pockets in the mounts to make sure they are smooth. Test the plunger. If it is too tight, lightly sand the surface of the 3 lobes with 400 or 600 grit paper and water. Rinse thoroughly so you don't introduce grit into the mechanism and test the fit often (after rinsing). Once the fit is perfect, keep the mount/plunger pair together.

I lubricate the plunger with a little Vaseline or white lithium grease - VERY little!

Printed mounts with FSRs inserted. Note that one of the silicon pads in the UltiBots kit goes on top of the FSR before the plunger.

Mounts attached to the Rostock Max base. You can also attach them to aluminum 15x15 or 20x20 extrusions.

The plunger is screwed to the bottom of the snowflake insulator on the Rostock.

This is the little holder for the JohnSL board

Holddown for the Kossel 250 version.

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On the Taz where did you place the sensors? In 2 corners and mid bed opposite them, or under points defined by a maximum equilateral triangle solution?

I am going to use a set on a Folgertech FT-5. So using 3 sensors I believe the easiest solution (mechanically, as bed screws are near these locations)would be:
0X 0Y
300X 150Y
0X 300Y

(However the solution is not optimal, since most 3-point leveling solutions work best with the largest possible equilateral triangle using axially non-collinear coordinates)

The the largest equilateral solution for 300 x 300 bed would be:
0X 0Y
300X 80.38475Y
80.37475X 300Y
Each side =310.5828541230249

Ps. It was great meeting you at MRRF2017, please send me a pm, I lost your contact info.

Sorry for the late reply, I was traveling this week.

I placed 1 at the front left, 1 at front right and 1 in mid back as you described in your post. Hmm, I'll have to plot that out I thought the largest equatorial would include the longest edge (300mm). That's interesting.

Thanks for the reply.
on the triangle, nope, common misconseption. instinct tells you that, but the largest equilateral intriangle solution is always one point in a corner, sides 15deg. angle from the side of a square. (oragami with my eldest).
so on any greatest equalateral intriangel on a given square is Vert A,B,C 60 Deg. where A,B,C,D 90 Deg. Point A0,0 on both.

the easiest way to solve for sides a,b,c on the triangle we need, is to solve for the one we don't need using that right triangles hypotenuse.

Given Square A,B,C,D 100 and a,b,c,d 90. Solve for the unwanted RT. Triangle at the base of the build plate. where: a15 B100 c90 yields a Hypotenuse of 103.53. Its always greater than A on any given square.

where a15 b? c90 A? B100 C? Pythagoras tells us a15 b75 c90 and A26.79 B100 C103.53

Since we only really care about the squares Cartesian coordinates for leveling, this triangle gives us everything we need for optimum leveling of the given square with an inset equilateral triangle at x0,y0 x100 y26.79, x100,y26.79 and each side measuring 103.53.

additionally, these points map the plane more accurately across the center of the bed, than say the more customary x0,y0 x300,y0 y300,x0
and makes the math easier on your CPU. I know you are all about the details. hope this was at least interesting.

I have 7 deltas and an FT-5 under construction, so leveling math has been foremost in my mind today.
Cheers, Mike

The 250 mount is huge when opened in Cura

You must have a scaling issue or imported in the wrong scale. About 500 folks have printed this and I've printed dozens myself. I don't know Cura so I can't help but most slicers do allow you to scale or change from metric to inches. I suspect you are loading the files in inches.

I'll have to look again. I can open the threaded insert version just fine.

  • Thanks for the file!

You might be right, I jus dowloaded it myself except it is too small in KISS. It apparently was saved in inches and needs to be scaled to mm. In KISS that can be done with the Inch->mm menu option.

On the rostock mounts, do you use the silicone pads? Would you mind sharing how you mounted the bottom piece to the printer base? Thanks!

Yes or neopreme washers - one above the FSR is all that's needed.

Mounts look nice. Your print quality is superb! Thanks for your support - Brad

Do you still use the same plunger for the 250 Mount set-up? Looking at the pictures posted, there doesn't seem to be much clearance between the 250 bed stands, and the heated bed.

Yes I do. I'm not sure I understand your comment though.

Ok, I took a look at the STL for the motor mount screw holes. They are much much wider than this FSR mount. It looks like the best bet is to mount the FSR mount to the base plate on the Rostock Mini.

Thanks. I don't know so probably not! What is the required spacing? I've not seen a mini, is there a photo of one available?

There are two models on Thingiverse that I am aware of, http://www.thingiverse.com/thing:318971 and http://www.thingiverse.com/thing:318685. I only ask as I am at work currently, planning on printing out a test copy once I get home.

Rostock Mini Pro by 3D Printer Czar
Rostock Mini Pro Minifab.net

Nicely done. Do you happen to know if the spacing on the side rails of the FSR mounts will match the spacing for the screws that attach the bed to the motor mounts on a Rostock Mini? I have been looking to clean up the installation of my sensors.

Don't forget that the FSRs have a sticky back. When everything is ready, peal off the protective plastic and stick the FSR in the pocket on the mount.