Parametric Moen Posi-temp Single Valve Assembly Shower Knob

Overview:

This is, mainly, an OpenSCAD design so you can adjust all the parameters of the design as desired or needed.  

The following are provided:

• One .scad file containing the parametric model.  You will need OpenSCAD for your OS of choice to use this.  Refer to OpenSCAD's documentation for details on how to make your .stl or .obj file of the handle if you need to change shaft or stop parameters.

• One .stl file that is basically a shaft tester so you can print that fairly quickly to determine if you need to adjust parameters up or down for the shaft.

• One .stl file that is the knob, as it was for my shower valve and the default settings for parameters for the .scad model.
   

Preparation for Print:
 

Print the shaft tester.  It should slide right on, maybe with a bit of resistance.  If it doesn't slip on or is loose, you will need to adjust the screw_shaft_id or the screw_shaft_flat parameters a bit.  Don't do too much on the screw_shaft_id if you're enlarging with that parameter as this will eat away on the shaft's wall strength.  You have a little bit of play with enlarging the shaft that attaches to the valve's shaft.  This would be the screw_shaft_od value.  If you go more than 1.0 mm larger with the settings it may impinge on other parts in the valve assembly. 

Measurements with a caliper on the valve shaft can help with these settings to know if you're in the proper ballpark or outside of it.  This is a fairly precise thing.  Getting it too far off may allow slop in the knob's operation on the valve or, obviously, not fit at all on the shaft.

You will want to refer to your broken shower knob for stop arc size and position relative to the pointer which is the zero degrees position of the whole knob.  The values for the knob_stop_range and knob_stop_angle are in degrees.  The angle parameter is the start point of the arc on for the stop on the interior of the knob  The range parameter is the number of degrees past the start point of the stop arc on the knob.  The stock values are what is roughly the values for replicating the stop on a Danco replacement shower knob, which may work on your configuration, but with the variability of this stop (Several different variants have shown on the non-parametric knobs on Thingiverse, including the half the knob variant this design was adapted from), you will probably want to verify and may have to adjust to match your particular valve assembly.

Measurements with a protractor will help with making sure the knob basically follows what your original knob has for the stops on the knob.  However, these are not as critical as the shaft geometry ones, so eyeballing these two are fine.

IF you are re-generating the .stl file with OpenSCAD, note that the preview behavior in OpenSCAD has a possible rendering bug that makes it look like there's a pie-wedge thing going on and doesn't look right in the preview.  Don't panic- it IS a bug if you see this as it's an artifact of how the CSG is generated and quick rendered by OpenSCAD for the stop geometry. 

Rendering the model for prep for export of .stl/.obj files will clear up the issue and it provides the right geometry for print.

Ultimately, the main parameters are adjustable.  Knob top, etc. are all values in the parameters.  If you have problems with sizing, you should tinker around a bit with it in OpenSCAD.

 

Slicing/Printing:

• Recommended filament material: ABS/ASA/PETG-GF due to operational conditions- I used ASA for mine.  Unfilled PETG should work.  Some others off of whether your printer can cope with high-temps for Polycarbonate, etc.  PLA is likely to be unsuitable unless you know that the high-temp capable PLA you might want to use is also good with water conditions, etc.  The main concerns are heat resistance and moisture resistance.  Regular Nylons are going to have issues because of the Hygroscopic nature of this material.  PPA may work, though it might be too brittle for use.  Try to stick to the three I recommend if you can here.  They work out nicely enough. 

• Print resolution: 0.2 mm with a 0.4 nozzle.  I used a stock Ender 3 0.2mm, “normal,” print profile with a Revo 0.4 nozzle. No further speed or other settings changes were applied.

• You want 4+ perimeters on this design for strength.  If you don't, you may have it fail on layer lines, etc.

• You want ~40% infill, preferably a Gyroid or Honeycomb for strength.

• You don't precisely need supports for the screw inset if you print the user-facing side of the knob to the print bed.  It's a bridge, but it's small enough that it shouldn't cause issues in printing if you're using ABS or ASA.

Licensing:

This is licensed under the licenses I obtained the original design and pie module under.  

It's all under the Creative Commons - Attribution license (https://creativecommons.org/licenses/by/4.0/).  

The main design was obtained from the user NorthernMaker on Thingiverse.
The pie cylinder module (pie) was obtained from the user ex-nerd on Thingiverse.