Insert for TFA thermo-hygrometer

This model is an insert that is designed to fit an analogue Ø 71 mm TFA Dostmann thermo-hygrometer model 45.2041. This thermo-hygrometer is less precise than a digital thermo-hygrometer but will not require any battery. This thermo-hygrometer can easily be found on amazon for exemple. This is originally designed for building a custom dry-box.

Link:

• Analogue thermo-hygrometer with metal ring | TFA Dostmann (tfa-dostmann.de)

List of parts

Printed Parts

Insert

This is the main part fitting the thermo-hygrometer.

Insert Nut

This nut is used to fasten the insert with the dry-box wall.

Spacer

The thermo-hygrometer has a convex gauge view. The spacer is used to create a gap between the gauge and the insert view.

Back Nut

This nut is used to secure the thermo-hygrometer with the insert.

Other Parts, Tools and Consumable

View

You need to cut a 72 mm view. I recommend using 2mm plexiglass. If you have a routing tool or routing table you can use the profile tool below for a perfect cut.

View Routing Profile

Optionally print this part and use a profile with a routing tool to cut a perfect plexiglass view.

Silicone Sealant

Optionally apply some silicone sealant for a airtight dry-box.

Printing Instructions

I recommend printing in PLA with a .4 mm nozzle. I also recommend printing all parts with screw filet with .10 mm layer height for a better definition and using the feature avoid crossing perimeter to avoid stringing and polluting the filets.

All parts except the Back Nut will print with no support. The Back Nut will require supporting material.

Insert

Preferably printing with .10 mm layer height for a better definition of the screw filet. Print with the front face down the build plate.

Insert Nut

Preferably printing with .10 mm layer height for a better definition of the filet. Print with the back face down the build plate and the pressing face up (refer to assembling instructions to identify the pressing face).

Back Nut

Preferably printing with .10 mm layer height for a better definition of the screw filet. Print with the back face down the build plate and make sure the 3 windows on the back are supported.

Spacer

This part can be printed with .20 mm layer height.

Routing Profile

This part can be printed in draft mode. Print with the screw chanffer down the build plate. No top layer is needed.

Assembling Instructions

Post Processing

Try screwing all part together. The fillets are designed with the required gap but if this too tight you can try brushing the fillets with a brass brush to remove the excess of material or apply some wax from an old candle for exemple.

Cut Plexiglass View

Cut a Ø 72 mm disk in a 2 mm plexiglass sheet. I recommend using a routing tool to finish the disk edge. The routing profile provided can be screwed with a 4mm flat head screw and the plexiglass can be glued with the profile tool using double sided tape.

Seal the Plexiglass View

1. Apply a light ring of silicone sealant inside the groove around the view.
   
2. Insert the plexiglass view in the Insert followed by the Spacer and the thermo-hygrometer. Screw the Back Nut to press the plexiglass view with the sealant.
3. Wait until the sealant is fully dried and remove the excess on the front view.

Open the drybox wall

Open the dry-box wall at desired location with a Ø 80 mm hole.

Final Assembly

1. Apply a light ring of silicone sealant inside the groove around the Insert.
    
2. Install the Insert with sealed View in position.
   ⚠ be careful with the orientation, the one of the 3 windows on the back should be located on the top.
3. Secure the Insert with the Insert Nut.
   ⚠ be careful with the orientation of the Insert Nut, the pressing face should apply against the dry-box wall.
   
4. Install the Spacer followed with the thermo-hygrometer. Tighten the Back Nut until the thermo-hygrometer is secured and align the 3 windows on the back to ensure the air is circulating inside the devise easily.
   ℹ if you can't properly align the 3 windows from the Insert and the Back Nut, you can slightly increase the spacer thickness by up on the Z axis in the slicer. The filet is M80x3 so increasing the thickness by .5 mm will give 1/6 of a turn.