What sealant should be used

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Spikeysonic
Posts: 23
Joined: Wed Mar 01, 2017 12:07 am

What sealant should be used

Postby Spikeysonic » Fri Mar 10, 2017 5:06 pm

been told I need some form of sealant, thread or ptfe sealant on the throat screw threads on the hot end but there seems to be many with different heats and some appear to be glues (Don't want to permanently lock it.

Can you guys recommend the right ones to use for Raise 3D 300 degree c printers and which to avoid that are available in the uK. Ideally with links or photos please

Jetguy
Posts: 1045
Joined: Tue Mar 22, 2016 1:40 am

Re: What sealant should be used

Postby Jetguy » Fri Mar 10, 2017 5:51 pm

No, no sealant on the planet will seal the threads of the extruder. Whoever told you that was dead wrong.
The nozzle must seal to the thermal barrier by how they are screwed into the heater block.
The thermal barrier tube AKA throat screws in from the top of the block. The nozzles screws in from the bottom.
In the middle of the block they tighten against each other. That is the seal.
Last edited by Jetguy on Fri Mar 10, 2017 6:30 pm, edited 1 time in total.

Jetguy
Posts: 1045
Joined: Tue Mar 22, 2016 1:40 am

Re: What sealant should be used

Postby Jetguy » Fri Mar 10, 2017 6:12 pm

https://www.raise3d.com/pages/instructi ... assembling

Again, while they show and list high temp silicone, this has never been something I recommended to the group and does nothing- less than nothing to seal against leaks. It cannot. realize that because the filament is only 1.75mm in diameter and the extruder feeder can push with a few pounds of force on that, that the hydraulic pressure inside the hotend system is minimally several hundred pounds per square inch and easily could reach 1k PSI. Silicone or any other sealant under temps of above 200C, and pressures over 500PSI- nothing short of a metal on metal deformation seal is going to seal against that.

Again, if the filament is 1.75mm diameter, then Area=Pi*Radius Squared.
1.75mm diameter is 0.875mm radius (1/2)
0.875mm = Area of 2.41mm
1 square inch = 645.16mm
645.16/2.41= 267.70 ratio
So for 1 pound of pressure pushing the filament into the hotend and nozzles results in 267.70 PSI
Anything over 4 pounds of push by the extruder results in over 1K PSI inside the hotend and specifically at this joint between the nozzle and thermal barrier where this is liquid plastic.

That's why sealant is not going to do anything meaningful and is a step that can be removed.
Last edited by Jetguy on Fri Mar 10, 2017 6:32 pm, edited 1 time in total.

Jetguy
Posts: 1045
Joined: Tue Mar 22, 2016 1:40 am

Re: What sealant should be used

Postby Jetguy » Fri Mar 10, 2017 6:30 pm

If you insist on exactly following the instructions and adding sealant- then use automotive high temp rated silicone based sealant.
https://www.amazon.com/Permatex-81160-H ... B0002UEN1A

Again, it does nothing for actual sealing, If you don't get the assembly correct and the nozzle and thermal barrier are not tightened against each other inside the heater block- no amount of sealant or type of sealant will stop hot molten plastic from leaking out of the threads and making a huge mess.

Ari
Posts: 12
Joined: Fri Dec 23, 2016 3:18 pm

Re: What sealant should be used

Postby Ari » Sat Mar 11, 2017 12:04 pm

The raise3d hot end assembly instructions refer to high temperature silicon grease (not a sealant). Presumably this is to make it easier to release the threads of the throat tube the next time it needs to be removed.

Jetguy
Posts: 1045
Joined: Tue Mar 22, 2016 1:40 am

Re: What sealant should be used

Postby Jetguy » Sun Mar 12, 2017 6:31 pm

While the instructions say the word grease, I assure you that in the 7 V2 hotends all straight from Raise 3D, that is not grease. It is in fact some type of sealant and it's dried hard in the threads when you take these apart to adjust the nozzle. In fact, if you Google the label on the tube of adhesive- NOT GREASE- used in the pictures, it's https://www.aliexpress.com/item/Kafuter ... 31485.html

Again, I'm saying avoid adding anything. Just about everything you do add burns, chars, and degrades under the heat. It has no possible way of actually sealing anything under the pressures present. In fact, some things you could put there would be more prone to stripping out the threads in the heater block than others.
Last edited by Jetguy on Sun Mar 12, 2017 6:44 pm, edited 1 time in total.

Jetguy
Posts: 1045
Joined: Tue Mar 22, 2016 1:40 am

Re: What sealant should be used

Postby Jetguy » Sun Mar 12, 2017 6:43 pm

Kafuter 611 Polymer liquid sealant Non-toxic glue Silicone Rubber Adhesive sealant
Product features:
With high polymer synthetic rubber as main material, with reinforcing agent,antioxidant and solvent refined.
No particles of white sticky paste; easy disassembly, convenient repairing again; adhesive after curing elastic; have good seismic sealing performance;resistance to various engine oil, gear oil, gasoline, diesel oil and water media

Properties and Uses:
Wipe moisture sealing parts and oil; glue evenly coated on sealed surfacesor threads; normal open about 5 ~ 10 minutes; closure sealing surface,tighten the bolt assembly; such as the sealing gap is bigger, to be used in conjunction with other gasket.

Scope of application:
Automobile, motorcycle engine cylinder pad, oil pan pad, pad into the exhaust manifold and the gearbox, also for thread locking and sealing.
Attachments
1_30ca4145-74ff-4619-a4bd-19a82932a5d3_large.png
Kafuter611.jpg
Kafuter611.jpg (11.19 KiB) Viewed 71 times
5_26a9ed82-fc03-4562-acbd-5fb279699e4a_large.png


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