1 .Make sure that the insert washer is able to pass a piece of filament loosely thru the center hole.

1. Ensure it easily fits inside the cooling block threaded countersink, so it is not stuck later during maintenance activities.
2. Check that the ptfe fits thru the cutting guide/guage.

1. Prepare the hot end
2. Heat up the hot end
3. Remove filament
4. Remove the bowden tube and its fitting
5. Remove the nozzle
6. Use ptfe to clear any plastic in throat by passing the ptfe top down thru the heat block several times
7. Make sure no plastic on mating surface/back of the nozzle and re install
   take temperature to 20` over operating temp and final tighten nozzle supporting heat block while tightening

1. Use the cut guide/gauge to cut your ptfe piece for inside the hot end.
   Ender-3 length should be 31.2 to 31.4mm long
   CR10S Pro should be 48.2 to 48.4mm
   CR10 original should be 29 to 29.2mm
2. Tubing can come from the original tube, or upgrade by using capricorn xs, or TH3D tough tube for this hot zone piece
3. Have a piece of filament cut to about 100mm for testing fitment and a guiding assembly
4. Put the cut piece of tubing into the heated hot end
5. Put the spacer washer into the top of the cooling block
6. Hand screw the bowden fitting in until it just touches spacer washer
7. Put filament thru washer and slowly move it up and down while tightening the bowden coupler down on the spacer till its tight enough it wont easily back off in use.
8. There will be a small space between the shoulder of the fitting and cooling block. This is normal, and ensures the spacer is being compressed and compressing ptfe lightly into nozzle inside the hot end.
9. Push your supply ptfe into the fitting till it stops, pull up on lock collar and zip tie or put clip on.
10. Load filament

You are Done

Enjoy your new less back pressure flow, as the small void left by the push pull nature of the design of the original flow path have been eliminated. and your bowden fitting will see less forces trying to push the tube back.

See the pdf in files for e step calculation and flow rate tuning for your now better flowing hot end.

Congratulations, you should have many months of clear printing without void artifacts.
For nozzle cleaning purposes, in your start g-code, add a purge at left front corner, to keep clogs from occuring. I offer this g-code, or alter your own. I want 45mm purged at F300. This may cause an occasional skip due to scrubbing forces.

Does this effect routine maintenance of nozzle.
No, as the tube should remain in place when removing and replacing a nozzle.

How do I get the cut ptfe out for changing it.
Remove Bowden coupler, use a small Allen key to fish out the spacer, remove nozzle and push through while hot end heated with an 3mm Allen key wrench.

My spacer was a bit big and its stuck , not able to remove from top end.
Heat up the hot end, remove the nozzle , use 3mm Allen key to push ptfe and washer from the bottom end , out the top.

How much skill does it take to do this mod?
If you can handle removing a nozzle and Bowden fitting, routine maintenance, you should be ok to use this mod.

Does this alter my printer permanently. No, with the understanding that if you cut the primary bowden tube, it could be short on travel if you stop using mod and were to try and use tubing you cut.

The CR10S pro has two set screws that lock the position of the throat in the heatsink.
Because of this , there is no way to pre determine the cut length for the ptfe tubing. So i picked an appropriate length that should work for all the MK10 hot ends. Because of this, you will have to remove the heat block as part of the set up for the system to work. This is a one time activity. Afterwards, you will just remove the nozzle to swap out the ptfe insert for maintenance.

Print the cut guide and spacer.
Remove filament from the hot end.
Remove nozzle
Remove ptfe tube and fitting.
Now while hot run ptfe thru throat and out of heat block a few times to clear any residual filament out.
Unbolt heat break from frame
Screw the heat break/throat out of heat block
Loosen the 2 grub screws to the throat.
Put cut length from guide provided into heat break, then put spacer on pushing it in.
Screw the fitting into spacer firmly.
Now adjust the throat so that the ptfe protrudes aprx .2mm from the throat. Reference the photo in this file to see what it should look like.

Reassembly
Heat up heat block to 215°
Install nozzle, turn in till tight, then back off 1.5 turn.
Screw the now adjusted heatsink and throat into the nozzle till its firmly against nozzle.
Screw the heatbreak back to frame.
Adjust the heat block to be square to the frame
Heat up to 245°, or 20° hotter than the material temperature to be used.
Final tighten the nozzle while supporting heat block
Put the bowden tube into the coupler, pull the lock and install a clip or zip tie to lock it in place
Congratulations, you should have many months of clear printing without void artifacts.
For nozzle cleaning purposes, in your start gcode, add a purge at left front corner, to keep clogs from occuring. I offer this gcode, or alter your own. I want 45mm purged at F300. This may cause an occasional skip due to scrubbing forces.

A3S, A5, and A5S Hot End Fix

If your having problems with a clogged nozzle this should fix it. Matt from Home Science Ideas has made a video showing how it is done so please watch his video and if you have questions please post them on his video. He is always happy to help anyone!

Video Here on YouTube

There is no spacer for the JG series

stock length is 23.65 I have no tolerance range to offer, but +-.05 would seam to be a good goal.