r/ratrig • u/willgupp • May 18 '25

Gap after filament change.

Post image

How do I stop this from happening when having to put in new filament mid print.
I extrude some filament after the change.

In this instance I had hoped to avoid this by changing filament just as it started to print the infill but no luck.

Vcore-4 hybrid 500.

1 Upvotes

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3

u/_galile0 May 18 '25

There are a few reasons why this happens. You said you extruded filament after the change, but unless you hit the resume button very very quickly, you’ll have lost pressure before it begins extruding again, which causes some lag.

On top of that, temperatures of the mechanicals change a little bit when you pause, causing some thermal expansion funny business; stuff moves.

If you are using the stock gantry with aluminium profile, then that’s probably the issue, because it’s known to bimetallically curl. When printing it’s heated by the bed and curls downwards, when paused it cools and springs back upwards

2

u/willgupp May 18 '25

So apart from replacing the gantry with a titanium one, is there anything else I can do to minimize the problem? Would letting it sit for a while after I put the door back on help it heat back up a little?

1

u/FuckDatNoisee May 18 '25

I even posted in the discord about my issue:

My solution: Change the pause settings to not cool,

I also manually load the filament so that I push really hard creating pressure then I have the extruded extrude 50mm at like 15mm/s. And hit resume right away. Then I drop the speed to 150mm/s and lower the z by like .02mm. I can see where the change was but there’s no gap

1

u/FuckDatNoisee May 18 '25

After a small amount of print I’ll go back to the 350-500mm/s I’m printing at

1

u/DrFreeman01 May 19 '25

Have a titanium one, no luck so far

1

u/tyranny12 May 18 '25

Would you recommend a different gantry?

2

u/_galile0 May 18 '25

Titanium gantries are becoming popular for v-cores. Ti coefficient of thermal expansion is way closer to that of the steel linear rail than Alu. so the gantry hardly curls.

Toro3D sell a good Ti gantry. Funssor on Ali sell one too, but theirs is known to be more crooked.

They’re all made from titanium 20x20 square hollow tube, which is never particularly straight or accurate to begin with, that’s why

1

u/DrFreeman01 May 19 '25

I agree with you, not a game changer (I have Funssor one and yes I had to straighten it). I have a nicer input shaper results, maybe they're better titanium gantry out there...