Printing directly from heated dry box via reverse bowden and warping
 
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Brad
 Brad
(@brad-2)
Eminent Member
Printing directly from heated dry box via reverse bowden and warping

I have a reverse bowden setup on my Mk3S+ with the filament fed directly from a heated drybox. I have noticed that my prints are more likely to warp off the bed when the heater is on (and I am therefore printing with pre-heated filament). I would be interested if anyone else has experienced/noticed this?

Posted : 21/06/2021 11:38 pm
cwbullet
(@cwbullet)
Illustrious Member
RE: Printing directly from heated dry box via reverse bowden and warping

No experienced this, but I am curious.  How hot is the box and which box are you using?  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 22/06/2021 10:19 am
Brad
 Brad
(@brad-2)
Eminent Member
Topic starter answered:
RE: Printing directly from heated dry box via reverse bowden and warping

@cwbullet

The box is a Sunlu and it seems that when set at higher temperatures (55 degrees for PETG and 45 degrees for PLA), larger objects have a tendency to warp off the bed more than when the heater is turned off?

I have a decent filament drier and really only use the Sunlu box and reverse boden setup to prevent filament absorbing too much moisture during long prints.

Posted : 22/06/2021 10:29 am
Swiss_Cheese
(@swiss_cheese)
Prominent Member
RE: Printing directly from heated dry box via reverse bowden and warping

That's interesting, I've noticed exactly the opposite, I heat my filaments out of "Print dry" systems as I'm printing and it has done nothing but improve the quality of my prints, more then just a little, regardless of the filament type.

 

Regards

 

Swiss_Cheese

The Filament Whisperer...
Posted : 23/06/2021 2:31 pm
Brad
 Brad
(@brad-2)
Eminent Member
Topic starter answered:
RE: Printing directly from heated dry box via reverse bowden and warping

@swiss_cheese

Thanks for that info. I will definitely do more tests then but so far for me, it seems that although the prints are really nice when the filament is pre-heated, they do seem to have a tendency to shrink or warp more.

Posted : 23/06/2021 11:26 pm
Swiss_Cheese
(@swiss_cheese)
Prominent Member
RE: Printing directly from heated dry box via reverse bowden and warping

@brad-3

 

This is just a thought,

 

but maybe some how the closed drying system you created with the reverse bowden setup is trapping the moister in the system and somehow reintroducing it, causing the warping.

 

I would consider experimenting in some way with trapping the moister its supposed to be releasing if you keep the system closed, perhaps adding several desiccant packs of color changing verity of some sort so you can get a sense of whether its actively working or not. perhaps a small fan also circulating the air in the box so it will pass over the desiccant.

 

have you considered other sources for the warping? e.g, drafts blowing in that area or temperature changes around that printer.

 

Good Luck

 

Swiss_Cheese

 

 

The Filament Whisperer...
Posted : 24/06/2021 2:29 am
bobstro
(@bobstro)
Illustrious Member
RE: Printing directly from heated dry box via reverse bowden and warping
Posted by: @brad-3

[...] larger objects have a tendency to warp off the bed more than when the heater is turned off?

What filament type are you getting warping with? Larger parts can be tricky, especially if the print itself is at an uneven temperature from top to bottom. In addition to brims, mouse ears, and other adjustments, I find sometimes cooling the bed a bit so the temp at the bottom of the print isn't as different from the top helps. You need it hot enough for adhesion, but not so high as to cause significant temperature differences that induce warping. Make sure there are no breezes (AC) on the print. Consider a make-shift enclosure if it's a persistent problem.

 

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 24/06/2021 4:25 am
Brad
 Brad
(@brad-2)
Eminent Member
Topic starter answered:
RE: Printing directly from heated dry box via reverse bowden and warping

@swiss_cheese

Great minds think alike!

I had the same thoughts so added a fan inside the heated box and colour changing desiccant and humidity stays below 10%. I also have a makeshift draft shield that I place in front of the printer and the printer is in a temperature controlled environment so I can keep the room temperature within one to two degrees of my target temperature.

I generally have a handle on warping but notice it more when the heater is on so tend to turn the heater off when printing larger objects that have more material in them.

Because no one else has noticed the issue, I will try and find some time to do some definitive and repeatable tests to prove or disprove this theory. I will keep this topic updated with any results.

Thanks again for your comments - it is useful to hear from someone else with a similar setup that has not experienced the issue.

Posted : 24/06/2021 11:51 am
Brad
 Brad
(@brad-2)
Eminent Member
Topic starter answered:
RE: Printing directly from heated dry box via reverse bowden and warping

@bobstro

Thanks for your input. I am primarily using this topic to try and investigate the possibility that pre-heated filament (e.g. from heated dry boxes) may increase warping issues when compared to filament fed at room temperature. I feel that I have otherwise got a handle on warping generally.

I am trying to avoid turning this topic into a general anti-warping thread .... but your comment about turning the bed down to reduce warping is interesting. I usually do the opposite to fight warping in the belief that turning up the bed (a) raises the temperature of the bottom of the print to reduce the temperature difference with the hotter part that has just been or is being printed and (b) to increase bed adhesion - especially on the edges of a larger print where the bed is usually cooler. I will give that more thought...

Thanks again.

Posted : 24/06/2021 12:10 pm
bobstro
(@bobstro)
Illustrious Member
RE: Printing directly from heated dry box via reverse bowden and warping
Posted by: @brad-3

[...] I am primarily using this topic to try and investigate the possibility that pre-heated filament (e.g. from heated dry boxes) may increase warping issues when compared to filament fed at room temperature. I feel that I have otherwise got a handle on warping generally.

That's an interesting observation. I haven't tested printing directly from a heated PrintDry myself. I would *think* warping would be influenced by the temperatures of extruded filament, so filament warmed up to anything lower before going through the hotend has no way of "knowing" it has been pre-heated, but I'm no materials expert. Do you see this effect with all filaments? PLA vs Nylon, for example?

I am trying to avoid turning this topic into a general anti-warping thread .... but your comment about turning the bed down to reduce warping is interesting. I usually do the opposite to fight warping in the belief that turning up the bed (a) raises the temperature of the bottom of the print to reduce the temperature difference with the hotter part that has just been or is being printed and (b) to increase bed adhesion - especially on the edges of a larger print where the bed is usually cooler. I will give that more thought...

I was inspired to try it after reading through the Taulman MDS for their various nylons and noticed some of the more difficult types suggest lower bed temperatures.

Interesting that you're using a reverse Bowden. Can you just feed the filament from the heated dryer without the bowden connected to compare? The tube would keep the filament from cooling somewhat as it feeds into the extruder. I could see this affecting feed, but again, not sure how it would affect warping. Data is data though, might be worth a shot.

I'm assuming these are large-ish prints with a bit of height?

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 24/06/2021 3:57 pm
Brad
 Brad
(@brad-2)
Eminent Member
Topic starter answered:
RE: Printing directly from heated dry box via reverse bowden and warping

@bobstro

I would agree that it shouldn't matter what temperature the filament was at before it went into the hot end but I'm not a materials expert either!

The best way for me to test this is to clean the bed properly and run a test print at the back of the bed with the dry box heater turned off, turn on the heater in the drybox, remove the print, wait for box to warm up properly and then run the same print at the front of the bed. I will then look at the underside corners of both prints to see if there are any signs of slight lifting/material shrinkage. I'll use the smooth sheet because it is easier to see signs of shrinkage when the underside is smooth.

Once I know for sure if the issue really exists or not, i'll update the thread...

Posted : 24/06/2021 5:02 pm
Swiss_Cheese
(@swiss_cheese)
Prominent Member
RE: Printing directly from heated dry box via reverse bowden and warping

@brad-3

 

I couldn't explain to you why although I have a theory, but I'm seeing a marked improvement printing out of my active filament dryer (by active I mean power on fan circulating).

The Filament Whisperer...
Posted : 24/06/2021 7:12 pm
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