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PETG Sequential Printing tips??  

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LayersOfUs
(@layersofus)
Active Member
PETG Sequential Printing tips??

Hey everyone,

So I've had some mixed results trying to print with PolyMaker PETG. I was using a downloaded profile from their website that was working decent with small objects, including sequential printing of several of those small objects. But anything with a larger base was lifting from the bed during printing and warping the final print. That Polymaker filament was printing  245/70 for the first layer and 240/70 for subsequent layers, and 10% fan speed.

To combat the warping on larger prints, I switched to using the "PRUSA PETG" profile - which worked great for the larger prints but now my sequential prints of small objects are starting to lift. This profile is 230/85 for the first layer and 240/90 for subsequent layers and 30-50% fan speed.

I'm just wondering if anyone has advice about how I can tweak either of these profiles so I can have some success with larger prints and small sequential prints. I can't help wondering if the PRUSA PETG profile is failing on Sequential Prints because the bed temperature changes at the start of every object.

 

 

This topic was modified 2 months ago by LayersOfUs
Posted : 19/07/2021 6:17 am
Dan Rogers
(@dan-rogers)
Noble Member
Check your Z

I would not think to control bed adhesion with a filament profile myself - it is usually a problem with live Z adjustment (get it to stick).  If your large bottomed parts are warping while printing, techniques to fight warping include adding a 3 or 4mm brim to the part during slicing, adding bunny ears during slicing, controlling cooling to prevent warping (using an enclosure or print tent), or redesigning the part to fight the warping that long straight filament strands cause in the printed part.

 

Posted : 19/07/2021 6:46 am
fuchsr liked
Swiss_Cheese
(@swiss_cheese)
Noble Member
Experiment, Play, Learn.

@layersofus

 

I can't help wondering if the PRUSA PETG profile is failing on Sequential Prints because the bed temperature changes at the start of every object.

 

 

That will definitely cause that problem, especially on the outer edges of the bed. When printing sequentially I tend to use the same temps for First Layer and Other Layers, (for example) if I'm printing Prusament PETG Carmine Red, I find that it prints best at 260C-265C and with a bed temp of 90C, so I'll set first and other layers to the same temp if I know I'm printing sequentially on a textured or satin sheet, If I'm printing on a smooth PEI sheet I might just not put Windex or (some other kind of separator) on the outer edges to help with adhesion and in those cases knowing that the PEI sheet doesn't like to let go of PETG I might, depending on the product set my First and other layers differently.

 

The reason for temps of first and other layers being different is to assist with adhesion, so common sense says if fluctuating bed temps are causing your parts to let go when sequentially printing them you need to eliminate the fluctuating bed temperature.  This does work.

 

Yet another option would be to customize your G-code, an example would be to make it print all fist layers before starting other layers, although I think that's silly.

My suggestion is that you find a temp that the filament your using will like from first layer to finish and use that for First and other Layers.

Hint: you can also Gain a bit of control using the cooling Fan and\or multiple extruders.

 

Good Luck

 

Swiss_Cheese

The Filament Whisperer...
Posted : 20/07/2021 5:45 pm
LayersOfUs
(@layersofus)
Active Member
Topic starter answered:
Fan Speed?

Thanks Swiss_Cheese,

I had another look at this problem. I noticed that the PRUSA PETG profile has a fan speed much higher than the POLYMAKER (50% vs 10%). I was getting small parts to stick no problem with the POLYMAKER until I changed the fan speed up to 50% and then the small parts started lifting right away. I also thought it was the bed temperature, especially the cycling of the bed temperature as you mentioned when it starts new layers on a sequential build at a different temperature. But more importantly, it seems that a faster fan speed causes the prints to warp off of the bed.

I'm still new to this, trying to figure out what variables cause what problems - but I wasn't expecting fan speed to cause warping. Maybe the fan is cooling down the bed in that one local area too much.

To PRUSA: Maybe the next version could have a "smart bed" with a grid of temperature sensors, a microcontroller and mosfets to control the heating current to individual areas of the bed.

 

Posted : 23/07/2021 5:43 pm
bobstro
(@bobstro)
Illustrious Member
Sounds nice, but...
Posted by: @layersofus

[...] To PRUSA: Maybe the next version could have a "smart bed" with a grid of temperature sensors, a microcontroller and mosfets to control the heating current to individual areas of the bed.

How much would you be willing to pay for such a feature?

 

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 : 23/07/2021 5:49 pm
LayersOfUs
(@layersofus)
Active Member
Topic starter answered:
Smart Bed

 

Posted by: @bobstro
Posted by: @layersofus

[...] To PRUSA: Maybe the next version could have a "smart bed" with a grid of temperature sensors, a microcontroller and mosfets to control the heating current to individual areas of the bed.

How much would you be willing to pay for such a feature?

 

At PRUSA quantities: An additional microcontroller, 9 mosfets and 9 temperature sensors would only add a few dollars to their BOM and the programming would be pretty straight forward. The bed could communicate with the main controller via SPI or other data transfer protocol instead of running passive thermocouple wires from the bed to the main controller. If it's a feature that helps with more consistent prints and sets PRUSA products even further ahead of the competition, it could be interesting. Anyways, not meaning to arm-chair criticize things here - the current design obviously works well enough. My full time job is electrical engineering and product design, so I always see problems as wanting solutions. Of course the easiest solution here is for me to turn the fan speed down 🙂

Posted : 23/07/2021 6:26 pm
bobstro
(@bobstro)
Illustrious Member
Not a bad idea, just thinking about Prusa competitiveness
Posted by: @layersofus

At PRUSA quantities: An additional microcontroller, 9 mosfets and 9 temperature sensors would only add a few dollars to their BOM and the programming would be pretty straight forward. 

I don't mean to sound overly critical. It simply doesn't sound like something that could be done with the existing Mk3 hardware and limits of the 8 board controller. Prusa is already criticized for pricing and does have to worry about remaining competitive. I just wonder if such a feature would matter enough for customers to be willing to pay more for it, and whether using a better class of bed heater might be simpler.

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 : 23/07/2021 9:10 pm
LayersOfUs
(@layersofus)
Active Member
Topic starter answered:
"Smart Bed" is less work on the controller

 

Posted by: @bobstro
Posted by: @layersofus

At PRUSA quantities: An additional microcontroller, 9 mosfets and 9 temperature sensors would only add a few dollars to their BOM and the programming would be pretty straight forward. 

I don't mean to sound overly critical. It simply doesn't sound like something that could be done with the existing Mk3 hardware and limits of the 8 board controller. Prusa is already criticized for pricing and does have to worry about remaining competitive. I just wonder if such a feature would matter enough for customers to be willing to pay more for it, and whether using a better class of bed heater might be simpler.

No, it would actually be less work for the controller. Since the hardware would just be telling the bed what temperature to be, and then my "smart bed" microcontroller would do the heating and monitoring PID for each of the 9 zones and just report back. The main controller is no longer attempting to balance the bed temperature by cycling the heating element on/off.

As for what it would do for the pricing and if it makes sense from a marketing perspective, that's no longer my wheelhouse nor my company. 🙂

 

Posted : 24/07/2021 7:11 pm
bobstro liked
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