Hi everyone, happy to be here. I’m making custom brackets for motors for my flight sim. PLA works great. The PETG-HF I am having a bit of trouble. I am using the textured gold plate. I dried the PETG-HF in the dryer for 12 hours and it went into my AMS box which is filled with desiccant. I tried the default bambu petg-hf profile. When I look in preview I see these white seems and these showed up as indentations on my print. At the top of the inner circle I have a bit of spaghetti and small 6.5mm holes are oblong. I made the part in fusion, exported as .stl binary. In the preview mode o have these flat spots in the circles and what looks like steps. Is there a way smooth that out?
I also noticed after printing the holes that are supposed to be 40mm center to center are 44mm. I did check to ensure in the priview I measured center to center. My model is accuarate. I also printed this with profile 0.28nn extra draft. Not sure if that made a difference. Nozzle is .4.
The flat spots are just layers and are a limitation of FDM. You can use adaptive layer thickness or just thinner layers to minimize them.
On drying, the desiccant in the AMS doesn’t really dry your filament. It keeps it dry by keeping humidity low in the AMS. At room temperature water is very slow to leave filament. It’s why dryers are heated. But filament does pick up significant water at room temperature which is why desiccant in the AMS is needed. But for all practical purposes the AMS isn’t effective at drying filament.
Most consumer filament dryers are limited by ambient humidity. Just drying for some amount of time at some specified temperature will remove some water in high humidity conditions but may not get the filament to where it prints well. When drying it’s important to also note the chamber humidity when you pull a spool. That can help tell the tale of how well it might have dried.
I’m not sure what you are referring to as a strength profile but there was a thread here recently about PETG HF having low interlayer adhesion when insufficiently dried. Are you seeing strength issues too?
Print orientation can be very important to getting the best prints. I’m not familiar with what you are printing to say if a different orientation would help, though. But it absolutely can make the difference between good and poor prints. It can also affect dimensional accuracy but that’s not huge and may or may not be important. Sounds it is in your case.
Drying in the X1 is going to depend on ambient humidity for sure. Might get a hygrometer so you can see what you’re dealing with for humidity in the printer when drying, but weather reports can get you ballpark information. Just be aware relative humidities at temperature extremes may be far from indoor relative humidities.
The dimensional differences you’re seeing between the CAD model and printed object may be due to normal material shrinkage when cooled. PETG-HF may be worse than other filaments. I’ve certainly experienced frustration with tight tolerance fits. You’ll have to find ways to compensate by either adjusting the CAD model or tinkering with some of the print settings and options available (e.g.: bed / filament / cabinet temperatures, print speed, surface thickness, infill types, etc.). It takes experimentation.
I would use extra-draft for prototyping, go to 0.20mm layers standard profile when you are comfortable with the prototype.
Export from fusion as STEP, it will give the best resolution afaik. Though now there is a quality option on import to bambu studio in the latest version, I haven’t messed with but with such a simple model highest quality should be fine.
Measure in fusion, I have no idea how that works in bambu studio, maybe it is being measure correctly but 10% over seems insane to me.
Slant 3D made a perfect video on this subject as an FDM printer has
As the printers cannot print in mid air and the filament itself acts differently when it cools down, there are limitations of what you should expect when printing wholes, especially in that orientation. Here is the video: How to hole.
Basically the design needs to approached differently than you would by injection molding or drilling into casted pieces.
Plus, there is a really cool feature called Smooth speed discontinuity area you should use (technically its toggled on by default but do check.)
Hope it helps.
@Lenyo I did measure in fusion and here is how I did in fusion. I made an unlisted video. I used extra draft proto for the 1st test but noticed that difference on the tolerance. I will try exporting as step see if that’s any better. I will scale down the print so I don’t use so much material.
@MZip Hi, I made a vid above, you’ll see where you can select the different profiles there appear to be a few. As for the hygrometer. I have a few of those. Current RH indoor is 31%. In the ams sitting with the silica it’s less than 10%. I didn’t change the scale that’s why I measured it in Bambu studio
@gyropilot Hi John, Is there any material you’ve used that stays dimensionally close?
@Sigama_Crafts Thank you for the suggestions. I’m going to take a look at the video.
You dont need to scale it down, if you used infill. Just change the infill to a 10-15 support cubic or lightning and keep walls at a minimum 2. 2 bottom top and walls. Basically making a shell of what it needs to be.
Even better, cut the object in the slicer into parts. Printing the exact thing that interests you. 2-3 centimeter parts should be perfect.
Edit: I just returned and measured the printed part and now the holes line up. I measured after it was done printing. After the print was done, I opened the door. Now today, after cooling overnight it contracted back to the dimension. I still need to figure out how to fix the spaghetti mess at the top and why these odd white seems show.
what white seems ?!. Are you reffering to this?
Thats the slicer telling you that is a different line from a normal wall line.
(its basically a seam. The intrerruption of a continuous line)
I don’t have an explanation except center-to-center vs nearest circumference to nearest circumference maybe? If they are 4mm dia holes that would account for a 4mm difference?
40 vs 44mm distance errors are too big to be shrinkage at least in my experience.
The reason it showed up in your print is because the printer actually stops in that point. Stopping usually leaves a bulge as the extruder does what its supposed to do… extrude so the Seams are visible in any print you make, unless you make it random or hide it on other sides
I have printed over 100 stars like this one. Almost 20% of them failed for some reason and I had no idea why until I tried to submerge them Under hot water and try to make them fit again. Little did I know that my set up for my filaments was using the fan at 60-80% just for a couple of seconds. I realised that PLA once submerged dilates hence I realise that whenever I’m printing the stars each part of it becomes a little bit larger than it is if it’s not cool down on spot. Since then, I put my fans at 100% all the time, none of the stars failed.
so the Seams are visible in any print you make, unless you make it random or hide it on other sides
