Preparing for large PET print  

Re: Preparing for large PET print

Hi Marten

I would think it probably better to build some sort of box for the printer, but I think it should be OK without. The heat generated by the bed will be fairly localised, as long as there are no drafts.

The slicer used should give quite a precise estimate of filament usage. Unfortunately, I don't use repetier, so I can't really help with that.

Peter

EDIT: just checked one of my GCode files; the estimated filament usage is included at the end as a comment, but this is slicer dependant.

Re: Preparing for large PET print

Thanks Peter. Density is 1.38 g/cm3. The gcode says 469 cm3, so 647 g. One roll will be enough!

Re: Preparing for large PET print

That is a pretty big print! Whats your infill set at?

Re: Preparing for large PET print

Infill is set at 30% 3D honeycomb. All walls are 6 layers thick

Re: Preparing for large PET print

Well, I guess that's one way to use up filament. Have a look at this:

Peter

Re: Preparing for large PET print

Ok, I have decreased perimeter layers to 5 and infill to 15%. One kg will be enough to print two peices. It is going to be a treble horn for my stereo, so lots of material should be good for sound quality. But the first try doesn't need to be perfect.

Re: Preparing for large PET print

Marten

I wonder if ABS would be a better choice for that model. To get the best sound, the print would need to be perfectly smooth and an acetone bath works for ABS; not sure about PET.

Peter

Re: Preparing for large PET print

One other thought; 5 perimeters inside and outside = 4mm+ thickness. Is that not enough by itself?

Peter

Re: Preparing for large PET print

It failed misarably. I choose PET becaus it is recommended for larger objects becuse of the stability. The support material did not stick together and the nozzle pulled pieces off. It is like the plastic is too soft for too long. Support material config is default, can it be improved?

I don't want empty space inside the horn, so I really want infill material. The support material will break any standing waves inside th horn, and dampen resonances between the inner and outer walls.

Re: Preparing for large PET print

Marten

I presume you mean infill and not support material. What temperature and speeds are you using? Particularly infill speed? Can you upload a photo of the failed print?

Peter

Re: Preparing for large PET print

Marten

I presume you mean infill and not support material.

Thanks, I have corrected now it says

don't want empty space inside the horn, so I really want infill material.

Re: Preparing for large PET print

The first 4 mm contains a lot of support material. This is the place for the aluminium mounting plate. Support material settings:
Overhang threshold: 40
Enforce support for the first: 0 layers
Raft layers: 0
Contact Z distance: 0.05
Pattern: rectilinear
Pattern spacing: 1mm
Pattern angle: 0
Interface layers: 3
Interface pattern spacing: 0
Don't support bridges : unchecked

Print speed is 50 mm/s for support material and 40 mm/s for the rest

Extruder temperatature si 240 and heatbed is 100.

I will try to decrease temperatures:
http://3dprintingfromscratch.com/common/3d-printer-filament-types-overview/#pet : 160-210 degrees

I will try 230/90.

Re: Preparing for large PET print

I'm on track. The problem was too less PET juice. Now the first layer sticks fine to the prepared surface. If the strength is not enough I will increase temperature next iteration.

Re: Preparing for large PET print

Marten

I still think that you are too hot. Maybe first layer at 240 then drop to 230/220. Also try printing with a brim.

Peter

Re: Preparing for large PET print

This print failed too. The problem is the first layer on top of the support. This layer doesn't stick to the support properly.

Perhaps there is too much distance between support walls? The support pattern spacing of 1 mm doesn't seem to be honored. I believe it is the default 2.5 mm.

Or maybe it is the layout algorithm, ripping previously laid paths by laying them side by side. I cannot find any setting to adjust layout algorithm.

Tomorrow I willl try higher nozzle temperature.

The proper parts printed where strong and flexible. The rectilinear support as well.

Re: Preparing for large PET print

Marten

If you want me to slice the file with a different slicer, just unload the STL and let me know the print details.

Peter

Re: Preparing for large PET print

Hi Marten,
I only print in petg from extrudr and put the bed temperature to 80°C and nozzle temp 235°C. That works so well that I do not use a rim anymore because it sticks so well to the bed. And I print directly on glass, no glue or juice... That gives a mirror finish on the bottom... The first layer i calibrate the height so taht it is somewhere between lines touching and so close that i can see through the material. Overhangs print also quite fine with this setting. I am uncertain how pet prints different from petg, but if you are really out of options try the filament I use... I can upload some pics if required

Re: Preparing for large PET print

Thanks Alexander

I have 2 kg PET and will use it all up before trying another filament.

I raised the temperature to 235 and also not using the fan. It failed at the same spot as yesterday. Maybe I can post a picture tomorrow. It was not as bad as yesterday, maybe only 10% was bad compared to 40% yesterday. After aborting the print I touched the piece, maybe the surface was 40 degrees celisus.

I believe the bed is too cold. Is the setting "support material interface" this layer. Will decreasing improve things?

Mårten

Re: Preparing for large PET print

The room is pretty cold so I am putting the machine inside a cardboard box. The bed temperature is very difficult to get to 100 degrees, so I am sticking with 90. I will increase nozzle temperature to 240.

The properly printed parts are very strong so I will try to use 2 interface layers.

The honeycomb pattern was too sparse as well I believe, so I am trying rectilinear grid.