Taz 5 Heated Bed Bending @ ABS Temperature

Hi ,

I have received my Taz 5 printer a week ago, I had done printing (around 5 - 6 models) using PLA material.
Recently when I have tried using ABS material, I saw the very first layer of the print is getting ripped off all the time and
messing up the nozzle from outside.

At first, I have tried to clean the Heated Bed PEI surface with IPA(as per the manual). But problem was still the same.
Then I have tried to calibrate the Y axis and found out the clearance between Nozzle and the PEI bed is uniform at the corner
but as I go to the middle of the PEI surface it seems to reduced gradually.(With heated bed @ temperature 110 Degree)

Because of that the layer printing is messed up all the time. Would you please help.
What could be the possible reason for the PEI bending?

I read some posts from the forum and I guess it would be the non-uniform distribution of heat on PEI surface. Also one post suggest the
temperature for ABS material should be set to 85Degree instead of default setting 110degree.<Post: TAZ Heatbed: Use 85C not 110C>

Please advice

Thank you

It is the weight of the printer carriage bending the rods on the X Axis down, and not the glass plate or the PEI sheet.

The 85 degree recommendation are for the older heat beds that old printers used at the time. The newer beds now in use do not have a recommended upper limit of 85 anymore. It might also have been the older lower wattage supplies could not reach and maintain a higher temp than 85 on the heat bed. But only AO support would know the real answer to that. :neutral_face:

I have done the surface leveling test in two different scenario

  1. Heated Bed @ 60/110Degree Centigrade
  2. Heated Bed @ room temperature

In case first I can observe the bending in middle of the PEI surface, on the other side at room temperature the distance between the
nozzle and PEI surface is uniform.

I agree with kmanley57, the print head sags under its own weight which makes it seem like the bed is bowing in the middle.

For your ABS adhesion issues.

It sounds like you need to get the nozzle closer to the PEI bed to help the first layer adhere. For eSUN ABS, I use an extrusion temp of 245C and a bed temp of 110C. Use a business card or two layers of paper to establish the initial nozzle to bed gap. Bring the hotend to extrusion temp, home the Z axis while the business card is under the nozzle. Pull the business card out, there should be slight friction. Adjust the Z-endstop and perform the business card tests until the friction is felt.

Next step is to inspect the extruded filament. See the pictures in the following article:

Once the z-endstop is adjusted to get the right extrusion width, check that the bed is level. Use the business card test at each corner, then print the attached ring. Review the extrusion pattern of the bottom. It should be uniform throughout… if one corner is too low (nozzle gap too big) the extrusion pattern will look like adjacent round tubes rather than the more oval shaped extrusion.

More tips for printing with ABS:

  • Use a 3-5mm brim. This increases the surface area of the initial layer to help with adhesion.
  • Turn off the extrusion fan. ABS likes to contract when cooling… causing the warping or lifting of edges.
  • A slightly abrasive sponge can help removing any left over extrusion on the PEI bed. Magic eraser, green scrub pad or sanding with a low grit sandpaper.
  • Use the Z-Offset to tweak the nozzle to bed gap. Use a negative to bring the nozzle closer to the bed (more adhesion), and positive value to increase the nozzle to bed gap (less adhesion).
    -Calib Disc 100x1.5.stl (95.2 KB)

I am interested in why kdsonone is seeing the hump when the bed is heated but not when it is at room temp. That would seem to indicate it is not the weight of the print head.

Thermal expansion of the nozzle.

There’s a thread with a lot of observations and details about the sag… I’ll look for it, but it was a few months back.

Thermal expansion of the nozzle would be a function of it’s temperature not a function of the X position.
I do believe there is some sag but I also think it is reasonable to assume the bed changes shape as is heats up.

All I have is a mini so the effects are smaller, but one of these days I should drop it off with QC and have them check the bed flatness (cold and hot) on their equipment.

This was your original comment. Therefore no heat, no thermal expansion of the nozzle. :slight_smile: Radiant heat from the bed can raise the hotend temp when the nozzle is Z-homed.