Object coming off bed

Hi,

I am having issues with printing objects with a large flat bottom. I was heating the bed to 65 degrees and at the corners, it was raising up first on the furthest side from the printer, then on the max y position. Over time as the print goes on it gets worse. I tried raising the temp to 85 but it still does it.

Machine: Ormerod 2
Print size: 18 cm by 18cm
Bed Temp: 85
Extruder Temp: 200
Layer Infill Speed: 40mm/s

Any thoughts?

Thanks

From the extruder temp, I guess you are printing in PLA. Here are the likely reasons:

1. The bed temperature is much too high. At that temperature, the plastic will be above its glass transition temperature. On my Ormerod 1, I use an indicated bed temperature of 65C if printing directly on the glass (which only works for some PLA filaments), or 55C if printing on solvent cement. The actual temperature on the top surface of the glass is about 10C lower than the indicated value.

2. On the Ormerod 1, there is substantial backwash from the fan. This has been observed to cause warping of large parts on the side to the rear of the fan. The solution is to fit a fan inlet duct. See [www.thingiverse.com] for the one I use. If you have an Ormerod 2 with printed hot end ducting, then this probably affects you too. If you have the newer Ormerod 2 with a laser cut spacer and no ducting, then I don't know whether there is still significant backwash from the fan or not.

3. Draughts in the room, or a cold ambient temperature (which will create draughts towards the heated bed) will also cause warping.

4. To print objects that large, you need to either have the bed very level, or have auto bed compensation working very well. Otherwise the nozzle height above the bed will be too high in some places, which will make adhesion poor.

Edited 1 time(s). Last edit at 03/01/2015 03:06PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Interesting. You are right that its PLA I am printing with, apologies for not including that. I had read somewhere (cannot remember where), that the PLA would start to rise if the bed was too cold, hence me switching it up a notch. Will try shifting it down to 55 (am printing onto Kapton Tape on the glass). Will try the fan duct as well.

Thanks.

If I could just throw my opinion in. If you want to save some material and worried about bed adhesion I started using a glue stick to promote bed adhesion. I have found it quite effective. Here is the link to the original article.

Elmer's Glue Stick