Do I have to print on glass?

I am working with an I2 printer and plan on using only PLA. If I clip down a sheet of glass to the bed the glass surface becomes uneven due to the tension from the clips. I do not have springs on each corner of the board to easily adjust it. Is it okay to just print directly on the bed?

You'll probably find that the bed surface isn't flat enough to print on. That is why people usually put a piece of glass on it. The other problem is one of design- there are usually 4 screws to level the bed at its corners. 3 points define a plane. 4 points define a potato chip. Turning any one of the leveling screws will cause the bed and undercarriage to bend, not to become level. I don't know why they keep using 4 point "leveling". It's just dumb.

Something else they probably didn't tell you- though they may have claimed compatibility with ABS filament, the bed probably won't get hot enough to get prints to stick without adding glue and since the printer isn't enclosed, if you try to print anything but small ABS parts they will delaminate.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

If you are using 3mm glass, try 4mm. It's a lot more rigid.

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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].

If the glass is bending when the clips are put on, then your bed is not flat. Fix that first.

You can also use 3M blue painters tape on either the bed or the glass when printing PLA. It will also work with ABS, but sticks too well and is hard to remove from the part.