Circular hole coming out oval

New to 3D printing and have bought a CTC Makerbot dual clone.

First thing I have done to upgrade the printer is a larger print bed, by printing extenders.

But as you can see the holes have come out a little distorted and are more oval than circular.

Any ideas on how to fix?
Thanks


Used Makerware software to export file.
Printed on masking tape, was a little adhesion problems where the corners came off a little.
But this hole is in the middle of the print which stayed on the bed well.

Used ABS filament, bed at 100-110
Extruders at 260

Attachment 8130

Being new to 3D printing, you really started off with a pretty big mod for you bot..

I'm thinking your temps are way too high at first glance. I would shoot for bed temp of ~100C and extruder temp of ~220C. Are you using blue painters tape or that whitish masking tape? I've read blue masking tape works much better. (I use glass and hairspray).

The extenders were printed on normal masking tape, I couldnt find any blue painters tape.
And by blue painters tape, it is just blue masking tape but thicker?

I've printed the 3 extenders, not perfect but good enough to now place on a thin glass sheet.

Now printed out the extruder guide, but again the holes are warped.

To save time, and increase efficiency, I think I'll try printing out a few small washers, see if they come out circular or not.

I'll try different temps as well.
Read that with these cheap chinese ones the termocouples are also cheap ones and temps could be as much as 20 degrees off!

Attachment 8134


OK so at 220 the filament extruder but sticks to the nozzle, so guess it's not hot enough.
230 degs and it just manages to make a print, but the washer is warped
240 degs still clings onto nozzle slightly, but not as much. Still warps

Left one is 230, right one 240
So again I dont think this is a temp problem, rather a setting with the printer.

Attachment 8135

So question is how do you tighten the belts?

As the filament is extruding, (while loading) does it come through the nozzle nice and smooth? It should be extruding in a nice even, steady amount and should extrude straight down. If it's not, then mostly likely you have a clog or a problem with the Teflon tube.

Still think your temps are way too high, but may not be your primary problem. What is the manufacture of the filament?

Looking at you o-rings my guess is that the first layer is not bonding well and the nozzle is dragging the plastic away.

Use a piece of paper and spend sufficient time to level the printing bed as throughly as you can. Lots of links and google is your friend here, including youtube vids etc.

You may also have the printing speed of the first layer way too high. Your slicer will allow you to adjust the speed of the first layer. I generally keep it down to a max of 20 mm/s for the first layer. The first layer accounts for most of the final print quality, do not try to save time there.

As to blue versus white tape, the blue tape has a surface finishing (seems like parafinic to me??) which makes a better bond. It is not the tape itself, but the finishing which is the clue here.

I have dispensed with blue tape and kapton a long time ago. I exclusively use glass and hairspray/3DLac now in all my printers with excellent results. Much easier and far better.

I've tried leveling as much as I can, still the prints come out oval.

Just install sailfish firmware, but still seems it wasnt a firmware issue either.

I removed a Y belt to see if I could tighten it, but pulling as much as I can, and now the belt seems looser than before somehow. So no idea how they get it tighter when the manufacturer built it.

what are you printing on ? looks like plain aluminium.
That won't work :-)

You either need tape or - better imo - a few layers of gluestick pva. Pretty much everything sticks to that.

I suspect the printer is fine, you just need soemthing for the plastic to stick to :-)

On glass with glue spread on it.

I think the glue isnt good enough if it really is a sticking issue. Will be trying abs juice tomorrow.

edit

90% SOLVED: I was looking at the wrong Y belts. I found that the short belt connected to the Y motor on the back right of the printer, which actually drives the Y axles, was loose.
Loosening the motor and them pushing it further down and re-tightening the screws, tightened the belt and now the circles are a lot better, though still not perfectly circular.

Before
Attachment 8445

After

Attachment 8446