Beginner 3D printing - CTC dual

I've bought a CTC dual from ebay.de a couple of weeks ago, for significantly less than 400E, shipped from Germany. Here are my experiences with it, as a complete beginner.
This will be a text-only post, if there is enough interest I will post some pictures and pictorial guides later.
It's a FlashForge clone which is in itself a Replicator Dual (2X?) clone.
It has a heated bed, dual extruder, wood panels and acceptable build quality and components.

TL;DR version:
- print simple objects no bigger than 5(W)x5(D)x2(H)cm if you want no issues
- install a glass plate on top of the bed
- use masking tape on the bed
- experiment with temperatures for each new filament
- install sailfish
- pre-order 40mm cooling fans
- install active cooling
- cut polycarbonate covers to size to keep heat inside

In the box

The printer came pre-assembled, saving about one week of fiddling. It also came (mostly) calibrated, I just did a basic plate leveling, which might have not been necessary. The build timer showed 16h and there was some residual filament oozing, which means that they probably printed some parts for the printer during testing. I think that's awesome.

The ebay ad said it would ship with 1kg of filament, I haven't measured that but it seemed more like 500g. Yes, I've measured all the parts and scraps. They shipped black PLA by default (you can ask for a ABS and/or a different color). For initial testing the 0.5kg lasted me less than a week.

There were a few bits and ends (screws, SDCARD, allen keys) that were mostly not needed in the beginning.

I just unpackaged everything, assembled the head (2 mins), power cord, powered up, mounted the filament 'toilet tube' support and leveled the bed.
I laid yellow painter's tape from the start, the 3cm wide one, on top of their 5cm wide blue tape. It took 8 strips., but that's what I had laying around.

The included manual is pretty hard on the English with a strong hint of automated translation. They 'hint' to bed leveling as an important part but fortunately the printer menu (2x16 LCD) explains everything.

First prints

I inserted the included 2GB SDCARD into the slot hidden in the right side, took a random file and hit print. I have no idea what it was supposed to be, some kind of bull I suppose, printed halfway until the tension of the filament caused the extruder to grind idle.
The filament does not have any guide tube nor any guides so the extruder has a hard time unravelling the spool.
I initially printed this double-guide: http://www.thingiverse.com/thing:141309
Well, it doesn't fit, and it made things worse.
I then printed 6 of these clips: http://www.thingiverse.com/thing:752544 but ended up using only 2 of them - because they also cause binding.

The seller replied that guide tubes were removed from later versions as they cause binding and I should use the printer as-is.
So the warning is to make sure your extruder can pull the filament freely, otherwise your 4h build might fail after 3h.

Setup

All the subsequent prints from above were exported from MakerBot Desktop (3.7.0.95) with no adjustments, sent to the SD-card, inserted into the printer. The default settings for MakerBot were for ABS (bed 90-110C, nozzle 230C) but the PLA objects still printed fine.
The STL files were downloaded from thingiverse.com, drag-and-dropped into MakerBot and either hit export or print (when connected via USB).
The USB connection worked out of the box with MakerBot, no additional settings were needed. Unfortunately you cannot preheat the unit or level the bed or do any other adjustments from within MakerBot Desktop.

ReplicatorG did not work at all, complaining because of a missing Python installation. I have tried one hour to get it working.

The printer firmware identifies itself as 'The Creator - ver 1.0' and the vendor says it cannot be updated. However, MakerBot displays that it can upgrade it. Better safe than sorry. I will look later into upgrading to SailFish.

So far MakerBot Desktop fills the need to 90% - though I would like to customize things based on layer number or time (like bed and nozzle temperature) without editing the G-Code.

Settings

This is a moving target for which I do not have a definitive answer.
Basically you have to adjust everything each time you change the filament vendor.
I started with a bed temperature of 90C, went down to 50C, now up to 67C (glass bed on top).
Nozzle temperature for PLA went down from 230C to 195C, but 200-205C seems right with the current filament provider (Firstcom, 1.75mm, black).

ABS - not yet possible. I've tried for 3h to set up the thing but it still fails.

Designing parts

Unless you spend your life designing things in CAD, thingiverse.com will provide answers to most of your needs. To get to the next level there are customizable parts (like metric screws, parametric phone cases, name plates).
You can then use some OpenSCAD software to design your parts. Even openjscad.org is pretty ok, though I could not get it to work with thingiverse models or any scad files.
For the final level, the latest kid on the block is cad.onshape.com. It's a full-featured parametric design software that runs inside the browser and on any mobile (web) platform. It's a steep learning curve but well worth it.
In the past I've played a bit with AutoCAD, Sketch-Up, Illustrator (not really 3D), Autodesk 123D and they all have significant flaws compared to OnShape.
Hopefully OnShape continues to remain free for small use or I would have to adjust my opinion. I will do a full review later as it challenges a lot of the current technologies and mindsets.

Printing quality and mods

The first few prints came out acceptable, if they were the standard box-shaped ones with plenty of support from the previous layers. However, curved items showed a jagged edge(1), big objects printed with solid blobs(2) and high objects either came detached or a blobby mess(3).
Issue (1) was caused by the default extruding speed being set to high 150-90mm/s instead of the recommended 120-60mm/s.
Issue (2) was caused by improper nozzle/filament size calibration. Still working on that, but I had to reduce the filament size from 1.77mm to 1.68mm (real size is ~1.75mm).
Issue (3) was caused but not cooling the parts as they build up. Putting a big fan on the piece after the 5th layer solved most of this. Also caused by warped bed.

I cut a piece of glass 230x150x2mm and overlaid it on top of the original plate (with the blue tape still on). The pieces now print much more reliably - previously I had to choose a favorable position on the plate - but they seem not to stick as well. So now I have to push the filament gently into the extruder for the first 2 layers.
I tried hair spray and 80-grit sandpaper to get the glass to adhere but had to go back to the masking tape solution.

The mod above also allowed the left extruder head to be moved to its level position - from the factory it was about 2mm higher. I assume that was set because the uneven bed would cause the left head to hit the parts that were already printed by the right head - which happened to me as well.

For cooling I printed a part similar to this http://www.thingiverse.com/thing:577557 which requires the extruder fan to be rotated for sucking instead of blowing. I am not yet convinced of its efficacy, it caused the nozzle to clog at least two times.

Printing with rafts is a huge pain - the rafts cannot be easily removed.

Reliability

The bed was warped from day 1 with a 0.5mm variance. This is a lot when the layer height is by default 0.1 or 0.2mm.

Blower fan on the driver board (RAMPS) started making loud noises after 1 day. I took the sticker off and put a few drops of fine mechanical oil, but it will need replacement. I think they did the same at the factory as the sticker was not holding on very well.

Right extruder fan started making noises after an additional 25h of printing. It starts up with a low whine (radial vibration?) like cheap computer power supplies, then it goes full speed after 30s-1m.

Right extruder started making noises under medium load after 20h of my printing. If I feed the filament manually the noise goes away. If it has to draw the filament from the spool it makes creaking noises like and old windmill.

Z-Axis positioning makes a vibrating noise from the start, not sure if this is intended or not.

It somehow seems that the right extruder does not have the same volume as from the factory, missing the first few millimeters at the start of the print - after ~20h of my printing.

The X axis rods (parallel to the front) might have a slight warpage to them, 0.1-0.2mm, causing the right nozzle to be higher at some point than the left one, when moving along the left-right horizontal. This can be 'fixed' by rotating the rods along their axis but it will either increase the drag or cause offset in another dimension.

Build quality

Everything is build with laser-cut plywood, 3 panels, totaling to 5.6mm wall thickness.
The nuts are not captive which means you have to be really careful when unscrewing things and work like a surgeon when putting things back together - alight the nut with the screw and the slot using tweezers.
The SD card slot has double the width - which means you can insert the card into the space between the card slot and the slotted hole in the box. If you manage to drop the card inside the unit, you have to take the bottom panel off to fish it out.
Several zip ties came loose (low quality ties).
The 'low noise' fans are really not. You cannot have a speakerphone conference in the same room with the running printer.

Other than the above I cannot really fault it, for the price.

Power consumption

Given the increasing electricity prices, these figures might prove useful.
- idle: 37-39W
- heating: 60-200W. Probable average about 75W, the heated bed takes the most power
- during operation 60-80W, probable average 70W
Obviously printing ABS is going to take a lot more power than PLA. It also takes a significant amount of time to get the parts up to temperature. Expect 3-5 minutes to start a PLA print from cold and 10 minutes for ABS.

Conclusion

Out-of-the-box it performs like a second-generation 3D printer - it give out decent results with little effort. If you want high quality or demanding parts you have to invest a lot of frustrating time.
Expect hours of watching the printer do its thing, manually unspooling filament and feeding it and 'adjusting' parts while printing with a thin scalpel.