picclock's modified i3 3d printer attempt

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efrench:
Are you removing the part before it has cooled to room temperature? Try using a larger brim and/or adding pads at each corner to help it stay attached to the bed.

For ABS, I start the first layer at 240 degrees for the hotend and 115 for the bed, then drop these to 230 and 100 for subsequent layers. My bed is 8mm cast aluminum with a 2mm glass mirror on top, so the actual bed temperature will be somewhat less. I'm using ABS juice and if the print shows any signs of lifting, I'll give that spot a little squirt of the juice being careful to just get it on the brim.

I think it's more important to eliminate drafts than it is to heat the entire chamber. I'm using this to enclose the printer. I printed a few brackets to attach it to the aluminum extrusion.

picclock:
Hi efrench

This is not a problem about bed adhesion, though I found that tricky at first. I'm using 100 or 110 for the bed and 260 for the filament - which may be a bit high but it generally seems to work well. I usually print with a brim and I don't get corner lifting, or if I do its very minor. Some of the best results seem to come when using a raft which effectively throws away the first three layers. The trouble with using a raft is that the finish is poor on the detached face.

Using PVA and a light smear of abs juice attaches prints almost too well, but that is not an issue. I always wait for prints to cool but once released they start to warp. The upper individual strands are under tension, the lower under compression and the only thing resisting this change is the stiffness of the material. I did a test with a heat gun warming a part and the warp increased from about 3mm to 7mm over 100mm.

Clearly this is an issue that needs solving. I understand that Ultimaker uses a fan blowing temperature controlled air across the top layer during printing as a way to improve this issue. Having thought about the heated chamber idea a bit more it occurred to me that I could do something similar and attach it to the print head. By attaching a conical hot air duct (made using soldered tin can) to the nozzle and heating the air with a couple of 40W cartridge heaters with a heat exchanger, I could use the waste air from the head cooling fan to cool the extruded bead in a controlled fashion, hopefully eliminating (or at least minimising) the problem. It should be possible to control the air temperature and set it just below the glass temperature of the plastic being used. Ramps and marlin allow for a second extruder so the temp control is already there with the addition of a thermistor. Not sure if that makes much sense but it is very much an idea in progress :coffee:

Best Regards

picclock

efrench:
Have you tried normalizing the print with the heat gun before removing it from the bed? It might work. I haven't had any warping problems when the print stays attached to the bed, so haven't tried this.

I had a jamming issue which turned out to be lousy diameter control on some cheap filament. Before I discovered the source of the problem, I increased the temp to 260. While this lessened the jamming problem, it didn't cure it. After putting on better filament, I printed a temperature calibration object (just a tall single wall rectangle). I edited the gcode to change the temperature 5 degrees every 10mm. After inspecting the print I lowered the temperature to 240/230.

picclock:
hi efrench

The reason for 260C temp was to try to improve layer bonding. On tall objects there are visible gaps in part of the layers which start typically at 2-3 cms and occur every few cms after. I suspect the layer bonding and object warping are all part of the same problem. Thanks for the idea of heat treating the part before removal. It may well be a simple, viable solution and I will give it a try. I am not overly keen on it as it may introduce other dimensional errors but its certainly worth a shot. I suspect the trick is just to supply the right temperature for the right amount of time .. . Also thought I might experiment with a heated chamber using my heat gun as a 1 off to try it - probably about 100C should do it.

Best Regards

picclock

Pete49:
picklock just a quick question if I may. :poke: Now I have my kit printer working well :) I was looking at the miles of wiring and wondered if I could cut it to a more reasonable size, not the motors they seem to be just right but the other wires such as the sensors and limit switches.. I was hoping to cut and resolder them rather than have them coiled up but that seems to be the norm. Would this affect the components?
Now returning you to the previous program errr thread. :beer:
Pete

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