Help with Botmill printer?

hi Folks,

I got my replacement printer from Botmill. I got the nozzle as close to the bed as I could and did some test prints. I started with the short piece of white ABS filament that was already in the printer. I stuck to the bed fine at just 200 degrees. It would even ooze at that temp. When I ran out I started using the black ABS filament that was in a bag that came with the printer. This black filament however seems to need much higher temps. Is this normal that a different color of the same material may need much higher temps? It comes out as a very fine thread at 230 that still won't even stick to the bed. It looks as if its already solidified the second it comes out of the nozzle.Thing is, I'm not sure if the temp is the only problem here. When I press the "home all" button in repsnapper, the nozzle goes to its "home". Then when I do a test print, the bed starts moving as it should, but the z axis moves as well. At "home" position it starts at about .15 mm and as the bed moves, the z axis slowly raises by another .5mm or so within the first 3 cm's. The extruded plastic doesn't even stick when it's at its closest to the bed, let alone when its .7mm or more above it. So I probably need to the raise the temp even higher than 230, right? But why does the z axis move? I'm thinking there must be a setting that's off but I don't know which one.
Any help would be greatly appreciated.

Good Afternoon,

The white filament in the printer, which was the filament we used during our testing phase, is PLA. This is why you noticed proper behavior at 200 degrees. The black, however is ABS as you know. So you will want to increase the temperature. While 230 should be ok, try increasing it to 240-250, as we've learned with the use of a thermocouple that the readout in the program tends to vary between 5-15 degrees higher from the actual temp.

Furthermore, When you command the Z-Axis to go "home", it's standard procedure for the Axis to go down, move up a hair, and finally settle in it's home position. This is because within the realm of the sensor itself, the actual trigger to stop at home is in the center of the sensor, so it lowers itself, then raises until the flag is approx in dead center of the sensor.

I would suggest getting the nozzle the perfect height that it needs to be for a print, which frankly looks so close to the bed that to the naked eye it almost looks like it's touching. Utilizing the 0.1 movement inputs in RS can make things easier. Between that and a slight up/down adjustment of the sensor (i mean very slight) you should have no problem getting the nozzle in the right spot.

Finally if you still cannot get the material to stick then perhaps an increase in temp to 240-250 should be in order, however usually when the material is not sticking to the bed it tends to be a Z-height issue.

Feel free to send me an email if you have any questions. Via email we can also arrange an appointment this week to discuss over the phone.

Good luck in your endeavors and keep us posted.

Happy Printing.

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Shaan Dholakia
BotMill 3D Printers
[www.BotMill.com]
shaan@botmill.com

Ah, I didn't know it was PLA. I assumed it was ABS because that's what it said on the bag of the sample material.
I'll try to get the bed closer and raise the temp and see what that does.
Thanks.

Well, I got the nozzle a little closer to the bed and raised the temp a little at the time. But even at 260 it still won't stick to the bed. It will stick a tiny bit but then curls up right afterworths, and it follows and sticks to the nozzle making a big mess again. Maybe the bed temp isn't high enough? I hope that's not it because if I'm not mistaken I don't have control over the bed temp. (Right?)

Since I only have 1Lbs of ABS and 10 Lbs of 1.75mm PLA, I'd rather use the PLA, but what do I have to change to use the PLA instead? Do I have to get a whole new hotend? If so, Shaan, is there any way I can just swap this hotend for one that uses 1.75mm PLA?

For PLA i set my hotend to 210º C and the bed to 90º C for the first layer and 60º C for the remaining layers.

You can also try cleaning the glass with acetone/windex/ammonia/zippo fluid. This will remove the dust and oils and help it stick better.

I've also noticed that overheating the PLA causes it to form a viscous chunky ooze that doesn't stick well. Extrude some filament into the air and see what speed you get a thin consistent extrusion.

The same hot-end can be used for both ABS and PLA - it's just the temperature for each material that's different.

nb99 Wrote:
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> The same hot-end can be used for both ABS and PLA
> - it's just the temperature for each material
> that's different.


Size is different too. The ABS I'm using now is 3mm, the PLA I'd like to use is 1.75mm.

You need a whole new extruder then with a smaller bore all the way from the hobbed bolt to the nozzle.

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[www.hydraraptor.blogspot.com]