Calibrating E-steps

[Rockel83]

I'm calibrating my new printer, Geeetech A20M at the moment. It's printing fine so far, but seems the step/mm values are a bit off, because the dimensions of printed parts are a bit off. So guess I need to start to calibrate the E-steps first. It's a printer with a bowden tube. And I've tried to calculate the E-step vallues in 2 ways now. With and without the tube.

- I get around 430 steps/mm as a value when keeping the bowden tube connected and feed 100mm through the heated hotend.
- I get around 400 steps/mm when removing the tube at the exit of the extruder and feed 100mm directly cold through it.

It's verry logical that it gets more presure when trying to push 1,75mm to a heated 0,4mm nozzle And so the extruder needs to work harder.But I believe there should be no diffrence in values by using the tube or not? Right?

[fred_dot_u]

If you are getting a slower feed through the nozzle, your extruder is slipping or your nozzle temperatures are too low. One of the methods I've seen for setting e-steps is to make a mark on the filament (direct drive) upstream of the entry point to the extruder, with a frame reference to determine starting point. Make a mark 100 mm farther away from the first. Command the 100 mm feed. If it's incorrect, adjust as needed. In your case, I'd suggest to ensure there is no slipping and that temperatures are correct.

[Rockel83]

If you are getting a slower feed through the nozzle, your extruder is slipping or your nozzle temperatures are too low. One of the methods I've seen for setting e-steps is to make a mark on the filament (direct drive) upstream of the entry point to the extruder, with a frame reference to determine starting point. Make a mark 100 mm farther away from the first. Command the 100 mm feed. If it's incorrect, adjust as needed. In your case, I'd suggest to ensure there is no slipping and that temperatures are correct.

Thanks for the response.I've measured 120mm from the entry point, and then measured the remaining distance after extruding 100mm. So this is somewhat the same technique. Another possibility is to remove the bowden tube, cut the filament flush and extrude another 100mm. Then only need to measure the actual extruded filament. This saves a lot of filament.I believe both values of both methods should be (nearly) the same.

So it has to do something with the preasue I guess. Doesn't seems like something is slipping/skipping because I have a lot of tension on the clamps and the gears keeps even turning while extruding.

Maybe it's the filament I used. It's quite old and t seems to generate gases in the nozzle.

So suppose its vaporizing moist and building up extra pressure?

[fred_dot_u]

If you think the filament has collected moisture, you may be able to mitigate that by dehydrating it in a source of heat. I purchased a simple food dehydrator and chopped away the internal food trays to accommodate a spool. The maximum temperature for the dehydrator is just about right to force out the water over a day.

I hadn't considered it before but if you're getting water in the nozzle, it may indeed affect the feed rate.

[Rockel83]

If you think the filament has collected moisture, you may be able to mitigate that by dehydrating it in a source of heat. I purchased a simple food dehydrator and chopped away the internal food trays to accommodate a spool. The maximum temperature for the dehydrator is just about right to force out the water over a day.

I hadn't considered it before but if you're getting water in the nozzle, it may indeed affect the feed rate.

Oh thanks for the tip! I could try this, since it's almost a full spool of filament.
It was laying around for over a couple of years. I had it put in a plastick sack, but gues it still could have collected moist over the years. It's pretty old too I guess...

But since it's almost a full spool I thought it would have been good for testing purposes. And not to spill anny new fillament this way.

But I noticed that at drips verry diffrently from new filament and that it pusches out some airbubles so now and then out of the nozzle. Don't see this with the other (new) filament.

So maybe this is giving me the errors I encounter.

Maybe calibrate the printer with fresh filament, and use this spool for prototyping or support. Trying to dehydrate is a good idea btw! I'm going to look for a food dehydrator too I guess, if it works well.
But for now placing it in a heat source will do well too? What temperatures should I use?

Water vaporizes at 100, and it's still way beneath the melting point of PLA. Or is it still too hot?