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Next Problem: Layer Hight

A project log for Wire 3D Printer

A 3D printer for printing with welding wire

Dominik MeffertDominik Meffert 03/25/2020 at 14:297 Comments

Now, that the wire feeder works reliable the next problem is the Layer Hight.

When the nozzle is far away from the buildplate the hight of the melted material layer gets higher as it should. This would also not work by FDM printing.

But when the nozzle is near to the melted material and the heat reaches the nozzle after a short period of time the wire gets stuck in the nozzle.

I tried different settings and could print near the melted material without that the wire got stuck in the nozzle.

It seems like as long as the feedrate is high enough the wire gets not stuck in the nozzle.

The parts from the latest tests are also very strong. I tried cutting them with pliers and was not able to cut them per hand. I think they are stronger than plastic but at the moment a bit weaker than massive steel.

The problem that remains at the moment is that after some time the "extruded" material reaches the hight of the nozzle.

So far, I had the best results when the nozzle is as close as possible to the surface of the printed object but does not touch it.

When the nozzle touches the surface the current flows no longer only through the wire, so that the wire gets less heated than it should and the "extrusion" gets brittle.

Discussions

Krzysztof wrote 03/25/2020 at 16:48 point

I know I'm repeating myself, but faster movement speed would PROBABLY help with wire melting in nozzle. I don't know what speed you can achieve with threaded rods.

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Dominik Meffert wrote 03/25/2020 at 17:03 point

No problem, I will try it out.

Have to do more testing with different settings.

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Dominik Meffert wrote 03/25/2020 at 19:00 point

Tested with 1200mm/min and it worked very well until the nozzle hit the printed object and kicked it loose from the build plate.

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Krzysztof wrote 03/26/2020 at 09:26 point

That is probably overextrusion. No idea how to fix this apart from very slowly tweaking parameters until they are good. Or some dynamic current checking, so that nozzle delivers enough current to melt those stubs.

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Dominik Meffert wrote 03/26/2020 at 12:27 point

Yes I think so, too. I successfully finished a print for the first time that was not brittle by changing the extrusion rate while printing. I started with 200% for the first layer and got down to 50% for stable printing. Another problem is the buildplate which bends due to the heat.

That's a good idea. The nozzle can melt small pieces which stand out the printed material, but not the finished layer because the current and heat spreads out in the whole part. This happened to me several times and through the heat the whole part unwelds itself from the buildplate.

I had a similar idea: To measure the current or voltage and change the extrusion rate depending on that. But maybe automatic bed leveling with a proximity sensor could help.

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Krzysztof wrote 03/26/2020 at 12:36 point

> To measure the current or voltage and change the extrusion rate depending on that.

I don't know what adjustments you want to make for extrusion based on that, but probably that's where those "voxel based" extrusion works, I think digital alloys check how much metal they have extruded already and extrude only as much as needed to fill gaps. As for proximity sensor, with induction sensor you can map surface you just have printed (it's metal after all). But I believe tweaking parameters so that you have more stable prints (open loop) is better way for now.

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Dominik Meffert wrote 03/26/2020 at 13:01 point

That was fast :)

Yes I will try to keep the printer as simple as possible, so that it stays easy to build. Just want to use the inductivity sensor for initial bed leveling to work on an already deformed buildplate and keep it open loop.

Hope also, that I can print without using shielding gas to keep it simple. The last print worked good without it.

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