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3D Resistance Welder

My attempt to build a machine which uses welding wire for 3D printing.

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My attempt to build a sort of metal 3D printer which uses resistance welding for welding/melting welding wire.

I started this project because I ever wanted to print metal parts since I bought my first 3D printer back in 2017 but there still are no affordable and easy to use metal 3D printers out there.

Inspired by

https://www.digitalalloys.com/technology/

which uses joule heating / resistance heating to melt metal wire to print solid metal parts I wanted to figure out how I can build something like that by myself with off the shelf parts.

The cost of the machine parts and building material should be the same as on a normal 3D printer and the operation should be very similar.

A test of melting metal per hand.

  • Resistor Plate and Temperature Test

    Dominik Meffert02/08/2020 at 23:21 0 comments

    I upgraded the 5 resistor plate to a actively cooled 12 resistor plate to limit the current draw and therefore the power and heat created in the components (resistors, cables, printhead, transformer).

    With the resistor plate and the continuous current operation I could measure the current draw for the first time - my amperemeter couldn't measure the 250ms pulses before.

    When idle, the system draws 1,240A and if the transformer secondary is shorted (toolhead on buildplate, copper on copper) it draws around 3A.

    I also measured the temperature while testing with a infrared thermometer.

    When idle the resistors and the transformer stay below 50°C. The system can stay idle the whole time without overheating.

    I tested measuring the temperature when shorted, too but unfortunately the area of the cable above the toolhead got too hot, so that I must abort testing. The toolhead will definitely need some cooling. The nozzle got very hot, too and changed its color to a more brown color.

    I tried to measure the current while melting wire and it looks like it even drops under the measurement form idle mode, but it's hard to say whether this was a correct measurement because I could not hold the hight and feedrate steady per hand. Will continue working on X, Y, Z and E axis for testing it again.

    A thought about cooling:

    I think I could use a powerful water cooler for the hotend if air cooling would not be enough and if the cables heat up too much I could use 35mm² or 50mm² cables. For the resistors it seems like air cooling would be good enough, but will see that in longer test runs. Maybe I could add heat sinks underneath the fans for better cooling if needed.

  • 3D Printer Frame

    Dominik Meffert02/08/2020 at 05:33 0 comments

    Here is a picture of the machine frame, which is made of 12x 500mm 3030 profiles.

    Will build the X, Y, Z axis and if the dimensions are to small I will use greater ones. The electronics and filament spool could be later mounted on the sidewalls.

    The next thing will be upgrading the power supply with more resistors.

  • Continuous Current

    Dominik Meffert02/07/2020 at 07:17 0 comments

    I tried to weld a wire per hand with continuous current. It's not easy to feed the wire fast enough per hand, therefore the sparks. The wire melted in droplets, which welded good to the surface for which I used this time a sheet of metal instead of the fly screen. With stepper motors the wire should melt in a connected line. The energy from the power supply is enough and could maybe be less, but the resistor block gets too hot to touch after a few seconds and would likely fail after minutes. I think the printing speed will later depend on the power used and the power could be regulated through on and off cycles.

    Will order more resistors to divide the load between them.

    Tested to melt serveral "layers" of wire on top of each other.

    The "printed object" welded very good to the surface - could almost lift the buildplate on it until it broke on the weakest spot - I tested to break it in two halves and it was solid and very hard to break - like wire.

  • Quick Update

    Dominik Meffert02/06/2020 at 20:38 3 comments

    I did a quick test of the new concept and first it works both welding and softening luckily without welding the head to the surface. I tested both with a 250ms pulse and ca. 2645A which works good. But then I burned the fly screen by a softening test and the steel from it get stuck to the nozzle. Since then the wire get stuck in the nozzle like @Bharbour said.

    So I will try to weld or melt the wire with pulses from the spot welder power supply when it touches the workpiece with clearence between the nozzle and the workpiece. It seems like the machine is turning more and more from a 3D spot welder to a 3D resistance welding machine by excluding ways which not work.

    Will also test whether the power supply can handle short pulses without upgrading it like eg. 25ms on, 250ms off, 25ms on and so on. Doing so it should be possible to regulate the intensity of the heating by the duty cycle of the power supply like the temperature of the extruder on a 3D printer.

    Maybe it works with this attempt.

  • Idea: Better Working Method

    Dominik Meffert02/05/2020 at 06:34 10 comments

    I had an idea how I can change the working method to be simpler and more reliable.

    I want to change it from bending, hopefully hitting the wire and welding to hopping from spot weld to spot weld.

    I ordered welding contact tips which should act as spot welding electrode and wire nozzle. Doing so will hopefully make the whole concept a lot simpler and more reliable by removing the 4th axis and the risk of missing the wire. This would also simplify the electrical setup, firmware and software. Maybe with this method it could also be possible to do things like cutting the wire at some point and laying a new wire at another for travel moves.

    I will test the new concept as soon as the parts arrive.

  • Toolhead Prototype

    Dominik Meffert02/02/2020 at 14:30 0 comments

    Here is a prototype of the wire bending & spotwelding toolhead.

    The toolhead consists of a copper electrode in the center and a wire feeder which can rotate around the electrode to bend the wire in the moving direction.

    There are still a few things to figure out:

    - Using this kind of toolhead the machine will later have 5 axis (X, Y, Z, E and rotation) which requires software and firmware which supports it.

    - The rotation axis needs an endstop, too. Maybe I could use a hall-effect sensor on the top plate and a magnet on the gear. Will test that the next days.

    - There could be a problem with the bowden tube colliding with the gantry system.

    - The wire is directed at the electrode, but if the electrode misses the wire the print can fail. Maybe a greater diameter electrode could help, but it could also increase the distance of two wires next to each other.

    I addad a hall sensor to the toolhead to act as an endstop.

    - Ordered a ∅6mm copper rod for using it as electrode, so that it's more likely that it will hit the wire.

    The next step will be building the frame and finding a way in which the PTFE tube can move without colliding with the rest of the spot welder.

  • Metal Filament / Building Material

    Dominik Meffert01/28/2020 at 14:07 0 comments

    Until now, I used tie wire / floral wire for testing but today I tested welding wire. I was concerned that it could be too conductive because of the thin copper layer on it but it welded very good to the bottom layer and to itself.

    I think welding wire could be the perfect building material because it is available in spools, it is high quality material and it's very cheap - sometimes even cheaper than e.g. PLA filament.

    - Flux core wire and stainless steel wire works, too.

    - Will start testing with 0.6mm wire rater than 0.8mm wire because it is easier to bend.

    "Metal 3D printing filament"

    5kg spool of 0.6mm welding wire next to 1kg spool of 1.75mm Black PLA filament.

  • The Buildplate

    Dominik Meffert01/25/2020 at 17:12 0 comments

    Bottom Layer Material:

    The last few days I was searching for the best material on which the first layer can be welded. I tried some sorts of fences, metal meshes and fly screens made of different materials and came to the conglusion, that galvanized steel fly screen could be the best bottom layer material. I also tried stainless steel mesh and I could weld the wire on it, but because of the higher resistance of stainless steel vs galvanized steel I wasn't able to weld more layers on top of each other. The greatest amount of heat was created in the stainless steel mesh instead between the wire layers. With aluminum fly screen I had the opposite problem because of the low resistance of aluminum almost no heat was created in the fly screen, only in the galvanized steel wire.

    So I stayed with galvanized steel fly screen.

    Buildplate:

    The buildplate is made of an 250*250*5mm aluminum plate with a M4*40mm countersunk screws in each corner and a copper plate taped on it with double sided tape. There is also the 25mm² cable with a cable lug and a M6*20mm screw and twelve 41mm paper clips to hold the fly screen on it.

    The buildplate could be mounted like in the Hypercube Evolution 3D printer and move only in the Z direction. This printer design could also be good to create a closed enclosure, so that the fumes can be kept inside and the air could be filtered before returning into the room.

    Next thing could be building the toolhead.

  • MOT Spot Welder

    Dominik Meffert01/13/2020 at 01:26 0 comments

    I have built a Microwave Oven Transformer Spot Welder from an old microwave tansformer, a jump start car cable and some parts I had laying around.

    It works so far but the circut breaker tripped randomly all 5 welds or so and the connection

    was not really stable.

    Another test with different wire and one electrode clamped to the surface. This time the weld quality was better and the connection was very strong. But until now the wire does not welt to the surface.

    I tested again with the first wire type and it worked like the other, it seems like the one electrode placed on the surface and the other placed at the material makes the difference.

    Instead of welding the wire to a piece of sheet metal I tried to weld it to a piece of wire fence and it worked. The fence is also a lot cheaper than sheet metal and can be easily cut off after the object is finished. This fence has a 13*13mm mesh but I think for automatic welding it should be denser.

    Update:

    I actually wanted to build a capacitor based welder but I have read that if the capacitor gets shorted it will not last for long...

    So I solved the circuit breaker tripping issue by connecting five 4 ohm 100W resistors in series with the transformer primary winding. Doing so it should limit the current to around 11.5A. I did a short test and after 10 welds the resistors get barely warm. They will be mounted on a heatsink for a long duration test to see whether they can work in continuous operation.

    I let the machine run in 50ms welding, 500ms pause, 100ms welding, 1000ms pause intervals for about half an hour and the resistors stayed cold enough that I could touch them afterwards without burning my skin. They can operate up to 200 °C, so that should be good enough for continuous operation. After a while the 25mm² cable got warm, too. The transformer stayed cold the whole time.

    The spot welder should be ready for working with it so the next thing could be working on the buildplate and bottom layer.

  • Getting started

    Dominik Meffert01/10/2020 at 13:44 0 comments

    I started this project because I ever wanted to print metal parts since I bought my first 3D printer back in 2017 but there still are no affordable and easy to use metal 3D printers out there.

    Inspired by

    https://www.digitalalloys.com/technology/

    which uses high current to melt metal wire to print solid metal parts I wanted to build a machine which bends welding wire and uses high current to spot weld it layer per layer on top of each other.

    The cost of the machine parts and building material should be the same as on a normal 3D printer and the operation should be very similar.

    The first thing I want to do is building a DIY spot welding machine from the internet to getting started.

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Discussions

Bharbour wrote 02/05/2020 at 14:34 point

How do you insure that the wire disconnects from the welded spot? It seems like the opportunity to just weld the head in place is very high.

  Are you sure? yes | no

Dominik Meffert wrote 02/05/2020 at 14:49 point

Hi,

It should be as followed:

As long as the electrode is made of copper it should not weld to the workpiece. The most heat is generated at the point of the greatest resistance, so the copper electrode stays cooler because of its low resistance and greater diameter and should not melt.

I tested it many times and it never welded in place.

  Are you sure? yes | no

Bharbour wrote 02/05/2020 at 20:40 point

I meant the welding wire not separating from the welded spot

  Are you sure? yes | no

Dominik Meffert wrote 02/06/2020 at 01:27 point

Yes that could be a concern, thanks for the hint. I will test it and if the head welds to the welded spot I will maybe need another nozzle with an orifice shifted inwards or something like that.

  Are you sure? yes | no

Martin wrote 01/28/2020 at 16:09 point

I remember a project, a friend did in the late 1990ies. In that time they called it "rapid prototyping" and not so much 3D printing. They tried to melt metal like iron with an induction coil or some welding torch to build up an object layer by layer.
But that led to massive thermal distortion. AFAIK they tried even grinding each layer with a good (6 axis) CNC mill, but in the end they could not design a reliable 3D printing process.

  Are you sure? yes | no

Dominik Meffert wrote 01/28/2020 at 19:45 point

Hi Martin,

I think that's the thing with metal 3D printing. Many people have worked on it, but only a few companies were successful with complicated and costly methods. It seems like it's extremely hard to get usable results at low cost.

The objects which I want to print/weld will likely be more partially together welded wire parts than solid metal parts, but I think it could be a cheap way to create 3D printed/welded parts at all. Maybe later the process can be somehow improved to create solid metal parts.

  Are you sure? yes | no

Wayne Wayne wrote 01/25/2020 at 22:09 point

Very cool, have wanted to see a 3D printer operate like this. 

  Are you sure? yes | no

Dominik Meffert wrote 01/28/2020 at 21:01 point

Thank you,

there are still some things to figure out but I think it should work.

  Are you sure? yes | no

Dan Maloney wrote 01/14/2020 at 18:08 point

I really like this idea. I can see it starting out really simple, with wires tacked to the build plate to make "low poly" shapes. Then you increase the number of spot welds to improve the resolution, and then build up layers. Really cool idea.

One place you might have trouble is the duty cycle of your spot welder. You might have to build a pretty beefy welder to keep it more or less continually operating.

Good luck, and keep us posted.

  Are you sure? yes | no

Dominik Meffert wrote 01/14/2020 at 20:07 point

Thank you,

I hope I can build a capacitor based spot welder that can work for hours, like a 3D printer. Maybe with multiple capacitors to switch between them for reducing time between two welds and for using double pulse spot welding if needed.

  Are you sure? yes | no

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