extruder nozzle design - why they are bad May 15, 2014 06:25PM |
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Re: extruder nozzle design - why they are bad May 15, 2014 06:44PM |
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Re: extruder nozzle design - why they are bad May 15, 2014 06:47PM |
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Re: extruder nozzle design - why they are bad May 15, 2014 08:45PM |
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martinfromoz
Hi,
I'm new to 3d printing. I'm in the process of researching my first printer, how they work, the capabilities and limitations of 3d printers. I do, however have 12 years of manufacturing experience with plastic extrusion and injection moulding. Maybe this has given me and insight or maybe this has been discussed before?
Re: extruder nozzle design - why they are bad May 16, 2014 07:39AM |
Registered: 10 years ago Posts: 41 |
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vegasloki
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martinfromoz
Hi,
I'm new to 3d printing. I'm in the process of researching my first printer, how they work, the capabilities and limitations of 3d printers. I do, however have 12 years of manufacturing experience with plastic extrusion and injection moulding. Maybe this has given me and insight or maybe this has been discussed before?
The FDM/FFF type of extrusion printing has been around for the better part of 30 years. Checking out some of the patents particularly from Chuck Hull will give you insight to what's been going on. It's not the shape of the orifice in and of itself as there many other issues at play. My suggestion would be to build a starter printer and get familiar with the process. There are some similarities with other processes but it's a process in and of itself and has specific limitations and parameters that aren't either obvious at first or behave in a way that someone without the background in FDM/FFF would be aware. Specific to layer ridges there are some other issues to consider. By the time the next layer is laid down the previous layer is already cooling and add extrusion control and whatever mechanical abnormalities the machine introduces and it's not so cut and dry. For example there is a phenomenon known as "Z wobble" that is responsible for many if not most of the layer irregularities people encounter. There will be slight ridges on even the most sophisticated and advanced machines though certainly not to the extent of the less capable machines or machines that don't use quality parts or accurate assembly and calibration.
With patents expiring and the current round of SLS and SLA printers coming online there will be some opportunity to address some of the issues of the FDM/FFF process. I think once you get in and get some hands on it will give you a better perspective to base your decisions on what can be improved. No doubt extrusion is an area for improvement but it's not going to be as simple as changing the geometry of the nozzle outlet.
Re: extruder nozzle design - why they are bad May 16, 2014 01:04PM |
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Re: extruder nozzle design - why they are bad May 16, 2014 01:27PM |
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Re: extruder nozzle design - why they are bad May 16, 2014 03:25PM |
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Re: extruder nozzle design - why they are bad May 16, 2014 05:00PM |
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Re: extruder nozzle design - why they are bad May 16, 2014 08:45PM |
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Polygonhell
I fought Z Wobble on my MendelMax for months...my current belief is that lead screw based Z axis are just not a good match for most 3D printer designs.
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Sublime
That is not to say an overbuilt CNC style machine is bad just that you can get just as good of results using engineering to overcome the need for a 1000lb machine.
Re: extruder nozzle design - why they are bad May 16, 2014 09:33PM |
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Re: extruder nozzle design - why they are bad May 16, 2014 10:17PM |
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Re: extruder nozzle design - why they are bad May 16, 2014 10:40PM |
Registered: 11 years ago Posts: 474 |
I agree that just throwing money at it although it may work probably isn't the best design. But I've designed plenty of machines in my life and if you run the figures for the vertical z rods with a extruder mounted to the X carriage the flex in the center of 14 inch piece of round Rod in the middle is terrible it is not designed correctly. Why everybody keeps bringing up the screws always baffles me it's the guide rods that are at fault this is what you design to hold the axis and this is where Mendel reprap is wrong in the design. That's why people like light designs Bowden extruders Delta style printers all of this is because the z-axis are not stiff enough obviously the Bowden lightens the mass in the Delta redirects a lot of the moving mass to up-and-down and also has a very light X and Y moving massQuote
iquizzle
I'm sure it's possible to have a heavy enough extruder with high enough accelerations to flex the leadscrews. But even within that statement, there are many variables to consider. What are the diameter of the rods? How long are the rods between the constraining points? Carbon steel, plain steel, stainless steel? Are the rods constrained in the x-direction by both x-ends or just one?
I believe that in most cases with hobbyist-designed 3d printers (where very little modeling is ever done in the design phase), good implementation of "standard" parts will yield equal or better results than poor implementations of expensive parts. You don't always get what you pay for, and expensive things touted as upgrades might simply be a patch to add needless "rigidity" to what is essentially a design flaw.
No design is ever perfect. I just think that if you can solve a problem with the parts you already have and the parts that people generally use, then you have contributed something to the collective knowledge. If you just go buy a bunch of expensive linear slides, ballscrews, aluminum extrusions, etc then you haven't really done any engineering. You've just substituted money for knowledge.
Re: extruder nozzle design - why they are bad May 17, 2014 01:22AM |
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Re: extruder nozzle design - why they are bad May 17, 2014 01:48AM |
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Re: extruder nozzle design - why they are bad May 25, 2014 11:31PM |
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Re: extruder nozzle design - why they are bad May 26, 2014 09:06AM |
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Re: extruder nozzle design - why they are bad May 26, 2014 02:07PM |
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