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First Printer, 225mm^3 printer / mill combo build

Posted by Tired2 
Re: First Printer, 225mm^3 printer / mill combo build
June 05, 2014 10:08AM
my e3d is working great but I'm using ABS it's probably not the best finish that I've seen I think that's more to do with the outside shape nozzle this is something I printed the other day and sprayed some lacquer on
A2
Re: First Printer, 225mm^3 printer / mill combo build
June 05, 2014 07:30PM
There presently isn't any math that I'm aware of to describe the orifice land length for 3d printer hot ends, maybe someone in the business of extruding knows.

There is plenty of math for large production extruders, and rule of thumbs have be created, they generally read like this, and are strongly dependent upon the resin ability to flow, the extrusion pressure and the size being extruded: 10:1 to 25:1 land length to orifice diameter, and barrel ID diameter/land length should be less than 0.5, none of these rules work for 3d printer hot ends.

I did read some where that for really tiny orifices diameters <1.0 mm on industrial extruders a land length of 0.50 to 2.0 mm is used as a general guide. I think that you want the land length long to encourage laminar flow, which helps deal with the high extrusion pressure, and to reduce meltfracture at high extrusion rates.

The answer might be in this paper:

A review of melt extrusion additive manufacturing processes: I. Process design and modeling
[www.emeraldinsight.com]

[forums.reprap.org]
A2
Re: First Printer, 225mm^3 printer / mill combo build
June 23, 2014 11:23AM
Quote
Tired2
NEMA 23 Triple stacks at 286oz/in holding torque. 0.6 ohms, 5.6 amps, 1.8 degree per step by Automation Direct.

I'm interested in learning more about your stepper motors, what is the part number, and link if you have it.

Is this it?
[www.automationdirect.com]

Chart
[www.automationdirect.com]

How is the acceleration, and is it a fast motor?

Tks.

Edited 2 time(s). Last edit at 06/23/2014 12:01PM by A2.
Re: First Printer, 225mm^3 printer / mill combo build
June 24, 2014 09:21AM
A2,

The motors are: stp-mtrh-23079

Be sure to read the first few posts... I'm only running them at 2.5A, so I'm leaving a lot of torque on the table. The speeds seem good, much faster than the extruder can keep up with, so that is fine for me.

Check out the youtube videos if you have not:

[www.youtube.com]

They also make a hell of a noise on 24v that is pretty annoying, but I think most of that is the drivers I'm using (drv8825) from panucatt.

I've been too busy to 3d print anything in the last month or so, but I hope to fire it up soon and finish up my build series. It mostly works well, I still need limit switches, Z probe, bed mounting system, and some wiring cleanup, but I'm really happy with it so far.

Oh, and I need to find out why I built a 3d printer in the first place... I'm having trouble finding things I want to print. I know of some stuff, but I've had no time to model things up. Hopefully the 3dp will fit into my next project smiling smiley
A2
Re: First Printer, 225mm^3 printer / mill combo build
June 24, 2014 10:12AM
Tks.

How about modifying your machine into a router, print components that allow you to quick change to lead screws, or try to use it as is with the belts. Mount a 200W RC motor + PCB controller + ER-8 collet.

The motor spec says it's Rated Current (A/phase) is 2.8A, and you're running at 2.5A, doesn't seem like that would drastically reduce your torque, or am I missing some thing? I think it's due to operating the motors at 12V that reduces the torque, the chart uses 32V, 48V, and 70V.

I read that dampeners help a lot with resonance/missed steps, and motor noise.

Microstepping: Myths and Realities
[www.micromo.com]

Motor Drive Current:
The performance of a stepper motor is strongly dependent upon the driver. As the velocity of a motor increases, the driver's ability to deliver current is impeded by the back EMF of the motor, the non-zero inductance of the motor windings, and the rail voltages applied to the driver. The diminishing current results in a loss of torque and a reduction in dynamic accuracy.

Stepper Motor Dynamics Analyzer
[www.euclidres.com]

Microstepping Versus Gear Reduction
[www.ebay.com]
Re: First Printer, 225mm^3 printer / mill combo build
June 24, 2014 10:45AM
Thanks for the links, I'll look more at them when I get some more time. I've seen a few of them before.

I am running my motors at 24V. The board I'm using can handle up to about 30 or 35V or so before the regs get mad. The drives can handle 42V, but there is no need.... The torque is reduced, but at the speeds I'm running I get most of the torque I want.

It is unclear to me in the 8825 datasheet if the 2.5A current limit is Per-channel or Per device (2 coils per drive). I think that means 2.8A * 2 = 5.6A that the motors can pull (2.8A per coil). The 8825 I believe can only supply 1.25A per coil, leaving half (or so) of the torque on the table.

There is also a decay mode I can change, but for now I just have a noisy printer, it is not a huge problem currently.

Quote
A2
How about modifying your machine into a router, print components that allow you to quick change to lead screws, or try to use it as is with the belts. Mount a 200W RC motor + PCB controller + ER-8 collet.

Did you start on page 1 of this thread? Look closely, you can see I've modeled in a dremel and left space for it on the tool plate. I don't own one though, which is a problem since the one I want is about $240.
I think it will run fine on the belts, no screws needed. I have friends with real deal CNC mills, so it is not at the top of my todo list. The next project I have in mind is a quite ambitious and long term, and requires a good bit of milling and electronics fab, so I might go for it then.
Re: First Printer, 225mm^3 printer / mill combo build
July 01, 2014 10:14AM
I found the DRV8825 to be quite noisy and fussy to work with, but I may have had too-cheap stepper drivers, or I didn't work with them long enough.

I am using them in a similar capacity - under driving high current (low resistance) NEMA 23 steppers, so I felt like that was part of the issue, as when I used a smaller NEMA 17 stepper, the drivers would work fine.

You might consider the massmind.org THB6064AH driver - it "just works", at least for me.

I can also drive the THB6064 with 48 volts, which gives me personally more options with the slow ballscrews I use.
Re: First Printer, 225mm^3 printer / mill combo build
July 01, 2014 11:27AM
Thanks for the info. The main thing I've been meaning to try is the decay mode pin, but I've yet to give it a shot. Even if it does quiet them down, it may have other detrimental effects that I don't like (poor current control).

$35 per driver is a lot different than $10 per driver, but it will do a better job I'm sure. I'll be looking at casing / packaging my electronics soon enough, so I'll need to decide if I want to fork out $140 for 4 "quiet" drivers. For now it is not that pressing of an issue, I can still work with the noise going on.
Re: First Printer, 225mm^3 printer / mill combo build
July 29, 2016 12:26PM
Evan - did you ever get the CNC mill portion working?

As best I can tell the Azteeg X3pro isn't compatible with GRBL or TinyG.

Bob
Re: First Printer, 225mm^3 printer / mill combo build
August 09, 2016 08:47AM
Quote
bob.kuhn@att.net
Evan - did you ever get the CNC mill portion working?

As best I can tell the Azteeg X3pro isn't compatible with GRBL or TinyG.

Bob

Bob,

I have not actually gotten to the mill part, but I still have a reserved spot on my tool plate. If I do any time soon I'll post my results.

I'm not sure why X3 pro wouldn't work with GRBL, but it may take a good bit of pin defining and such. As I recall, Marlin was a fork of GRBL a while back, so it should work, maybe not "out of the box".

My initial plan was to simply run the mill stuff on Marlin. It has most of the commands I need, and even though spindle speed will likely be manually controlled, I theoretically could hook it to the 12v outputs and send analog command values to a speed controller. I'd just have to config the CAM post processor to know what M codes to send, etc.

I've not tried it, but I assume I can just run GRBL g-code on Marlin, maybe with a few tweaks to the CAM postprocessor to avoid outputting codes I don't use.

Of course, things like G54 offset and such might not be included in Marlin (I've not checked), but I can work around it for most of what I'd use it for.

If I get back into it, I plan to convert my controls over to machinekit anyway, and I know it can handle the milling. It is more of a challenge to get it working for 3d printing I imagine. Of course, I'll need ARM hardware or x86, machinekit won't run on the X3 PRO.

Likely I'll do nothing :-/
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