Welcome! Log In Create A New Profile

Advanced

X and Y counterweight?

Posted by jes@holmstrup.com 
X and Y counterweight?
January 18, 2018 11:20AM
Greatings

Has anybody any experience with counterweight on the x and Y axis for reducing vibrations?

Back in the days IBM had a needle printer called 5224. The printhead was very heavy, and they had a counterweight on the oppesite side of the belt. It worked very well.
Its farely easy to mount a equivalent weight, but am I the first trying this?

Jes.
Attachments:
open | download - counterweight.jpg (15.7 KB)
Re: X and Y counterweight?
January 18, 2018 12:12PM
What problem are you trying to solve?


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: X and Y counterweight?
January 18, 2018 12:31PM
While you can compensate the implus with this you double the amount of torque needed to accelerate. So yes, it can create smoother movement, at the same time you need stronger motors and more power as well as stronger belts. For me it sounds like a lot of effort for little gain. Decreasing the moving mass to a minimum will also reduce vibrations with the added benefit of costing less power and allowing for faster acceleration.
If you have to noticable vibrations try to adjust acceleration and jerk before investing in new mechanics.


[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]
Re: X and Y counterweight?
January 18, 2018 01:47PM
I have Diamond hot ends with 5 E3D titans on a dual CoreXY. The mass each gantry is around 2kg in the Y direction so 4kg combined. The limiting factor on print speed is how fast you can melt the filament. Feeding all the melt chambers simultaneously using a separate extruder for each one, allows me to print at up to 300mm\sec. See here [somei3deas.wordpress.com] and here [somei3deas.wordpress.com]

I use acceleration of 1,000 mm\sec^2 for non-print moves but slow it down to 500mm\sec^2 for printing. That's only because the entire printer rocks about a bit when I throw 4kg around at over a metre above ground. So I always have a little chuckle to myself when I see these sorts of posts. Reducing mass would be a good thing if the mass itself was a limiting factor but it isn't. In the grand scheme of things, it makes hardly any difference to the time it takes to print anything because the melt rate if the filament is what limits the speed and not the moving mass.

Oh, and I use Nema 17s and 6mm belts - both of which are more than adequate.


[somei3deas.wordpress.com]
Re: X and Y counterweight?
January 18, 2018 02:13PM
Hi.

I just want a peace and quite printersmiling smiley
I know it takes bigger motors and regarding the belts, I dont think its a problem. They are tough enugh. Its not the belts that brakes, its everything else.
About the effort. Thats why I want to do it. winking smiley
Re: X and Y counterweight?
January 18, 2018 03:02PM
If quiet is what you want, get a Duet controller that can run 256:1 ustepping.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: X and Y counterweight?
January 18, 2018 11:50PM
Quote
jes@holmstrup.com
Hi.

I just want a peace and quite printersmiling smiley
I know it takes bigger motors and regarding the belts, I dont think its a problem. They are tough enugh. Its not the belts that brakes, its everything else.
About the effort. Thats why I want to do it. winking smiley
What is your actual problem? If you say the bigger motor doesn't bother you i can only assume that motor noise is already no problem so silent drivers are not helping any more because they are already used. This leaves the mechanics. If you think countermass is the solution i can only assume that acceleration is the problem and produces noise, this can only happen if your mechanical components aren't realy all that good. Cheap bearings, rubbish bushings or cheap linear slides can and will contribute to unwanted movement and noise.
If the mechanics are good a silent driver, like the one used on the Duet, should resolve your problems, if the mechanics are crap a countermass might actually increase the problem over time.


[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]
Re: X and Y counterweight?
January 19, 2018 06:13AM
Hmm. It could reduce ripple a bit. Accelerating or decelerating causes force being applied on the guiding rods which in turn bend and relax. An acceleration of 1000mm/s^2 and a 0.5kg carriage causes 0.5N of Force which results in a deflection of 60µm at the center of two 8mm 40cm steel rods, according to online calculators.
Re: X and Y counterweight?
January 19, 2018 06:49AM
Quote
lukie80
................ Accelerating or decelerating causes force being applied on the guiding rods which in turn bend and relax..............

Huh???? How does accelerating a mass travelling parallel to the guides rods apply a force to those rods?


[somei3deas.wordpress.com]
Re: X and Y counterweight?
January 19, 2018 07:15AM
Quote
deckingman
Quote
lukie80
................ Accelerating or decelerating causes force being applied on the guiding rods which in turn bend and relax..............

Huh???? How does accelerating a mass travelling parallel to the guides rods apply a force to those rods?
I mean that movement on the X-Axis of a Prusa printer bends the smooth rods of the Z-axis.
Re: X and Y counterweight?
January 19, 2018 09:45AM
Quote
lukie80

I mean that movement on the X-Axis of a Prusa printer bends the smooth rods of the Z-axis.

Really?


[somei3deas.wordpress.com]
Re: X and Y counterweight?
January 19, 2018 10:04AM
Yes. Hold something really heavy and pull it towards you. Your body will move forward. Your body are the Z Rods and the carriage is the heavy object. But I overestimated the effect, I forgot the mass of the X-Motor. So the bending will be much less.
Re: X and Y counterweight?
January 19, 2018 12:26PM
Quote
lukie80
Hmm. It could reduce ripple a bit. Accelerating or decelerating causes force being applied on the guiding rods which in turn bend and relax. An acceleration of 1000mm/s^2 and a 0.5kg carriage causes 0.5N of Force which results in a deflection of 60µm at the center of two 8mm 40cm steel rods, according to online calculators.

The deflection computed is for a static force, here it is a pulse. The mass of the motor, gantry etc... acceleration duration will lead to a lower value. Calculus has to be called here smiling smiley

Just saw you corrected your answer.

Edited 2 time(s). Last edit at 01/19/2018 12:29PM by MKSA.

"You failed to maintain your weapon, son" (Harry Brown )
Re: X and Y counterweight?
January 20, 2018 01:23AM
Quote
lukie80
Yes. Hold something really heavy and pull it towards you. Your body will move forward. Your body are the Z Rods and the carriage is the heavy object. But I overestimated the effect, I forgot the mass of the X-Motor. So the bending will be much less.

Yes, I understand the theory. It was the practical interpretation that the force would bend the rods enough to affect print quality that bothered me.


[somei3deas.wordpress.com]
Re: X and Y counterweight?
January 23, 2018 08:18AM
Ok.
The genaral anwser must then be no and yes.
Nobody has any experience with counterweights, and yes I am the first.
I had hoped that somebody had tryed it.

Thanks everybody.

Jes.
Re: X and Y counterweight?
January 24, 2018 12:16AM
The answer is that it is not worthwhile here compared to simpler method.

Don't assume you are the only one who thought about it. IBM did it as you know but the idea is used in many other mechanism. It is just physics.

Now, it would be nice if you could make it and show it working for a 3D printer.
That would be a first, indeed.


"You failed to maintain your weapon, son" (Harry Brown )
Re: X and Y counterweight?
January 24, 2018 03:05AM
thumbs uppoint taken.

Then I'll better be the first.
My project is to build a vertical windmill, with wings 3 meters high, each build in 3 modules. So my new printer must ether have a 1 meter hotbed or a building height of 1,1 meter.

Jes
Re: X and Y counterweight?
January 24, 2018 04:54AM
Quote
jes@holmstrup.com
thumbs uppoint taken.

Then I'll better be the first.
My project is to build a vertical windmill, with wings 3 meters high, each build in 3 modules. So my new printer must ether have a 1 meter hotbed or a building height of 1,1 meter.

Jes

I like your sense of humor smiling smiley


"You failed to maintain your weapon, son" (Harry Brown )
Re: X and Y counterweight?
January 31, 2018 04:19AM
I'd go the "low acceleration" route...as written above, it doesn't add much to print time but gets a lot smoother movement and less rattle (and nicer prints, I'd say).
Re: X and Y counterweight?
January 31, 2018 09:08AM
Quote
jes@holmstrup.com
My project is to build a vertical windmill, with wings 3 meters high, each build in 3 modules. So my new printer must ether have a 1 meter hotbed or a building height of 1,1 meter.

Is 3D printing really the best way to make those wings?

This will be something that's outdoors and exposed to sun, weather, and a lot of mechanical force. By the time you get done with the necessary post-processing of the prints, you could have easily made the wings out of other materials/methods that would be more appropriate for the task.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: X and Y counterweight?
February 01, 2018 02:13AM
Quote
the_digital_dentist
Quote
jes@holmstrup.com
My project is to build a vertical windmill, with wings 3 meters high, each build in 3 modules. So my new printer must ether have a 1 meter hotbed or a building height of 1,1 meter.

Is 3D printing really the best way to make those wings?

This will be something that's outdoors and exposed to sun, weather, and a lot of mechanical force. By the time you get done with the necessary post-processing of the prints, you could have easily made the wings out of other materials/methods that would be more appropriate for the task.

It is why we have to refuse the legalization of drugs, any drugs ! smiling smiley
Or may be it is the ABS fumes ?

Edited 2 time(s). Last edit at 02/01/2018 02:15AM by MKSA.

"You failed to maintain your weapon, son" (Harry Brown )
Re: X and Y counterweight?
February 04, 2018 03:23PM
@deckingman

Your CoreXY has separate extruder and hot end, isn't that to reduce weight from the print head?
Re: X and Y counterweight?
February 13, 2018 09:20AM
I plan to build it in modules and then fix them together with a long, I dont know the right word for it, bolt and nuts. google translate calls it a threaded rod.
Maybe its gonna be a lighter print and then swept in fibre Glass. But still with the threaded rod through from top to bottom.
Attachments:
open | download - 20100726091701000601850.jpg (80.6 KB)
Re: X and Y counterweight?
February 13, 2018 10:00AM
Srek pretty much covered it here:
Quote

While you can compensate the implus with this you double the amount of torque needed to accelerate. So yes, it can create smoother movement, at the same time you need stronger motors and more power as well as stronger belts.

Adding mass to the frame is generally much cheaper than doubling your motor torque, so counterweights are rarely used. Printers are an unusual case because the cheapest stepper motors are arguably overpowered, and frame rigidity is the limiting factor. It is possible that a counterweight could reduce ringing, but you would have to be careful not to impart a twist onto the frame so it might not be a trivial addition.

Note that higher acceleration is always better, assuming you can achieve it without degrading the motion in other ways. It allows you to maintain a constant speed through corners (reducing the need for pressure advance) and arguably increases print speed more than max velocity does because FDM toolpaths are full of direction changes. A frame that can withstand high accelerations will be quite heavy though.
Re: X and Y counterweight?
February 13, 2018 10:12AM
Developing a 3D printer so you can print those wings is about the maximum amount of trouble you could possibly go to. It would be pretty easy to make a wood jig with a hot-wire to cut foam to the necessary shape. Put a couple layers of glass and epoxy on it and you're good to go. You might even finish the project before you die.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Sorry, only registered users may post in this forum.

Click here to login