Re: [Emc-users] Beam Stiffening?

[gene heskett]

On 5/13/24 16:47, Todd Zuercher via Emc-users wrote:

Anyone have any brilliant ideas to stiffen a woefully inadequate cross beam on a gantry router 
without adding too much mass?  What is there now is a 4" x 8" rectangular 3/8" 
walled extrusion that is 145" long.

That has got to be north of 100 lbs of flying weight.


Under normal jogging commands the two servos control the ends of this gantry 
reasonably well, but while the axis is homing the thing shakes and wobbles 
terribly bad.  Also If I put a dial indicator in the center of the bridge and 
hit the bridge forward or backward it will flex and wobble enough to displace 
the dial indicator +/-0.03 and it takes nearly a dozen wobbles to dampen it.  
But on the ends the servo's only have a few thousandths of give.

I'm less concerned about the actual stiffness and more worried about dampening 
the wobble.

This might be a place to use a technique the 3d printers are using. 
Called input_shaping. In the printers case the testing wiggle is 30 to 
150 hz but in something this massive you might want to start the 
frequency of the scan at 1hz. The amplitude of the motion is then 
recorded by an accelerometer chip, usually an adxl345. The data 
collected is then used to program a digital filter, which does not 
effect the speed of the machine as it works to reduce the amplitude of 
the drive at those frequencies where the system is resonating. Such 
fancy math has been responsible for a 4 to 8x increase in the machines 
actual speed as it controls the ringing.


Another different technique I have found helpful by accident is 
stepper/servo's. I am engraving some text of the sides of the printed 
nuts for the vise screws I'm building. Using normal steppers that bounce 
back and forth magnetically, that ringing restricts the speed of the 
printer to about 30mm a second if the text is not to be destroyed by the 
ringing. Switching to stepper/servo's has allowed me to drive the 
printer 10x faster and the text remains readable.  The stepper/servo is 
actually dampening that magnetic bounce in real time. And they can do 
that on less power than a normal stepper, aided by the switch to higher 
voltage power supplies, up to 110 volts vs the 40 or so normal steppers 
limiting the bandwidth of the lower voltage normal steppers. The reduced 
power is because they are now using the detected error to control the 
motor current, motor working easy=low current and negligible heating, a 
difference you can see in your shops power bill. I'm now using 5 of them 
in the garage and have 3 more to put on my GO704. Capable of stopping 
linuxcnc in it tracks if they hit an immovable object, well tested, just 
one problem. It has yet to happen running a job!


Check out Hanpose for the higher sized stuff you might need to replace 
the two servo's you are using now.


Drives a closed loop nema 42 motor rated 12NM from a 220 volt line. With 
a matching motor and the right set of belt pulleys it can turn your 
house around. For probably < $350 an axis.

Todd Zuercher
P. Graham Dunn Inc.
630 Henry Street
Dalton, Ohio 44618
Phone:  (330)828-2105ext. 2031


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Cheers, Gene Heskett, CET.
--
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis



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Re: [Emc-users] Beam Stiffening?

[Dale Ertley via Emc-users]

 See cable beam stifferDo on 3 or 4 sides.Be safeDale
코스피

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코스피

코스피
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On Monday, May 13, 2024 at 08:07:14 PM EDT, Dale Ertley  
wrote:  
 
  Small blocks on the outside middle of beam on 3 or 4 sides of the beam with 
small aircraft cable attached to each end pulled tight.
Use small turn buckles to tighten the cables over the block on that one 
side.You may be able to reduce the mass of the beam with the added stiffness of 
the blocks and cables.
Be safe.
Dale
On Monday, May 13, 2024 at 07:31:34 PM EDT, Ralph Stirling via Emc-users 
 wrote:  
 
 Can you run a steel cable through it and tension it?  Might stiffen it up some.

-- Ralph

On May 13, 2024 1:46 PM, Todd Zuercher via Emc-users 
 wrote:
CAUTION: This email originated from outside the Walla Walla University email 
system.


Anyone have any brilliant ideas to stiffen a woefully inadequate cross beam on 
a gantry router without adding too much mass?  What is there now is a 4" x 8" 
rectangular 3/8" walled extrusion that is 145" long.

Under normal jogging commands the two servos control the ends of this gantry 
reasonably well, but while the axis is homing the thing shakes and wobbles 
terribly bad.  Also If I put a dial indicator in the center of the bridge and 
hit the bridge forward or backward it will flex and wobble enough to displace 
the dial indicator +/-0.03 and it takes nearly a dozen wobbles to dampen it.  
But on the ends the servo's only have a few thousandths of give.

I'm less concerned about the actual stiffness and more worried about dampening 
the wobble.

Todd Zuercher
P. Graham Dunn 
Inc.>
630 Henry Street
Dalton, Ohio 44618
Phone:  (330)828-2105ext. 2031


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Re: [Emc-users] Beam Stiffening?

[Dale Ertley via Emc-users]

 Small blocks on the outside middle of beam on 3 or 4 sides of the beam with 
small aircraft cable attached to each end pulled tight.
Use small turn buckles to tighten the cables over the block on that one 
side.You may be able to reduce the mass of the beam with the added stiffness of 
the blocks and cables.
Be safe.
Dale
On Monday, May 13, 2024 at 07:31:34 PM EDT, Ralph Stirling via Emc-users 
 wrote:  
 
 Can you run a steel cable through it and tension it?  Might stiffen it up some.

-- Ralph

On May 13, 2024 1:46 PM, Todd Zuercher via Emc-users 
 wrote:
CAUTION: This email originated from outside the Walla Walla University email 
system.


Anyone have any brilliant ideas to stiffen a woefully inadequate cross beam on 
a gantry router without adding too much mass?  What is there now is a 4" x 8" 
rectangular 3/8" walled extrusion that is 145" long.

Under normal jogging commands the two servos control the ends of this gantry 
reasonably well, but while the axis is homing the thing shakes and wobbles 
terribly bad.  Also If I put a dial indicator in the center of the bridge and 
hit the bridge forward or backward it will flex and wobble enough to displace 
the dial indicator +/-0.03 and it takes nearly a dozen wobbles to dampen it.  
But on the ends the servo's only have a few thousandths of give.

I'm less concerned about the actual stiffness and more worried about dampening 
the wobble.

Todd Zuercher
P. Graham Dunn 
Inc.>
630 Henry Street
Dalton, Ohio 44618
Phone:  (330)828-2105ext. 2031


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Re: [Emc-users] Beam Stiffening?

[Ralph Stirling via Emc-users]

Can you run a steel cable through it and tension it?  Might stiffen it up some.

-- Ralph

On May 13, 2024 1:46 PM, Todd Zuercher via Emc-users 
 wrote:
CAUTION: This email originated from outside the Walla Walla University email 
system.


Anyone have any brilliant ideas to stiffen a woefully inadequate cross beam on 
a gantry router without adding too much mass?  What is there now is a 4" x 8" 
rectangular 3/8" walled extrusion that is 145" long.

Under normal jogging commands the two servos control the ends of this gantry 
reasonably well, but while the axis is homing the thing shakes and wobbles 
terribly bad.  Also If I put a dial indicator in the center of the bridge and 
hit the bridge forward or backward it will flex and wobble enough to displace 
the dial indicator +/-0.03 and it takes nearly a dozen wobbles to dampen it.  
But on the ends the servo's only have a few thousandths of give.

I'm less concerned about the actual stiffness and more worried about dampening 
the wobble.

Todd Zuercher
P. Graham Dunn 
Inc.>
630 Henry Street
Dalton, Ohio 44618
Phone:  (330)828-2105ext. 2031


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Re: [Emc-users] Beam Stiffening?

[andy pugh]

On Mon, 13 May 2024 at 22:50, Chris Albertson 
wrote:

> Adding anything inside is the worst place to add material.


Yes, without a doubt, but it seems fair to assume that the ganry has slides
and other components on the outside, but not on the inside.

The base beam has an Iyy (bending in the plane of the smaller dimension )
of 22in^4
Doubling it internally gives: 34.2in^4, so about 50% stiffer
Doubling externally gives: 57in^4 so getting on for 3x as stiff.

I admit I was imagining a thinner wall thickness relative to the overall
dimensions, where the difference would be smaller.

There is less to be gained than you might think from making the section
solid. You can do the experiments here:
https://amesweb.info/section/second-moment-of-area-calculator.aspx

If stiffness is the key, then add a stiff material.
Aluminium is 68GPa (moving away from measuring in bananas)
Steel is 200GPa (this is the same for all iron alloys, hardened or
unhardened, including cast iron)
Titanium is 114GPa, so good for light, not for stiff.
Carbon fibre is 181Gpa for uindirectional fibres, but more typically around
50GPa.
Tungsten carbide is 600GPa (which is why solid carbide boring bars exist)
Beryllium is 287 but probably out of both budget and COSHH limits.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is designed
for the especial use of mechanical geniuses, daredevils and lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912

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Re: [Emc-users] Beam Stiffening?

[Chris Albertson]

Adding anything inside is the worst place to add material.   Add it outside.   
Stiffness is the cube of the beam thickness, so you really want to make it 
bigger.

Then secondary to making it bigger is to improve the shape to remove those 
parallel sides.  

So it you are just going to epoxy something on, try adding something like a 
channel section to the top or side of the beam.




> On May 13, 2024, at 2:11 PM, andy pugh  wrote:
> 
> On Mon, 13 May 2024 at 21:51, Todd Zuercher via Emc-users <
> emc-users@lists.sourceforge.net> wrote:
> 
>> 
>> I'm less concerned about the actual stiffness and more worried about
>> dampening the wobble.
>> 
> 
> Maybe you could epoxy a smaller (aluminium?) extrusion or box inside the
> existing one? The epoxy interface should add some damping.
> 
> 
> -- 
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is designed
> for the especial use of mechanical geniuses, daredevils and lunatics."
> — George Fitch, Atlanta Constitution Newspaper, 1912
> 
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Re: [Emc-users] Beam Stiffening?

[Chris Albertson]

> On May 13, 2024, at 1:45 PM, Todd Zuercher via Emc-users 
>  wrote:
> 
> Anyone have any brilliant ideas to stiffen a woefully inadequate cross beam 
> on a gantry router without adding too much mass?  What is there now is a 4" x 
> 8" rectangular 3/8" walled extrusion that is 145" long.
> 
> Under normal jogging commands the two servos control the ends of this gantry 
> reasonably well, but while the axis is homing the thing shakes and wobbles 
> terribly bad.  Also If I put a dial indicator in the center of the bridge and 
> hit the bridge forward or backward it will flex and wobble enough to displace 
> the dial indicator +/-0.03 and it takes nearly a dozen wobbles to dampen it.  
> But on the ends the servo's only have a few thousandths of give.
> 
> I'm less concerned about the actual stiffness and more worried about 
> dampening the wobble.


What is the extrusion made of, I assume it is some kind of aluminum alloy.
The simplest but expensive option is to replace it with a stronger/stiffer 
material with the same dimensions.   Of course Titanium comes to mind but that 
is maybe not in the budget.Carbon fiber could work and it is possible to 
DIY carbon fiber beams with just hand tools.   I have made 4 meter long racing 
kayaks with carbon, using just a paint brush and scissors in one weekend.   

The first class way is to make a female mold and polish it well so the part 
looks nice.   The cheap way is to make one like they make surfboards.  You 
start with a foam block, shape it then wrap it in fiber and resin.

The neat thing about carbon composite is that you are not limited to the 
extrusion shape.   I would make the entire beam a compound curve with no flat 
or straight or cylindrical sections,  Maybe like a very elongated American 
football but with ovil cross section.

I like to use the car hood story.  A flat sheet of sheet steel is bendable by 
hand.  But after they stamp it into the shape of a car hood it becomes rigid.   
So rather then a square tube, way not oval but with a larger diameter in the 
center where all the bending force is?

The way you make it is to first make a full-size model out of wood and bondo. 
Do a test-fit and give it an automotice grade paint finsh and then paste wax.  
Make a fiber glass mold, then from that your part.   Yes that is a lot of work. 
 This is why you have an aluminum extrusion there now, because that was easy 
and cheap.






> 
> Todd Zuercher
> P. Graham Dunn Inc.
> 630 Henry Street
> Dalton, Ohio 44618
> Phone:  (330)828-2105ext. 2031
> 
> 
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Re: [Emc-users] Global Named Parameter?

[John Allwine]

I still think analog inputs/outputs could be a good way to go. I haven't
run any of this, but something like this for the Python HAL component:

https://gist.github.com/jallwine/1a0ad4ffcee00f31e286c485ea38a609

And something like this to hook it up in HAL:

https://gist.github.com/jallwine/da023f11d859a7ae4d4a8b6974524386

Then you can use "M66 E0 L0" to copy the offset for joint 0 into #5399 if
you need to know what it is in G code. You can also use "M68 E0 Q0.1234" to
set the offset for joint 0. Change the E value to change which joint you
want to configure.


On Fri, May 10, 2024 at 12:56 PM Todd Zuercher via Emc-users <
emc-users@lists.sourceforge.net> wrote:

> Is there a way to bring out a tool offset to a hal pin?
>
> Here is a better description of what I'm trying to do.  On this gang
> router machine I'm working on.  I created an extra joint for each of the 8
> stepper motors that move each of the 8 spindle Z axis.  In the config I
> have the Z axis connected to a dummy joint that doesn't actually do
> anything.  I have 8 enable signals from a gladevcp that can turn on/off
> each spindle.  When a spindle is enabled the spindle run signal is
> connected to the VFD for that spindle, and the position command from the
> dummy Z axis joint is connected to that spindle's extra Z-axis joint plus
> an offset.  I want to use that offset to adjust for tool and material
> height differences between each of the spindles.  When the spindle is
> disabled, the spindle's extra joint is moved up to it's "zero" home
> position and the VFD is disabled.
>
> I want the machine operator to both be able to manually make adjustments
> to that offset between the Z-axis command and extra spindle joint, and be
> able to use a probing routine to touch off the tool using a touch probe.
> Initially I thought it would work well to use 8 tool offsets for this, but
> I'm unsure of the best way to put those tool offset values on hal pins to
> connect them to the offset pins.  The machine will not be using T codes or
> G43 tool offsets in the G-code, so using the tool table in not quite the
> normal fashion shouldn't cause any problems.
>
> Todd Zuercher
> P. Graham Dunn Inc.
> 630 Henry Street
> Dalton, Ohio 44618
> Phone:  (330)828-2105ext. 2031
>
> From: andy pugh 
> Sent: Thursday, May 09, 2024 7:33 PM
> To: Enhanced Machine Controller (EMC) 
> Cc: Todd Zuercher 
> Subject: Re: [Emc-users] Global Named Parameter?
>
>
> [EXTERNAL EMAIL] Be sure links are safe.
>
>
> On Thu, 9 May 2024 at 18:55, Todd Zuercher via Emc-users <
> emc-users@lists.sourceforge.net>
> wrote:
> I would like to create a few persistent global named parameters.
>
> Hmmm
>
> You can make numbered parameters persistent simply by adding them to the
> .vars file.
>
>  So one way would be to run a subroutine in STARTUP_G_CODES which
> transfers persistent numerical parameters into named ones.
> But that leaves the storage of them unsolved.
>
> I did something like you describe with a Python HAL component a while ago.
> Maybe this can be modified to do the trick for you?
>
>
> https://forum.linuxcnc.org/38-general-linuxcnc-questions/50010-stmbl-pseudo-absolute-resolver-behaviour#280386
>
> It basically loads some values from a file at startup, then saves the
> values to file at shutdown.
>
> https://forum.linuxcnc.org/38-general-linuxcnc-questions/50010-stmbl-pseudo-absolute-resolver-behaviour#280386
>
> --
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is designed
> for the especial use of mechanical geniuses, daredevils and lunatics."
> - George Fitch, Atlanta Constitution Newspaper, 1912
>
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Re: [Emc-users] Beam Stiffening?

[andy pugh]

On Mon, 13 May 2024 at 21:51, Todd Zuercher via Emc-users <
emc-users@lists.sourceforge.net> wrote:

>
> I'm less concerned about the actual stiffness and more worried about
> dampening the wobble.
>

Maybe you could epoxy a smaller (aluminium?) extrusion or box inside the
existing one? The epoxy interface should add some damping.


-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is designed
for the especial use of mechanical geniuses, daredevils and lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912

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[Emc-users] Beam Stiffening?

[Todd Zuercher via Emc-users]

Anyone have any brilliant ideas to stiffen a woefully inadequate cross beam on 
a gantry router without adding too much mass?  What is there now is a 4" x 8" 
rectangular 3/8" walled extrusion that is 145" long.

Under normal jogging commands the two servos control the ends of this gantry 
reasonably well, but while the axis is homing the thing shakes and wobbles 
terribly bad.  Also If I put a dial indicator in the center of the bridge and 
hit the bridge forward or backward it will flex and wobble enough to displace 
the dial indicator +/-0.03 and it takes nearly a dozen wobbles to dampen it.  
But on the ends the servo's only have a few thousandths of give.

I'm less concerned about the actual stiffness and more worried about dampening 
the wobble.

Todd Zuercher
P. Graham Dunn Inc.
630 Henry Street
Dalton, Ohio 44618
Phone:  (330)828-2105ext. 2031


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Re: [Emc-users] Global Named Parameter?

[andy pugh]

On Fri, 10 May 2024 at 21:11, Todd Zuercher  wrote:

> But I need to read them when they are not applied.
>

You could apply them, read them, then revert.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is designed
for the especial use of mechanical geniuses, daredevils and lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912

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