Re: [Emc-users] linuxcnc-sim on Mint 17.1 LTS

[Gene Heskett]

On Friday 02 January 2015 10:19:12 Sebastian Kuzminsky did opine
And Gene did reply:
> On 01/02/2015 08:04 AM, Gene Heskett wrote:
> > On Thursday 01 January 2015 23:12:22 Sebastian Kuzminsky did opine
> > 
> >> I personally prefer Debian Wheezy, which works "out of the box"
> >> using the new Live/Install Image.  Instructions for that are here:
> >> 
> >> http://www.linuxcnc.org/docs/2.7/html/getting-started/index.html#_ge
> >> tti ng_linuxcnc
> > 
> > This wheezy has a pae kernel?  Downloading now.
> 
> Yep, on Wheezy we have an RTAI kernel for i686 with PAE.

So I see Seb, as I've spent 4 of the last 6 hours installing and loading 
it up for bear hunting, or whatever.  The other two were spent carving up 
some screw hole plugs out of ebony, I took a break IOW.  The 4 spline 
decorators are done, and now 6 of the 12 screw covers are done & glued in.

Wheezy is a breath of fresh air, hell, even the networking worked once I 
filled in the blanks.  Anything with a buntu label on it for the last 8 
years has made me do it my way and mark everything related immutable so 
networkmangler can't screw it up.  I've done that so many times, including 
with this 10.04.4 LTS install, that I can do it in my sleep I think.  But 
wheezy Just Worked(TM), as did synaptic so what took me several days when 
I loaded this 1.04.4 LTS originally, will likely be done to the point of 
even having my web server in the sig back on line by the next time I 
switch drives and reboot to it.

Another pleasant surprise is that KDE is an older version, so kmail is 
1.13.7 and should not have a huge config problem bringing that back up as 
this one is 1.13.5.  I am half tempted to just copy the older .kde subdir 
in my /home to that one and see if it makes anything puke.

That way I'd already have all my filter settings, accounts, the whole 
maryann.  I am positively drooling at that prospect. :)

So if my web page works, and kmail works, this drive then becomes a 
mountable cache to go get the stuff I forgot.

Many many thanks for the wheezy suggestion from linuxcnc.org Seb.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 
US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS

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Re: [Emc-users] Advanced bipod question

[TJoseph Powderly]

On 01/02/2015 12:10 PM, John Kasunich wrote:
>
>
> On Fri, Jan 2, 2015, at 01:03 PM, andy pugh wrote:
>> On 2 January 2015 at 17:58, John Kasunich  wrote:
>>> Also, I have a simple mechanical question:  How is the cutting wire
>>> kept tight?  Cable bipods don't have any ability to resist tension
>>> perpendicular to their plane.
>>
>> The archetypical version uses a wooden C-frame to tension and weight the 
>> wire:
>> http://www.cnc-hotwire.de
>>
>
> In that case, you only have the errors caused by the controlled point(s) 
> moving
> out-of-plane when the cutting wire is tilted.  Small for modest tilts, but 
> increasing
> rapidly with angle.  Dan mentioned angles up to 22.5 degrees.
>
> If one controlled point could be constrained in all three directions, then 
> the kins
> to compute the location of the other controlled point (and all four bipod 
> cable
> lengths) are relatively straightforward.
>
>
re hotwire foam cutter xyuv like wedm stuff
our german friend left for the forest and took down most of his videos
but heres some info on his implementation
i saw videos of the two xy pairs in motion
he was magic33de  or  ??? in the irc ichgoodlive??
he mad a boatload of linuxcnc videos and tutorials
https://code.google.com/p/emc2hotwinch/
hth
tomp tjtr33

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Re: [Emc-users] Advanced bipod question

[John Kasunich]

On Fri, Jan 2, 2015, at 01:03 PM, andy pugh wrote:
> On 2 January 2015 at 17:58, John Kasunich  wrote:
> > Also, I have a simple mechanical question:  How is the cutting wire
> > kept tight?  Cable bipods don't have any ability to resist tension
> > perpendicular to their plane.
> 
> The archetypical version uses a wooden C-frame to tension and weight the wire:
> http://www.cnc-hotwire.de
> 

In that case, you only have the errors caused by the controlled point(s) moving
out-of-plane when the cutting wire is tilted.  Small for modest tilts, but 
increasing
rapidly with angle.  Dan mentioned angles up to 22.5 degrees.

If one controlled point could be constrained in all three directions, then the 
kins
to compute the location of the other controlled point (and all four bipod cable
lengths) are relatively straightforward.


-- 
  John Kasunich
  jmkasun...@fastmail.fm

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Re: [Emc-users] Advanced bipod question

[andy pugh]

On 2 January 2015 at 17:58, John Kasunich  wrote:
> Also, I have a simple mechanical question:  How is the cutting wire
> kept tight?  Cable bipods don't have any ability to resist tension
> perpendicular to their plane.

The archetypical version uses a wooden C-frame to tension and weight the wire:
http://www.cnc-hotwire.de



-- 
atp
If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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Re: [Emc-users] Advanced bipod question

[John Kasunich]

On Thu, Jan 1, 2015, at 04:40 PM, andy pugh wrote:
> On 1 January 2015 at 02:16, poormansairforce H
>  wrote:
> 
> > I have been trying to join the forum but can't get past the registration
> > page, says there are errors:(
> 
> You will get better answers here anyway.
> 
> > I have a question about setting up a bipod hot wire cutter. Simply, in CAD
> > I have figured out that on my dream machine setup, at a 4' 6" cutting
> > length when the wire is angled 22.5 degrees on the vertical axis the wire
> > moves 3mm from its intended position due to the attach points swinging in
> > to compensate for the shortening of its length.
> 
> I don't quite get what you are saying. Is this an effect in addition
> to the simple calculations in the kinematics module?
> 
> Can you expand the "its" into the actual components being discussed?
> Maybe you are looking at the effect of the pulley diameter not being
> infinitesimal?
> 
> -- 

I think he's saying he has two "Hektor" type cable bipods, each
controlling one end of a hot-wire to cut foam.

Normal Hektor kinematics assumes that the controlled point moves
in a plane.  In this case, there are two parallel planes, separated by
the length of the cutting wire - but only when the cutting wire is
perpendicular to each plane.  When the cutting wire is angled, you
have two possibilities:

1) the controlled points remain in the original planes, but the distance
between them (and thus the length of the cutting wire) changes.
This case lets you use the standard hektor kinematics, but has 
difficult mechanical issues with constraining the controlled points
to stay in the planes, and managing the variable length cutting wire.

2) one or both controlled points are pulled out of the original planes
so that the cutting wire length doesn't change.  Pulling a controlled
point out of its original plane invalidates the hektor kinematics.  The
error is small when the controlled point is far from the pulleys, but
gets larger close to the pulleys.  (And, when you get sufficiently
close to the pulleys with a sufficient angle, the whole thing fails.)

I'm pretty sure he is asking about case 2.  This will require custom
kinematics.

In addition, case 2 is under-constrained.  When the cutting wire is
angled, it will pull inward on both controlled points.  How much does
each controlled point move inward?  The corrections needed depend
on how the inward movement is divided between the two bipods.

Also, I have a simple mechanical question:  How is the cutting wire
kept tight?  Cable bipods don't have any ability to resist tension
perpendicular to their plane.

If I was building such a beast, I'd be tempted to use cable tripods
on each end.  Turned sideways, so that the tension on the cutting
wire keeps all six tripod wires tight.  I'd add a spring in-line with
the cutting wire to absorb any minor errors in the kinematics.

It would still require custom kins, but the system is fully constrained.
First compute the X,Y,Z position of one controlled point, then use
U and V angles plus the length of the cutting wire to compute X,Y,Z
for the other controlled point.  Then compute the lengths of the six
tripod wires by solving for the distance between each controlled
point and the winch points.

-- 
  John Kasunich
  jmkasun...@fastmail.fm

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Re: [Emc-users] linuxcnc-sim on Mint 17.1 LTS

[Sebastian Kuzminsky]

On 01/02/2015 08:04 AM, Gene Heskett wrote:
> On Thursday 01 January 2015 23:12:22 Sebastian Kuzminsky did opine
>>
>> I personally prefer Debian Wheezy, which works "out of the box" using
>> the new Live/Install Image.  Instructions for that are here:
>>
>> http://www.linuxcnc.org/docs/2.7/html/getting-started/index.html#_getti
>> ng_linuxcnc
> 
> This wheezy has a pae kernel?  Downloading now.

Yep, on Wheezy we have an RTAI kernel for i686 with PAE.


-- 
Sebastian Kuzminsky

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Re: [Emc-users] linuxcnc-sim on Mint 17.1 LTS

[Gene Heskett]

On Thursday 01 January 2015 23:12:22 Sebastian Kuzminsky did opine
And Gene did reply:
> On 01/01/2015 08:59 PM, Gene Heskett wrote:
> > So, what amd64 flavor of Ubuntu stands the best chance of working
> > with the existing repo's?  And which name do I then put in
> > /etc/apt/sources.list?
> 
> I run LinuxCNC on Ubuntu Precise (12.04) on some of my machines.  I'm
> not a fan of the Ubuntu UI, but it works.  Instructions here:
> 
> http://www.linuxcnc.org/docs/2.7/html/getting-started/index.html#_insta
> lling_on_ubuntu_precise
> 
> 
> I personally prefer Debian Wheezy, which works "out of the box" using
> the new Live/Install Image.  Instructions for that are here:
> 
> http://www.linuxcnc.org/docs/2.7/html/getting-started/index.html#_getti
> ng_linuxcnc

This wheezy has a pae kernel?  Downloading now.


Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 
US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS

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