Re: [Emc-users] Using CNC mill to hack a gantry Crane

[Gregg Eshelman]

Some weld metal is very hard. Try a hand file on a weld bead to see how easy it 
cuts. If you can't shave off a decent amount with moderate hand pressure you'll 
have a heck of a time milling the weld.
How thick is the tubing wall? One solution could be to cut the end off, leaving 
a short stub, about 1/4" long. Mill the inside to a precise square, about 
halfway through the wall thickness. For the shortened beam, mill flats on each 
face then round the corners so you get a snug fit into the inside of the stub.
Then weld a big fillet over the original weld, perhaps after grinding much of 
it away.

 
  From: hubert 
 To: Emc-users@lists.sourceforge.net 
 Sent: Saturday, October 15, 2016 8:57 PM
 Subject: [Emc-users] Using CNC mill to hack a gantry Crane
   
I am wanting to cut down a 1000lb rated gantry crane to a size that will 
fit my Shop.  This crane is made from 2" rectangular tubing.  I will do 
the initial cutting with a Harbor Freight band saw, but I can't count on 
it giving true 90 degree cuts.  My thoughts are to true the cut surface 
with my mill.  I will also be cutting off the flange that will be welded 
back on the tubing.  My thoughts were to use the mill true the surface 
of the flange.
    My questions are related to the welds that I am trimming off. Will 
they cause problems for the mill?  Is it better to use High steel or 
carbide?
   
 
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Re: [Emc-users] Wat OT: Question about injection molding of PVC

[linden]

  When I worked  for a semi conductor tool manufacture we used to 
plastic weld the drip trays out of PVC and Chemistry tanks out of other 
plastics for HF, H2SO4 and other nastiness.

   The process is very similar to Tig welding metal. We used a hot air 
gun and a filler rod to fuse and fill the seems. As with Tig welding 
joint prep and weld temp is key. With a little practice it is not hard 
to get sound joints and it is much easer than metal as you can see what 
you are doing and work with out gloves. The only real issue are the 
fumes released from the melting plastic.

You probably already have a miter saw to cut with and a good table to 
clamp your PVC to the cost of a welder filler rod and some scrap to 
practice on would most certainly be less than building an injection 
machine and certainly more versatile.   Not as fun mind you;-)


  n 2016-10-15 08:33 PM, Erik Christiansen wrote:
> On 15.10.16 22:44, Leonardo Marsaglia wrote:
>> Yes the idea is to machine the four strips and then joing them strongly. To
>> clamp the mold I was thinking about mechanical ways like eccentrics or may
>> be screw clamps. That way I can hold the mold together when the injection
>> takes place. I really don't worry about the time consumption on open the
>> mold and close it again.
> <2c>
> If joining by solvent is too weak or unsightly, have you considered "pvc
> welding"?. I haven't used the process, but google offers myriad hits.
> I've seen ¼" thick PVC with a rippled joint looking much like a weld in
> steel. It may have been done on both sides, though, for complete
> penetration. (I don't recall.)
>
> OK, if molten plastic injection into the joint were a viable option,
> then the mould restraining force would be _much_ less than if moulding a
> large flat object from scratch, but just clamping four sheets for
> welding is orders of magnitude simpler & cheaper. I can't imagine that
> plastic welding gear is in the same ballpark as injection moulding,
> either.
>
> I suspect that molten filler material would need to be run straight from
> nozzle to every point of joining, i.e. run a nozzle along the joint. If
> injected at a central sprue, it would be too cold to melt the PVC strips
> for adequate fusing. (But that is speculation.)
> 
>
> Erik
>
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Re: [Emc-users] Wat OT: Question about injection molding of PVC

[Gregg Eshelman]

Look up how PVC house window frames are made. They use extrusions, cut the 
corners at 45 degrees then melt them together.
Here's a video on a portable corner welding machine. 
https://www.youtube.com/watch?v=cni6XdgOTj0



 
  From: John Kasunich 
 To: emc-users@lists.sourceforge.net 
 Sent: Saturday, October 15, 2016 7:33 PM
 Subject: Re: [Emc-users] Wat OT: Question about injection molding of PVC
   
Injection pressure will be trying to force the two sides of your mold apart.
That's why injection molds are made of tool steel, and injection machines have 
VERY sturdy construction to hold the mold closed.  I saw a machine that might 
be big enough to make your parts - the mold closing cylinder was about 2 feet 
(0.6m) in diameter, and the four steel tie-rods that held the machine together 
against the clamp force were about 100mm diameter.

Could you make it out of four strips with some kind of joining at the corners?

John Kasunich

   
 
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Re: [Emc-users] belt calculators, a PITA

[Gene Heskett]

On Saturday 15 October 2016 22:29:50 MC Cason wrote:

> Gene,
>
> On 10/15/2016 08:53 PM, Gene Heskett wrote:
> > Greetings all;
> >
> > I just spent about 3 hours playing around with the 20 or so belt
> > calculators google gave me links to, but not on of them could give
> > me any answers.
> >
> > One would think, for an XL belt that
> >
> > 1. width is a never mind since xl's are available in a plethora of
> > widths, none of which should have any effect on the profile the belt
> > assumes when snug enough to do the job.
> >
> > 2. Its a pair of pulleys for xl belting, and the pitch diameter can
> > be instantly defined by the belt profile, xl in this case, and
> > minorly the number of teeth might have a slight effect when dealing
> > with very low tooth count pulleys.  The belt pitch is a nearly
> > constant height above the teeth, and the teeth diameter is derived
> > from the xl tooth length times the number of teeth.
> >
> > I am shooting for a shaft center to center between 4.875 and 5.0".
> >
> > Given that center to center on a pair of xl pulleys of 20 teeth and
> > 40 teeth, that really should be all that its needed to know to tell
> > me I need a 112? tooth belt.  Then its up to me to see if I've room
> > for the pull needed to use the next higher tooth count belt.  Or do
> > I mount an idler to adjust it so a stock belt will work?
> >
> > I am probably going to go thru that same eye of the needle for the Z
> > belt, but I've some mounting brackets yet to be whittled out to get
> > a 2505x1450mm screw mounted straight.
> >
> > Does anyone have a belt calculator that actually works?
> >
> > Thanks everybody.
> >
> > Cheers, Gene Heskett
>
Looks good. I didn't look to see if they had a 79 tooth version, likely 
not, but I can probably rig it so the 80 tooth will work.  But I'll have 
to call them Monday since their checkout is actually a registration.

> This is my go-to belt calculator:
> https://sdp-si.com/eStore/CenterDistanceDesigner
>
> Desired center distance: 4.8750"
>79 grooves - 4.8582"
>80 grooves - 4.9591"
>81 grooves - 5.0599"
>
>Actual screenshot sent to you as PM.

Thank you very much MC Cason.

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 

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Re: [Emc-users] Wat OT: Question about injection molding of PVC

[Erik Christiansen]

On 15.10.16 22:44, Leonardo Marsaglia wrote:
> Yes the idea is to machine the four strips and then joing them strongly. To
> clamp the mold I was thinking about mechanical ways like eccentrics or may
> be screw clamps. That way I can hold the mold together when the injection
> takes place. I really don't worry about the time consumption on open the
> mold and close it again.

<2c>
If joining by solvent is too weak or unsightly, have you considered "pvc
welding"?. I haven't used the process, but google offers myriad hits.
I've seen ¼" thick PVC with a rippled joint looking much like a weld in
steel. It may have been done on both sides, though, for complete
penetration. (I don't recall.)

OK, if molten plastic injection into the joint were a viable option,
then the mould restraining force would be _much_ less than if moulding a
large flat object from scratch, but just clamping four sheets for
welding is orders of magnitude simpler & cheaper. I can't imagine that
plastic welding gear is in the same ballpark as injection moulding,
either.

I suspect that molten filler material would need to be run straight from
nozzle to every point of joining, i.e. run a nozzle along the joint. If
injected at a central sprue, it would be too cold to melt the PVC strips
for adequate fusing. (But that is speculation.)


Erik

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[Emc-users] Using CNC mill to hack a gantry Crane

[hubert]

I am wanting to cut down a 1000lb rated gantry crane to a size that will 
fit my Shop.  This crane is made from 2" rectangular tubing.  I will do 
the initial cutting with a Harbor Freight band saw, but I can't count on 
it giving true 90 degree cuts.  My thoughts are to true the cut surface 
with my mill.  I will also be cutting off the flange that will be welded 
back on the tubing.  My thoughts were to use the mill true the surface 
of the flange.
My questions are related to the welds that I am trimming off. Will 
they cause problems for the mill?  Is it better to use High steel or 
carbide?

Thanks
Hubert

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Re: [Emc-users] Hacking a sim runtime mode

[Dewey Garrett]

Trajectory planners used with all LinuxCNC releases have
employed trapezoidal velocity profiles (e.g. fixed accels,
no jerk limiting).  With trapezoidal planning used for both
rapids and feed moves the only individual segment motion
types are:

  1) velocity ramp segment:
 v = a * t
 x = 0.5 * a * t^2
 time for a segment: t = sqrt(2 * x /a)

  2) fixed velocity segment:
 x = v * t
 time for a segment: t = x / v

To speed up by a factor K (with resulting elapsed times of
t/K) for both segment types, it is necessary to set:

a' = K^2 * a
v' = K   * v

For testing, it is convenient to use a sim configuration
that just connects motion cmd pins to motion fb pins.
Gcode programs used for testing prediction linearity
should have no:
   pauses
   waits for spindle speed
   tool changes
   probes
or any other commands which take fixed or variable amounts
of time unrelated to motion planning.

I used a script to set inihal pins for velocity and
acceleration and to measure program run times. The script
accepts a multiplier (K) and:

  1) increases all inihal velocity pin settings by K
  2) increases all inihal acceleration pin settings by K^2.
  3) uses halui pins to increase the feed override by K
 (For the axis gui, the setting [DISPLAY]MAX_FEED_OVERRIDE
 should be set to a large value so that halui feed-override
 settings are not limited.)

I tested using a gcode program based on nc_files/tort.ngc
modified to:
  1) eliminate the single pause (m0) line
  2) put the main code in a subroutine and run multiple
 iterations to get a total program runtime of about
 90 minutes (at normal speed/accel settings).
  
Test results:

K (multiplier)= 1 measured time =   5406 secs (baseline)
K (multiplier)= 2 measured time =   2704
K (multiplier)= 5 measured time =   1083
K (multiplier)=10 measured time =543
K (multiplier)=20 measured time =270
K (multiplier)=50 measured time =109
K (multiplier)=   100 measured time = 56
K (multiplier)=   200 measured time = 30
K (multiplier)=   500 measured time = 14

So, predicting runtimes by scaling (acceleration, velocity,
feed) may be good enough for this example for scaling
factors up to about 100.  For higher scaling values (or
shorter gcode programs), time offsets unrelated to motion
and/or second-order affects reduce the usefulness of the
prediction -- i didn't investigate further.


-- 
Dewey Garrett


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Re: [Emc-users] belt calculators, a PITA

[MC Cason]

Gene,

On 10/15/2016 08:53 PM, Gene Heskett wrote:
> Greetings all;
>
> I just spent about 3 hours playing around with the 20 or so belt
> calculators google gave me links to, but not on of them could give me
> any answers.
>
> One would think, for an XL belt that
>
> 1. width is a never mind since xl's are available in a plethora of
> widths, none of which should have any effect on the profile the belt
> assumes when snug enough to do the job.
>
> 2. Its a pair of pulleys for xl belting, and the pitch diameter can be
> instantly defined by the belt profile, xl in this case, and minorly the
> number of teeth might have a slight effect when dealing with very low
> tooth count pulleys.  The belt pitch is a nearly constant height above
> the teeth, and the teeth diameter is derived from the xl tooth length
> times the number of teeth.
>
> I am shooting for a shaft center to center between 4.875 and 5.0".
>
> Given that center to center on a pair of xl pulleys of 20 teeth and 40
> teeth, that really should be all that its needed to know to tell me I
> need a 112? tooth belt.  Then its up to me to see if I've room for the
> pull needed to use the next higher tooth count belt.  Or do I mount an
> idler to adjust it so a stock belt will work?
>
> I am probably going to go thru that same eye of the needle for the Z
> belt, but I've some mounting brackets yet to be whittled out to get a
> 2505x1450mm screw mounted straight.
>
> Does anyone have a belt calculator that actually works?
>
> Thanks everybody.
>
> Cheers, Gene Heskett

This is my go-to belt calculator:
https://sdp-si.com/eStore/CenterDistanceDesigner

Desired center distance: 4.8750"
   79 grooves - 4.8582"
   80 grooves - 4.9591"
   81 grooves - 5.0599"

   Actual screenshot sent to you as PM.





-- 
MC Cason
Eagle3D - Created by Matthias Weißer
github.com/mcason/Eagle3D



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[Emc-users] belt calculators, a PITA

[Gene Heskett]

Greetings all;

I just spent about 3 hours playing around with the 20 or so belt 
calculators google gave me links to, but not on of them could give me 
any answers.

One would think, for an XL belt that

1. width is a never mind since xl's are available in a plethora of 
widths, none of which should have any effect on the profile the belt 
assumes when snug enough to do the job.

2. Its a pair of pulleys for xl belting, and the pitch diameter can be 
instantly defined by the belt profile, xl in this case, and minorly the 
number of teeth might have a slight effect when dealing with very low 
tooth count pulleys.  The belt pitch is a nearly constant height above 
the teeth, and the teeth diameter is derived from the xl tooth length 
times the number of teeth.

I am shooting for a shaft center to center between 4.875 and 5.0".

Given that center to center on a pair of xl pulleys of 20 teeth and 40 
teeth, that really should be all that its needed to know to tell me I 
need a 112? tooth belt.  Then its up to me to see if I've room for the 
pull needed to use the next higher tooth count belt.  Or do I mount an 
idler to adjust it so a stock belt will work?

I am probably going to go thru that same eye of the needle for the Z 
belt, but I've some mounting brackets yet to be whittled out to get a 
2505x1450mm screw mounted straight.

Does anyone have a belt calculator that actually works?

Thanks everybody.

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 

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Re: [Emc-users] Wat OT: Question about injection molding of PVC

[Leonardo Marsaglia]

2016-10-15 22:33 GMT-03:00 John Kasunich :

> Injection pressure will be trying to force the two sides of your mold
> apart.
> That's why injection molds are made of tool steel, and injection machines
> have VERY sturdy construction to hold the mold closed.  I saw a machine
> that might be big enough to make your parts - the mold closing cylinder was
> about 2 feet (0.6m) in diameter, and the four steel tie-rods that held the
> machine together against the clamp force were about 100mm diameter.
>
> Could you make it out of four strips with some kind of joining at the
> corners?
>

Hello John.

Yes the idea is to machine the four strips and then joing them strongly. To
clamp the mold I was thinking about mechanical ways like eccentrics or may
be screw clamps. That way I can hold the mold together when the injection
takes place. I really don't worry about the time consumption on open the
mold and close it again.

The concerning part I have is if It's a good idea to move the pistons for
the injection with a screw and a common 3 phase AC motor. My idea is to
load the piston, wait for the plastic to reach the temperature and then
inject no less than 30 seconds. I probably have to preheat the mold too.


-- 
*Leonardo Marsaglia*.
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Re: [Emc-users] Wat OT: Question about injection molding of PVC

[John Kasunich]

Injection pressure will be trying to force the two sides of your mold apart.
That's why injection molds are made of tool steel, and injection machines have 
VERY sturdy construction to hold the mold closed.  I saw a machine that might 
be big enough to make your parts - the mold closing cylinder was about 2 feet 
(0.6m) in diameter, and the four steel tie-rods that held the machine together 
against the clamp force were about 100mm diameter.

Could you make it out of four strips with some kind of joining at the corners?

John Kasunich


On Sat, Oct 15, 2016, at 08:12 PM, Leonardo Marsaglia wrote:
> Hello to all.
> 
> I'm sure here I'm going to find good answers so I decided to start from
> here.
> 
> I'm planning to do some thermoforming production work but the sheet plastic
> I need to use is rectangular with a rectangular hole in the middle (I
> attached a picture so you can see). So to use regular PVC sheet would imply
> a lot of waste.
> 
> I came up with the idea of injecting the PVC using a manual clamped mould
> and injecting it with a screw driven piston. The difficult part comes here,
> I need to inject almost 3 kg of PVC. The moulds are going to be pretty
> simple as you can see but I would like to know if there's any good source
> to determine the approximate power I would need to drive the screw that
> moves the piston.
> 
> There's the possibility of using two pistons one on each side to make
> things easier. Off course I would need to reduce the motors with worm and
> gear and then connect the gear to the screw that drives the piston. But my
> main concern is if this approach is correct or if I should forget about it.
> 
> I didn't even consider the hydraulic pump because the cost would be a lot.
> Also take into account that I'm not intending to make lots of these
> injections per hour, so injection times could be slower than the industry
> standard.
> 
> I hope I've been clear about my doubts and I would be thankful if you can
> point me to any source of info about this, or help me to be more sure about
> the dimensions of what I need to do.
> 
> Thanks as always!
> 
> -- 
> *Leonardo Marsaglia*.
> --
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> Email had 1 attachment:
> + shape.png
>   360k (image/png)


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  jmkasun...@fastmail.fm

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Re: [Emc-users] Linuxcnc on arm

[Jon Elson]

On 10/14/2016 09:50 PM, Chris Albertson wrote:
> No, it would not get you to ns levels.
>
>
>I've
>> wanted to set this up on X86 through the parallel port for
>> some time (since about 2002, in fact) but it would take some
>> serious hacking on the PPMC driver.  It looks like it might
>> be easier with the uspace / rt-preempt kernel than with
>> rtai.  It would reduce latency/jitter to ns levels.
>>
Yes, actually, it WOULD.  All the Pico Systems motion 
control boards can latch the position when the internal 
timer ticks.  So, the position latching would be accurate 
down to the jitter of the crystal oscillator.  (If multiple 
boards were used, then the latching would be accurate to the 
difference between the clocks on the different boards, so 
jitter would increase to 1 us, maximum, or 100ns if the 
encoders were updating at 10 MHz clock.)
The master board sends the latch command on the parallel 
port bus to other boards on the bus, as well as the 
computer.  The computer would have the luxury of responding 
before the next timer tick, nominally 1 ms.
As long as the computer never took more than the timer 
period to complete its work, it would never cause ANY 
latency at all!  The computer's updated velocity info would 
not become effective until the next timer tick.

Jon

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Re: [Emc-users] Pico Systems Universal Stepper Controller Power Connection

[Jon Elson]

On 10/14/2016 07:19 PM, Joshua Glenn wrote:
> Hello all. I am wondering if the universal stepper controller from Pico
> Systems requires an external 5V power supply or not. And, if so, what is
> the current requirement and to what terminals should I connect it?
>
It requires an unregulated source, somewhere between 9 and 
24 V DC. It can supply a modest amount of regulated +5V.  
Power consumption is normally less than 300 mA.

Jon

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Re: [Emc-users] Linuxcnc on arm

[Jon Elson]

On 10/14/2016 12:09 PM, Erik Friesen wrote:
> I guess I am not following how a hardware interrupt gets mapped to the
> userspace/lcnc servo thread.  Any pointers on this?
>
>
Supposedly, this is fairly easy to do on the rt-preempt 
kernel.  It seems it was harder to do this through RTAI.
Michael Haberler says he has tested this on machinekit, but 
of course the interrupt system on the ARMs is totally 
different than on X86.

Jon


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Re: [Emc-users] Hacking a sim runtime mode

[Todd Zuercher]

I stripped the config bare, except for motion, and the timer component. had the 
command connected to the feedback, to try to get as little cpu overhead as 
possible. I tried setting the thread speed to 1, and it didn't make a 
difference.  But by jacking up the acceleration, I think I was able to get 
reasonably accurate sim times.

You or some others should give it a try and see what you think.  Especially if 
you have some very long files you have ran before, with known runtimes for 
comparison.

Modifying time.comp was very simple.  (I think I only added 1 lines of code and 
modified another.)

- Original Message -
From: "Danny Miller" 
To: "Enhanced Machine Controller (EMC)" 
Sent: Saturday, October 15, 2016 1:51:42 PM
Subject: Re: [Emc-users] Hacking a sim runtime mode

Ah, I was about to say "no, it's just 100x the accel, not 100x^2 the 
accel, we're just changing the time frame".

But I started to question myself and did the math logically. Duh.  YOU 
are right, I've had that all wrong.

That 25% gap seems troublesome.  Because, like I say, I need to use it 
to tune the params, but there's other factors at work here, which was 
kind of expected.  The concern is say I could sim  it and find trading 
off accel for velocity yields a 10% runtime improvement in sim, but in 
reality that's just a idiosyncrasy of stepping 100x faster and in 
reality maybe this change makes it 5% slower, not faster.  In that case 
it's foolish to try to tune with it.  Chasing unicorns.  You'd never 
know if you actually made it better or worse without a 1x run, making 
the sim useless.

Did you loopback the position command, or just disable the motors?  I 
wonder if the DIR_SETUP and DIR_HOLD are mucking with the accelerated 
timeframe.

Hey, wait- try changing the SERVO_PERIOD given to loadrt emcmot too.  
That should change *everything*.

So I heard the part about looping back the position command. Could we 
leave the vel and accel normal, let the motion component believe that 
it's running at its normal rate, but then run the motion component at a 
much faster rate than real time?  Hack the time base?

The motion component's EMCMOT, right?  My understanding is quite crude, 
but is it like a 1ms thread that just increments its own time counter by 
1ms every time it gets called?  If so then the answer would be to leave 
it believing it's on a 1ms time base but reschedule the thread execution 
for 0.01ms, or 0.001ms, or any number.  It will reliably sim could how 
many ms the program takes regardless of how often the thread executes.


I do see the loadrt loads emcmot thread at SERVO_PERIOD.  Of course 
there's no hook to change the concept of time inside emcmot from the 
scheduler, because it's not normally done.


I don't see how you could change it on the fly either.  I mean there'd 
be a VCP button for "switch to sim run" that could easily loopback the 
position command, but it would also have to tell the scheduler that 
emcmot thread needs to run at a much different rate and I don't know how 
you'd do that from VCP.

Danny


On 10/14/2016 1:32 PM, Todd Zuercher wrote:
> I seem to be having some success with this.  I have a simulation config set 
> up with max velocities set to 100x, and max accelerations set to 1x, 
> feed-overide set to 100x.  Using my scaled timer set to 100x the estimated 
> run time seems to be pretty consistently about 25% too long for a 20 minute 
> engraving file, but a slow 1 hour long single move tests just right.
>
> So I increased the acceleration still further, until I started to get 
> runtimes approximately the same as an unscaled simulation.  I ended up with 
> the acclerations set to 2x the original configuration that I am trying to 
> simulate.  It doesn't hardly seem right but is what seems to be working.
>
> - Original Message -
> From: "Todd Zuercher" 
> To: "Enhanced Machine Controller (EMC)" 
> Sent: Friday, October 14, 2016 9:52:18 AM
> Subject: Re: [Emc-users] Hacking a sim runtime mode
>
> A quick stupid question, if i'm scaling time 100x, velocities should increase 
> 100x, but what about acceleration, should that be increased 1x or 100x?
>
> - Original Message -
> From: "Todd Zuercher" 
> To: "Enhanced Machine Controller (EMC)" 
> Sent: Thursday, October 13, 2016 9:30:34 PM
> Subject: Re: [Emc-users] Hacking a sim runtime mode
>
> I think you are probably right.  Running the simulation at 100x was much more 
> accurate than 1000x.  Tomorrow I'll have to play with the servo thread speed 
> some and see if and how much improvement I can find.  But not sure how much 
> improvement will be possible in a sim config on a VM.
>
> - Original Message -
> From: "Stephen Dubovsky" 
> To: "Enhanced Machine Controller (EMC)" 
> Sent: Thursday, October 13, 2016 3:52:42 PM
> Subject: Re: [Emc-users] Hacking a sim runtime mode
>
> I think the error of this approach (using N times higher accel/vel) is
> coming from the piecewise linear approxim

Re: [Emc-users] Hacking a sim runtime mode

[andy pugh]

I wonder of the stand-alone interpreter is a better place to start a
time-estimator?
http://linuxcnc.org/docs/2.7/html/code/rs274.html

It would need tweaking to calculate acceleration, velocity and time,
and it would still be inaccurate unless it grew to replicate all of
the arc blending code.

I have a feeling that SAI is what is used for the Gremlin preview, but
I might be incorrect about that.

-- 
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, 1916

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Re: [Emc-users] Misc implementation questions

[andy pugh]

On 15 October 2016 at 14:54, Erik Friesen  wrote:
> #1.  What method could be used for a tool change recovery sequence?

That rather depends on what it takes to recover the situation, but
there is scope for reporting tool-changer errors through HAL and a
"magic comment"
If you control the tool change sequence through a G-code subroutine you can use
http://linuxcnc.org/docs/2.7/html/remap/remap.html#_error_handling_dealing_with_abort

> #2.  Door switch safety?

Again, it rather depends on what behaviour you require. The logic can
be configured many different ways in HAL.

> #3.  For a brushless servo system without halls, how to get phases in
> sync with encoder.

The "bldc" component offers a few options. If there are no hall
signals then using the encoder index (if there is one) is probably
best.
http://linuxcnc.org/docs/2.7/html/man/man9/bldc.9.html

-- 
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, 1916

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Re: [Emc-users] Hacking a sim runtime mode

[Danny Miller]

Ah, I was about to say "no, it's just 100x the accel, not 100x^2 the 
accel, we're just changing the time frame".

But I started to question myself and did the math logically. Duh.  YOU 
are right, I've had that all wrong.

That 25% gap seems troublesome.  Because, like I say, I need to use it 
to tune the params, but there's other factors at work here, which was 
kind of expected.  The concern is say I could sim  it and find trading 
off accel for velocity yields a 10% runtime improvement in sim, but in 
reality that's just a idiosyncrasy of stepping 100x faster and in 
reality maybe this change makes it 5% slower, not faster.  In that case 
it's foolish to try to tune with it.  Chasing unicorns.  You'd never 
know if you actually made it better or worse without a 1x run, making 
the sim useless.

Did you loopback the position command, or just disable the motors?  I 
wonder if the DIR_SETUP and DIR_HOLD are mucking with the accelerated 
timeframe.

Hey, wait- try changing the SERVO_PERIOD given to loadrt emcmot too.  
That should change *everything*.

So I heard the part about looping back the position command. Could we 
leave the vel and accel normal, let the motion component believe that 
it's running at its normal rate, but then run the motion component at a 
much faster rate than real time?  Hack the time base?

The motion component's EMCMOT, right?  My understanding is quite crude, 
but is it like a 1ms thread that just increments its own time counter by 
1ms every time it gets called?  If so then the answer would be to leave 
it believing it's on a 1ms time base but reschedule the thread execution 
for 0.01ms, or 0.001ms, or any number.  It will reliably sim could how 
many ms the program takes regardless of how often the thread executes.


I do see the loadrt loads emcmot thread at SERVO_PERIOD.  Of course 
there's no hook to change the concept of time inside emcmot from the 
scheduler, because it's not normally done.


I don't see how you could change it on the fly either.  I mean there'd 
be a VCP button for "switch to sim run" that could easily loopback the 
position command, but it would also have to tell the scheduler that 
emcmot thread needs to run at a much different rate and I don't know how 
you'd do that from VCP.

Danny


On 10/14/2016 1:32 PM, Todd Zuercher wrote:
> I seem to be having some success with this.  I have a simulation config set 
> up with max velocities set to 100x, and max accelerations set to 1x, 
> feed-overide set to 100x.  Using my scaled timer set to 100x the estimated 
> run time seems to be pretty consistently about 25% too long for a 20 minute 
> engraving file, but a slow 1 hour long single move tests just right.
>
> So I increased the acceleration still further, until I started to get 
> runtimes approximately the same as an unscaled simulation.  I ended up with 
> the acclerations set to 2x the original configuration that I am trying to 
> simulate.  It doesn't hardly seem right but is what seems to be working.
>
> - Original Message -
> From: "Todd Zuercher" 
> To: "Enhanced Machine Controller (EMC)" 
> Sent: Friday, October 14, 2016 9:52:18 AM
> Subject: Re: [Emc-users] Hacking a sim runtime mode
>
> A quick stupid question, if i'm scaling time 100x, velocities should increase 
> 100x, but what about acceleration, should that be increased 1x or 100x?
>
> - Original Message -
> From: "Todd Zuercher" 
> To: "Enhanced Machine Controller (EMC)" 
> Sent: Thursday, October 13, 2016 9:30:34 PM
> Subject: Re: [Emc-users] Hacking a sim runtime mode
>
> I think you are probably right.  Running the simulation at 100x was much more 
> accurate than 1000x.  Tomorrow I'll have to play with the servo thread speed 
> some and see if and how much improvement I can find.  But not sure how much 
> improvement will be possible in a sim config on a VM.
>
> - Original Message -
> From: "Stephen Dubovsky" 
> To: "Enhanced Machine Controller (EMC)" 
> Sent: Thursday, October 13, 2016 3:52:42 PM
> Subject: Re: [Emc-users] Hacking a sim runtime mode
>
> I think the error of this approach (using N times higher accel/vel) is
> coming from the piecewise linear approximations of the curves going bad.
> If you try to follow a curve N times faster, then there are N times fewer
> samples along that curve for a fixed time sampling period.  That introduces
> errors.  There may be others but thats at least part of it.  Its the same
> problem w/ discrete time vs continuous time systems.  There is divergence
> between the solutions as the sampling rate goes down.
>
>
> On Thu, Oct 13, 2016 at 3:08 PM, Todd Zuercher 
> wrote:
>
>> I was just working at this a little bit.   The first thing I did was to
>> modify time.comp, to make a new sim_time.comp.  The sim_time.comp is
>> basically just the same as the regular timer component with an input pin
>> added to scale the time to what ever factor you speed up the simulation
>> run.  Then I made a dummy config of one

Re: [Emc-users] ATS-667 advice

[Gene Heskett]

On Saturday 15 October 2016 02:55:39 Chris Albertson wrote:

> Actually it's easy.  You use a hot air re-work station.   Basically a
> hair drier with a 1/8th inch diameter nozzle.
> Hold the little part in place with a wood tooth pick and aim the hot
> air generally at the part.  The solder on the part and the PCB melt,
> release the toothpick and surface tension then aligns the part on the
> PCB pad before the solder resolidifies.   You can do it with a solder
> iron but it's harder.  Hot air stations have gotten cheap, as low as
> $40.

Already have one, sitting about 3 feet away ATM. :)

> > >They are cheaper than the through hole caps that I normally
> > > buy. Hand soldering them will be a royal PIMA!
> >
> > At .2mm x.4mm, you have that right, the pain will be in My Ass. My
> > hands are just starting to get nervous,


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 

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Re: [Emc-users] ATS-667 advice

[Gene Heskett]

On Saturday 15 October 2016 02:38:59 Chris Albertson wrote:

> A source for 0.1 bypass caps?   I buy most everything fro eBay now.
> But you don't want a film cap, you want a "Multilayer Monolithic
> Ceramic Capacitor".  I just happen to have one here on my desk and a
> copper US penny too.  I place the cap on the penny and see it is about
> 2/3 the size of Mr. Lincoln's head   or maybe 4x6 millimeters.   They
> typically sell for 1 cent each.
> Here is a random vendor, the first one Google found
> http://www.ebay.com/itm/0-1uF...
> pacitor-100-pcs-LW-SZUS-/181932472979?hash=item2a5c053a93:g:NxMAAOSwiwV
>WT0bI>

Thats about right, I put a bag of them in my cart for $0.99.

> This shows how an RPM sensor from a Chinese mini lathe is mounted.  I
> build these using perf board for robot joints and wheels.  In this
> case their sensor points up from the PCB but you can bend the leads
> and have it look parallel to the PCB.  The picture shows an optical
> sensor but hall effects mount the same way  There is always room for a
> tiny passive part http://littlemachineshop.com...
> roductID=1945>

I didn't see any all effect sensors, and that optical is too big unless I 
put one of Lester Caine's wheels clear out on the rear of the spindle.  
And there's nothing out there but air to bolt it to. The swingout cover 
on the left is empty now. I'll put a sheet metal roof over the z drive 
belt thats using an inch of that space.  Ditto the X drive belt but I've 
not quite visualized that one, yet. Possibly route a cover profile in 
1/4" alu, with a groove to hold some 24 gauge alu.

At least I don't have to sweat carving an optical encoding wheel with the 
ATS667's watching that 60 tooth bull gear.  Ack the docs, quadrature 
accuracy is off a couple percent, but I have a hal file kit that does 
a /4 to that error if needed.

Hint, use it only in the feedback path to the PID driving the spindle. I 
need to do that in both the G0704 and TLM's hal files after standing 
back to see the whole picture.

> One of my goals for my CNC mini-mill is to make PCBs by routing the
> space between the coper traces then I can convert to using surface
> mount parts even for one-off prototypes but for now I use these little
> radial lead 0.1 capacitors.  The surface mount equivalents are less
> than 1/4 the size.

I do that routing by hand, almost in a varoni style. 100x faster than 
trying to do something like that in eagle. I'll need, on the left face 
of the indexing 667 bracket, wire wrap pads for 5 surface connections, 
expanded out to where I have pads big enough I can paste the 
interconnect cable to it. Then I can use wrapping wire the last 1.5" to 
the devices.  And it all comes off as a unit with one 5mm bolt thru the 
front of the spindle houseing when I'm done. Where the index 667 is, I 
still need to carve a path for its 3 wires to that pad on the pcb. Its 
mounted in reverse in the trench, but the trench wasn't cut clear thru 
to the left end so the wires will have to go back by it to get out. I 
made the trench wide enough I can stuff the wrapping wire into the gap 
and spot them in place with a bit of superglue.

Next subject;
Time to check the gaskets in my dishwasher, it put a couple ounces of 
water on the floor during this run.  Real life is always bothering me 
with piddly stuff. :(

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 

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[Emc-users] Misc implementation questions

[Erik Friesen]

#1.  What method could be used for a tool change recovery sequence?

#2.  Door switch safety?

#3.  For a brushless servo system without halls, how to get phases in
sync with encoder.

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Re: [Emc-users] ATS-667 advice

[Chris Albertson]

Actually it's easy.  You use a hot air re-work station.   Basically a hair
drier with a 1/8th inch diameter nozzle.
Hold the little part in place with a wood tooth pick and aim the hot air
generally at the part.  The solder on the part and the PCB melt, release
the toothpick and surface tension then aligns the part on the PCB pad
before the solder resolidifies.   You can do it with a solder iron but it's
harder.  Hot air stations have gotten cheap, as low as $40.



> >They are cheaper than the through hole caps that I normally buy.
> > Hand soldering them will be a royal PIMA!
> >
> At .2mm x.4mm, you have that right, the pain will be in My Ass. My hands
> are just starting to get nervous,


-- 

Chris Albertson
Redondo Beach, California
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