Dual bipod winch foam cutter

hello Brian

honour to whome honour is due.
This is the page of the inventor of the machine (Hans), its not me.
www.cnc-hotwire.de/
I have only made the EMC2 adaption. Hans uses his own software.

In europe, there are more than 60 reproductions meanwhile, Hans maintains "serial numbers" for each one.
If you want, provide some pictures and details of your machine for the galery.

Back to your problem:

First we have to make your individual motors move in joint mode correctly.
I think SCALE = 15.748031 is ok, according the data you posted.
With your hal data (base period = 100000, reset disabled), max pulse rate is 5000 p/sec.
It should give you 317 mm/sec, which is by far enough for this type of machine.
Try in joint mode:
Select Incremental jog 10 mm and measure how much longer or shorter the rope is at the end.
"+" shall make the rope longer, "-" shall make it shorter, exactly 10 mm.
Try at different velocities, all axes.
All axes behave the same way ? No error messages from EMC ?
Decay mode has no significant impact due to my experience. Not sure what value I selected currently.

I will explain kinematic parameters in another post. (have to cut some of my trees in the garden now )

Gerd

andypugh wrote:

bvandiepenbos wrote:

And motors run but not smooth.

That seems strange. Steppers normally either move smoothly, or not at all.
it is sometimes possible for a stepper to turn when wired wrongly.
You say that the motors have 6 wires, how did you work out which were which? I have some 8-wire motors where the actual motor wiring and the documentation are not in agreement. If you haven't checked with a multimeter then it is probably worth doing.

-scale is not right, 100mm G0 mdi move gets...
X= 70mm V=120mm
Y= 180mm U=80mm[/quote]Can I suggest that you unhook the wires and mark the pulleys with a pen.
Then, with the scale set to 1, request a move of 400. That should give exactly one revolution. with your stated microstep settings.

It all sounds like your motors are missing steps. Perhaps it is worth trying lower accelleration limits.[/quote]

Hello Andy,
I wired using docs with color coding on wire, I don't remember if I put a meter on it... I will double check that.

yes, scale at 1 with 400 move gets exactly one revolution, on all 4 motors.

I will try changing accels

~*Brian

step4linux wrote:

hello Brian
First we have to make your individual motors move in joint mode correctly.
I think SCALE = 15.748031 is ok, according the data you posted.
With your hal data (base period = 100000, reset disabled), max pulse rate is 5000 p/sec.
It should give you 317 mm/sec, which is by far enough for this type of machine.
Try in joint mode:
Select Incremental jog 10 mm and measure how much longer or shorter the rope is at the end.
"+" shall make the rope longer, "-" shall make it shorter, exactly 10 mm.
Try at different velocities, all axes.
All axes behave the same way ? No error messages from EMC ?
Decay mode has no significant impact due to my experience. Not sure what value I selected currently.

Gerd

Hello Gerd,
yes, rope length + - works correctly for all joints at different speeds.
( I used jog increment of 25.4mm so I could measure 1.0 inch easier)
no EMC error messages.

In world mode moves do not move as commanded G1 distance.

~*Brian

bvandiepenbos wrote:

yes, rope length + - works correctly for all joints at different speeds.
( I used jog increment of 25.4mm so I could measure 1.0 inch easier)
no EMC error messages.

In world mode moves do not move as commanded G1 distance.

So it seems everything is ok with the motors now ?

Back to kinematic / world mode:
Have a look at the wiki "Anpassungen", although its in german (sorry).
Look at the picture under "Kalibrierung".
As you can see, D01 (D67) is not exactly the distance between motor centers (hope the picture is clear).
The ropes shall be located as indicated. Double check that ropes becomes longer/shorter with jog +/-.
Important is to measure the distance "HOME" for each motor, and enter this value as HOME and as HOME_OFFSET parameter in the ini.

XU0 and YV0 are just offsets for the reference point. They are not measured, you can enter what you want.
After a "homing" you shall see these values as actual position in worldmode.
Note: You may use touch-off in axis as well to define an offset.

Gerd

step4linux wrote:

bvandiepenbos wrote:

yes, rope length + - works correctly for all joints at different speeds.
( I used jog increment of 25.4mm so I could measure 1.0 inch easier)
no EMC error messages.

In world mode moves do not move as commanded G1 distance.

So it seems everything is ok with the motors now ?

Back to kinematic / world mode:
Have a look at the wiki "Anpassungen", although its in german (sorry).
Look at the picture under "Kalibrierung".
As you can see, D01 (D67) is not exactly the distance between motor centers (hope the picture is clear).
The ropes shall be located as indicated. Double check that ropes becomes longer/shorter with jog +/-.
Important is to measure the distance "HOME" for each motor, and enter this value as HOME and as HOME_OFFSET parameter in the ini.

XU0 and YV0 are just offsets for the reference point. They are not measured, you can enter what you want.
After a "homing" you shall see these values as actual position in worldmode.
Note: You may use touch-off in axis as well to define an offset.

Gerd

Gerd,
yes, motors seem OK now.

AHAA! ...light bulb moment! I think I get it finally.
The picture on the wiki really helped along with your descriptions here in this message.
many, many thanks!!

I am pretty sure these are my errors...
-cables are not leaving drums correct direction.
-I did not measure my cables home length, or even put it in my .ini
-I used motor shaft center to center for D01 distance, instead of spacing of where cable leaves drum.

I am really excited to try it out when I get home later today (yes working on Saturday, one of the many 'perks' of owning your own business)


Question,
I am thinking of running cables through a tiny (.020" diameter) guide hole to help eliminate the shifting of where the cable leaves drum as Y position changes.
Do you think this will help accuracy of machine?

I am hunting for jets from a carburetor, thinking that it should be a tiny smooth orifice for cable to pass through.
Or drilling hole with smallest bit I can find.
What do you think?


~*Brian

bvandiepenbos wrote:

I am thinking of running cables through a tiny (.020" diameter) guide hole to help eliminate the shifting of where the cable leaves drum as Y position changes.
Do you think this will help accuracy of machine?

hi Brian,
you can do that, but do not expect too much impact. There are other sources of errors too, asking for compensation, but I would suggest start simple, gather experience and then improve step by step.

Another important thing: the windings on the drum must be a single layer, and the effective drum diameter is the bare drum diameter plus the diameter of the cable.
What kind of cable are you using ?

Gerd

step4linux wrote:

bvandiepenbos wrote:

I am thinking of running cables through a tiny (.020" diameter) guide hole to help eliminate the shifting of where the cable leaves drum as Y position changes.
Do you think this will help accuracy of machine?

hi Brian,
you can do that, but do not expect too much impact. There are other sources of errors too, asking for compensation, but I would suggest start simple, gather experience and then improve step by step.

Another important thing: the windings on the drum must be a single layer, and the effective drum diameter is the bare drum diameter plus the diameter of the cable.
What kind of cable are you using ?

Gerd

Hi Gerd,
bare drum dia. is .317"
measures .338 dia. with 1 wrap
.338-.317=.021 .021/2=.0105"
so cable is .0105" dia. ?
which makes my effective dia. .327" right?

Fishing line, Dyneema Spider Wire Stealth Braid 30lb test

~*Brian

Hi all,
I got all axis moving correctly now.

thanks everybody for all your help.

next is finishing building table, framework etc.
I also want to get it to move faster.


Any suggestions what to use for creating my g-code?
I am not going to be cutting wings,but other geometric shapes.

My code will have to move X&U together and Y&V together...
so the g-code is not very straight forward.
not like the XYZ mill stuff that I am familiar with.

Can I use .hal pins to move both pairs of bipods in sync, just using plain X Y code?

What about Arcs? like G3 X Y I J
how would you code G3 U V moves? (still use I J ?)


~*Brian

bvandiepenbos wrote:

bare drum dia. is .317"
measures .338 dia. with 1 wrap
.338-.317=.021 .021/2=.0105"
so cable is .0105" dia. ?
which makes my effective dia. .327" right?

Fishing line, Dyneema Spider Wire Stealth Braid 30lb test

Sounds good