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Oct 21, 2019, 01:28 PM
Aom
Aom
Registered User
Quote:
Originally Posted by dodo3441
As mentioned earlier in the thread using a bow for tensioning solves all the problems regarding the structures stiffness/flex. I did not like the idea at first because it requires a new bow if you want to increase the distance between your portals. However after several people reccomended this solution I gave it a try and have to say it is indeed the way to go. It allows for me to use 8mm rods which are not particularly strong and yet have no problems with flex. Also cuts are cleaner as wire tension is constant regardless of the cuts angle.
Well then i guess my second iteration goes out the window....
I never used a bow even, so i dont know how much tension needs to be on the wire.
The mdf I will be using is "free" so maybe worth to give it a go anyways, I like the idea of a spring tensioned wire, cant be that high of a force?!?
And the possibility to slide the towers together on rails, to be able to cut more tapered wings like the tails etc easily... hummmmmmm.....

This was supposed to be simple
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Oct 21, 2019, 07:33 PM
I hate propellors
emufingers's Avatar
Quote:
Originally Posted by modraude
I have a problem with my hot wire foam cutter.
the cut surface is undulated with a distance between the waves equal to the pitch of the screw. This happens in the same way with all people. the vit have 5mm pitch and are recirculating balls. I checked the alignment of the joints with precise tools. I tried to generate a phase shift between the axes. I changed wire temperature, motor current, microstep ... no change.
in the past I had a machine with DC motors and feedback encoders and this problem did not exist ....
do you have any ideas about it?
thank you
eduardo


I have a problem with my hot wire foam cutter.
the cut surface is undulated with a distance between the waves equal to the pitch of the screw. This happens in the same way with all people. the vit have 5mm pitch and are recirculating balls. I checked the alignment of the joints with precise tools. I tried to generate a phase shift between the axes. I changed wire temperature, motor current, microstep ... no change.
in the past I had a machine with DC motors and feedback encoders and this problem did not exist ....
do you have any ideas about it?

P.S. I saw the same problem in a machine with t12 screws with 8mm pitch and 4 principles with bronze nut ...
the piloting sw is always the same grbl ..
the problem is obviously with a motor turn ...
Check the following

Do your steppers on the x and U axis flex when cutting? solution add strength to mount

Is there backlash ? solution add another nut with a spring between the two nuts.
Oct 22, 2019, 02:39 AM
Registered User
Quote:
Originally Posted by Aom
Well then i guess my second iteration goes out the window....
I never used a bow even, so i dont know how much tension needs to be on the wire.
The mdf I will be using is "free" so maybe worth to give it a go anyways, I like the idea of a spring tensioned wire, cant be that high of a force?!?
And the possibility to slide the towers together on rails, to be able to cut more tapered wings like the tails etc easily... hummmmmmm.....

This was supposed to be simple
Yeah, the construction looks solid, Im sure it will work fine. Another option to consider would be using a weight & pulleys to keep the tension. This allows for constant tension + easily adjustable.
Oct 22, 2019, 08:40 AM
Aom
Aom
Registered User
Quote:
Originally Posted by dodo3441
Yeah, the construction looks solid, Im sure it will work fine. Another option to consider would be using a weight & pulleys to keep the tension. This allows for constant tension + easily adjustable.
Thats exactly what i was thinking!
Oct 22, 2019, 06:53 PM
Aom
Aom
Registered User
Got my board and stepper drivers today! Wohooo!

Succesfully uploaded the grbl firmware and could jog virtually and make changes steps per mm as described earlier in the thread and have it save my changes, but not all is well....!

I have bought tmc2208 drivers for this project and they are v1.2. It seems they have dynamic/active control over their setting via uart. Can i use this function with grbl? Im new to this arduino stuff so im lost here.... As far as i can tell they natively come configured to be run in this state and need some soldering and wires made to be able to control them from another set of pinouts. Ive found a library for them, is it just to upload this library to the board or does it need to be integrated with the grbl code? I really do want to bea able to use theese drivers, as they should be more smooth, silent and as strong as the rest of the competition
Oct 23, 2019, 02:49 AM
A.K.A sir Crashalot
methuso's Avatar
About bows and dog leashes
I have used bows for years and thought they were the only way to go. BUT. When i got to a part with very high angles the bow was in the way, hitting parts of the machine, lifted the wire from its holders and even fell off the machine.
the part (an air intake of saab j29) has about 45 degrees taper all around. but i made it only 6mm long.
now i thought about using a spring but going 45 degrees the distance stretches alot.
Tried pulleys an weights but that put too much bend in the pivot point making the wire stick too much

so.... selfretracting dog leash it is.
i got a 5 meter one, that seems not powerfull enough to collaps the towers.
seems to work realy well and having it tied to a wall 2 meters away with wire most of the way there, i can move the towers apart for different lengths without changing wire.
if i was not concerned with steep tapers, I would use a bow, since you can tighten the wire without affecting the towers.

Sorry for the rant... bored in a hotellroom....

/Ulf
Last edited by methuso; Oct 23, 2019 at 03:15 AM. Reason: spelling
Oct 23, 2019, 02:58 AM
Aom
Aom
Registered User
Quote:
Originally Posted by methuso
About bows and dogleeches
I have used bows for years and thought they were the only way to go. BUT. When i got to a part with very high angles the bow was in the way, hitting parts of the machine, lifted the wire from its holders and even fell off the machine.
the part (an air intake of saab j29) has about 45 degrees taper all around. but i made it only 6mm long.
now i thought about using a spring but going 45 degrees the distance stretches alot.
Tried pulleys an weights but that put too much bend in the pivot point making the wire stick too much

so.... selfretracting dogleech it is.
i got a 5 meter one, that seems not powerfull enough to collaps the towers.
seems to work realy well and having it tied to a wall 2 meters away with wire most of the way there, i can move the towers apart for different lengths without changing wire.
if i was not concerned with steep tapers, I would use a bow, since you can tighten the wire without affecting the towers.

Sorry for the rant... bored in a hotellroom....

/Ulf
Tack ulf, not sure what a dogleech is but i have wrong stepperdrivers right now so going through hell that is banggood customer support...
Oct 23, 2019, 03:18 AM
A.K.A sir Crashalot
methuso's Avatar
MB spelling
I ment dog leash. Its what dogs use to get enough momentum to rip your arm off.
Oct 23, 2019, 10:11 AM
Registered User
Hi, sorry was a little busy this week, and it seems I didn't explain my problem wery well. I understand the coordinate system, and the two profiles the hotwire travels along. What I don't get is, from where to import the airfoil when using foam XL, and when trying to use jedicut, why won't it work, as it only writes out a load of error windows.
Oct 23, 2019, 06:07 PM
I hate propellors
emufingers's Avatar
Quote:
Originally Posted by timomo
Hi, sorry was a little busy this week, and it seems I didn't explain my problem wery well. I understand the coordinate system, and the two profiles the hotwire travels along. What I don't get is, from where to import the airfoil when using foam XL, and when trying to use jedicut, why won't it work, as it only writes out a load of error windows.
search with google for airfoil.dat and you will find lots of source. Down load the files you want. Use note pad to look at files and to remove the first line with the airfoil name. Save with a .dat extension in you own folder. In foam excel you can load the data points from your file.
Oct 25, 2019, 08:10 AM
Registered User
I did that, but XL saus value in the warning line, and it won't generate the gcode, it just writes out "run time error 13: type mismatch."
Oct 25, 2019, 08:24 AM
I hate propellors
emufingers's Avatar
there are characters in your downloaded file may e the header. or you have downloaded file tht excel interprets as characters.

Open excel and import your data into a new Excel document. Check that you have two columns of numbers.

if not, use Excel parsing tool (text to number on the Data tab)

If you can't work it out, post your data file as an attachment here so we can see what your are doing.
Oct 25, 2019, 03:56 PM
Registered User
vichito's Avatar

My 4 axis hot wire


This is my projet, more coming soon
Oct 27, 2019, 03:31 AM
Registered User
Here is my modified file:
Oct 27, 2019, 04:23 AM
I hate propellors
emufingers's Avatar
OK

The file you sent was a chrome htm file. I am not sure how you generated it. There is no need to use html.

The file consisted of a single data string, Each pair of points in the string is an xy pair.

I dropped this into excel and manually moved the data into their pairs.

Here is the outcome pasted direct below. This is what a .dat file should look like. You can copy and past into a notebook file and then load into foam xl. I checked it out and it works fine .
1.0000 0.00014
0.99754 0.00151
0.9907 0.00419
0.98037 0.00623
0.96698 0.00919
0.95044 0.013
0.93064 0.0172
0.90775 0.02213
0.88202 0.02757
0.8537 0.03335
0.82309 0.03944
0.79048 0.04581
0.75616 0.05236
0.72043 0.05893
0.68359 0.06539
0.64594 0.07161
0.60778 0.07745
0.56937 0.08278
0.53099 0.08745
0.49265 0.09138
0.45435 0.09455
0.41638 0.09689
0.37887 0.09835
0.34204 0.09886
0.30609 0.09832
0.2712 0.09666
0.2376 0.09383
0.20549 0.08982
0.17504 0.08469
0.14648 0.07851
0.11999 0.07137
0.09576 0.06334
0.07395 0.05453
0.05468 0.04523
0.03811 0.0361
0.02433 0.02764
0.01338 0.01975
0.00548 0.01212
0.00098 0.00497
0 0.00001
0.00098 -0.00493
0.00548 -0.01164
0.01338 -0.01784
0.02433 -0.02329
0.03811 -0.02826
0.05468 -0.03288
0.07395 -0.03724
0.09576 -0.04136
0.11999 -0.04512
0.14648 -0.04825
0.17504 -0.05067
0.20549 -0.05246
0.2376 -0.05376
0.2712 -0.05461
0.30609 -0.05501
0.34204 -0.05493
0.37887 -0.05433
0.41638 -0.05323
0.45435 -0.05162
0.49265 -0.04955
0.53099 -0.04709
0.56937 -0.0443
0.60778 -0.04124
0.64594 -0.03798
0.68359 -0.03461
0.72043 -0.03121
0.75616 -0.02782
0.79048 -0.02446
0.82309 -0.02118
0.8537 -0.01802
0.88202 -0.01506
0.90775 -0.01233
0.93064 -0.00987
0.95044 -0.00778
0.96698 -0.00638
0.98037 -0.00522
0.9907 -0.00344
0.99754 -0.00117
1 -0.00001


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