Pen Holder

[Anonymous]

[Dan]

Nice. What bearings did you use? is that polycaprolactone plastic (the white stuff)?

I have noticed that the pen tip wobbles more as the center of balance gets further from the wall. Do you concur? One solution would be two sets of belt to hold the pen at two points. It doubles the cost of belt and pulleys AND the motors would need extra long shafts.

[Anonymous]

Bearings:
Inner diameter:17 mm
outer diameter:30 mm
thickness: 7 mm

the white stuff is „Installation glue” (literal translation) 370kg/10cm² strong „Silyl Modified Polymers“ https://www.youtube.com/watch?v=O2ctlTV4s0s

>>I have noticed that the pen tip wobbles more as the center of balance gets further from the wall. Do you concur?<<

Yes, exactly.
It is important that you do not get any gaps in the line. If the center of balance gets closer to the wall, the pressure on the pen decreases and you get gaps in the line 🙁

>> One solution would be two sets of belt to hold the pen at two points. It doubles the cost of belt and pulleys AND the motors would need extra long shafts.<<

The cost increase because of the timing belt is minimal. That should not be a problem.
The weight of the timing belt could lead to the need for more powerful stepper motors…

I do not know if it works, you have to try it. I will try something.

[Anonymous]

I do not think the height of the pen is really the problem. Whether 1 cm or 3 cm – that’s not it.

The problem is the too fast acceleration of the stepper motors, which makes the gondola jump.
A little more weight helps, but it should not be too much weight.

In the clip:
The 25 cm sticks, the stiffening, help reduce the wobbling of the pen. The 25 cm sticks help a lot.

To avoid the wobbling of the pen, a softer acceleration would be maybe the solution?

is it possible to make the stepper motors accelerate smoother? (and move faster when idling through gentle acceleration?)

Maybe servo motors could be a solution? … and they are quiet 😉

[Dan]

acceleration can be lowered in settings, or with gcode.

G00 Annn

change acceleration to nnn

[Anonymous]

Does it also work with text?
I do not feel that the text is written more slowly …
And what about servo motors would it be an option?

[Anonymous]

[Dan]

> Does it also work with text?

The robot only knows that it is drawing lines. it works with everything. Make sure your gcode does not have G0 Ann commands, it might reset your instructions! eg you said G0 Annn, then ran gcode and that gcode has a G0 Annn which changes your instruction

> And what about servo motors would it be an option?

I don’t understand the question.

[Anonymous]

The stepper motors are loud (I can not run the machine when customers come and that’s a problem for me.) And the acceleration is jerky. I wonder if this could be a solution:

[Anonymous]

[Anonymous]

/G00 A100/ does not work.
if you write “X”, the pen moves slowly to the starting point and then it writes “X” fast. There must be another command that regulates the writing speed, right?
Watch the clip, from 2 minutes and on. G00 A100…

https://www.youtube.com/edit?o=U&video_id=LzvS8B8iURE

[Dan]

The A value will change the *acceleration*. The F value will change the *feed rate*, which is the speed.

G0 A100 ; set acceleration to 100
G0 F2000 ; set top speed to 2000
G0 X100 ; move to X100
G0 X0 F3000 A1000; combine all three in a single command for convenience

[Anonymous]

I tried with 3 weights.
17.2 grams
32.8 grams
49.8 grams (“Go Home” is no longer possible, the stepper motors are too weak)
The problem is the vibrations of the timing belts, which cause the pen to wobble.
The more weight, the less vibration.
To change acceleration and speed did not help.

[Anonymous]

I was wrong. It’s not just the weight of the gondola. It’s the size of the machine. Especially because of the length of the timing belt. The bigger the machine, the more vibrations. And I do not think you can do anything about it. But I’m happy with the result. 🙂

If somebody wants it to be more accurate, does he have to build an XY Core system? hmmm…

Maybe I will do it. At the moment I have to work a bit with my machine 🙂

[Anonymous]

1. way to make the system quieter is to match the stepper motor to the A4988 (turn the small screw):

2. way is to use another driver:

3. way: closed loop servo motor – expensive…

[Dan]

I hear 1/256 stepper drivers are really quiet, they’re used in Prusa i3 MK3.

here’s one such driver. We’re considering getting them for stewart platforms and the robot arm prototype.

SilentStepStick – TMC2100 Stepper Motor Driver

[Anonymous]

It’s just too bad that you have to reprogram … it’s not my strength 😉
I would like to have a motor that I can easily replace and is ready to go. Even if it costs something …

[Dan]

In makelangelo firmware configure.h change MICROSTEPPING from 16 to 256 and upload it to the board again. You’ll have to do that on every update.

[Anonymous]

okay, I will try it, must order the parts. There are probably two modes?
The “louder” mode is great. I do not think that the 2nd is important to us, right?

[Anonymous]

It’s the same as with the A4988. turn the small screw. But then it is really quiet …

[Anonymous]

Hi 🙂 I have mounted the TMC2100 and just tried it, without changing makelangelo firmware configure.h. – it is really quiet and works well. You hear a low hum, but it is not comparable to the A4988. Wow. Very quiet. Now you can hear the pen 😉

Why should I reprogram makelangelo firmware configure.h? What is that supposed to change?

[Dan]

The TMC2100 is 1/256 microstepping driver. it should be moving the pen 1/16 the expected distance if you use the default makelangelo firmware. this is because the firmware is set to 1/16 stepping, so the physical behaviour and the robot’s mental perception of its actions are diverging. The fix is to teach the robot it is now at 1/256 microstepping.

https://github.com/MarginallyClever/Makelangelo-firmware/blob/master/configure.h#L79

change

#define MICROSTEPS (16.0) // change this. microstepping on this microcontroller

to

#define MICROSTEPS (256.0) // change this. microstepping on this microcontroller

and upload the code again. As long as you are using 1/256 drivers you will have to make this change every time a new makelangelo-firmware is released.

[Anonymous]

Thank you. I will do it in the next few days. Maybe tomorrow 🙂

[Anonymous]

It does not work with 256 steps. the x / Y lengths are then no longer correct.

paper „Border“ of 400×300 mm and the pen goes through the floor 😉

back to 16 and everything works again … sorry 🙁

[Anonymous]

>>#define MICROSTEPS (256.0) // change this. microstepping on this microcontroller
#define DEGREES_PER_STEP ( 0.9) // change this. as <<

0.9 to 0.05625 ???

[Author]

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