Query about "Y" axis and type of step

[WANCHO]

Good morning, I need to make a query, if possible and there is already something about it, indicate a link where it is discussed. The "X" axis arm where the "Z" axis cutting head is supported, in some very old models I have seen that the step is made taking advantage of the rotation of the same lathe, but in other more current models it uses a spindle with a motor Step by Step. I'm assembling a small prototype at home but I don't know how much the rotation is and how much it should advance in the "Y" axis each time the plate makes a complete turn and records a groove to make way for the next one. Excuse me because it is a lot of information and I am starting in this world that seems wonderful to me. I thank you from the bottom of my heart for any answer will be well received.

[farmersplow]

Hello Wancho,

I welcome you and I am always glad when someone tries to enter the world of plate cutting.

Your question is good for me to understand and I may be able to help you with it - I will try:

First of all, you need to understand that the cutting head (whether cutting or pressing) needs a certain amount of space to get a signal into the groove. In doing so, the graver moves back and forth, and depending on that, it needs more or less space. The cutting width of the graver is usually 40µm.
Being from Europe myself, I will use the metric system [mm; µm] for explanation. This range of movement depends on frequency and recording volume and is between 0 (silent cut) and 300µm. (extreme case 400µm). Since you are still at the beginning of your development, let's assume a value of 160µm. So if the graver moves 80µm back and 80µm forth, it needs 160µm space plus the 40µm of the stylus is in total 200µm. One plate rotation further, the same game begins. So to prevent the cut groove from colliding with the cut of the previous one, there must be a "feed" of at least 200µm - better 220µm. (With embedding even more, because when a groove is pressed, small hills are created at the upper ends which require further space). - So 250µm spacing.
At a plate speed of 33.33 rpm, the plate needs exactly 1.8 seconds for one revolution. Accordingly, 250µm of forward motion must be performed in 1.8 seconds. That is a forward motion of ~140µm per second.


Now I assume that you are using a stepper motor. Each stepper motor is controlled by a stepper motor driver. For example, with a setting of 400 steps per stepper motor revolution.
I also assume that the drive is done by a spindle. Each spindle has a "thread pitch". This spindle pitch is, for example, 5mm (One revolution of the drive spindle corresponds to a forward movement of "5" mm).
Accordingly, 400 steps would correspond exactly to 5mm (5000µm). ...and one step exactly 12.5µm. Theoretically, 11.2 steps would be necessary (per second) to achieve 140µm/second. But practically this is useless, because the fast movement of 12,5µm would already produce a well audible noise!
(At 800 steps/revolution it would be a bit better, but still audible at a feed rate of 6.25µm). So a different spindle or gear ratio becomes necessary.

That's why I used a different gear ratio as a third assumption. For example, if the stepper motor is connected to the spindle via a gear or belt transmission. For example, a gear ratio [Y:1] of 10:1 (ten revolutions of the stepper motor result in one revolution at the spindle). Without a gearbox, the value = 1. With the spindle (5 mm) and the stepper motor (800 steps/red) with a gearbox ratio of 10:1, this would result in a feed rate of 0.625µm per step. That would be good.

In summary:
A groove spacing of 70µm to 400µm is required.
For experiments, a groove spacing of 250µm per plate revolution can be selected. (With the microscope the cut can be controlled, and the value can be adjusted if necessary).

...and then there is the variable feed control, but I don't want to explain it here in more detail.


I hope I could help a little

Greetings from Austria

[WANCHO]

Friend farmersplow, it is gratifying for me to have the experience and kindness on your part. I am going to analyze each information that you have provided me and I am lucky to have a team of R&D engineers at work who can help me with their data and choose the most suitable material. I will ask again as soon as I have any more questions and I will be posting images and designs of my project. Will I get it? I don't think so, but at least I will have tried and I will contribute experiences in assembly and improvements from my point of view.

Thank you very much for everything!

[WANCHO]

Well, greetings to all today I started my project and I put images of how it turned out, I have mounted it on an SL 1200MK2 to start. I only have the structure and tomorrow I will try to place the transversal and I will start looking for the linear spindle. Do you recommend any? Thanks to the explanations of the colleague I understand that the pitch/thread must be fine. Well I hope you like it, the entire structure is assembled with MayTec. Thank you all I will continue sending images of the evolution.

[WANCHO]

Hello to all the trolls, I take this opportunity to update the status of my thread on the slicer project based on that of the already well-known David Nelson. As you can see in the images there will be things done poorly (which I take into account) but they are like this because I want to deliberately make mistakes to see what results it produces, such as placing the motor directly on the X axis screw and not putting pulleys and belt. I'm going to leave this thread to post my progress little by little and I'll post photos and images of it here. You can give your opinion freely and I am open to recommendations, any questions you may have I will be happy to answer.

[WANCHO]

Here I upload some images of how I've been doing so far since I started.

[WANCHO]

As you can see, it occurred to me to place a fine-tip marker on a head prototype to simulate cutting on a cut-out paper disc. I will be able to test this when I move to the x-axis movement with the stepper motor. I am already close to the door. of this step.

[WANCHO]

And now I am immersed in the design of the cutting head, for this I decided to buy some 25W coils on Aliexpress, they are similar to ones that I saw in the design of some colleagues from Ukraine,This is the thread here you can see, they are purchased on Aliexpress

https://www.lathetrolls.com/viewtopic.php?f=15&t=9828&p=62518&hilit=Ukra#p62518

Logically I have had to considerably increase the size of the support and redesign it completely, the two coils weigh about 400 grams, this is not a problem if I counterbalance it properly on the opposite side to balance it on both sides and the Dahspot will do the rest

[WANCHO]

A small video and images of the cutting head design:

[WANCHO]

And until today that's all I hope you like my work and please you can ask me whatever you want. Thank you so much