Author Topic: First real test  (Read 6143 times)

oscyp

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Re: First real test
« Reply #30 on: March 22, 2018, 04:31:53 AM »

I have just realized that the plywood I was cutting was actually a waterproof plywood with some hard epoxy glue in it... that would explain the difficulties.
I will try to cut the other dry plywood with urea-formaldehyde glue soon to confirm it was the issue.


As for the lens: I searched for similar parts and here is what I have found - https://www.banggood.com/Triple-Glazing-Focusing-Lens-Collimating-Coated-Glass-Lens-Blue-Laser-Diode-405nm-p-1035471.html?rmmds=search&cur_warehouse=CN


Seems to be even cheaper and a little bit better (half thread vs. full thread).


I am only concerned about the mounting - does it fit inside the focusing barrel or is it replacing it? (some pictures of how it looks like on your machine would be great!)
« Last Edit: March 22, 2018, 09:24:35 AM by oscyp »

pedwards2932

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Re: First real test
« Reply #31 on: March 22, 2018, 04:55:56 AM »
I believe this shows the different parts.....you just have to remove the old lens and put the new one in the focus knob.   I believe I was confused on putting the new one in because you threaded the slotted end in first.   I had to use some Teflon tape to tighten the threads when I put the assembly in the laser.  This made it so it wouldn't wobble as the threads are kind of loose.
« Last Edit: March 22, 2018, 04:57:01 AM by pedwards2932 »

oscyp

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Re: First real test
« Reply #32 on: March 22, 2018, 05:02:37 AM »
hmm the dimensions of these parts are the same, so I don't know

so is it possible to use the original knob to focus the new lens? Or with the new lens a screwdriver is needed?


Do you have any focused-dot comparison? Is it really worth replacing?
« Last Edit: March 22, 2018, 05:03:11 AM by oscyp »

pedwards2932

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Re: First real test
« Reply #33 on: March 22, 2018, 07:50:43 AM »
Yes you use the old focus knob,  You just thread the new lens in after removing the old.  It seemed to make a big difference for me.  Here is some info.....I have a G7 but haven't tried it yet because it has a different focal distance and I was getting pretty good results with the 3 element lens.


3-element lens (Standard lens, best for low power lasers)
3-element lens has a long focal length, low divergence and clean beam profile but it has a very noticeable output loss.

Advantage
Tight laser beam with the cleanest beam profile
Downsides
70% efficiency (1W diode = 700mw with it)

G2 lens(best power)
G2 is a high pass single lens which allows more laser light to pass through, it is the lens for maximum power and engraving.

Advantage
95% efficiency, small beam aperture, perfect for close range burning
Downsides
Increase beam divergence(thicker beam) and affects the beam profile

G7 lens(Most balanced)
G7 is the second best high pass single lens but it won't increase the beam divergence like G2 does. G7 has a long focus length just like 3-elements lens, a well balanced lens between 3-element(divergence) and G2(power).

Advantage
88% efficiency, long focal length and tight beam profile

oscyp

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Re: First real test
« Reply #34 on: March 22, 2018, 09:30:13 AM »

Oh thanks for the explanation! I think that your words are perfectly describing this picture:





Anyway both linked offers doesn't say anything about the type of those lens. So how should I know?
However, I am not sure why high-power lens are making poor depth cuts...

oscyp

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Re: First real test
« Reply #35 on: March 23, 2018, 10:15:40 AM »
Ok, I have just made some tests with another type of 3mm plywood and it is far better. Here are the results.


Front side:



Back side (image flipped horizontally):



Front side again, after taking the squares out.



Square cut with a speed / no. of passes:
300/40, 100/20 - felt off very easily, almost spontaneously
300/35, 200/25 - felt off quite easy, a very little force was needed to push them out though
200/20 - felt off not so easy, some force was needed to push it out, but it could be done without any damage
300/30, 200/15, 100/15 - felt off very hard, quite much foce was needed to push them out, they were also torn while extracting


Conclusions:
- type of plywood makes significant difference
- dry plywood made of urea-formaldehyde glue can be cut 4.5 times faster (using speed 300: 180 vs. 40 passes to the same result) than a waterproof plywood made of epoxy glue
- speed 100 is still way too much over burning for me
- surprisingly speed 200 is not so bad this time


I hope that some people find this post useful.


I wonder how air assist would affect these tests...
« Last Edit: March 23, 2018, 10:17:20 AM by oscyp »

ggallant571

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Re: First real test
« Reply #36 on: March 23, 2018, 11:04:51 AM »
A pressurized air stream will remove the char and extinguish any flames.
SARCASM - Just one more service we offer here.

pedwards2932

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Re: First real test
« Reply #37 on: March 23, 2018, 01:47:08 PM »
I really suspect something is off with your focus.....It shouldn't take more than 5 passes if you have a 2.5 watt.  Do you have BCL or T2?  I use index cards stacked to the thickness of the plywood and BCL to cut a series of focus lines until I have the thinnest line possible line. My reasoning is your kerf line looks burnt out because of the number of passes.  Also I would look into ordering plywood that specifically says for laser. I was using this{
https://www.amazon.com/gp/product/B01N5CHME9/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1

It says that it is for laser.

oscyp

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Re: First real test
« Reply #38 on: March 23, 2018, 02:04:46 PM »
Yeah, dry plywood with urea-formaldehyde glue is so called "plywood for laser cutting".

Regarding the focus - it is really hard to do it manually with a knob. I tried to get the best focus I could. Anyway, it is still only a visual check afterwards. I am considering to add a Z-axis, but this would lead to changing the controller board as well...

oscyp

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Re: First real test
« Reply #39 on: March 23, 2018, 03:51:46 PM »
Ok, I was so curious that I found a can of compressed air and was blowing it constantly while cutting.
Here is the comparison:


So air assist is indeed helping with burnt edges but it does not affect the cutting abilities at all.... same number of passes - same results but less burnt.
« Last Edit: March 23, 2018, 03:53:16 PM by oscyp »

ianchia

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Re: First real test
« Reply #40 on: March 23, 2018, 04:40:08 PM »
If you use transfer tape or masking tape, you can eliminate most if not all of the charring.

I use this stuff:
"600mmx20m Low Tack Paper Application Tape / Transfer Tape for Sign Sticker Vinyl"
https://www.ebay.com.au/itm/600mmx20m-Low-Tack-Paper-Application-Tape-Transfer-Tape-for-Sign-Sticker-Vinyl/251368075287?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2055119.m1438.l2649

- Ian

oscyp

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Re: First real test
« Reply #41 on: March 23, 2018, 04:44:47 PM »
it looks like a usual paper tape (like for wall painting or so)

pbucc

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Re: First real test
« Reply #42 on: March 23, 2018, 04:46:41 PM »
it looks like a usual paper tape (like for wall painting or so)
It is. Even blue painter's tape would work.

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oscyp

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Re: First real test
« Reply #43 on: March 23, 2018, 04:50:43 PM »
Won't it burn itself? :D

pbucc

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Re: First real test
« Reply #44 on: March 23, 2018, 04:53:22 PM »
Won't it burn itself? :D
From what I've seen online when you cut its ok. And engraving burns the tape. You could try it and see if it helps.

Sent from my LG-H873 using Tapatalk

2500mw A3 eleks maker.
Windows 10.
T2 Laser.
"I'm new to this. Please be gentle"