Chinese laser 50W, 50x30cm - bad/good stuff, mods, problems etc.

[iuliusdobre]

This thread is meant to share all the good/bad stuff, the modes, the problems, the setting... all related to the Chinese laser 50W, 50x30 cm. So, I'll start sharing all my experience with the machine.

1. The first impression is that for 1600€ (what I paid for mine), the machine is awesome. Don't expect the built quality of a 15.000€ Trotec, but it does the job. You'll have to align the lens. Very important... you need grounding. I recommend checking all the cables.
2. Now the bad one... I was the unlucky one and it came with an issue... it doesn't find the origin at startup and the rotatory accessory is not working well (or I don't know how to use it properly). For more info, read here.
Despite all this, I can do the jobs. Until now I cut/engraved 5 mm MDF, 5 mm acrylic, I cut paper.
3. The software RDWorks V8 (also called Laser Cut) is the not best but it does the job. Also it can be installed as a plugin for CorelDraw up to X7 version and Adobe Illustrator (that I haven't tried). Sending the job from Corel, for me, have some issues... sometimes, instead of engraving is cutting. So, my works from Corel I export them as .ai and then import them with RDWorks.
4. Another issues that I encountered is that at the bottom of the cutting area, the laser power is lower that at the upper part. What is cutting in the upper part, in the lower one is not doing it so good... I have to increase the power/ lower the speed to cut all.

Here is my control hardware


I made a support from an old table that I added some wheels. Also I made an MDF support for the evacuee tube (I cut it with the laser)

In the future I intent to change the evacuee tube, the working bed, to add a thermometer (an arduino) in the water recipient, to add some car antifreeze in the water and some other staff. Hope some other users will share their experience here.

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[iuliusdobre]

I made a thermometer for the water recipient. I used an arduino uno, a LCD 16x2 and 2 temperature sensors (one for water and one for air).

[iuliusdobre]

I made a thermometer for the water recipient. I used an Arduino Uno, a LCD 16x2 and 2 temperature sensors (one for water and one for air).

[iuliusdobre]

I found on youtube a guy who made some useful videos about this machine.
https://www.youtube.com/user/SarbarMultimedia

[iuliusdobre]

After watching the videos from the previous post, I tried to cut at 60% power what I was previous cutting at 95% power. The conclusion is that cutting at 60% was doing a slightly better job than an 95%. So, what the guy said that cutting at over 60% is doing nothing else that over drain the tube is true.

[TehPepper]

After watching the videos from the previous post, I tried to cut at 60% power what I was previous cutting at 95% power. The conclusion is that cutting at 60% was doing a slightly better job than an 95%. So, what the guy said that cutting at over 60% is doing nothing else that over drain the tube is true.

It is going to depend entirely on how the laser power supply happens to be "calibrated". At best it will be "50 Watts" at %100 which is more than that 850mm tubes can handle for a good length of time. I watched his series of videos this week and the whole time I was like just get an ammeter! It would have saved a lot of time, guessing, experimentation and a laser tube!

Typical max current for an 850mm tube is 16 to 18mA. The first laser power supply in my machine output that at "70%" the replacement did that at "50%". The power output means noting unless you measure what you are actually getting. Over current kills tubes rapidly, an ammeter is a ridiculously good investment!

Some additional info here http://www.cnczone.com/forums/genera...are-forum.html

[robertk925]

I added an ammeter to my laser to monitor the power going to the laser tube. I bought this ammeter on Amazon:

85C1 DC 0-30mA AMP Current Panel Meter Analog Ammeter - Multi Testers - Amazon.com
It measures from 0-30mA.

I cut an acrylic plate (in purple!) to replace the metal end cap on the laser chamber. An Adobe Illustrator file for this plate is attached. If you buy a different ammeter, you may have to change the cutout and screw mounting hole sizes/locations.



I didn't have time to unscrew the plate to take a picture of the ammeter connections, but it is really quite simple. I purposely mounted the ammeter in this location because it is very close to the wire that you need to tap into.

-Needless to say, but I will say it anyway, turn off and unplug your machine.
-Unscrew the blue metal plate. To get access, open the electronics access door. Be careful, some of the screws have nuts, which you will want to reuse.
-Attach your ammeter to your acrylic plate. My ammeter required M3 nuts for both the mounting and the wire terminals.
-The laser tube has two wires going to it from the power supply, a red wire (caution, high voltage, don't cut this wire!) and a black wire. You want to cut the black wire.
-Connect the black wire coming from the power supply to the + terminal on the rear of the ammeter. I used a circular wire terminal and a M3 nut.
-Connect the black wire going to the laser tube to the - ammeter terminal.
-If you hook them up backwards, your ammeter indicator will rotate the wrong way (and possibly damage the ammeter if run this way for a long time, but a quick pulse shouldn't hurt it).
-Screw your ammeter acrylic plate onto the machine, making sure you don't pinch any of the wires or push the black wires too close to the red wire.

I found that a 65% laser power setting (which I marked with a small pen mark on the ammeter) uses 20mA, which is supposedly the max you are supposed to supply to a 50W tube to maintain a long life. So the ammeter has been very helpful so far. I would also recommend the SarbarMultimedia videos on Youtube (who also sets his maximum power to 65%). The whole series is extremely helpful for owners of this laser (although I am not completely convinced by some of his testing methods, they still serve as good food-for-thought).

[Gozzie]

I suggest everyone use the amp meter to know what 100% power is.
I cant imagine how many tubes have been burned up over powering them.
Then once once you know what is 100 % I would back off to the 80 - 90% mark.
Your tubes will last much longer.

Excellent reading thanks,

Gozzie

[robertk925]

Thanks Gozzie. The complication is that each wattage has a different recommended maximum power, and with the laser tubes being mislabeled (e.g. our 50W tube is most likely a 40W tube) it is hard to know what the max power should be for the longest life. I looked at a lot of different tube manufacturers and they each had slightly different recommended maximum power ratings.

[Gozzie]

Thanks Gozzie. The complication is that each wattage has a different recommended maximum power, and with the laser tubes being mislabeled (e.g. our 50W tube is most likely a 40W tube) it is hard to know what the max power should be for the longest life. I looked at a lot of different tube manufacturers and they each had slightly different recommended maximum power ratings.

Boy aint that the truth. I saw posts that say you can get pretty close by measuring the length and diameter of the tubes. A person could probably search that
fairly quickly. You were very wise to install a meter. Mine already had one. When I first started it up I found that 75% was 100% max on my 130 watt SPT tube.
What I haven't figured out yet (partialy because of laziness) is that if you lower your min power the power ratings go down and 75% on the controller isn't 100% on the tube anymore.
That being said, I don't know if the manufactures calibrate them with a min power of lets say 20% and max power at 100% gives 100% at the tube.
But.... I calibrated mine with min and max power both set the same and found that at 75% it gave 100% at the tube so I feel safe about it. I don't run mine over 65 % for a safety margin
Some day I will play with the min power setting and see if it scales at some kind of ratio. I just don't know what that feature is really intended for. I apologize for the long rant.

Gozzie

[robertk925]

Very interesting. I haven't tested it, but I am guessing that the minimum power is more for raster engraving, rather than cutting.

[Wooden_Pepe]

Hi,
can this machine cut 5mm MDF if I use better lens ?

Thank you.

[robertk925]

I have never cut MDF, but it sounds like iuliusdobre (who started this thread) has cut 5mm MDF. See the first message.

I cut 1/4" acrylic (6.3mm) all the time, and even 3/8" (9.5mm), although it is slow and the edges aren't straight/great quality.

[iuliusdobre]

Yesterday I installed the amp meter (a similar with the one used for robertk925). The installation was very simple... just like robertk925 described it. Also is the same way SarbarMultimedia did it on his youtube video. I noticed that at 60% power it's using 15mA. 60% is what I always use for cutting.
Regarding the 5 mm MDF... I'm cutting it pretty much. I use 60% power and 8m/s. For this material I've changed the bed... I made some kind of nails with the sharp point up to narrow the contact surface with the wood. Less contact, clean cut... Much contact, it leaves some king of wax that is stains both the wood and the bed.

[robertk925]

Thanks for reminding me. I have a really simple pin table that I made from perforated steel plate (you could also use aluminum) like this:
Amazon.com: A36 Steel Perforated Sheet, Unpolished (Mill) Finish, Hot Rolled, Staggered 0.125" Holes, ASTM A36, 0.12" Thickness, 11 Gauge, 12" Width, 24" Length, 0.1875" Center to Center: Industrial & Scientific

and slotted steel roll pins like this:
McMaster-Carr

I had to reduce the length of the plate from 24" to 22" (as I have a ruler mounted on the table that it indexes against). I also had to cut the lower right corner to clear one of the Z-axis screws.

Mark the rows and columns with a marker. Mine are spaced approximately 1"x1". Place the plate on a hard, flat surface (I used my garage floor). Start gently hammering in the roll pins until they bottom out on the hard surface. They won't all be perfect, but you can flip the table over later and use a small piece of aluminum or acrylic to flatten the pins to the backside of the plate. While it may not be most perfectly flat surface, I haven't had any problems using it to cut for a few months. It really reduces the backsplash, and is sturdy enough to hold almost any material.

[iuliusdobre]

I found another tutorial about adding an ammeter to the machine.... LensDigital - How to add ammeter to 50W Chinese laser cutter from eBay

[robertk925]

Great link, I hadn't seen that one before.

[iuliusdobre]

Indeed, great tutorial. I believe is made by a user of this forum.
This is how I did mine...

This way I haven't made any modification to the machine, except cutting the wire from the laser tube to connect the ammeter

And this is how my bed looks:

It is made from two 40x30 cm MDF boards cut with my laser machine. In the corners I put 2 small magnets. This way is locked. Now I got zero reflection.

[robertk925]

Nice job on both! Always great to make updates to your machine using that machine. Another improvement I made to my unit was to put weatherstripping/gaskets on all doors to guide the airflow from the front (and prevent rattling).

Later on I will upload pics of my dual laser pointer holder.

[iuliusdobre]

I'm looking forward to see your dual laser pointer holder and the weatherstripping/gaskets. Also, to see your ruler and the motorized bed