Archives December 2012

In a few other blog entries, I described getting and modifying my laser cutter/engraver. You can read these here:

• Unboxing
• Modification
• Final touches (coming soon)

This post however is a review on the laser, as it comes from the eBay seller. I’ve broken it into a few sections, and pointed out where my experience has differed from other stories I’ve heard online.

Packaging and Delivery

So, the packaging wasn’t too bad. It was obviously shipped from China, and just redistributed from Portsmouth with no actual unpacking. The outer wooded crate was quite battered and falling apart, with lots of packing tape. Thankfully, inside the crate was lots of polystyrene, and the actual device was in good shape. The x/y carriage was secured with a bit of ribbon, and all electronics were well secured. Now, from various other blogs, I know this was very lucky for me as many other people complain of loose connections and missing screws. About the only complaint I have on the whole packaging front is the way the water cooling tubes were tied in knots. This put some rather bad kinks into the tubing which could restrict the water flow.

Software

The software is the worst part of this device, which is why I threw it away as soon as I’d tested the machine was working. That being said, I can give a few observations from my short lived interaction with it. First off the software is very much Chinese with very basic translations. If you haven’t got the Chinese localisations installed on your computer, then the install process will show lots of strange characters, not that it will be much better unless you can read Chinese. This means installing the software is pretty much blind.

If you manage to stagger through the install process, you’re presented with a whole wealth of configuration options, drop downs, and a big canvas area. At this point, I managed to get one of the example files loaded and the laser tested. After that I didn’t really use the software again. I do know you can import Corel Draw pictures, and possibly even get a plugin of Corel Draw. There are lots of videos on using the software, and if you don’t want to customise the machine, you’re best off watching them.

Laser

Once again, from reading other blogs, I believe that I was rather lucky in that the test fire worked first time. Many other people have to go through an alignment process of tweaking the mirrors or even actually moving the whole laser tube. I can see why they would have these issues as this whole machine isn’t what I’d call well built. Lots of rough edges and no real finish to it in any way, but you get what you pay for. The extractor unit is very basic, and the slot for it is not a good fit. It is well worth taping it into place to get a better seal, and hence better suction to extract the fumes. For cooling you get supplied with a small aquarium pump which needs submerging in a bucket of distilled water to keep the laser cool.

The main area with the x/y axis is actually not too bad, with it all running quite smoothly. The x axis is very slightly out of alignment, which is something I still have to correct, but overall I’m fairly impressed with this. The axis are controlled by standard stepper motors, with endstops being hall effect sensors. The main drawback however is that the cutting area isn’t sealed, so the extractor doesn’t work as well as it should do.

Safety

I think this deserves a section all to itself. This device is built with absolutely no safety features at all. The laser can be running with the lid open to allow people to put their hand in the (invisible) beam of the laser, there are no interlocks either to stop the laser if the water isn’t flowing or the extractor fan fails. I could see no fuses at all within the electronics enclosure, and from one blog I read it was pointed out that some short circuits could put 20kV through to the control panel. Also, the cutting area is not sealed from the electronics area either, so fumes can easily pass through and escape.

Summary

You get what you pay for. This is a very cheap (for laser cutters) machine, with no regard to build quality or safety. If you want to get a laser cutter that works out of the box for commercial reasons, then spend three times more and get something better. That being said, if this is for someone who is technically adept and has experience in cartesian robots such as Reprap or other CNC machines, and wants something to experiment with, this could be a good purchase. My other posts describe what needs to be done to get this working to an acceptable standard, and it will cost a bit more money. I’ve probably spend another 50% on top of the original cost to get it working properly with safety features. If you do go down that route, then this can turn out to be a nice little machine for a hobby or hackspace. Once tuned and tweaked, cutting materials up to 5mm may be possible.

I’m pretty happy with it, and it was a good way to experiment with laser cutters without spending thousands of pounds. I am already thinking about going the entire homebrew route for my next one, if this turns out to be useful for me.

A slight detour from laser based articles. We’re off on another convention next weekend, and Joy is taking some special gin. 🙂

A lot of people make Skittle vodka by dumping a load of Skittles into bottles of vodka, but this involves a lot of filtering afterwards, and still leaves the vodka cloudy. By using Jolly Ranchers you can totally skip the filtering stage, and they also dissolve a lot quicker.

So, here’s the recipe for making Jolly Rancher Gin. Not exactly hard, but thought it was worth writing up.

Requirements:

• Gin – a 1.5l bottle will be more than enough. You may have enough with just 1l.
• 5 x 250ml flasks. We got these: Eddingtons Roma Bottles 250ml x 6
• 1 x 14oz bag of Jolly Ranchers. People in the UK can get them from here: Jolly Ranchers Original – 396g

Thats it, nothing special. Start off by making sure the bottles are thouroughly cleaned if you’ve just got them from the distributor. Then open your bag of Jolly Ranchers and start sorting them into the five flavours

 You will need approximately a dozen of each flavour, but it will depend on how many of each flavour comes in the bag. No doubt you’ll find too many of one, and not enough of the other. Next, unwrap all your sweets and start popping them into the bottles.

Once the sweets are in, start filling the bottles with gin. Slowly fill up until you hit the bottom of the neck. Once filled, simply put the lids on and give them a good shake.

All that needs to be done now is to wait for the sweets to totally dissolve. This takes between 12 and 24 hours, and will probably need a shake or two to stop it forming into layers and to speed up the dissolve.

Thats it, dead simple, and so much easier than skittles. Enjoy!

Last week I took delivery of a nice laser CNC engraver/cutter. This was a very cheap chinese machine, model number K40-III. When I got it, I knew the controller and the machine itself were very limited but there was an open hardware project call LaOS that I hoped would solve some of the issues. Couple that with a bit of my own customisation, hopefully I am going to end up with a fairly decent machine, for a lot less than a commercial model. I’m not the first to attempt this, as these machines are very common on eBay. I haven’t seen any success stories on my browsing so hopefully I will be the first.

I’m not going to put all the details on here, as I am updating the project wiki so its all in one place. This is going to be more of a log of what I do, so if you want the nitty gritty details, take a look at the wiki page for this machine.

So, on with the log. After making sure it was all in working order, the next job was to figure out what all the connections did, and what to do with them. Starting with a load of photos, I started to trawl the net. The controller board I knew was a chinese model, so punching the numbers off the silk screen into Google I managed to find a pdf with the technical details. One drawback, it was all in chinese! Thankfully Google translate came to the rescue and gave me enough details, coupled with details on the Laos wiki about other laser machines, to know what each of the connectors did. The other part that needed tracing was the power supply. Thankfully this turned out to be a simple case of checking continuity between the pins and the components on the control panel. After all this investigation, I knew how the stepper motors, the endstops, the control panel, and the power were connected.

The only difficult part was how to control the laser. This is a bit I struggled with as the documentation for the LaOS project is still being written, and there seemed to be multiple ways to control the laser. One of the power supply connectors allowed me to fire the laser, which was great for testing, but it didn’t honour the laser enable/disable button which I would rather leave in place and active. There was also another connector pin that was labelled as Laser, which in theory will control turning the laser on and off from the controller board. Experimentation will be needed I think.

With this knowledge in hand, I purchased a LaOS PCB, along with the PCB for the i2c LCD addon, and started putting the electronics together. Again, due to the project wiki being fairly new, and the team behind it being very small, it wasn’t quite as easy as other projects I’ve encountered such as RepRap. I’m fairly confident this will change over time, and I know I’ll be going through the wiki adding information once I’ve got it all working.

Once the electronics were constructed and ready, I unplugged the old controller, plugged in the new one, loaded up a test firmware and turned it on. I rather quickly encountered my first problem. A total school boy error of putting the wrong voltage capacitor on the board meant it blew up in my face… literally. Still, no harm was done to either the board or myself, apart from a bit of an adrenaline rush. I quickly swapped out the old capacitor with a newer one of the correct voltage and plugged it all in again. Nothing blew up this time, and I could confirm that all the voltages seemed correct. Next step was to try some of the motors and end stops. Moving the head back and forth showed that both home position endstops were working fine thankfully, and were inverted so that they turned off when homed. I guess its safer that way, and it told me I needed to set that up in the configuration.

Happy that things seemed fine, I put the real firmware onto the board and fired it all up. Success… kind of! The X axis homed nicely, but the Y axis sat and juddered in place. After a few posts on the forums, and a lot of messing with config files, and checking of connections, finally it homed to the correct position. With that seeming to work, I fired up the interface software called visicut, and tried to send a few test files to the machine. Well, things moved, but not exactly in the right way. Still, better than nothing and I was fairly certain that it was all down to settings in the config file. I was beginning to understand that the config file is the hardest part of setting it all up, but finally after a lot more tweaking of the file, I had both axis moving in the correct way and the correct amount.

Next came the laser. In some ways, I was dreading this. So far I’d been messing with things I knew about from building a couple of reprap machines, namely stepper motors and pololu stepper drivers. I was fairly confident if I blew either of these things, then I could fix or replace them. The laser was something totally new. However, from reading the documentation, and putting a multimeter onto the connection marked L on the PSU, I was fairly certain all I needed to do to active the laser was to pull the L pin down to ground. All this took was a single wire from L to one of the Laser On pins on the LaOS board, and the other Laser On pin I simply tied to a handy ground point (ie, the screw terminal on the board that came from the PSU ground).

With a little bit of trepidation, I powered up the printer and started visicut. I loaded a simple rectangle file to test with, and hit the execute button. A nice little rectangle was cut out of the test bit of card! Wow, that was easy! To say I was happy would be a little bit of an understatement. I quickly grabbed a bit of acrylic I’d got to test with and fired up inkscape to draw something. I only wanted something simple, so I decided to try and engrave my name into the acrylic, so a quick click on the text button, and I typed my name in. Up to the extensions menu, and select Lasercut Path and the image I created was loaded up in visicut. A click on engrave, and execute, and my name was being etched into the acrylic! It turned out rather nicely! 🙂

All in all, I’m very happy. I got a cheap machine off eBay with a lot of limitations and with the help of an Open Source hardware project, I’ve turned it into a networked laser CNC machine. It is still limited in the strength of the laser and the bed size, but I now feel confident enough that if I end up using it a lot, I can get a higher end cutter and convert that.

I’ve still got a way to go yet on this project. The CUPS driver isn’t working properly, so I’m relying on using visicut to do the actually printing work, but that isn’t too bad as it is a pretty easy to use program. I also need to put PWM onto the laser output so that the controller board can vary the laser cutting power itself. Lastly, there is the i2c LCD module to get working. For some reason if I plug the module in, the controller board won’t boot properly, but I haven’t done any investigation yet to find the reasons. Oh, and I think a few safety measures are needed such as a water flow sensor and lid sensor which deactivate the laser in the case of anything not working… better safe than sorry!