A perfect fit for the Mantis

A few weeks ago I received a package from Robin, someone I met on Domoticaforum Europe a few years ago, and who’s well known for his design skills. For example, in 2009 he helped me by designing the tickets for a very important soccer game for ‘our’ soccer club:

This would have taken me weeks to create, if I would ever succeed.. Robin finished it within the hour; at least, that’s how I experienced it 😉

And if you ever need a button for a touchscreen, iPad or whatever, Robin is the one to ask for help 🙂

Robin also attended the Arduino workshop and was very interested in the Mantis workshop I attended last year. Now this package he sent to me, contained a few sheets of wood and perspex. I knew a package would arrive, a few hints were already given by email and I knew that Robin was working on his own Mantis, so I had some idea what it was – a dust cover for the Mantis!

 

 

 

 

 

 

 

Wonderful, just what I needed. Lack of time and all kinds of other problems prevented me from working on/with the Mantis this year, but this beautiful gift will surely contribute to picking up the Mantis project again. Thanks Robin! I owe you one 🙂

 

First things first

Not good enough

Not good enough

Some time ago I did a 2nd test with my Mantis. This is not something you do in a spare hour or so; you really have to sit down for it for a while and prepare for it. The result has improved, but still needs a lot of work as you can see in the picture to the left. Is it the rotation speed, the cutter, what.

I decided to buy some extra cutters, and this week these cutters arrived. I bought them at Kafra Tools. Good price, fast delivery and no minimal order quantity etc. This evening I’m going to test these cutters and see if I can produce something better than this. If not, I’m going to replace the rotary tool with a faster one. And if that doesn’t help either… I don’t know yet; but first things first!

First test with the Mantis

After coming home from work yesterday, I had a couple of options to spend my time. I chose the Mantis, cause I really wanted to see how it would perform. I had already ordered 2 160×100 mm Copper Clad boards (learning new words all the time) some weeks ago, but…

Neh, the first try was done with pencil and paper; I wanted to see if all went well without the chance of breaking something.

This went well. Next – the real deal! I attached the board to the bed with a screw in each of the four corners (this MDF bed won’t live long cause i need one that’s a bit thicker) and homed the Z-axis with a ‘trick‘: when the cutter touches the copper plate, you could regard this as a “switch” closing, right? So I put the cutter and copper plate in parallel with the Z- end-stop as a 2nd switch! Now I could just move the cutter down to the copper plate and it would stop all by itself. That’s easy.. That’s a good idea for X- and Y- homing too I guess: a vertical metal plate and cutter both connected to the respective end-stop inputs. I’m gonna build something for that soon! The position of the cutter above the board is very important to achieve the right cutting depth; the copper clad board is 1.6 mm thick and cutting to deep would make it too fragile.

Back to the milling! Here’s picture of the milling process after 10 minutes. I chose a feed rate of 50 mm/min cause I had no idea what to expect. On this picture the cutting process looks OK, but you haven’t seen what it looked like after the next pass, and the next… there was a point where I began to doubt if any copper would be left on the board! I’m going to put the result on my flatbed scanner so I can analyze the result better.

First milling!

Some conclusions and ideas on how I’m going to try to achieve a better result next time:

  • The X-axis still needs some adjustment;
  • I think I need a better cutter (where to buy?) cause the edges of the cuts are rough;
  • The depth of the cut is constant in the area (40 x 60 mm) that has been cut;
  • I have to ‘tune’ the Eagle DRC settings to better match the cutter size;
  • The same goes for pcb-gcode.

Still lots to do, but the result of this not-so-well-prepared first try is encouraging enough to go on! 🙂

Added the end-stops

Last weekend  I spent some time on my Mantis again. The additional end-stops had arrived, so I mounted them:

Y+ end-stop

Y- end-stop

X+ end-stop

Fun

After that, I was busy doing all kinds of things, but none of them Mantis related: a X-Mas tree, some ‘experiments‘ with LEDs and LEGO, repairing a laptop and 2 movies later, the weekend was over. But I do get very close now to some serious testing! I saw the X-axis needs some more adjusting cause it’s fitted too loose to be accurate, but apart from that, I’m almost ready to go!

Now the software part gets important; I’ll have to read a bit more about G-Code and the most important codes, so that I can ‘read’ the G-Code myself and understand what it all means. And once I’ve created a G-Code file that works, the first test run will probably be with a pen or pencil instead of the rotary tool and a piece of paper on the bed, just to make sure the Mantis doesn’t make any sudden movements that can be damaging.

Would I manage to create something useful before the end of this year?

Adding the end-stops

Sometimes it’s good to follow a certain path to a goal; not skipping those less interesting things that have to be done to build something that’s really finished. That’s why I decided to not go rushing towards building something  asap with the Mantis, but take one step at a time; all the steps! One of those is adding end-stops to the 3 axes. The Ultimaker board has 6 screw terminals to which you can connect switches; in this case, micro switches. Each axis can be ‘protected’ by 2 micro-switches, so that the stepper motor will automatically be halted by the software when a limit is reached. Sounds like a good idea to implement, so I did, although I was tempted to skip it – I want to see the Mantis building something! I have to restrain myself, or I’ll end up with a partly finished “thing”; and we all know what happens next with those.. nothing!

So I didn’t skip adding these end-stops, cause I know that if I skip this step now, I’ll never do it.

X- end stop Z- end stop

So no rush, taking it one step at a time… and to be honest, with the current weather conditions I don’t really feel like starting a garden irrigation project anyway! 🙂

Surfacing the spoil board

Yesterday I had a few hours to devote to my Mantis. The power supply, Ultimaker board with Arduino MEGA had to be attached to the back of the Mantis, the wire  mess needed to be taken care of and some other things needed to be dealt with before I got to the point where I could let my Mantis do some first serious milling. The closer I got to that point, the more I sensed some nervousness; after working on this machine for 5 evenings and an afternoon, would it really work???

The last issue I took care of was the spoil board. The one that was supplied wasn’t thick enough (caused by a design hickup), so the cutter couldn’t even reach the original spoil board at it’s lowest Z position. So I took a piece of 18 mm MDF plate and made my own. With the additional 6 mm in thickness, the cutter could now cut into the spoil board deep enough to perform the initial surfacing.

Now it was time to really start doing serious stuff instead of clicking the X, Y and Z buttons… so I mounted the spoil board, hooked up the Mantis to my laptop, started ReplicatorG, opened a G-Code file to surface the spoil board and clicked the build button.

YES, it works! OMG, this is beautiful! 🙂 Some issues though…

The cutter moved too fast. I could hear that the rotary tool didn’t like the speed with which it had to cut. I modified the G-Code and adjusted the feed rate (the F variable) to slow down the movement of the cutter, but that didn’t help; so after that I created my own G-Code with help of a facing tool and decreased the stepover percentage to 10%. That did the job; now the rotary tool no longer ‘complained’ and in 20-30 minutes the spoil board was done.

Another issue is the dust. Maybe the amount of dust that was produced is caused by the use of MDF as spoil board, but doing this in a room of 4 m x 6 m x 2.10 m with 4 PC’s nearby is not a wise thing to do I guess; when the slots for the floor heating were cut into our concrete floor earlier this year, 2 DVD players stopped working afterwards; I hope this won’t happen again!

Also, the connection between ReplicatorG and the Mantis isn’t 100% yet; whenever I use the Control Panel to manually control the Mantis and try to do a build after that, the Mantis doesn’t respond; only after disconnecting the USB connection and restarting ReplicatorG, a build will succeed.

Despite these issues I’m pleased with the results so far. I uploaded some images and below you can watch some video’s of the surfacing process.

The Mantis

Mantis

Mantis

Yep, time for something completely different! Is it? Not for me, although the relation with Domotica might be less obvious. Last Tuesday I attended the 2nd evening of the Mantis workshop which is held at ProtoSpace.

Protospace Protospace is not just a standard laboratory; it is based on the FabLab concept of MIT professor Neil Gershenfeld. It’s a typical place where designers, inventors, artists, students and educational institutions can meet and bring their ideas to life.

What we are building is a modified version of the Mantis-9 CNC Mill, which is described in detail here. The workshop consists of a total of 4 evenings, so half of the workshop is already over. Time really flies! The construction still needs quite an amount of work, so that’s why we were given some ‘homework’ in the form of soldering the PCB that will be used to control the Mantis. This leaves more time to spend on the construction during workshop hours. The PCB that will be used to control the Mantis CNC Mill is the Ultimaker Board, which is also used in the Ultimaker project. The PCB and a bag full of loose components should result in the following:
This PCB is in fact a large Arduino MEGA shield, cause that’s what is also needed to control the Mantis – the Arduino MEGA will act as the ‘link’ between the PC and the Mantis.

What do I need this Mantis CNC Mill for?
Nothing in particular, but a lot of things! And I’m sure the rest of the family will come up with enough ideas too, when they get a notion of what you can do with the Mantis. The first thing I want to accomplish is PCB milling. I hate experimental PCB’s and volumes are too low to have PCBs made at an affordable price (tooling costs…). The Mantis looks like a great way to get around this ‘problem’. From there we’ll see what the next focus will be. And the main reason of course why I enlisted for this workshop: it’s lots of fun to build it!