Trying to get a fan

Yesterday to try and keep out of the heat I stayed inside and tried to get some work done on the CNC Mill. I have tested all of the steppers and everything looks good there. However the Pololu stepper drivers I have only have a fairly small heatsink on them. I am not exceeding the rating that is recommended with the supplied heatsink, but I am at the limit of what can be done there. So with that in mind, I would like a bit more headroom.

When LMC built this control box they quite kindly left a fan shaped cutout for me. Unfortunately the fan that was originally in there ran from the 110V mains this was set up for. So I plan to use one of the PC fans that I have sitting around here instead.

This fan is close enough to a good fit in the cutout that it will work fine. However, upon testing I found that it would not spin. The cogging effect was increased though. Then I looked at the small print. It is a brushless DC motor. I do not know much about these, but it seems they need a varying DC waveform rather than pure DC.

So where in here can I get a varying DC waveform from? One of the PWM outputs from the BeBoPr Beaglebone cape of course. The plan was to get machinekit running and then set up a user controlled variable to adjust the PWM duty cycle until I found the sweet spot. Then set it u so that whenever the machine is turned on in Machinekit then the fan would start.

That was a good plan. Except for the fact that because I haven't done anything with this for months and months. I couldn't get machinekit to run at all. Then I tried a new, clean image to make sure that there wasn't a setting causing the problem. However then I ran into a problem with my HDMI to VGA adapter. Apparently the Beaglebone Black doesn't supply enough current over the HDMI port to run a passive adapter. So I either have to hook this up to the TV in the loungeroom, buy an active adapter or I can mod the passive adapter. I actually have all the parts I need to be able to regulate the 12V down to 5V needed and wire up the regulator. So I might end up doing that.

So keep an eye out for either a fan installation, or modding a passive HDMI to VGA adapter.

Cheers,
Rex



Actually I just remembered that I have a fan in one of my servers that is run from a molex connector for the disk drives. That means it runs from 5 or 12V DC and can be made to work here. Seeing as I am not using the servers anymore I might just re-purpose it for this.

CNC Mill Moves, With evidence

The mill is running again, in it's new spot inside the house so I should be able to get to work on it a bit more often. This is where it is now, on the new desk with my laptop beside it running the controls

I had the lab power supply out to see if I could run the spindle off it. However even with the knob for current all the way up it was still getting limited so I think that's going to be a no-go. The good news is that I can still run it from the accessories port on the Lathe control box because I haven't gutted it yet.

It's a little bit dirty but not too bad and with the shield shut then there shouldn't be any issues with bits getting into the rest of the room which is good considering this is above my servers.

Here's the interface I am using for now. I'm hoping to get Machineface/Cetus/mkwrapper working so I can use any computer to control this, but for now I'm connecting with a VNC connection because mkwrapper doesn't seem to like being run in such a way as it can be accessed from outside that computer.

Finally, here is a short video I took while I was making sure everything still worked. I still need to set the maximum speed and tune the acceleration for each of the axies but I will get to that eventually. You can hear that when it's set right it's nice and smooth. But otherwise it sounds like somethings grinding.



Cheers,
Rex

Mill Woes

Just a quick update on how the mill is going as that's the only thing that's actually had anything done on it recently. I finally got the software issues sorted and worked out a display, then when I pressed the go button to power on the motors they hissed like they should for a fraction of a second. Then.. all of the power died to the board.

A second test confirmed that this is consistent behavior unfortunately. I think what is happening is that the turn on current draw of the steppers is too high for the computer PSU and it trips the overload protection. To test this what I'm going to do is connect my bench power supply in parallel with the computer supply and then after starting the motors wind down the current. That should tell me if the computer PSU will handle the base load current.

If it will then I will probably put some kind of large capacitor across the 12V rail and GND to help minimize the surge. I may do a quick writeup on the display arrangement I finally got working, particularly if there is some interest there.

I'll report back how I go with this.

Cheers,
Rex

I've got the power

I've finally got more work done on the Mill. I was hoping to get a shot of the control box powered up with the laptop running the control software next to it for the cover photo. However it seems that I need to keep playing with the software a little longer.

Instead you get a photo of the finished product as it stands. I know the wiring isn't the neatest or prettiest. But you can take my word for it that it does work now. Follow on after the break to see how I got to this point.

Nearly time to start Milling

So one of the other projects I did some work on over the weekend was the Mill. I now can move all 3 axes and using the mkwrapper tool I can control it from my tablet, laptop or phone without having to put a screen onto the Beaglebone that is running the mill. Something I think I will have to add though is a button as part of the GUI that allows the Beaglebone to shut down cleanly without having to ssh into it. That shouldn't be too hard and will probably be one of the things I will work on along with the rest of the GUI now that it will move.

Below are some pictures of what I did. Not very exciting though mostly just soldering and tracing wires. I even managed to get 2 out of 3 motors spinning in the right direction.

 This is with the Z Axis and the X Axis wired up, Z on the right, X on the Left.

Now all 3 have been done. The 3 unconnected wires will be used for e-stop and some limit switches
I think, possibly for spindle speed manual override. I have another Cable that I will use for the other needed signals.

In the back right you can see the connections I have made so far. I will put a proper enclosure
over the connection before I call this project finished.

This is a closeup of the final connection. The knot is for strain relief in the main cable.

 Thinking back now even before I have finished there are some things I would do differently. If I were to start again I would probably not cheap out and use more plugs, one between each motor and an enclosure proably on the back wall, then the big grey cable would have a plug on both ends rather than being soldered to the mill at one end.

Anyway, full speed ahead and onward ho. If I get to the end and decide it isn't working then I'll change it.

I have another 1 or 2 projects that I got up to over the weekend coming up so keep a wearther eye out.

Cheers,
Rex

Beaglebone Progress... Or lack thereof

So I finally got my Beaglebone Blacks out last night to try and get started on the CNC controllers and what did I find? I found they need micro SD cards to store all their info on and don't come with them... So today at work I'm going to order some from Dick Smith and at least one mini HDMI to HDMI adapter so I can plug them into a monitor...


Edit: I have just ordered an adapter and 3 x micro SD cards, one for my phone. I should have them within the week now

Progress on the CNC's

Today I finally bit the bullet and ordered 2 Beaglebone Blacks and 2 BeBoPr capes so I can do some more work on the refit of my CNC Lathe and Mill. The BeBoPr Capes are not avaliable until the 15th of august however so I won't be able to do anything with those for a while.

Stay tuned for some initial insights when I get the Beaglebones.

Cheers,
Rex