Time to start testing

Tonight was a very significant step forward in the development of the new control system for the Mill. I have now reached a point where I trust the setup enough that I can start finalising the control parameters and start tuning the motors and so on.

I wrote a little G-Code program with some help from the Machinekit documentation so I can run some tests that will help me with this tuning. The main thing I am worried about at the moment is loosing steps because of incorrect speeds or acceleration. To test this I am going to set up a program that will cycle for about 10min or so just making movements in one axis to see if it drops any steps. If I note it's position when it starts and compare that to the position it returns to then I will know if it has lost any steps.

A very basic program so far. It only runs once but all it will be is a replication of this program many times to get the cycles needed for confidence in the setup.

This is a video of running this program. It is using a feedrate of 100mm/min which the motors seem to like. So this should be a good starting point that I can improve on.

I'm thinking about different ways I can share the programs between different computers. I am probably going to set up a Github or similar account that I can store the machine definitions in. Then if the SD card this is running from dies I still have the configurations and they can easily be transferred to other machines or shared.
For the G-Code programs I am probably going to set up a Resilio Sync installation on the controller. This way if I want to edit the files on a different, faster computer I can. Then once I'm finished editing the files it will be quite quick to move across to the controller.

Cheers,
Rex

Milling Madness

The end is in sight. I got some more work done on the Mill upgrade over the weekend and am now at a point where I am happy to start making chips.

Last time I tried to get some work done on the mill I was defeated trying to get a fan set up. This time I found a fan in my junk pile that works.

This is the old power supply that I installed in the control box here. Then I replaced it here. Although it has been sitting for over a year the fan still works from it. It is labelled as a brushless fan but I figured that the designers wouldn't have gone to the trouble to drive the fan with some kind of waveform and it could be driven with plain DC.

It turns out my guess was correct. So I now have a fan to go in the case. It was even exactly the right size for the mounting holes.

Here it is set up in the black box testing phase. I had it rigged up on the desk without plugging in the machine just to get this stuff sorted. Now that I have the fan and everything sorted it is time to move it off the desk onto it's home on the CNC bench.

Here you can even see the penguin power. I am planning on using just the mouse and the little numpad pendant as the interface for this as there won't be much call to type stuff in and this will keep the fairly crowded bench clearer. For now however while I am setting up the parameters for the stepper motors as a proper keyboard makes this much easier.

Now I just need to work out the toolchain to turn a CAD drawing into code to run on this machine. Getting it onto the machine should be fairly easy as it runs a quite up to date version of Linux so I can just set up an NFS share or similar for loading up programs.

Cheers,
Rex

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.

A Little more practice needed

So tonight I decided to have a little play with the Lathe. I probably should've gone to bed early for work tomorrow. but it was calling me.

You may remember that I am setting up a fixture on my mill to experiment with parts drawn in Fusion 360 then exported through to it. Unfortunately as you can see in the above picture the hold down bolts I have are a little too long. To fix this I could cut them down with the hacksaw. But I thought it would be a lot cooler and good experience to use the lathe.

So I set everything up as near as I could figure to correct.

I put a little oil on the part. I was planning to add a drop halfway through, but the spindle doesn't run with the face shield up so I had to put a drop on then just let it go. Probably not too big of a concern with this part at it's fairly small and although it will produce some heat it shouldn't get too bad.

The result of the first pass. The spindle started to load up a little then the tool seemed to jump over the little nipple that was left without actually cutting through it. So perhaps the tool is too high? Simple solution, lower it then.

Hmmm. Possibly too low. This picture looks much worse than it did in real life.

Here we go. I did add another drop of oil, but it had pretty much been thrown off by the time the tool came in, I probably won't worry in the future.

It worked. Kinda. It's a bit difficult to see in the pictures. But the surface finish on the part in the chuck isn't great and while it did cut through it wasn't particularly happy about it.

I thought it must be too low now so I moved everything around again and had another crack at this. Just for practice now.

Unfortunately this attempt was an unmitigated disaster. The tool got caught in the threads and was deflected off to the side. Then it started to cut. Thankfully I stopped the machine before anything snapped.

The Solution? Turned out not but it was a fun thing to try. I set up another tool opposite the parting tool. This is more or less how the machine was when I received it. I wish now that I'd played around more as it was. But hindsight is 20/20 and I knew even less then than I do now. However I was able to turn this to a fairly good surface finish quite easily.

The feed was set at about 10mm/min, the depth of cut was about what looked pretty good and the spindle was set at 1/4 of the way between 200 and 2000 on the dial for it. Not sure how accurate that is though.

So now that we have a nice flat surface that isn't going to deflect the tool lets try again.

This was the result. The tool just rubbed and pushed the workpiece around. It actually crushed some of the threads in the chuck so the steppers at least have a bit of go to them even if the spindle is a bit weak.

At this point I decided to call it a night and had a quick look at the turning insert I was using.

Thankfully no visible damage as I expected. However it is always good to double check.

I will probably go back to playing with the wax and delrin(?) blanks I have for a little while, at least until I get a better feel for how each of the tools work and getting them set properly. The good news there is that means I will probably get to the mill sooner again. I will rig up a fan that actually works to send some air over the stepper drivers as they do get quite hot although I think they are still just within spec for passive cooling. Then once that's done, I have worked out a method for driving the spindle so it will be full speed ahead for making some chips over there too.

Cheers,
Rex

How to hold this?

After going through building the stock for this part I'm going to make with the mill the other day I tried to work out how I am going to hold it in the mill.

As you can see there is a groove all the way around which I had planned to use to hold on to with some clamps and T nuts.

These ones in fact. However what I discovered is that all of the shorter screws that I have are a much coarser thread than what the nuts have so I'd need to pack underneath the longer ones quite substantially. Not impossible but I'd rather avoid that if I can.

So I figured I'd use the little vice that came with the mill. Some comprimises there also, but better than having to space it out by a mile. However do you think I could find it? Option C it is then.

Here we have some longer bolts that we faced the head down a little so that they will fit in the T slots. It isn't ideal as they have a hex head rather than a square head but they do lock in the slots nicely enough. The only problem is that the cutter is sitting on the block and the spindle is pretty close to the ideal height now so it would probably crash into the hold down bolts. Less then ideal.

But there is a solution. I have chucked the first bolt up in the lathe and I will part it off as short as possible which will give me plenty of length to hold this down.

Here we are, all set up and ready to go. I probably won't do this before the weekend as I don't want to be making too much noise at night and upsetting the neighbors. That can come later.

So keep an eye out and I will try to get some video of the parting off so anyone that knows a bit more than me can point out where I am going wrong.

Cheers,
Rex

Something a little different

So I dont like doing things the normal way. Here is more evidence.

This is an iMac G3 and I am planning on setting it up to control the CNC mill and hopefully I can find a way to use it to drive the lathe as well.

The Lathe still works

So I have finally got everything in place to use my CNC Lathe. To test it I ran it in manual mode. I stuck with the default settings of 80 mm/min, 0.25mm X incremental feed & 0.1mm Z incremental feed. I had a play with the spindle speed just to see what would give the best finish. There didn't seem to be much difference but I was just using a pretty soft piece of some kind of plastic.

This was all I did, the spindle is quite loud so I didn't want to be running this too late. I'm not quite sure what kind of plastic this was but I did get a fair few pieces of what seems to be Delrin that I will be experimenting with once I work out how to hold them as the chuck doesn't open far enough to hold them.

This machine is fairly old and is controlled from a 486 running windows 95. Not the world's oldest machine. But fairly old. The interface is all DOS based so to improve startup time I have disabled the windows GUI entirely and just boot into DOS. The interface, while definitely classic it isn't too hard to use or hard on the eyes, which can be a problem with some of these older user interfaces.

I shot a video of me machining this piece with my phone sitting on top of the safety shield. During the video you can hear the different pitches as I adjust the speed of the motor to see if that would change the finish. Watching the video and also while using the machine there is a lot of backlash evident in the Z axis so I will try to work out what is causing that and hopefully remedy it.

With this now working I should be able to power the spindle for the mill from the accessory port on the control box for the lathe. This will give me a chance to fully test and even start using it to make parts.

I have the manuals for this lathe so I will probably put together a program that will allow me to turn down the Delrin blanks so I can mount the securely in the better chuck. But we'll see about that.

Cheers,
Rex

Don't let fear stop you

Sometimes we come across projects or sub projects that we don't want to take on because we are worried what others might think, if it's safe, if others will think it's safe, if it's too expensive. The problem is that when we let these fears and concerns govern what we allow ourselves to do then we end up not accomplishing anything near what we are capable of.

This is something that I have struggled with on various projects over the years, is it safe? What will others think of me doing it? Whatever the case may be. On the instances when I have put these fears into their place by stopping and working out just what the impact will be, then after putting into place safety controls I have always found these projects to be worthwhile. This one today is one of them. Here was my problem:

The controller for the CNC Lathe runs on 110V not the 240V that comes from the walls here. When I got the machines I had a few cords that would connect them to a transformer box  so they could be used with a 240V wall supply. Unfortunately I have lost said cables and to be able to run the Lathe I need to get 110V to it. Bugger.

This is where fear came into it. From the time I have started playing with electronics there has always been an unspoken rule that you just don't have anything to do with line voltage as a hobbyist. This is a very safe rule. However in this situation it would've stopped me from being able to run the lathe again unless I found the power cord (Unlikely). So after taking stock of the risks (electrocution) and working out controls (unplug and leave for a while to let any charge dissipate, test to make sure nothing is shorted to the case before re-connecting) I realized that this could be fixed safely.

And here's the finished product. I can now use a normal power cord like I would use for a computer to power the lathe with 110V.

That's where the scaryness happens. The transformer is potted in epoxy so that's all quite solid.

Looks like I'm not the only one who chain drills and doesn't fully clean up the edges. I had to take off some of the peaks before the new socket would go on.

Testing all of the connections. I'm using an old analog multimeter on ohm reading to check for shorts. It does still work, certainly well enough to show a short circuit.

That's all for today, the next post will be my 100th post on this blog so I am working on something cool for that so stay tuned.

And remember, don't let your fears tell you that something can't be done. There's always a safe way.

Cheers,
Rex

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

Getting closer

So I finally have a space inside for me to work on the CNCs. This is a drastic improvement over where they were. outside. Where I would freeze in winter, cook in summer and be attached by mozzies at any time of the year.

I had planned to build a set of bespoke shelves that would allow me to put the servers above the machines rather than below them as you see here. However that didn't quite work out so in order to be able to actually get these inside before it gets cold I got a pair of shelves from Super Cheap Auto in town

I have not complaints about these shelves. They are fairly solid; and while I needed to give them a few taps with the hammer to get them to clip together fully that does mean that they won't be falling apart any time soon.

Each of the pieces are fairly flimsy, but once everything is together it becomes fairly rigid and I have no problems putting as much as will fit onto these shelves as inevitably will happen.

The next thing I am looking for is an old monitor that I can connect to the computer for the Lathe so I can control it and ideally a rack mount cabinet that I can fit both of the servers in along with the switch so that the cables are a bit neater and I can put them away from any possible shavings that might be leaking out of the machines.

I have a few things coming up. We got some good photos at the Lakemac Heritage festival so I will be sharing those. These CNCs will be running again very soon and I have a few things I would like to make with them that might actually happen now. And I have a Hard drive that I have been asked to destroy for data security so I will go through the details of construction with that.

Cheers,
Rex

Shelves for the CNC's

Even though I've been spending a fair bit of time recently playing with my computers and setting those up I am still working on my other projects. The biggest other thing I have been doing is preparing to make some shelves for the CNC mill and lathe to be put on so I can have them inside.

This is what it should look like. I sketched these up with the new CAD software at work over some lunch breaks to help familiarise myself with it.

I didn't get a picture of the stack of board before I started, but with a lot of help from +Ben O'Regan and +Nathan O'Regan we were able to rip down the sheets to a much more manageable size using a circular saw.

This was what we had after the first day. Unfortunately that had to be cut short as Nathan got caught by an offcut and we thought it prudent to stop there.

The evil piece that caught Nathan.

This is what is left of what we ripped down. We didn't fully optimize and allowed ourselves an extra length of 700mm wide just in case we made some mistakes cutting. Thankfully we didn't need this extra piece. However we do need a new saw blade. The one we had been using is pretty blunt now and wouldn't complain about being retired to use on soft pine.

All these black pieces are what's going to make up the shelves. After getting a wash though I think. It doesn't look like much but it was a very hot sweaty afternoon to get to this point. However we are almost there. Just need to route the rebates on some of the shelves and then fit it together. Then look for more CNC updates because they will be inside and I won't have to fight the mosquitoes to stay out there.

If you have any tips on cabinetmaking or other furniture manufacture please let me know. I need all the help I can get on this one.

Cheers,
Rex

The Mill moves again

On the weekend I had the opportunity to play with the CNC mill again.

We last left it running, with the power supply integrated into the case. The old computer power supply had enough juice to run the beaglebone, but unfortunately not enough grunt to energize the stepper motors. As soon as I tried to power them up some kind of overload protection would shut the whole thing down.

To help pinpoint the exact problem here I connected my benchtop powersupply in parallel with the computer supply over the stepper driver input. This worked and I could switch machine power on and off without issue. To see if the problem was just an initial surge overloading the PSU I unplugged the benchtop supply to see if everything would still run. It did; but the PSU started to make a funny sound and I'm sure I could smell something wrong. I plugged the benchtop supply back in and the noise went away immediately, with the smell disappearing shortly after.

So it looks like I don't have a big enough power supply. The solution? I've ordered a 240V to 12V 20A swichmode supply from eBay. At the price I decided to get the 20A model as it might be a little marginal at the rated power. By getting well over I should have plenty in reserve, particularly if I want to run the spindle off it as well.

Hopefully this will arrive by the end of the week and I'll be able to install it either next weekend, or the weekend after.

Busy times at the moment, I've got something else on order from eBay that should arrive early this week. That will be an interesting little project. And I picked up something interesting from the market today which I'll do a little post on as well. So keep an eye out for those coming up.

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.