lørdag den 14. juli 2018

PNC-3000 part 6

My 4jaw chuck is up and running, I had to grind off a few 0.01mm's of the jaws, and it is now running true.
In the meanwhile I had done a lot of speculations on how to make a new collet, problem is  that I need to slit it, but this can't really be done before it is drilled, and when it's cut off, I can't clamp it down to do the slitting. And if I don't cut it off the base stock, I won't be able to test the thread, and when it's cut off, it's difficult to correct the thread, hence my previous post..

I ended up taking a chance with the thread, which worked..

It ended up quite nice, but when I tested it for runout, it had the exact same as the original collet, and it was synchronous with the original collet. I guess this must have something to do with the way the thread is pulling.
I concluded that given the very similar properties of the two collets, attempting to make another one, would just be a waste of time.




The spindle itself has a runout of 0.01mm, which isn't impressive, just ok..

Despite having a ER11 chuck in the mail from China, I decided to make one myself instead, this way I could turn the internal taper, while the chuck was mounted in the spindle assembly all mounted in the Late, which in theory  sohould give me zero runout..


The two triangles I put on the drawing, helped me to indicate the angle of the top slide, to get the two tapers spot on.

In the lathe it all looked like this.

The steel used for the collet is 34CrNiMo6.. No I didn't come up with this particular choice myself, but I have a good friend, who knows something about steel. It's 35-38HRC, and has a bit of tendency to work harden, this gave me some challenges especially when drilling, since I only has HSS-G drillbits at hand, my guess is that HSS-Co would have been better, but the end result was pretty ok.

The taper was turned using a 6mm carbide end mill, and touched up with 600 grid sand paper.

So now the mill takes ER11, but somehow the 0.01mm runout still exists despite that I haven't had the chuck removed from the spindle..

But it's still ~5 times better than the original collet.

søndag den 8. juli 2018

PNC-3000 part 5

Next on the list is tooling.
There is only one collet for the mill, which only accepts things with a 6mm shaft, and it comes with a 0.05mm runout.
It is possible to get an adapter to ER16, but this sticks out quite a lot, taking away some of the 150mm Z travel, and it's also it's a bit pricy. I did order a loose ER11 chuck, so I intend to try out the concept in a DIY fashion, but I't probably won't be the future strategy.
The initial plan was to make something like a weldon style collet, and make a bunch of them, this would make swapping tools relatively easy, but since I don't have a CNC lathe this is a relatively time consuming task, so instead I have tested tool sleves.

Both works relatively well, the runout is obviously better in the bottom one, both sleves is made so that the tool bottoms out. This gives a repeatability of ~0.05mm in length, which is fine for most of what I do.
I'll still need to make a new collet, and this needs to be relatively precise. At least better than the old one that came with the mill, or else the it would be a waste of time to make a new one.. The collet isn't overly complex, but it still has a number of features, I did try to make one in stainless, that turned out really nice, apart from the thread, where I got the major diameter 0.5mm wrong.
I failed epicly in trying to correct the error.


This was the final argument in the process of deciding to get a 4 jaw for my lathe, I managed to find a really nice Burned chuck at a good price relatively close to the property. Only problem was that it was for a Boxford lathe (I think), so I needed a backplate for it. So most of the weekend was spend in the garage, making an adapter plate.


This opens up a whole new world of possibilities, for special tooling and fixtures, remounting stuff in the chuck without runout, and maybe even taking over the world..

It's not all joy though, as I seem to have an issue with the jaws not being perfectly squared to the chuck.

The mill has a toolsetter, but I also need an edge finder, which is a bit of a problem since almost all edge finders comes with a 10mm or 20mm shaft which won't fit in the mill. So I'll attempt to make one myself. The concept is pretty simple, a diode lights up, when the probe makes contact with the stock, or anything else which is grounded to the mill.
The probe end needs to be isolated from the rest of the machine, to facilitate that I have epoxied  a brass tube around a iron shaft.

 Initially I planed to turn down the end of the probe in the mill, to make sure that it would have zero runout, but since the mill has quite a bit of runout, and I'm now in possession of a 4 jaw chuck, it will be finished up there, when I have got the runout under control.

tirsdag den 3. juli 2018

PNC-3000 Part 4

The weekend was used designing and fabricating the PCB for the LinuxCNC interface.

The 4503 buffers to finish off the board wasn't yet in the mail, so it wasn't until Monday that I could do the final assembly and test of the board. It had the pleasant side effect that I also got a chance to enjoy the nice weather. The PCB was milled on my old 3D printer.


When everything was assembled the final result looked like this.


I had to do a bit hardware debugging before things was running smoothly, that's why there is an extra transistor and resistor on the board.. Sometimes things cannot be fixed in software..! :D

I can not take credit for the initial idea of pulling the 8255 chip and intercepting the control signals inside the mill, this was first done by this guy: https://www.youtube.com/watch?v=KTfs9lgCk1w
But he's design deals with SMD, which is a bit of a challenge when milling PCB's, and I thought that designing it myself, it would be a fun little project to activate the dormant brain cells.
When I'm done debugging, I'll post the design somewhere.. probably GitHub.

I had a bit of an issue, with the counter logic build into the mill.

The display has a resolution of 0.01mm, but the mill is specified to have 0.005mm, resolution both specifications is true, the last one being a modified truth. But I noted that when jogging the mill around, or if I ran some gcode, the display would get out of sync with the controller (LinuxCNC). Also the mill had a different sound, when running from LinuxCNC than with the build in controller.

The reason for this might be a bug/flaw in the counter logic, where the counter is incremented on the first pulse of the clock, which is actually ok, since 0.5 should be rounded to 1, but if the direction is changed when the position is at x.xx5mm the counter looses a count, and things gets out of sync.

Roland seem to have circumvented this issue in the firmware, by making sure to pulse the steppers an even count of pulses on every move, this is clearly visible on a osciloscope, where pulses can be seen paired, spaced with a few mS, you never see just one pulse..

This fix limits the resolution to 0.01mm with the build in controller, and explains the difference in sound, between running of LinuxCNC.

The issue is only cosmetic when the mill is controlled from LinuxCNC of Mach3, but never the less annoying..

Tonight I could take the first chips....



fredag den 29. juni 2018

PNC-3000 part 3

The bearings has arrived.. :)



To install them I needed a a couple of different pressing tools.


Once installed vibrations was mostly gone, I still get some resonance at specific RPM's but I hope this will be better when I get a new belt.


So now most of the mechanics is done, and it is starting to look good again.


During cleanup I noticed a tiny bit of backlash in the X-Axis, for a start I won't do anything about it, but I'll probably need a new ball screw later.
 I haven't made any progress with the electronics, apart from ordering a hand full of buffer chips.

onsdag den 27. juni 2018

PNC-3000 Part 2

While waiting for the bearings for the spindle and motor, I might as well start looking at the electronics. The back of the mill looks like this:


It might look a bit complex, but really it isn't.. Looking at the schematics was a trip down memory lane, the design is a classic microprocessor construction with everything you'd expect to find in such a design. RAM, ROM, address decoder addressable IO chips, external serial driver etc.

The plan is to hook into the clock, step, and power down signals for the three axis, which comes from a 82C55 IP chip, so first step was to remove this.

I must admit that it does hurt a bit doing this to vintage electronics like this, but in the end it should end up being a much more versatile mill, while still being almost original.

Preserving the original electronics means that the coordinate display will still be working, but it will only be possible to display the machine coordinates, not your work coordinate system, since there is no way of feeding offsets into the machine.




Since I already had access to the electronics, I figured that I might as well take a backup of the EPROM's, and no backup is complete without also testing if you can restore it again..


I haven't programmed EPROM's for a while.. 😁

mandag den 25. juni 2018

New Toys

For a long time I have considered building a desktop mill, I have a great deal of the parts and materials needed, and tools shouldn't be a problem either, only time, and the right design.

But then during a random search for CNC stuff for sale, an interesting  desktop mill showed up. The Roland CAMM-3/PNC-3000 Computer Aided Modelling Machine.. :) The price was fair, so I phoned up the seller and made a appointment to pick it up.
It was a bit of a gamble, as it was in the other end of the country, but the machine looked relatively ok given it's age, and to the best of my knowledge Roland doesn't produce junk. And compared to sourcing linear rails, bearings, stepper drivers, all of the material and parts I was missing, and using countless hours in the garage, this could hardly be a bad option, almost no matter how banged up the mill was.

So 9 hours of driving later the mill was at the compound.

The mill had seen a great deal of use, and needed a cleaning job, it's from 1987, and designed to mill plastic, wax, soft metals, and other soft stuff. The collet is 6mm only and not fantastic, but it has apparently done the job since the mill was new.

According to the seller the spindle needed an new drive belt, which was a reasonable assumption given the amount of noise and vibration it was able to generate when it was running.

The original plan was to tear the mill completely apart and clean it, but I ended up with a more lightweight solution.

I started with the spindle, the belt vibrated like crazy no matter how tight or loose it was, and when the spindle was turned off, it gave off a strange whistling noise, for some time after. This turned out to be the top bearing, that was spinning freely inside the spindle housing.


The whole spindle assembly can be removed for servicing, when I got it apart, it was filled with aluminium dust, and someone (maybe me) had managed to loose one of the balls from the thrust bearings, I'm pretty sure it wasn't me..
No biggie, I'll just order 3 new bearings, and everything will be fine.. Well.. hmm.. The thrust bearings are 7003C, relatively innocent looking, but is, judging from the price, only available in solid platinum or unobtanium.. Most places I found was asking ~100-150€ a piece, and I ended up paying 80€ for a set of non brand name bearings, but from a German supplier. After all the spindle is only doing ~10K RPM.

After the spindle housing was cleaned up, and a bushing to make up for the lost material around the bearing was fabricated, it looked like this:



While waiting for the bearings, I started on the rest of the machine, it was clear the previous owners hadn't given it much love..




Work in progress:


One of the other problems I noted was the dust covers especially on the z-axis was curling up, so I added a pair of tig welding wires behind them, to keep them in place, this worked really well:


After cleaning It looked like this


I also decided to take the motor apart to check the bearings, which showed up to be a great idea


And one could ask.. why didn't you wait ordering the spindle bearings until you knew, if you might also be needing bearings for the motor..  well.. please don't..

Now I just have to wait for the bearings to arrive, until then I can use some time on getting LinuxCNC to control the mill, since it only understand HPGL, but more on that later.

lørdag den 24. september 2016

The adventures of Mango no. 99

TLDR: When riding any form for bike, including a velomobile, wear your helmet, but don't crash on a busy road during rush hours, at least not if you expect any great deal of assistance.

About a year ago, I bought a used Sinner Bikes, Mango velomobile, it haven't seen much use since then, I think around 1200km, but it's a fun ride, and a nice way to get some excersise. So last Thursday the 22'nd of September I took it for a spin commuting to work.



Unfortunately, on my way home in the crossing between Ballerup Byvej and Knardrupvej https://goo.gl/T8OI2F the trip ended rather dramatically.
Those who have been there before will know that going out of town towards the crossing, is a nice long downhill ride, and those who have done it on a bicycle will know, that the window of oppotunity for bicycles to time the green light, is rather slim, but today it seemed like the timing was right, so I stomped some extra joules into the pedals, and went for it. In the post mortem analysis of the event, the maximum speed on the computer showed 63km/h, which I know for sure, was reached on that exact slope.

Towards the crossing I was slowly overtaken by a group of 4-6 motorcycles, of which apparantly none of them had noticed my presense on the bike path just next to the road on which they were driving. Or maybe they were just being rude, when all of them turned right in the crossing, right in front of me. Well, actually it loked like one of them had seen me, as it looked like he was stopping up, but when the rest of the group showed no intend of doing the same, he continued anyway.

Braking was no option, and braking and steering at the same time, is a sure recipee for disaster, but magically I managed to steer just behind the last ones of them, and I even managed to show them my right middle finger, while swearing at them.

Unfortunately some office warrier had decided to place a traffic island in my path, which I hit with my left front wheel, sending it into the air, leving me driving on the right front wheel and the rear wheel.
The Mango velemobile isn't constructed for two wheel drive, so after a few meters, the momentum from when I hit the curb, had spun the velemobile all the way onto it's right side, and I was now sliding on the asphalt in the velomobile at considerable speed.
Needless to say, everything went rather fast, but I did remember to appriciate sliding next to, and not into the signs showing the direction and distance of nearby cities. I reckon that a close encounter with a 40mm galvanized steel tube, solid founded in the ground, would probably had been a grim exierence for both me and my ride.

At some point in the slide, I had transisioned from asphalt to grass as the sliding surface, which provides a bit more traction, thus bumping me a bit more around inside the velomobile, and my head into the ground a couple of times.

After having slid approximately 15 meters the velomobile finally came to a stop, using the last of the kinetic energy I had managed to put into it on the downhill slope, to pop back up on all three wheels, with the nose pointing 180 degrees relational to my original travelling direction.

I sat there in the velomobile a few seconds, before checking that I was still alive, which fortunately seemed to be the case. Next thing was my hand which I had used as a signalling tool to the motorcyclists, to make them aware that I was not impressed with their style of driving. This hand had a strange sensation, a bit like when everything is just covered in blood. Luckily this wasn't the case, it had just been smashed into something sometime during the accident .

So I climbed out, and did a quick system check of myself, which apart from two sore shoulders, an sore arm and a sore hand, seemed to be in one piece. The right side of the velomobile was badly scratched, and the left front wheel, though still turning around, wasn't round anymore.
The motorcyclists were all gone, and not a single soul cared to stop and ask if I was ok after having crashed my velomobile at 60km/h.

I figured that if I wanted to have a just a tiny chance of getting the damagages done to me and my ride covered, I would have to call the police, which I did. When I came through, the lady in the other end was less than impressed with me, because i hadn't just dialed 112 (the equvivalent to 911) in the first place, then she couldn't find the roadname that I spelled to her from the sign hust next to where I was standing, but in the end she sent a police car and an ambulance.

Finally 5 minutes after the crash while waiting for the police, the first person, a guy on a bicycle,  cared to stop an check if I was ok. We talked a bit, and he went on with he's buisiness, in retospect it might had been a better idea if I had asked him to stay and wait for the ambulance, which he did offer, since I at this point had sligthly started to feel the impact to my head, and was thus looking forward to the ambulance arraiving.

The police and the ambulance arrived at the same time, so we had a bit of conflicting interests, as the police wanted to know what had happened, and paramedics wanted to to check that I was ok. But we managed to sort things out, and the paramedics really wanted to invite me on a ride to the hospital, an invitation I accepted. So the police locked the velomobile to the sign I had just slid past, and I went off to the hospital in the ambulance.

At the hospital I made a deal with the paramedics, that if I promised not to pass out on the way in, I could walk in, instead of being brought in on a stretcher. After a nurse had done a quick check on me, and offered me some pain killers, I was left to wait a total of 4 hours, before the doctor had time to check up on me.

When I was not just waiting, I used the waiting time to arrange transport home for both me and my velomobile, I did try to use my PC, which fortunately had survived the crash, but not knowing if I had got a concussion I figured that that might not be the best idea of the day, so it was quickly packed away. Also I was unfortunately enough to arrive just after dinner time, so I had to surrive on juice and coffee. About an hour before the doctor had time, I got a bed so that I could lay down and relax.

Finally when it was my time, it took 10 minutes, and the doctor was unable to find anything wrong with me, he asked me serval times "60 km/h?" and concluded that I might had been just a tiny bit lucky, which probably isn't all wrong.

At ~23:00 I was picked up, THANKS for doing this, you know who you are. We drove past the crash site, to pick up the velomobile, which fortunately was still there, and around midnight I was finally home, 6 hours late.

Before I went to bed, I took some painkillers, just to give myself a chance of falling asleep. At this point I was really starting to feel the events of the evening, I couldn't lift my right arm above my head without it hurting like hell, and my neck was stiff like if I had got a crick.

I didn't managed to sleep much, and when I got up, my upper body was trashed, my neck shoulders and arms was hurting, and my left shoulder had red stripes from knocking against the inside of the manhole in the velomobile. I think what best described how I felt was "how you feel the day after you had a lucly escape from a 60km/h crash in a velomobile".
It did help easing the pain, to get up and move around, but not a lot happened today, I did however managed to pick up a new rim from the local bike shop, when I was out shopping for lunch. And inspect the damage to the velomobile, which seemed to be, a lot of sctarches to the right side, a trashed left front wheel, structual damage to the rear, which I have no idea of how had happened, and two missing side mirrors, on the right mirror the holder was torn out of the glass fiber, I found one of the mirrors in the bottom of the velomobile. Impressively enough the front suspension hadn't suffered any damage.



The day after I started rebuilding the velomobile, switching out the rim was relatively simple, though it took some time to true it up, but the end result wasn't too bad at all. After having replaced the rim, I noticed that the rear wheel was tilted to the left, and upon closer inspection I found that the 12mm axle holding it had suffered a bend, and it needed to be replaced.

Getting the axle out proved to be quite a challenge, and I had to disassemble the whole rear suspension, since the bend prevented removal of the rear wheel, the way it was supposed to be removed, but eventually I got it out, and could confirm with a ruler that the axle was in fact bent.

I made a new axle on the lathe, and assembled everything again, just to find out that the rear wheel was still tilting to the left, though not as much, still clearly visible.  This could only mean that the rear suspension arm was twisted, and sure enough when I had once again disassembled everything the twist was obvius.


Using some of the larger tools in my collection, and a purpose made mandrel, I managed to untwist the suspension arm, and when I got things back together, it finally looked right.



The structual damage to the rear was fixed with a couple layers of glass fiber and some epoxy, of course I forgot to fix the hole left by the right mirror, so this will have to be be fixed another day. When the epoxy has cured, the velomobile will be rideable again, and then I can fix the cosmetics during the winter.