Member postings for Muzzer

That link seems to focus mainly on PCBs warping but I suspect what Andrew is referring to is slightly different.

This link **LINK** summarises copper balance for both warpage (1) and plating thickness (2). In my experience, adding lozenges for copper balance is usually to address the latter.

Like him, I've had problems with unauthorised lozenges(!), as they are usually added by the PCB manufacturer, sometimes without asking.

Murray

This is almost certainly a permanent magnet synchronous motor that needs to be driven by a sinusoidal waveform. You can check that by driving it (slowly!) and looking at the back emf if you have a scope handy, For a synchronous motor, you need to tell the motor drive the position of the rotor, hence the encoder, resolver or whatever. Presumably there is some form of position sensor on your motor?

BLDC motors are usually driven with fairly simple on/off waveforms and the position sensing can be much simpler ie Hall effect sensors buried in the motor. It's possible you have one of these but seems less likely.

VFDs are available with encoder inputs, so if you can find one of these you may have a solution. Judging from the voltage rating you will be using a VFD running directly from AC rather than through an isolation / reduction PSU - some servo systems run 48VDC or similar.

I've just been looking at something very similar myself from a local (to me) company **LINK** which would cost about 200 quid. It would almost certainly work with your motor although there may be something available more conveniently for you. I'm sure you could find something on ebay or Ali Express....

Murray

Is there a cutoff age for MOTs? Perhaps if I wait ling enough my 1967 Honda S800 (car) will make it back on to the road without the palava of trying to get it to meet current requirements? That's an exciting development! I'd have to move back to the UK first, mind.

JES

Here's what I did. It becomes impossible to remove the ballnut from the screw once you have machined the end of the screw down without them falling out unless you have some form of keeper. I had to remove the nut so I could machine both the screw and the nut. Windows 8 has forced me to load the photo at 90 degrees but you can see what I've done. Mine's a 16mm ball screw BTW.

The nut contains a length of rod that is threaded M8 internal at each end and is currently preventing the balls from falling out. I have a bolt and washer at each end to keep it in there! The other rod is bored to fit over the reduced end of the screw and threaded M8 so it also screws into the other rod - it's only used to transition the nut from the screw onto the keeper. Once the nut has been persuaded onto the keeper and the bolts fitted, you can breathe again!

BTW, both the screw and the nut are machinable if you use carbide tooling. Keep the speeds up and keep flammable materials away when you do it!

Murray

I must be missing something. Surely these engines run stink hot and the pistons will run a fair bit hotter than the barrels, so if you have effectively zero clearance when cold you will have issues when the piston heats up. Certainly, the conditions will differ considerably from those described during machining. The other difficulty concerns the lubrication. You need a layer of lubricant (the fuel mix presumably) which requires a gap - is 2 microns enough?

Whether or not this claimed level of accuracy is actually achieved, what is believed to be driving the requirement? You aren't going to be losing much mixture (compression) between the barrel and the piston and the heat transfer isn't going to be affected either. Are there dyno results that show some form of benefit?

To be honest I'm not convinced these values are required, achievable or even measurable in this environment.

Merry

That's interesting David. Thanks for posting your experience. There seem to be any number of ways to do this but many of the stepper-based conversions seem to be massively overspecified, almost certainly due to lack of clarity about the loads and speeds required. When you look at the torque-speed and power-speed curves for steppers, the ratio has very little effect on the thrust you can get when the motor is flat out. The higher the pulley reduction, the greater the torque is geared up but almost equally the achievable torque is less due to the higher motor speed. It almost boils down to what rapids you want.

Very few of these systems have PSUs above 300W or so, which rather gives you a clue about the thrust x speed (= power) you can achieve. And given the finite spindle power that you have to begin with, there is a limit to what you can actually make use of in terms of X and Y feed.

I removed my 32mm Y-axis nut and it's 39.6mm OD which is particularly annoying, as the (25mm) metric ballscrew nuts are 40mm. Which leaves me with a problem - do I try to machine either the double ball nut or the yoke. Or do I make a new yoke up? I will probably machine the nut down. Mine's a Taiwanese BP clone with a mixture of metric and imperial dimensions which may explain the odd size.

I'm looking at using these closed loop stepper motor/drive combos **LINK** driving the X axis directly and the Y axis through a toothed belt so I can retain a handwheel. I know the purist CNCers will say you don't need manual operation but I'm sitting on the fence on that one.

Murray

Towards the end of his career, my father was the senior safety manager for one of ICI's divisions (remember ICI - like GEC, it used to be a major UK industry). The German factories were the worst of the European factories when it came to industrial accidents and the electrical accidents stood out in particular, not least when you considered fatalities. It's not what we would expect from our cliched view of the Germans but the numbers spoke for themselves.

It's never going to be possible to get H&S to where everyone is happy with it and there are some silly things going on with some regs but the data for injuries and fatalities has improved over the last few decades so some of it must be working. If you want to see what happens when there is no consistent H&S standards, take a look at some of the videos of Chinese factories and ask yourself if you'd want your offspring working in them!

Murray

Don't have the beer vouchers to buy the ballscrews yet and even if I did, I haven't worked out the dimensions etc I need to convert my BP clone X and Y axes to ballscrews and servo steppers. I have initially modelled how the current X-axis setup looks. I think I've got it about right now, so the next step will be to design a replacement left hand end bracket to take a stepper motor and a suitably modified ballscrew to mate with that. It's clear that the dimensions of my clone differ from the original BP, so it's just as well I didn't just copy standard conversion parts from the drawings.

It's probably true that I could figure out the lengths etc quicker using a ruler and pencilCAD but converting those dimensions into a series of dimensioned 3D parts ready for machining is so quick and easy this way once you've got a finished assembly. If you change a part, the assembly and drawings update automatically and you don't get caught out. But this is also an opportunity to learn how to use 3D CAD - Solidworks in this case. I'm pleasantly surprised how easy it is to learn it to a useful level.

Murray

Edited By Muzzer on 02/05/2014 07:49:48

Wikipedia's armchair reckons the Vernier scale somewhat predates 1766. It may not be gospel but is usually pretty accurate.

"The vernier scale originated in ancient China as early as the Xin dynasty (9 AD). It was reinvented in its modern form in 1631 by the French mathematician Pierre Vernier (1580–1637). Its use was described in detail in English in Navigatio Britannica (1750) by John Barrow, the mathematician and historian"

Handbags and armchairs, eh!

Edited By Muzzer on 24/04/2014 17:15:51

Good old Wikipedia: **LINK**

Andrew's out and about, gliding and soaring in the skies somewhere Oop North. But here's a photo he sent me of his Clarkson.

Can't tell you much about it although I doubt the chuck key was made that way. Apparently the chuck itself seems to have survived the process.

Murray

The transition from hideous plastic to solid metal is progressing reasonably well. My Z-axis stepper drive is about 90% complete now. I await the pulleys and belt (should be here tomorrow) and I have a few bolts etc to machine up.

The last part completed was the bracket that connects the ball nut to the quill (this is a Bridgeport clone). I would have made it in steel but I know the loominum will withstand the stresses and there are few wear points, so this will do to get me going and is quicker to machine up than steel. This is another part that would be almost impossible to design without 3D CAD and make without a DRO.

At the back of the collection is the (black) stepper motor which is a rather nice closed loop servo stepper from Leadshine. This has the driver and an encoder packaged together into the motor, so you get the performance of a servo (almost) at the same cost as a std stepper motor and driver board. I'm driving it with a Mesa 5i25/7i67 board and LinuxCNC. Or at least I've managed to spin the motor for now!

Murray

Ian I also found that if you bore out a piece of 2" round stock and then try to slit it lengthways in the bandsaw, it pinches the blade every time. I suppose the answer would be to normalise it with the blowlamp after boring which I obviously didn't do. In my case, I was able to extract the blade from the work (just) using a screwdriver and much patience. After 3 such incidents the blade still cut but had a pronounced series of wobbles. You'd certainly struggle to normalise a 6" diameter bar with a blowlamp....

Murray

Needed to reduce the flange on a (hardened) recirculating ballnut. Don't have any sensible grinding equipment so I followed Andy Johnston's lead **LINK** and turned it on the lathe using carbide tooling. I found 0.1mm depth of cut and something like 8 thou per rev worked nicely. You have to get the speed right up there, so I gave it 2000rpm and it cut nicely. Took it down from 48mm to 32mm diameter and the length of the flange is 10mm.

This is how it started out:

This is what it's like in action. Stand back!

The finished part:

I actually turned it using an indexable boring bar behind the workpiece with the machine running in reverse. I do this quite a bit, as you can turn inside and outside surfaces this way and also make internal and external chamfers without having to change the topslide. You just need to remember to select the correct direction of rotation every time....

As before, I made most of the parts on the 3D printer to check fit etc and I am gradually swapping the plastic parts out for metal as I make them or they arrive in the post. When you are making parts up to fit an existing complex body it seems to me to be the path of least effort and risk (try modelling a Bridgeport head with all its lumps and bumps this side of Xmas).

Murray

Edited By Muzzer on 16/04/2014 07:20:43

Sounds like a classical wrecking bar to me. You just lift it up a couple of feet and bring it down point first as hard as you can. Not many things stand up to that. Great for smashing up concrete floors etc before they invented those Kangol things. They are best used by themselves without a sledgehammer - the bigger and heavier, the better.

Murray

Further to John AS's comments, as a Brit living in Canada, I was almost shocked that find that there is more metrication in general here in Canada than in the UK. It's true that metric is the default in the UK (and indeed almost anywhere outside of the US) but there is so much imperial stuff hanging on outside of the engineering world.

In the UK the vehicles work in miles, beer is in pints, distances are often measured in inches and feet and you can still buy food and drink measured in pounds (albeit also measured in kg). In Canada, vehicles use km and litres. Food is generally in litres and kg. Engineers work in SI units, unless they are working within a US-centric business.

Where it all falls down is the local availability of metric tools, fasteners etc. Mostly the supply of these parts piggy backs on the back of the US supply chain, so I've ended up having to buy a variety of imperial drills and threading tools.

Of course, the most shocking thing is the almost complete lack of pubs in the accepted meaning of the word. And when you finally find one and order a pint, they give you something that is almost 20% short. That's hard to live with as a Scottish-blooded Yorkshireman....

Murray

The original question was how to get 2 motors to turn at the same speed. At some point you are going to have to either acquire some measurement of the actual individual motor speeds and use a closed loop to try to get them fairly close, or you are going to have to use a motor + drive system that will faithfully deliver what you ask ie feed forward.

The first (servo) solution will require significant effort to get it anywhere near the requirement and you are some way from that right now. The second is relatively simple if you implement a stepper motor + drive for each motor and provide them both with the same direction and step signals. School children around the world are doing this as we speak and the parts are not surprisingly readily available. You can even play about making your own drivers if that is your thing.

I agree it's fun to mess about with electronics and make stuff rather than buy it ready made but there needs to be some plausible path to the end goal?

I don't know how old your car is but they have been using PWM in car HVAC fan control for years.....

Murray

I got spare holders for my Bantam from either Chronos or RDG (forget which). They are Indian I think (Soba?) and perfectly good for my needs.

Teehee the Rotagrip prices are removing yellow fluid! Anyone buying stuff there should get sacked.

Murray

I've now had a 700lb/in "super heavy dooty" die spring in there for some time now with a decent preload. I've also done some stress testing to check for any signs of movement and to see what the machine will do. Looks pretty good.

I plunged a 3/4" hogging cutter right through a piece of 3/4" loominum rectangular stock for several inches at 1000rpm and something around 10-15 IPM feed. This must generate a fair amount of pull-out. The inverter tripped at one point (I've changed the settings now as they were too low) but otherwise this is probably about as harsh as I will get. I've also run a 12mm slot drill along a 12" length of mild steel, followed by a tee-slot cutter, generating a sizeable tee slot in 2 passes. I wouldn't have done this dry but it didn't complain and there were no dings.

I've been using this quick change system quite intensively now for the best part of 3 months and I can honestly say this is one of the best additions I've made to the machine. Along with the DRO. And the power feed. And the VFD....

Murray

I was looking at Mark C's estimate based on 50p / gram. Sounds as if that is how commercial operators are pricing their work ie 20:1 markup on the material cost? I suppose it's a simple formula and presumably covers amortisation, time and profit as I said.

MichaelG - yes, I saw the announcement from HP yesterday. Quite amusingly simplistic for their marketing rep to suggest that they have "solved the problem" of speed and finish - so we can all go home now. Like anything, in practice it will be a steady journey to drive the cost down and improve the quality. I suppose they get paid to say stuff like that!

If it's anything like the inkjet market, HP will be looking to make their money on the consumables by locking owners into proprietary materials / refills. I suspect that will be more successful in the consumer market, whereas the hobby / ME sector will be more resistant. I wonder if it will ever come to the point where they give away 3D printers free, as they do with inkjets.

BTW, to illustrate some of the related developments that may be closer to our interests, here is a "subtractive" 3D machine (call it a mini CNC) that's very closely related to what we know as 3D printers or 3D routers. THey all use g-codes. The gap between this kind of beast and full CNC systems can only narrow,,,,

**LINK**

Murray