Member postings for Andrew Johnston

I use Easy-PC, good value for money, but even the cut down versions are probably a bit expensive for occasional hobby use. I use it professionally, mostly for 4 and 6 layer boards, which are largely surface mount. It has some limitations but these wouldn't be a problem for the hobbyist.

There are extensive libraries available for Easy-PC, but I prefer to make my own symbols, PCB footprints and components as it allows me to fine tune for schematic capture, PCB layout and manufacture.

I've used autorouters ranging from free to hundreds of thousands of pounds. I'm not overly impressed. Cheaper ones often didn't work and expensive ones leave a mess. The circuit board is an integral part of the circuit so I prefer to layout interactively. With push and shove routers it is pretty quick, although Easy-PC isn't at that level yet!

It's been years since I used Veroboard. I used to do a lot of prototyping with wire-wrap, and there used to be a system by Vero called Speedwire? Basically each pin had slots underneath and you pushed the wire in with a pen and moved on to the next connection. The pin cut into the wire to make contact. Very good for analogue, but expensive.

If I do prototype these days it is always dead bug. I don't prototype complete curcuits, just key analogue sections so dead bug is fine.

Andrew

I'm not sure what a dual phase motor is? If you mean dual voltage then that will be fine. For the purposes of a test even a motor designed to run only on 415V will be fine. Running a motor intended for 415V on a VFD that outputs 240V will work, but just won't be able to produce full power.

As for a sewing machine foot pedal I don't know, it's all down to the details of the specific foot pedal. If it has switches then it should be possible to make them work.

Andrew

The video is rather short on technical detail, but it seems like all capacitors are disconnected and the start winding is used as a second 'phase'. We never actually see a motor running. It may well turn, but who knows what the torque/speed curve looks like. Start windings are generally for intermittent use so may not like being in circuit all the time. Just because something is available to buy doesn't mean that it actually works!

Andrew

The notification system is unreliable. It used to work for me, but then stopped for reasons unknown, even by the IT people. Now, after many months, it seems to be working again, if somewhat intermittently.

I tend not to bother answering highly technical, and unsolicited, PMs from members with few, if any, posts. The chances are they arrived via google search, joined, flashed off a post or two and a few PMs, and then disappear for ever. I've wasted enough time answering technical questions that then go unread for months.

Andrew

Yes!

Andrew

PM sent - Andrew

The important factor is not how long it takes the cutter to reach its end of life, but how much metal is removed during that life. if you run the cutter without cutting anything it will last for ever, but the result isn't very useful.

Maximising metal removal over the life of the cutter means using correct feeds and speeds, and maximising use the flute length. Doubling the depth of cut doubles the metal removed without affecting the cutter lifetime. Chip removal is vital too, as mentioned above.

There are two rules for buying cutters:

1. Don't waste money on cheap cutters

2. See rule 1

I use YG-1 K2 cutters from Cutwel for general machining, and have also found the premium cutters from Arc to be excellent.

Andrew

Dealing with the easy bit first it is possible to control a VFD using a foot switch. The precise details will depend on the footswitch and VFD input configuration. But there is no need to sweat over the details at this stage, as it can be done.

The much bigger problem comes in wanting to run a single phase motor from a VFD. Particularly as a 3 to 1 speed range is required. The short answer is that it isn't possible. However, something can be cobbled together for some specific types of single phase motor. If the motor is shaded pole or permanent split capacitor then it would be possible, albeit with poor performance.

So the next step is to identify if the existing motor is one of the two types listed above. From a practical point the motor is unlikely to be shaded pole as they are usually only available in limited power outputs due to their inefficiency.

Personally I wouldn't start from here as it will result in something that at best won't work properly and most likely won't work at all. Best thing is to beg, borrow or steal an appropriate 3-phase motor.

Andrew

That's normal operation, and is how the cutter is intended to be used. Unless one is plunging the cutter into the work vertically the flutes always do the cutting. Even for shallow depths of cut. The teeth on the end are ground slightly hollow so they don't rub when cutting horizontally.

Andrew

Sigh, the unit is a thyristor phase angle voltage controller. It does not change frequency so will not change the speed of an induction motor. As an aside note that the 4kW rating is for a resistive load, which a motor certainly isn't.

It would be much better to tell us what you want to achieve and then those forum members who understand the technology can advise on the best solution.

Andrew

The point Noel was making is that some single phase motors have poor performance when run from a VFD, and many types of single phase motor simply won't work with a VFD. Ideally you need a shaded pole or permanent split capacitor motor.

Andrew

Edited By Andrew Johnston on 12/01/2023 22:22:11

I wasn't at all surprised that the mill stalled. The motor was struggling more and more as the width of cut was increasing, as can be heard. It's a plus in a sense, as I now know where the limit is. So I can run the machine hard but without overdoing it.

Andrew

Wow, that's a man size mill! Properly set up it should be able to shift some metal. It looks like the head swivels, although I can't see a degrees scale on it? Seems to be a good range of tooling too. The machine vice looks more like a shaper vice, but will do fine on the mill as well. The universal Elliott dviding head has considerable value, especially with the low lead drive shaft. Did it come with the all important tailstock, banjo and the change gears? The dividing is sitting on what looks like a rotary table?

Backlash isn't the problem it purports to be; there are workarounds. With a DRO it simply isn't a problem. My secondhand industrial machine tools have significant backlash, up to millimetre or so, but it simply isn't an issue.

Which university are you attending? Presumably your course is biased to mechanical engineering?

Andrew

Quandary solved; the seller accepted an offer from someone else. For their sake I hope it works.

Andrew

I have finally got around to testing out the 160mm diameter face mill kindly lent to me by Jelly:

Material is hot rolled steel. I dropped the spindle speed to 210rpm, about 105m/min surface speed. Width of cut was 150mm. I initially kept the feedrate at 430mm/min for a chip load (10 inserts) of about 0.2mm. However, I got some chatter. This may be because the cutter body is held to the spindle only with 4 1/2" BSW SHCS into the face of the spindle. So, despite my efforts, it is running noticably eccentric with consequent variation in chip load. I am also not sure that the inserts are consistently located in the pockets. I dropped the feedrate to 285mm/min for a chip load of about 0.13mm/min and that cured the chatter. Chip width measures 0.15mm, which is about right, as chips tend to be slightly thicker than the feedrate would suggest.

I have sent JasonB two videos which I hope will be posted in due course. The first run was with a depth of cut of 2mm. Changing units that is about 5.38 cubic inches per minute. The mill had no problem with this. I then increased the DOC to 2.5mm (6.72 cubic inches per minute) and stalled the cutter. I think that the squeal towards the end of the video is the motor belts slipping. I did some tidy up passes and have run the mill in a range of speeds and it all seems fine. I'd be pretty niggled if it wasn't. The stall was quite gentle and an industrial machine should be designed to survive that without damage.

When I stalled the cutter it chipped one insert so the next task is to order another batch of inserts from Ebay.

Andrew

Edited By JasonB on 08/01/2023 20:10:46

Not quite what I wrote.

I increase feed and depth of cut. I tend to leave speed as is. Although I may move speed up or down if the chatter is particularly persistent.

Andrew

It all depends on what is meant by a large hole?

I suspect that on a small lathe there is little to be gained by step drilling. There are not many things more tedious that continually changing drills going up in small increments. A drill is an efficient way or removing metal if the width of cut is large. I normally go up in steps of half or three quarters of an inch on diameter and use feedrates of 20 thou per rev or more, if I can wind the tailstock handle fast enough. But I have a large geared head lathe that will push a 1" drill through cast iron with no pilot hole if needs must. On a small lathe it is probably just as quick to go up in steps with a boring bar.

It's a myth that chatter equals resonance. They are two different things. Chatter is a forced oscillation. It might coincide with the resonant frequency of the boring bar but mostly doesn't. The important parameter for boring bars is stiffness. So bigger diameters are better. But using a large diameter boring bar with reduced shank to fit the toolpost is pointless. Increasing the stiffness can also be achieved by a change of material. Carbide boring bars are much stiffer than tool steel, but are also eye-wateringly expensive, especially in larger sizes. A lot of the old techniques such as adding lead or weights are aimed at damping any vibration that does occur.

Always operate with minimum tool overhang. Like Jason I run with my topslide in the mid position, but with the gib screws locked and the seperate topslide lock done up. I've never needed to use the cross slide lock to get a parallel bore. I find the best way to deal with chatter is to increase the feedrate and depth of cut. That loads the tool more and reduces the effect of the inevitable tool deflection on the cut.

Coring out the work beforehand can be useful, but for me is not worthwhile unless the core is going to be 1.5" or more. It is tedious but in my case I can use power downfeed on the mill quill and a bolt pattern on the DRO:

I've looked at annular cutters, but they don't seem to be available in the sizes and depth of cut that I would need.

Andrew

No it doesn't; It says the fan is single phase and does 2300rpm at 50Hz.

Andrew

In my experience 99 times out of 100 this sort of issue is down to the software. Even if the fault looks like a hardware problem. Put a 'scope on the data line and see what it looks like and if it is what is expected.

Andrew

Module cutters are always numbered in reverse order compared to DP cutters.

Andrew