Member postings for Muzzer

Hmm, the Schaffner filter specified and supplied by Yaskawa would struggle to fit that description, Schaffner being Schaffner.

This is the one specified and supplied by Yaskawa. That's a cool £25 +vat and delivery but as noted, the VFD bolts to the fixings shown and the flying leads are even precut and crimped to the right sizes. Being Schaffner (Swiss?), it's a well engineered part. Although described as obsolete here, it's available from inverters-uk.co.uk which is where I got mine.

Murray

No, not that simple. They are designed for industrial applications, to be built into cabinets etc. The requirement is for the final, completed system to be compliant and the degree of filtering required to achieve that will be very specific to the particular installation. That's why most VFDs are sold without filters. However, if you buy the specified filter (as I mentioned above), it will generally get you close to the "Class A" limits as a standalone unit, (these are are the limits that apply to industrial equipment), if used correctly.

Not a good idea to fit a general purpose EMC filter to the output unless you want to generate lots of smoke. There are filters you can buy for the outputs but they should be correctly specified for that application, ideally by the VFD manufacturer. The output waveform is a rectangular PWM voltage of ~340V amplitude and typically 5-10kHz or so, so a capacitive filter won't go down at all well.

Murray

Could have been a Lambo....

You wouldn't be able to meet the legislation (EN55011 etc) without caps to ground ("Y" caps) and caps across the phases ("X" caps). Of course, there's no obligation to meet those levels in your own installation but that's the basis of most pukka VFD filters.

You can get any number of different EMC filters, so you have little or no idea what effect most would have, other than perhaps finding that your radio works after fitting one. However, if you buy a matching filter from the manufacturer of the VFD, it's likely to be to some degree appropriate for that product. So my Yaskawa VFDs have Schaffner filters that are specified for those particular models. They are even fitted with threaded inserts so that the VFDs piggy back onto the filter box. Very neat.

Murray

Most CAD programs will allow you to import a scanned image and manipulate it (scale, opacity, colour, position etc), then create a 2D sketch on top. You don't need layers as such, as you can simply turn object visibility on and off or even delete the sketch when finished and save as another version.

If you are going to bother drawing it up, you'll probably want to enter the correct dimensions based on actual measurements once you've got the shapes right. Of course, you might then go the extra mile and extrude etc the sketches to create full 3D models.....

Like Dave, I make sketches with accurate dimensions then go straight to CAD. You'll struggle to correct the perspective etc on a photo of a large machine, so I'd give that step a miss.

Murray

My tables on my milling machines got a nasty case of surface rust from being outside over winter while the workshop was built around them. But it takes a lot of water and time to make serious ingress and I recovered them without undue grief using WD40, green scouring pads and a power sander (with hook and loop which holds the scouring pads very nicely). There remains some visual evidence if you look closely but as pointed out, once stoned flat, there's no lasting damage to the function and certainly no benefit in grinding.

After 30 years, it might be a different matter. A very light skim may be necessary if it's in a real state. What's the alternative - scrapping it? But if it's been sitting that long then it's not been getting any wear so there is an upside to it!

Murray

This evening the Battle of Britain Memorial Flight visited our locality. Southport is spitting distance away, so as I arrived home this evening at 8pm, the Red Arrows did their thing, followed by various Spitfire, Hurricane and Lancaster events.

I'm guessing this is the Hurricane? Hard to tell from this but from what I recall it has a longer thinner nose than the Spitfire.

Murray

Ed - the manufacturer's data for those inserts recommends 90 - 200 m/min surface speed for Austenitic steels such as 316.

At a diameter of 30mm, that comes out at 950-2100rpm. Try increasing your speed to within this range.

The "BF"chipbreaker geometry is designed for feed rates of 0.08 - 0.18mm / rev and depth of cut of 0.2 - 1.8mm. Taking a cut of 0.8mm pre rev sounds heroic! Again, it doesn't sound ideal.

Murray

PS - on reflection, it seems very unlikely you are actually cutting at 0.83mm / rev. I suggest you check your sums and gear settings!

Edited By Muzzer on 01/07/2018 16:02:39

I assume the 4th axis would use a rotary table or similar to achieve a reduction ratio, in which case 8.7Nm must be wonderfully OTT. Calculate what torque would be available at the work and ask what you could possibly need that for. You could destroy significant parts of the machine with that. Even 4Nm for the main axes must have a pretty large safety factor.

One thing to understand about steppers is that their torque falls off rapidly with speed. When I plotted a variety of stepper motor characteristics (torque vs speed), I noted that they display a characteristic that is very close to constant power. What that means in practice is that you might as well drive the ballscrews directly rather than gear the motor down through a reduction stage. That's the most common arrangement for steppers but you do see some with a reduction stage. With the latter you simply reduce the all-important(?) "rapids" whilst doing nothing to increase the torque / force available at a given speed of movement. For a willy waver, the stall torque at the ballscrew might be legendary but if you ever tried to develop it, something would break....

If you spend more money and go for a proper servo motor rather than a stepper, you will find that the stall torque is less than he headline figure for a similar size stepper but generally that torque will be achievable over most of the speed range. So you would probably need a reduction (typically 2 - 2.5 is achievable) but it will achieve much better performance over the whole speed range.

Murray

I don't think you'll find many people advocating use of the std leadscrews. You simply can't make them accurately enough to give acceptable backlash whilst still being able to assemble the nut to the leadscrew. Even if they seem OK when brand new, they will soon bed in and you will have measurable backlash. The friction is also pretty high relative to ballscrews.

Ballscrews are readily available from AliExpress and ebay for starters. It's one of the first things people usually buy when embarking on a conversion.

Makes you wonder what else they have cut corners on? Check out the hundreds / thousands of conversions done on similar machines. I assume the generic design used by Warco is available under any number of other brand names.

Murray

I don't have any slitting saws and they probably wouldn't last very long if I did. But one thing I've know is that they have cutting edges only on the circumference ie can only cut radially and not axially. In contrast, circular saw blades for wood usually seem to have teeth (often brazed on carbide teeth) that can manage side cutting (axial) as well as radial. You can even cut sideways (at shallow depth), even though they aren't designed to. And of course, the wood is much softer than any metal. So it's not likely the wood could force the blade to deviate from its default position. With a slitting saw, there's no way for a blade to correct if it starts to deviate. I suspect that's part of the answer.

Murray

Railway track is carbon steel so it can be hardened. Ideal choice if you can get some.

Murray

Yes - it takes 400 thou off the diameter, which is often what you want on a lathe.

Murray

PS - I've never checked on my Bantam but I assume the compound / top slide is different ie direct reading, as it could move at any angle to the axis.

Edited By Muzzer on 24/06/2018 21:55:40

The MIG 29 claims to be uniquely capable of the Cobra Manoeuvre. Looks like a truly breakfast-producing event!

Murray

Essentially, yes. What we call "240V single phase" is just one phase of a "415V three phase supply". The Neutral is the centre point of the 3 phases, which is grounded back at the substation (so Neutral is pretty much at ground potential). Whether you connect a motor as 240V delta or 415V star, each of the 3 phase windings simply sees 240V across its ends. 415V = 240V x (square root of 3).

Nothing at all wrong with "running a 3HP motor off a 4.5kW inverter". Will work exactly the same, except there won't be any overload protection unless you correctly set up the current limits in the config. Either it was wired up incorrectly, the config parameters (most likely for voltage and frequency) were wildly wrong or the motor was crap. Even so, the protection features in a good quality inverter should prevent damage.

Murray

Yes, I saw that earlier today, David - very interesting stuff! Looking forward to seeing your build video when you post it.

Murray

Cockpit view of aerobatics. Starts off very sedately and then at about 16 mins, hell breaks loose.

**LINK**

Murray

They offer a similar vise to the Arc one called "Value brand" but it has limited jaw opening (142mm vs 199mm), despite being apparently the same basic design. I expect Arc (Ketan) worked with his supplier to optimise the design beyond the basic concept, which is something you get from the better purveyors of Chinese goods.

Murray

You need to clamp it to the table with tee bolts and a couple of slotted clamps. The larger ones don't seem to come with them but you need a clamp set anyway, which are on offer from MSC (but check your slot width)....

I notice that the MSC vise is on offer at £130 at the moment (page 13). Good deal!

Edited By Muzzer on 22/06/2018 23:12:22

Neil - why can't your pics be clicked on to open them? I've noticed this before - some pics can be, some can't, including the "For Sale" pics. On this page, SOD's pics can be clicked but none of yours can. Somewhat puzzling - and annoying.

Murray

Been a few years since I had access to a 3D printer (Ultimaker 2) but I found (as mentioned above) that ABS was more tricky, being prone to distortion and peeling off the bed as it cooled in the middle of the job. Although not directly mentioned here, I think the conclusion was that you need a heated bed for ABS and similar. The Prusa seems to have a heated bed but just check for that if / when you look at alternatives.

Murray