Vfd advice please

Two quick replies:

Emgee: Thanks for the comment. I bought the shaper some time ago, on a whim as it was available at the right price and I only had room for one that size. I don't suppose I've used it more than a couple of times in the last three years and only then to try it out.

mgnbuk : I'm afraid I don't understand to what you refer. The shaper cuts on the forward stroke and the traverse ratchets round on the return, ready for the next cut. That's how I understood it to work. There doesn't appear to be any way to alter that arrangement.

And yes, I agree, my setting up wasn't totally square and it cuts a bit on the skew, but it was only supposed to be a test of the effect of the different speeds to be sure I hadn't completely wasted my dosh on the 3-phase set up, really. I'll try to do better, next time!

John

Edited By John Hinkley on 13/02/2021 17:03:39

I'm afraid I don't understand to what you refer.

Hi John.

Your long traverse handwheel is rotating as the ram comes forward in the video, so the carriage is feeding on the cut stroke & the feed ratchet "freewheels" on the ram return stroke.

On my Boxford, the feed ratchet "freewheels" on the cut stroke & the table (on mine) feeds on the ram return stroke, so the table is not feeding during the cut. My limited understanding of shaper operation is that this is the usual way of working - certainly the way that planers I have worked with functioned.

Your VFD arrangement certainly wasn't a waste of time or money - it maybe due to the cabinet acting as a sounding board, but my Boxford running on a single phase motor is very noisy in comparison to yours. And I have the cabinet grouted in as well, which I had hoped would quiten things down but didn't ! I still have the (415V only) 3 phase motor it came with, so maybe have to refit that & try it with the static converter. Or bite he bullet & treat it to a similar arrangement to yours.

Nigel B.

Nigel,

I've had another look at the video and now I can see what you describe. It shouldn't do that! I'm now wondering if a previous owner has dismantled it and put it back together incorrectly, if that is possible? Tomorrow, I'll investigate as it's forecast to get a little warmer.

Thanks for pointing it out. It might also explain the squinty cut, too! Maybe my set up wasn't that bad , after all.

John

sorry-a post was put in wrong thread - please disregard this post

Edited By Jeff Dayman on 13/02/2021 19:19:01

Cooling air flow is a function of the cube of the fan speed.

I hope I got it the right way round, but what I mean is that slowing the fan (motor) speed by a half reduces the air flow by a factor of eight.

That may not be too important if: a) the fan was generously sized for normal 50Hz operation, b) the motor is not laboured for anything more than for a short time and c) the motor has been designed with good overload capability.

Unfortunately, some motors are not even rated for continuous running and can sail close to the wind, even at 50Hz operation. The onus is on the operator to run the motor without ‘letting out the smoke’.

I smiled at the comment from Andrew “even with a fan running at normal speed” but entirely agree with his post. I was wondering at what speed a motor becomes over-loaded.

Hi Guys, all very very interesting, I now have glazed eyes! However I have selected the inverter from inverter supermarket, in fact the one suggested.

Overall this has been a great and very helpful thread, many thanks

Good for you, Philip, there have been several people on this forum who have commented favourably about their after sales support, should you need it. I had a query, and emailed them, and got a swift sensible reply.

Lots of replies answering his question, but could I break the trend and suggest that you may face challenges if you use a 3/4hp motor for a 3" wide sanding belt?

Further, sanding and linishing (an abrasive machining process) generally requires a high surface speed to be effective. Thus, speed control downwards from a motor's synchronous speed, even if a two pole motor is used, may not be necessary.

Simply put, you want the belt to whizz along powerfully, not crawl along, slowing down as soon as you try to sharpen a pencil on it.

So you need to start with the surface speed you need, see what diameter drive pulley you will use and select a motor rpm to give that surface speed. Then look at what motor is required to produce the necessary torque at that rpm.

To me, the 3/4hp seems way underpowered.

Well, Axminster sell a trade belt sander with a 750W induction motor; or a craft sander with the same belt size and a 370W motor. 3/4 HP looks about right.  Both take 100mm wide belts, the trade one says the belt speed is 840 m/minute.

Edited By John Haine on 14/02/2021 09:56:36

Edited By John Haine on 14/02/2021 09:58:23

Hi again, food for thought in these posts... the reason I am using 3/4 hp 3 phase motor is because I have one. And again I have a 7" bar of nylon to use as drive. This should give a belt speed of about 820 m/min. However on YouTube ( always with pinch of salt) advice was when using thin steel there is a tendency to burn the burn the part with high speed belt, hence speed reduction. Of course the other demand is to convert single to 3 phase. . I could wire it into my static converter like my other machines, but I want to make this belt sander more mobile. I know there are many options to this, but its the onei have chosen.

Of course I could just spend my money on a new 1hp single phase motor!!

The traverse direction dictates whether the table moves on the cut or return stroke!

They're meant for sanding wood. If you intend using one to shape metal, as a belt-grinder, you'll quickly discover that they don't have enough power. Like trying to use an air-tool off a small compressor.

The power available to the belt could be maximised by making the drive gearing equal the 840m/min with the motor running at 80Hz, 1.6 times its standard speed. That would give greater power at the lower speeds which would be used more often.

I think my axminster 6" belt sander has a 3/4 Hp motor 1Ph. I can see no reason to slow it down. It is used for metal so beware of metal particles getting into ANYTHING electrical, smoke and sparks will ensue. Noel

I have a 2" vertical linisher, running @ 2750 over a 6" pulley.. ..um, think that's about 1300m/m? ..it burns wood like a taxpayer-funded power station on double-subsidy, but haven't noticed a problem with steel, I think it depends to a large degree on belt material / spec. and (especially) the avoidance of excessive pressure when cutting - I use it for both grinding HSS toolbits (fine 'blue' zirconia or 'red' ceramic), or rousting-off mild steel for fabricating etc., using coarse Alox..

I think if you have the 3ph motor anyway, variable speed will be handy for mixed workshop 'jobbing'.. ..Noel's right about the particles, I might add that neither would I have mine in the same room as any 'precision' machinery..

..I built it out of scrap - there's some pics in an album..