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New grinder & VFD switching (xmas in January)


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I've had issues with my one grinder for a while, failed bearing in the one wheel of the platten I think.

Built a new platten but I was greedy, made it too long so on the standard mounting points the track is too long for a standard belt.

During one of the attempts to get things to fit we stuffed up a bearing on one of the new contact wheels, time and hassle (need a press) to fix that made me shelve the project.

Few months ago I was doing last bit of grinding on a blade when I felt something was off, assumed it was the belt, turns out its a tear in the poly-whatever coating of the contact wheel.

Since then I'm only able to use belts with a thick backing, so I'm limited to 36grit, sanding from there.

Fixable, but finding the time to have it machined and the risk something goes wrong on the lathe has me holding back.
Justifications done :ph34r:
A friend bought a grinder while on holiday in South Africa, one of the new breed with the work rest below the wheel. I'd seen videos, but seeing it in action put me over the edge.
Contacted the guy, busy arranging transport, and I should have it in a few weeks.

Two biggest wins are I'm getting a small wheel attachment, and it can be used as an improvised surface grinder.  

My friend has only ever used his wonky home-built grinder, he's now churning out blades with the most perfect swooping plunges I've ever seen, watching him it's easy to see how.

Same friend also visited another maker, and apparently he has one VFD he uses for all his grinders, one at a time of course.

I assume all you need is a 4 channel rotary switch?  Please excuse my utter ignorance of the correct terminology.
Anybody else doing this, is my assumption correct, and what do I ask for at the electricky shop?

 

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The guy I bought my pillar drill from had 1 VFD and used industrial connectors between it and all the machines using it. Just make sure the VFD is completely discharged to zero V before messing with the connectors.

 

05A51603-45F0-443D-A367-D4C243369867.jpeg

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"The way we win matters" (Ender Wiggins) Orson Scott Card

 

Nos, qui libertate donati sumus, nes cimus quid constet.

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Just made the payment 5 minutes ago, now to get it here....pics to follow in about 2 weeks.

 

17 hours ago, Charles dP said:

The guy I bought my pillar drill from had 1 VFD and used industrial connectors between it and all the machines using it. Just make sure the VFD is completely discharged to zero V before messing with the connectors.

 

05A51603-45F0-443D-A367-D4C243369867.jpeg

 

Spoke to my friend and asked that he find out from the guy in SA, he wasn't very observant but apparently there was a switch at each machine.

I suspect it has to be a similar switch to what you use to bypass a big UPS, and those a pretty expensive as far as I know. 

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There are cam switches available at reasonable cost (at least here in the UK. I'm aware that getting stuff can be a problem there).  Kraus & Naimer are probably the best known manufacturer and they have a pretty wide range. I think you'd want a 3-pole X-position, where X is the number of machines you might want to run.

 

https://www.krausnaimer.com/gb_en/products/control-and-load-switches/10-25-ampere-screw-terminal

 

I use plugs and sockets though. With 230V single-phase-in, 230V 3-phase-out VFDs, the ones I've tended to use are the Blue 3P+Earth(Ground) IEC 60309 connectors (the 3P+E versions of the ones in Charles dP's link. These have become much harder to find over the last few years (and are 5-10 times the cost of the much more common common 2P+E). For 400V 3-phase, I use the Red ones, which are readily available. If it's your own workshop and there's no chance of anyone plugging things in to the wrong socket, you can use whatever you like. The reason I use sockets is because I don't want the risk of nudging the switch and starting a different machine, nor do I want to risk killing a VFD by disconnecting on the outlet side, by moving the switch whilst under power. 

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59 minutes ago, timgunn said:

. The reason I use sockets is because I don't want the risk of nudging the switch and starting a different machine, nor do I want to risk killing a VFD by disconnecting on the outlet side, by moving the switch whilst under power. 

Thanks, didn't know this.
My current grinders have a remote switch for on/off/direction and a dial for speed control, on the new grinder these adjustments are made on the VFD itself.
This is one part of the design I don't get, VFD is mounted on the frame with a clear plastic covering.
I informed the manufacturer not to bother with that, definitely going to mount it in my existing cabinet, even if that means minor discomfort of having to open the cabinet.

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No pics handy, unfortunately, but I have the VFD in a panel. The panel has a 3P+E socket on the front. It also has a control box on a trailing lead, long enough to reach any machine in the shop. I can plug the machine motor into the 3P+E socket and move the control box to whichever machine is plugged into the VFD. After a bit of experimentation, Velcro turned out to be the best way to hold the control box in place: 50mm self-adhesive Hook strip on the box and on the machine, 50mm sew-on loop strip to hold them together. The hook strip cleans ok with a vacuum cleaner. 

 

The control box has a Start button, a Stop button, a Forward/Reverse keyswitch and the speed control potentiometer. The Fwd/Rev switch is keyed so that the key can be removed when it's used on a machine that should not be reversed. The key is removable only in the Fwd position. 

 

All the buttons, switches and potentiometers are 22mm industrial items, albeit the cheap imported ones. I used to like the Telemecanique XB2 range, before they changed to the XB4 range. I don't know whether the production line went to China when the XB2 range was discontinued, or whether there are just very good copies being made (all parts seem to be interchangeable with the XB2 originals), but they are plenty good enough for our purposes.

 

22mm, 10kOhm potentiometers are readily available on Amazon and ebay, as are 4-hole switch enclosures for 22mm (7/8") switches. It's now quite cheap and easy to put together an IP65, or better, control box. It'sinfinitely preferable to opening the VFD enclosure to start/stop/adjust speed, etc.

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