Grinder design question/opinion

CWendling

CWendling

Knifemaker / Craftsman / Service Provider
Joined
Sep 10, 2005
Messages
528
Bought a Reeder grinder a month or so ago and for the most part am really happy with it. What Im not happy about is the vibration and will ask them about it, but wanted to see what the brain trust here thinks as well. For those unfamiliar, it is a hinged design for vertical and horizontal grinding with two hinges (basically door hinges). It has a direct drive motor on the rear and an arm to lock it in the front to hold it in the upright position. Ive tried starting it from zero on the VFD and ramping the speed up, but often have to kind of feather the speed up and down or it develops a shake/vibration. I think the cause is because the torque is being applied at the rear while the support is at the front and is compounded by the slop in the hinges (there is some play in the hinges when pushing on the frame). So my thinking is to either fab up another mounting location for the support (more toward the middle of the frame behind the locking knobs, I dont think it would affect the operation, but maybe I havent considered something in the design), or to purchase a set of milled/precision hinges that will remove the play. That being said, milled hinges arent cheap and if my thinking of the cause is wrong, Id hate to waste the money. So....thoughts?
 

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I've been down this rabbit hole with another grinder manufacturer.

Here's my thoughts, although they don't answer your query directly.

If you bought a new grinder, this isn't your problem, it's the manufacturer's problem. Before you start modifying it in any way, I would STRONGLY suggest getting their input on this, and letting them rectify it. If they counter with this being your problem and not their's, it seems to me that I'd be demanding a refund. You paid for a working machine, free of defect or flaw. If this isn't something the manufacturer can deliver, maybe they shouldn't be making them. The grinder world is absolutely overwhelmed with great choices, so it shouldn't be hard to find a good one.

Everything I've seen from the company you bought from, though, leads me to think that this is either a fluke or something easily corrected by them. I've never heard of anyone saying they weren't stand-up guys, so I'd think they would be very interested in helping you get squared away.
 
Just curios is this happening with a belt on or off the machine and are the wheels from the same manufacturer?
 
From what I've seen on those grinders, it gets mounted to a 4x4 on the bench right? Is the 4x4 you chose as long as possible? Is it solidly mounted to the bench/ grinder, and is the bench solid and level?
 
The hinge slop is not causing vibration, there is some kind of imbalance

Did the motor come with, or did you put your own on?

I'd put a dial indicator on each wheel and see if there is any wobble.

Loooking for a bent motor shaft
 
Maybe I didnt describe it great. Maybe a video would help but have to figure out how to post one ha. Im switching to this from a KMG, which didnt care what speed i started the motor at, but it was solid mounted of course. I have no prior experience with a hinged grinder or seen any others operate. Its really more a shake than a vibration i guess. If i start the motor at zero and ramp up, its not as bad. If i start the motor somewhere up on the VFD, it is very pronounced. Once I feather the speed a bit, usually go past where I want to be and come down the the speed I want, it goes away and the machine doesnt have vibration while running (which was the issue i always had with my KMG). Thats what lead me to believe it was something in the torque applied at the rear with the support at the front. Its mounted on a 4x4 that is pretty solid to the bench. Happens with or without belt. Wheels are from them. My motor. Have put both a leeson and iron horse motor on to see if the motor was the issue. And yes, the Reeders have been great to deal with and arent far from me either. I am going to call them today to see what they say.
 
Its not the shafts. The Lesson motor is what i use on my disk and it runs true. The iron horse is brand new and i put disk on it and it ran straight. What VFD settings would cause that? How would i check for wheel imbalance?
 
Does it do that without a belt? ETA Sorry I see you answered that.

Above are you saying that if you put your disc on this motor, and drive it with that VFD, the motor doesn't vibrate?
 
Thats correct. That was the first thing I did was swap the leeson motor from my disk to the grinder and ran grinder and put my disk on the iron horse to see if the motor was the issue. Disk runs true with both and the grinder shakes with both motors. Mostly at about 30%speed. Thats where its the worst
 
I have a similar vibration on my grinder. Like yours it only happens at certain speeds, slow but not real slow. Real slow and faster speeds are fine.

This only started happening when I changed from a 4 pole to a 2 pole motor and I put it down to the less smooth drive of the two pole motor causing resonance.

So it is not necessarily a mechanical in-balance.
 
Ive talked to Don and sent him a bunch of videos to see what he thinks is causing it. He said he hasnt seen it before. I used a couple of their machines at their shop prior to purchase and didnt notice it. Im confident he will work to resolve it.
 
It's really weird. If it was a balance issue I would tend to think that it would get worse with RPM and not mellow out.
 
I have the same grinder. It also vibrated. First thing I did was check all the connecting bolts to make certain that thay were tight. The top most bolt, the one that holds both sides together was very loose. I tightened it and that helped. But the vibration was in the VFD. From 27 hertz to 43 hertz the manhunt was unusable. I called TECO, who by the way have top notch customer service, and spoke with one guy who was unfamiliar with this issue. He checked with others there and helped me adjust the settings. The vibration vanished. Apparantly, the chip was trying to adjust to a built in use expectation. It needed to be instructed to by pass those readings. That's a very unscientific version, but I'm a money manager not a scientist. The upshot is that it happened to me and it is cured and my grinder is like family. The Reeders are fabulous people but they don't know much about my TECO BFD. Go figure. Good luck
 
I'm thinking it's your VFD. My gets "the shakes" around the first 10% or so, but smooths out considerably after that. There have been a few threads on the KBACs specifically, but no real solutions given, unfortunately. I notice on mine that if I change the jumper from CT (constant torque) to VT (variable torque) the vibration goes away completely across the whole speed range, BUT the torque complete drops out at the lower end, so it's useless to me.
I've just more or less learned to live the vibration, personally.
 
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