Troubleshooting a Noisy Moulder

      Experts chip in to help diagnose a moulder that makes a growling sound for mysterious reasons. October 4, 2007

I currently keep 2 Weinig 5 head moulders (non-jointed) running in our shop, but have been having some trouble with one. When running maple or other harder woods, the moulder will produce a growling noise with intense vibration. I have checked everything - fences, tables, balance, swapped pressure shoe assemblies. Everything is in line or parallel that is supposed to be. It won't start until the first piece passes over the last bottom and then all sides are effected with finish problems. The top and bottom heads are set properly, and checking with a 2 inch spacer, the pressure shoe is perfectly parallel to the bed plate. I properly added more spring tension to the shoe as well. I just can't think of anything else to check.

Forum Responses
(Solid Wood Machining Forum)
From Dave Rankin, forum technical advisor:
The first thing that I would check is the type of belt being used on the bottom spindle. If this is a flat belt and you are using the thick blue belts, this may be the problem. These types of belts have a memory in the belt, and they delaminate fairly easily. If you are running a timing belt, check the condition of the pulleys.

It is also possible that you are having a motor or spindle bearing problem. I would also check to make sure that the top and bottom dovetails and the top pressure shoe dovetails are tensioned correctly. On the top and bottom dovetails, check the location of the front of the dovetail against the main frame using a .002" filler gage. On the pressure shoe, check for any play and for parallel positioning to the table underneath. If the outfeed table is adjustable, check this dovetail as well.

From contributor R:
This is very basic information that you might have already done. Please take apart the cutterhead, weight the gibs and screws and knives, and make sure they are all correctly balanced.

From the original questioner:
Dave, thanks. However, I have checked everything that you mentioned already and all is good. The belt is also an original Weinig belt (seamless) and not the blue type. The machine is fairly new and the belts are in great shape. I have also checked the nut tension on the dovetails to the top head and feed beam. All is good. I don't know, man, this is a head scratcher.

I start the spindles without a head on them and they are as smooth sounding as can be. Even on wind down. (I have heard the bad bearing sound before.) So I'm just not sure what to check next.

Contributor R, yup, done that and all is good. And one step further. I can pull all the heads off from that moulder and put them on our other one and everything is perfect. I have hit a roadblock with this.

From contributor A:
The sound will reveal your problem. Have a helper feed pieces while you strategically go around to the back of your machine and other areas and get as close as possible (safely!) and listen to the different mechanical parts. If still too confusing, try breaking the problem down in sections. Run test boards through with the machine completely set up but only one spindle cutting per test run. When testing your last bottom, try running it by itself while it makes a heavy cut. Try running a piece through with the normal drag of hold downs, but no spindles operating, to see if it's your feed system.

Last but not least, check the spanner flange on the last spindle to make sure it is screwed on all the way. One time one of my guys spun a nut on so bad by the time we broke it, we had unwittingly unscrewed the flange to the bearing itself. It made that big old nasty growling sound too.

From contributor R:
Okay, let's check a little deeper. Can you tell if this spindle has been spun in the past? If so, then check the size of the spindle shaft. A lot of times somebody will spin a cutterhead and use sandpaper to take out the scar off the shaft. But in reality they have changed the size of the shaft, creating a spindle that is under size. This will cause your problem. If you can't check the size with a micrometer, then swap spindles with the one from the other machine. If problem goes away, then you will know it is in that spindle. The spindle tolerance should be about 4 to7 microns out of round. If more, say up to 12 to 15 microns, then change the bearings. If more than 17 or 18 microns out, then you must replace the shaft, and also the bearings. I hope that helps you find the problem. I think you're real close to solving this.

From contributor T:
Check your feed system. You have a variable drive, I bet...? P22N? Sounds like that's your problem. That's where I'd go first.

From contributor O:
Could be too much feed speed pressure. Not your heads. If it was your head, it would be only on that certain head. I had a moulder do the same and all it took was to tighten up the feed drive belt.

From contributor R:
Let me ask one more simple question. You say you added more spring tension to the pressure shoe. Please take a 2x4 and put it under the pressure shoe and lift up. Does the pressure shoe give about 1/8" in play before it stops? If so, that is a good thing and that is not your problem. If not and it is rigid, then you must loosen the nylon threaded bolt in the back side of the shoe till you do have about 1/8" play in the pressure shoe. The pressure shoe must be able to absorb any variables in the lumber. Please check that first. I like to check the simple things first; most of the time you can find the problem.

From contributor R:
Another way to tell is to look at the brass piece near the star knob that lowers the pressure shoe. You will see about 1/8" cut out with a small round end of a piece of metal in it. The metal end must be at the bottom of that slot, so the shoe can move up about 1/8". A lot of times people clean this area and tighten the nylon nut in back of the pressure shoe and don't realize which way this is supposed to be. Very common error among operators. I have done this myself in production. You must be able to see the pressure shoe move up and down when pressure is applied under it.

From the original questioner:
Thanks for the help. Tomorrow I will take this new info and run some more tests and let you know what I find.

I can't understand why, but I have suspected the feed beam with this, but haven't really tested anything about it yet except the nuts on the dovetail slides.

Contributor R, today I really worked over the pressure shoe assembly and everything is as it should be. I even made sure the dovetail slides (set screws) were tight. All checked out good and the shoe still has 1/8" movement. Before I had just turned the nut above the tension spring down 1/4" turn to add a little more down force. Maybe I should turn that back seeing it didn't fix the problem. Maybe created a new one.

Thanks again! I'll keep you posted on my progress. It's process of elimination. I'm just still eliminating.

From the original questioner:
Contributor T, I apologize for not answering your question. I'm not sure if it's variable drive or not. It's on a Unimat 500. I did change the gear oil once, but I guess I just haven't really looked to see how it all works. Is there a problem with variable drives that I should look for?

From contributor T:
Do you have to turn a handle to change feed speed? Vari-drives can be a problem, but usually later in machine life. You never know, though - bad bearing? Did someone adjust speed without feed running (warped pulley)? Try dead heading some material through without running any cutters, but under chipbreaker and hold down shoe pressure, and see if the feed vibrates or shudders. From your original post, it sounds like it all goes to heck when you get feed under complete load. Good luck. I will check U-500 specs for feed.

From the original questioner:
You do have to turn a round knob to adjust the feed speed. I know to do that while it's feeding, but who knows what happens otherwise. I really don't believe that has happened, but just can't be sure. But yes, it is adjustable via turn knob.

Contributor A had the same thought about running a piece through without the machine running. Something I will try tomorrow. I'll do it at lunch time when all is quiet.

From contributor J:
Looks like you're on the right track. Process of elimination. The only thing that I could think of adding to the suggestions is more of a "slippery" pressure shoe, but I don't believe that would remedy your problem. I have had issues with a U500 as well. My P26 will make that noise when the first feed roller is manually turned down too much. I turn it up so it just grabs lightly and it goes away. I would lean towards the feed with this as well. It works for me. I don't understand why, but it does.

From contributor O:
Check your feed roll air pressure. Someplace you have too much pressure on your feed rollers. Also you could check your beam that supports your feed rollers; it may have gone out of alignment and is placing too much pressure on your parts toward the end of the machine. I would remove a feed roller, one at a time, and see which roller is causing my problem and work from there.

From contributor O:
Remove the feed roller just after the last bottom head. Run the machine and see if problem goes away. Then do the same with the feed roller just in front of that last bottom head. This will tell you which feed roller is causing the problem. My guess is that you either have too much air pressure on your feed rollers placing a drag on your feed system or it is the last feed roller bearings going out.

From the original questioner:
Well, I ran stock through without any spindles running and no growling sound. I'll check the air pressure thing. I'm not so sure it's the feed anymore, but I will give Weinig a call and see what they have to tell me about this. Thanks to everyone who gave suggestions. I will post the results as soon as they come in.

From contributor R:
Have you swapped spindles yet? I still believe that you will find something here.

From contributor T:
You have an inverter direct drive. Forget about the variable drive thing. But if your feed is hesitating, you might need to ramp up a torque boost setting in the inverter. Without this set properly, at low feed speeds, the motor will jump, affecting the feed drive. You will have to call Weinig to get the scoop on how to check/change if needed.

From the original questioner:
So far, so good. They unbolted the whole pressure shoe from the frame and replaced it. I haven't run it enough since to be 100%, but I ran 2 small s4s jobs and it seems to be a lot better. I guess time will tell! Thank you again.

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