Troubleshooting Moulder Head Movement
Pros help figure out the problem with a moulder's top head. September 28, 2006
Question
We have a Profimat 23 moulder and have had problems with the top head not being consistent. When we change knives, we will set the top head, and run a few pieces. When the test pieces that we run come out within our specification, we will run our planned production batch. Our problem is that during the production run, the top head moves out vertically and we produce non-conforming parts. We have to constantly monitor the top head. When we set our top head, we do go past the number on the dial, and then move the top head back up again to remove any slack in threads. We have taken the top head apart, cleaned up the dovetail slides and removed a burr with a dye grinder and greased it. But we are still having issues with this. Any insight would be greatly appreciated.
Forum Responses
(Solid Wood Machining Forum)
From contributor R:
The gear box that raises and lowers the top head has two 13mm hex bolts that hold it to the casting. Check those bolts and make sure they are tight. Take a look at the locking clamp that locks the radial movement; make sure that the ring that locks it is not cracked or broken.
From contributor R:
The locking clamp I talked about is on the axial movement, not the radial - sorry to confuse you. The lock for the radial pulls on the gib and that should keep the top spindle slide from moving. Could the gibs on the slide need tightening?
From contributor S:
From your post, I am taking it to mean that your product varies in thickness from the initial specification that you set. Your statement, "...the top head moves out vertically..." is ambiguous. Does "moves out" mean up, causing the thickness to increase, or down, causing the thickness to decrease?
What is the spindle configuration of your moulder? What material are you processing, and what is the average length of run that you see this problem occur? How old is the machine?
Off the top of my head, I'd suggest you check the condition of, or at least the tightness of the bolts that hold the threaded brass bushing on the underside of the spindle's cast housing. That is, if I got your problem correctly. There could be other causes, of course, but we need clarification and additional info.
From contributor O:
The top head slide and feed beam slide are interconnected on that machine. It's been a while, so I can't picture the exact arrangement (I’ve slept since then). If the slides are sticky, the feed beam can move the top head around. Move the feed up and down and observe the top head slide as well as the feed beam slide. Make sure they are well lubricated and the grease lines are not plugged. Check the brass wear nuts at the jack screws as well.
From contributor J:
The P23 is a Weinig nightmare. They thought they could cut corners and be more versatile with the welded steel frame, but quickly found it wasn't worth it. You do need to explain a little better. Does the top head move up vertically or out horizontally?
From contributor J:
It's been a while, but if I remember right, the head will go up a ways before the feed beam joins in with the upward motion. I would look to see if there is any wear in the threaded rod that moves the head up/down. The cast part that the rod threads into would probably wear before the steel rod, but I'm not sure. Sometimes, if you're running multiple thicknesses but similar, that part of the threads will wear. Mark the threads where they don't get used and then the ones that are always used (put a mark on the threads just under the cast, power the head up, and mark the threads just above your mark).
Sorry if I have a different model in my head…
From contributor R:
I believe contributor J is on to something here as well as the other posters. Their responses trigger a new thought about your machine. Check the threaded rod that raises and lowers the top head. Look at the end of that rod - they were made originally with one (22mm or 24mm) hex bolt locking all the washers, needle bearings, spacers, etc. together. There was a problem, as you described, and we changed out many of them with a new style threaded rod which is longer and now has two locking (22mmor 24mm) jamb hex nuts at the end of the shaft, eliminating any further movement as you describe. If your machine only has one 22mm nut on the end of the shaft , call Weinig and order the new style one requiring two bolts. If you do this, I recommend ordering the shaft, a new brass sleeve, bevel gears, washers, keyways, and needle bearings. You are going to have to take it all apart anyways so you might as well start from scratch just in case you find something else while taking it apart. It is a little tricky getting replaced. Make sure your feed beam is as high as it can go before you kill the power and lock out. You will see the advantage while replacing.
From Dave Rankin, forum technical advisor:
I agree with the above comments and would like to add one thing to look into. The last P23 that I worked on that had a similar problem to what you have described was a couple of years ago. The problem we found was that the feed beam dovetail had worn. As the wood enters the machine, the first feed roller picks up and puts a lot of force onto the outfeed side of the dovetail. This was discovered as we test ran the machine and saw the beam actually rocking as the wood entered the moulder. We fixed this problem by removing the feed beam and scraping the dovetail and filling the worn areas with metal filler. This process was very time consuming and I would suggest if you see this problem that you contact a good tech.
