I'm a tool grinder for one of the top cabinet companies in North America, and have been grinding tools for them for 6 years. I have three types of grinders.
1. Deihl - Used for rough grinding profiles only
2. Rondamat 960 - Used for straight knife sharpening
3. Rondamat 970 - Used for profile sharpening.
Then we have 6 Weinig molders. We are starting to have some problems with a few things.
1. fuzzy parts
2. chatter and or snipe
3. tear out
I've been grinding the same way for the last 6 years, using the same style of moulder heads. We use North American hydro lock molder heads with a 10 degree hook, and we use optic steel (WKW) for our HSS and some piggy back cutters. I was told it might be a balance problem, and I don't know how it could be, when I balance the gib screws, gibs, and knives to within .1 of a gram of each other. I was also told it's the way I grind the tooling, which is the same as when I started 6 years ago. If anyone has any info that can solve this problem, that would be great.
(Solid Wood Machining Forum)
From contributor A:
The first that will help with the tearout is the use of shear angle cutterheads. I have used them for many years and you can do both straight and profile knives in them. Another development is the DGK tool steel. It has an advantage over other steels because it has the extremely hard surface on its face. It is ground using normal grinding wheels and jointed with normal jointing stones. Its advantage is that you can increase the angle of the back clearance and still have a knife that holds up against the cut. With other tool steels, when you increase the angle to try to reduce tearout and chipping, they have the negative side effect of less run time. The tool dulls quicker.
I think that the first place to start is with the setup of the moulder. Are the fences straight, are all of the holddowns in the proper location and parallel, and are the belts in good shape? If you are using outboard bearings, are they aligned correctly?
We are currently grinding our knives at one angle, no finish grind, with a 2mm borazon wheel and weíre not grinding axial constant because they donít think it will be beneficial.
It doesnít take much longer to grind axial constant. We have the equipment to do it and it would benefit both the moulders and the tool grinders right? The biggest finish problem is the moulders - right now some of the spindles are as rough as a corn cob and have had too many heads spun on them. I didnít bother checking the run out since the spindle felt like a corn cob. I didnít think I needed to look much further to know we have a problem.
Now all the hydro heads have been sharing the corn cob spindles so now theyíre pretty much crap too, or are at least no better than a straight bore head and probably worse when you pump them up on a crappy spindle.
I told them donít take my word for it - call the Moulder Doctor. We have 6 moulders so youíre talking a lot of money to replace all the spindles at one time so I recommended we start by replacing the top spindle doing the profiling since this is the hardest part to sand and purchasing heads that will only be used on this good spindle. Then if they do spin a head on this good spindle, replace the spindle and move the one that had the head spun on to a less critical spot. They have not noticed any difference in the past because they have not seen what a new hydro head and new spindle can do on a moulder that is in top shape
Now - grinding the cutters - cutters need to be clean, wiping the bore clean of saw dust or whatever. I prefer using ceramic or a vitrified grinding wheel. They are more cost effective and you can dress them, keeping the wheel the same shape as your pin and more accurate. However I am not opposed to using an older out a round borazon wheel to do the back clearance angle and then finish grind with a new borazon wheel so the profile is exactly like the template. Itís not as cost effective but easier for less experienced tool grinders.
Most of the species we run are fine with a 10 degree hook head except alder. This should be a 20 degree head ground with a 30 degree back clearance angle and maybe a 28 degree finish grind?
These are a few of the things I think we need to do. I donít want to make this too long a post so I will stop here and any input is welcome.
Six moulders, wow! I can't imagine how many operators those machines have seen over the years, with the moulder events being some multiple of that number. Anyway, sounds like there is more involved with your problems than simply the choice if hook and grind angles, and what wheel you choose to use. Eliminate the other variables on one of your newer (least abused) machines, then you can experiment with grinding angles and such.
Maybe your production manager should schedule a big pow-wow. Your concerns regarding your product quality, as tool room guys, is commendable.
Obviously, you wouldn't be here if you didn't care, and your co-worker too. I think you two should bring the condition of your moulders to the bossís attention. Corn cob spindles? Who trains these guys? Isn't spinning a head the one nightmare that is tough in the beginning? You guys know your stuff, and your company relies on that. Let them know whatís going on.
When planning some solutions on the moulder, clearly define the difference between set-up and maintenance. It sounds as though both are in need of help. I realize there are many people out there with experience and training available, but don't count Weinig out as a resource for extended training. They have an award winning program for moulder set-up training. These classes are going on all the time, just call Weinig to see when there is room. Of course having a Weinig tech stop in and look things over is always an option. Call the service department and try to set something up.
This question is for everyone. I have a Rondamat 970 and we use a 2mm CBN wheel. Can you use the diamond wheel dresser (not while it's running) to center the wheel into the hub? And will it center it to the tracing pin? If not, why?
Comment from contributor A:
If you are having trouble with a top head it could be a pressure shoe or chip breaker issue. Too little pressure will allow the part to move. Also improper pressure shoe alignment to the bed plate can cause issues with top or bottom. Bottom chatter can be pressure shoe issues or the bed plates are moved too far away from the cutters. If this is a Weinig and you have a student handbook read some of the solutions to chatter problems or call Weinig they are always very knowledgeable and helpful. The fuzz with alder is a constant issue. While the 20 degree hook and 30/27 grind angle will resolve some of it, it is a constant problem because of the wood and the moisture content.