Tuning Up a Small Moulder
Advice on getting the best finish possible from a small moulder. May 21, 2009
Question
I set up and operate a Bridgewood 757 5 head moulder. Our business has increased to the point that I need an optimal finish. Any thoughts on scales to check for balance on knives, gibs, and gib screws? Also, a good cutterhead setup stand.
Forum Responses
(Solid Wood Machining Forum)
From David Rankin, forum technical advisor:
Tooling condition is critical for all machines. On a moulder with 6,000 rpm spindles, balance is even more critical. Any out of balance condition will reduce the finish quality as well as reduce the life of the spindle bearings. 1 gram of imbalance is equal to a 22 pound rotational force.
I use both an O'Haus Harvard Trip Balance and an O'Haus Scout electronic scale. Be aware that during the cutting process of the tool steel a magnetic condition is common on the steel and you will need to use a demagnetizer to remove this magnetic field. If you do not, the electronic scale can misread.
Also, a better finish can be achieved by the quality of the grind, the feed rate and improved material control as the product passes through the moulder.
From contributor R:
A couple of things that will improve your finish product... Rough grind @ 25 degree, finish grind @ 20 degree. Make the finish grind very small in land area, 1/16" or less is better. This will allow the wood chips an avenue to escape, allowing your tool to remain cooler, thus getting a better finish and longer run time between sharpenings. Use 5 degree side clearance on any inclines over 60 degree. This will help you in your quest to run better mouldings.
From contributor A:
Once you have good quality balanced tooling, you should focus your attention on hold down and feed issues. For hold downs, it's important that pressure shoes are adjusted for squareness and wear on a regular basis. Chip breakers should be adjusted as close as possible to knives on each run (also check for wear). Bed plates should be checked for wear, and to make sure they don't accumulate built up dust underneath. With properly adjusted pressure and hold downs, your feed will perform at an optimal level.
Also, care should be taken to design profiles so they can be supported correctly through the cut. Ex: crowns should have two even hold down points, one on each side. If for any reason you can't design a moulding for good hold downs, then you must take steps like a split pressure shoe, felt, or reciprocal nylon shoes.
Once you are using good tooling, chatter and bad finish is caused by poorly tuned hold downs a large majority of the time.
I also use an O'Haus Harvard Trip Balance. I have both the mechanical and the digital. I very much prefer the mechanical though. With proper technique of balancing and switching sides, the mechanical scale can nail static balance to less than 0.1 of a gram.
From contributor J:
O'haus is our choice as well. Keep it covered when not in use. Just to elaborate on something Dave mentions - the feed rate. I assume your moulder is non-jointed where only one knife is doing the most work. You should keep your feed rate close to 30fpm for the optimal finish on that type of machine.
From contributor J:
The measuring stand I was talking about is called a Probe setting stand. I didn't realize how expensive they were. Looking at the old one we have, I don't think it would be too hard to build one using a digital set of calipers for the measuring device. Jump into monster garage mode and have at it. If you can't weld good like me, have someone else do it. It needs to be stable.
