Drum Sander Ripple Marks

Ripple or chatter marks on boards run through a drum sander may not be a maintenance issue, but just the nature of the equipment. April 30, 2009

Question
I have a new Woodmaster 38" Drumsander. It produces consistent ripples, or rotation marks, perfectly spaced, across every board I sand. There is also evidence of snipe, once you apply finish to the sanded stock and check low angle reflection. I have done all the checking listed in the manual, lubed every spot suggested, tightened down the tie bars, and etc. I have talked with Woodmaster three times, resulting in new Velcro (not a fun job), and advice to tighten the tie bars down on the screw jack posts. None of these has done anything to reduce the problem.

I found this link, and wondered if it might relate to my problem:

Modifications Cure Woodmaster 718 Chatter

I am really frustrated that having spent much money on a machine, I am spending more time troubleshooting than woodworking, not to mention all the hand sanding needed to get the ripples out of lots of beech shelving. Any thoughts, ideas, or experiences out there?

Forum Responses
(Solid Wood Machining Forum)
From contributor Z:
It sounds to me like you may have a balance problem. Can you feel any vibration? Snipe comes from misalignment or lack of support at the infeed or out end.



From contributor G:
By nature of design a drum sander will usually always leave ripple marks. Thatís why widebelt sanders have platens. You can try to minimize the marks by taking lighter passes and/or sanding to a finer grit.

How fine do you sand to now? I would try progressively sanding to 180 or 220g and random orbit sanding back with 150 or 180g. RO sanding is a given with a drum sander. The money you spent on a drum sander is not a lot. Compare it to the price of a widebelt and you will see you got what you paid for. I had a nice 24" Woodmaster for a number of years. It easily met all my expectations for a drum sander. However, I never expected it to leave a surface ready for stain. Even now with my doublehead Timesaver widebelt with a platten we RO sand if we want a really good finish. Shortcuts don't work. From my experience I do not think there is anything wrong with your sander. You are just expecting too much out of a $3,000 machine.




From contributor J:
I used to own a 38" Woodmaster. As far as drum sanders, it's probably one of the better ones. You might check the run out of the drum with a dial indicator. That may cause the chatter marks. Also, don't try to get too much life from your paper. Worn paper can cause chatter marks. What grits are you using? I sanded cabinet doors and edge glued panels. I started with 60 or 80 grit then went with 100, and finished with 150. You will still need to do a lot of RO sanding to get rid of the straight scratch marks, especially in hard maple.

The snipe is caused from heavy work pieces with no support as they enter and exit the drum. They need to be well supported until the area under both hold down rollers, and as they exit they need to be supported after the infeed hold down drops off. Woodmaster sells an extension roller kit that I installed that helped some. The cost was around $100 if I remember correctly. It was probably worth it.



From the original questioner:
Thanks for the input. I did the final passes with 220. My real frustration was that I had milled the stock to thickness, plus enough for finish sanding. When it came up rippled, I had to sand more, and lost fit in the housed lap joints these were destined for. Live and learn. Your input is valuable, in that I will know to leave enough stock for finishing sanding, after using the drum sander.


From contributor L:
Contributor G has the correct answer. A better option and even less expensive than a drum sander is a stroke sander. It will give a surface you can go right to finishing with. Itís one of the best forgotten machines of the past. It's a shame that folks have forgotten all about this versatile machine. Even with a widebelt the stroke sander would always have a use. I even put one in a custom metal shop where we sanded brass, stainless steel, etc.


The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor C:
It looks like a lot was covered concerning the drum and the abrasive, but it's also worth mentioning the conveyor feed mechanism. If there's a gearbox and a "flat spot" associated with it internally, the result will be a jerk on the conveyor at regular intervals. To troubleshoot this, run the conveyor at minimum and maximum speeds and measure the distance between chatter marks. If they stretch out during the "fast" cycle, the chatter is originating in the head assembly (drum, pulley, drive belt, bearings, and motor.) If the chatter mark spacing doesn't change, it's in the feed mechanism.