|Home » Forums » Solid Wood Machining Forum » Message||Login|
You are not logged in. Consider these WOODWEB Member advantages:
I am looking for my first widebelt and need guidance about the best configuration for my shop. Every piece of wood that comes out of the planer currently goes through a drum sander before cutting joinery, making face frames, door panels, table tops, etc. It was a lot of work to get and keep it set up, but it is accurate to several thousandths after multiple passes in opposite directions. It is a very slow process, but the value is in straight ,flat and uniformly thick stock with square edges to work with. I put this accuracy in stock prep at pretty much the top of my priorities in the equipment I use. I see claims of several thousandths across the width of a 36 inch sander, but how is that accuracy with stock 2 to 6 inches wide?
I can get that accuracy with the Sandya RCS that I have. Some keys are a firmer feed belt so that there is less give under the part, and the steel first drum is obviously more accurate on stock where thickness and or hardness might vary. The heads are fine adjustable to dial in the side-to-side consistency. You can easily kiss the feed belt with the first head to establish a reference surface from which to base your adjustments. The platen graphite can wear, but you can get that consistent as well.
I have experience with a Timsavers single head, a Ramco two head, a Cemco two head and a Butfering single head.
The Butfering was the latest machine and the most accurate. The set up tech had us marking veneered stock with a pencil, and removing half the pencil mark, repeatedly. It was not a veneer sander, but we often did sand veneered stock with it. We could easily get it to where there was no mill mark from the sanding operation, with the platen in use.
All machines had combination heads and rubber first head. The Timesavers had worn jack screws (you want four large diameter ones), so was impossible to get level, but the others were fine. The Butfering was German engineered and bearings and electrical, and the heavy iron and assembly was Chinese. It is a fine machine - had a hard belt, with no give, so it had accuracy and easy adjustments.
I think all wide belts will do better when given good belts, and belts are stored properly. We got excellent wear from our belts.
i've got a '97, 37" scmi sandya uno with (probably) warn hold downs and a feed belt that is on its last legs. with that said, we have a 1/64' - 1/128" dip in the middle.
i won't think this would be noticeable for general work that is sanded further.
I would need more information on what finish you are trying to achieve before recommending a machine. What types of products and what is the final finish you want to achieve?
Most machines are capable of being within a couple thousandths of an inch from side to side. I have done it on hundreds upon hundreds of machines. You can sand just as accurately with a soft drum as a steel drum. The only difference is that one can make the part flat while the other will sand a flat part and keep it flat.
Steel can be your friend in the accuracy department, but it hurts in the quality of the scratch pattern for finishing. Hardness means high shear angles and deep penetration of the grain into the wood. Softer drums mean more footprint so less depth of scratch.
You need a machine that has a fairly hard drum in the first position, whether that be in a combi-head or a two head machine. You also need a rigid pattern on your conveyor belt, but you don't want or need a very hard conveyor. A diamond or square pattern works well for creating an accurate part. A little softness (60 shore) helps with driving parts and you can hit your accuracy goals easily. You could go flat as well if the machine gives you short hold down roller distances.
No rough top belts. Those are crap for accuracy.
If most of your work is on flat parts sanding with the grain, I would consider a small two drum machine. Maybe an 80 shore rubber drum in the first position and a 45 shore drum in the 2nd. This will give a nice short scratch that is not as noticeable as the longer platen scratch in staining, but also give you very flat parts if used correctly. Viet makes single motor, two drum machines.
A single combi-head can be used as well. You just need to set it up right. Sand a part with just the drum, platen retracted. Then stop the head and run the part back under the head without moving the conveyor height. Most machines will let you reset the brake so you can turn the belt by hand as you lower the platen until you feel an increase in drag. This puts your platen just under the drum height, taking very little material so very little rounding with a nice scratch.
I don't care for steel in a combi-head machine. The scratch is too hard for the platen to remove effectively. A 75 shore drum is about as hard as one should go, which leaves out older Butferings and Kundigs that used 85-90 shore in their combi-heads.
I level machines with indicators I designed that rest on the steel under the conveyor on both sides of the machine. I indicate down both sides to get the machine within .001" and every hold down roller and shoe, and I measure the platen mount instead of the uneven platen itself. Once everything is calibrated a very light sanding on the conveyor with the drum will make the machine dead nuts within the limits of the jack screw tolerance. sometimes a slight tweek of the head level can fix it if the jack screws aren't perfect and the normal working height is off a few thousandths.
Make sure the drum is true. Don't stick sand paper on a piece of wood and screw it up yourself. Any used conveyor will not be flat at all. You don't want to dress that inaccuracy into your drum. Send it out and have it trued on a lathe and spin balanced. It's worth the time and money to have really great results.