Question
I am trying to design some custom shapers for dedicated milling operations. These are going to be similar to a router table but with 1 1/4 inch arbors. The cutterheads will be set up with insert tooling and the diameter of each individual tool will probably range from 3 to 5 inches.
I need some help with calculating pulley sizes for both the arbor and the motor. If, for example, you had a 3450 rpm motor and you wanted a 6000 rpm rim speed at the cutter, what would the pulley size be on the arbor? I'm guessing that different cutterhead diameters might have some bearing on this, but this kind of math is above my pay grade so I am just guessing. Would this be the kind of thing you might use a rheostat on to produce a variable speed motor?
Forum Responses
(Cabinetmaking Forum)
From contributor K:
You want pulley diameters that have a ratio of 1.739 to 1. Divide the spindle speed you want by the motor speed: 6000/3450 =1.739 or a ratio of 1 motor rpm to 1.739 spindle rpm. So, what you now do is choose the smallest motor pulley you can put on the shaft, determine its circumference, then multiply by 1.739 and that gives you the circumference of the spindle pulley. Do the math from that circumference to determine the diameter of the spindle pulley.
The formula for circumference is: diameter x 3.1416 (pi) = circumference
Formula for diameter: Circumference/3.1416(pi) = diameter
I recently decided to reclaim floor space by shifting my philosophy on shapers. I used to have dedicated setups with stacked tooling (and digital height gauges) for cutters using the same fence setting. This worked very well and made for very fast transitions. But 7 shapers ate up a lot of floor space. I am in the process of redesigning the process around 2 higher quality shapers. They take up less floor space, are very fast to set up, have ISO router style quick-change spindles, and give a better finish. Of course, we use batch production, so this works well for us. The other upside is that we now have room to grow a little more in our low overhead space. I just wish that I had started this 6 months ago so that it was easier to sell off the old shapers!
After getting rid of our dedicated machines, we ran with only one numeric Martin shaper for a few years, then added another numeric shaper for end coping and tenoning. Now we are in the process of setting up a Colombo stackable numeric tenoner for the end cuts. Built with some options tailored for our products.
Tooling is an important factor in this. If you are just starting with tooling, think about diameters, bore sizes and what machines you might eventually upgrade to. Our 18 piece set for windows is made so all the cutting circles for the sticker cuts are the same. Likewise for the cope and tenon heads. These cutters are all on sleeve so the height matches up for everything also. Our door tools built later are the same setup.
With the right tools you could get by without a numeric machine. We do a lot of other stuff, so the numeric control pays off for us.
The Martin has a quick change spindle. Originally I was going to buy a spindle for every cutter but decided changing the cutter is only about 45 seconds longer and pretty much do that. Sometimes we stack 2 or 3 cutters depending on the work. Cutters stacked on sleeve are a good option for setups repeated a lot.
SCM has a simple ISO 40 spindle they use on their small Ten 220 single end tenoner. The machine is nonnumeric, made to be used with constant height and diameter tools. The spindle releases and clamps by air and is very quick to change out single tools on dedicated spindles. There are a lot of options anymore for spindles with all these machines.
To the original questioner: Divide the motor speed by the spindle speed to get your ratio of .575, then multiply your spindle circumference by .575 to get the circumference of your motor pulley. Break that down to find the motor pulley diameter from the original circumference formula.
Did I get this correct?
We build all kinds of custom jigs for our products. Why not a custom machine? We crab power feeders onto anything, devise plywood sleds and use those little red clamps all over the place. Bolting a router to a tabletop isn't that different from sticking a spindle attached to a motor through a bigger tabletop.
Obviously there should be a cost-benefit analysis done for investing in a custom made or single-use machine. At some point in volume, a custom machine makes all kinds of sense. Determining that point is probably the difficult part.
Size is related to complexity. A typical shaper has the ability to change belt speeds, spindle heights and fence positions. Dust collection ports tend to come in from the back rather than the top, also increasing footprint. When everything is said and done it takes 16 square feet just to get 5 inches of cope.
I think my first shaper would be a real pain to produce, but the 3rd, 4th and 5th would be a breeze because I would already know which parts to order and which machine shops to hire for the things that could not be purchased off the shelf. Besides, if I was a real businessman I would probably own a laundromat.
I still question the idea of building your own machines. Are you trying to save money or do you think you can build a better mousetrap?
When we had dedicated shapers they were clustered in groups of 4 with the DC pipes going straight up. I didn’t use any of the stock fences and had shop built hoods and Weaver systems on most of them. I think the space for 4 machines was not any more than 16 sq. ft.
Weaver Sales wants $750 for a spindle setup. Throw a $350 motor at it. You are talking $1500 in parts, no labor. You could buy a bunch of cheap Taiwanese for less than that and replace them every 10 years (they might last you 25).
This is essentially a self managing line that can be balanced in order to make everything flow continuously. Think of it as one piece flow one product family at a time.
Ergonomics are very significant with fast paced work. Having more control over the footprint and configuration of each work station is more important than what the actual savings might be from buying an off-the-shelf shaper.
There are additional benefits from learning something about manufacturing machines. After you have a couple of them built, you can easily amortize the effort over several more. I'll sell ten of these machines to some of you on this forum (though some of you will have to pay more than others).
For the most part this stuff will be put together with off-the-shelf elements. Some of it will involve a DXF file and a waterjet cutter and some of it will just involve a local machinist. Other than the planning, most of the R&D is outsourced already.
The goal is to be able to staff a company with similar demographics to those people you might find working in a Starbucks. For the most part these people score very high good citizenship characteristics. While they are a migratory group they are also quite educated and easy to train. These people are probably generating profit quicker than most similar applicants in the woodworking industry.
I have about a dozen machines in my head right now and if any of those reach fruition I suspect they will beget a dozen more. Most of these machines do not exist today. The ones that do are not real conducive to small footprint or small budget.
A great example would be a vertical panel saw for drawer boxes. I need something to crosscut a 12 inch board and I would like it to fit within the district we build drawer boxes so as to minimize transport costs or scheduling conflicts.
A lot of the motivation for this concept comes from Taichi Ohno's memoirs. For him the perfect work cell could be run by one person if demand was low, but could also accommodate four people if demand was high. The work flow I envision could do just that. This is where our flexibility will come from.
Whenever somebody tells me that it doesn't make sense for a woodworker to design machinery, I am reminded of the founder of Tigerstop. He used to be cabinetmaker in Oregon. He saw a need and filled it.
