Pod and Rail Versus Flat-Table CNC Routers

      A long and thoughtful look at what flavor of CNC will best suit a particular woodshop's needs. December 8, 2010

Question
We are a small company looking to buy our first CNC router. What is the most versatile - pod and rail or flat table? Certainly the product we produce is one of the major determining factors, but in the current economy, we play in many fields. We go from high end built-ins, libraries, home theaters, even recording studios, to medical cabinets and casework for commercial and military installations. The next consideration is how we make the best use of our current machinery - a sliding table saw, edgebander, wide belt sander, line borers, hinge insertion machines, and all the other things one would expect in a non-CNC shop. Any advice?

Forum Responses
(CNC Forum)
From contributor J:
I am a used equipment dealer very familiar with this question. It of course varies based on your product. A pod and rail machine has an advantage over a flat table in that it can process the side of the part with horizontal boring, machining, cutting, etc. A flat table can also perform some of these tasks, but then the parts can't be nested and require to be raised. The parts also require more space to separate them to make room for the tooling to access the side of the part.

Cabinet bases/frames can quickly be produced on a flat table with all the construction boring completed in a matter of 5-10 minutes per sheet on a newer machine. This would take longer on a pod and rail machine.

It is also possible, though, to get a pod and rail machine and purchase an aftermarket retrofit kit to allow it to produce flat table parts. This does not hurt the machine and only requires a few minutes to convert. This retrofit can also be removed in a few minutes to allow production of pod and rail parts.



From contributor R:
Without a doubt a flat bed router and good software for nested based cutting is the best way for a small shop to go. I see a pod and rail or point to point for high volume production shop. Those parts would be cut in stacks on a beam saw and then machined on the PTP. You will not need your line boring machine. I have never used a sliding table saw, but a standard cabinet saw new is about $2700.


From contributor J:
Contributor R, what you said is true. But if you are machining custom parts made out of solid wood, that requires machining on the side and bottom of the part. A pod and rail is the way to go. A flat table can't perform those functions as easy. But if all you are doing is machining on the top of the part and cutting the part out of a sheet, then a flat table is all you need.

When you start to get into other areas, the type of machine becomes gray. I used to run flat table parts for making thermofoil and veneer raised panel parts. I also used it for nested based machining. Thing worked for another company that had a pod and rail and they used it for the machining of parts.

The type of machine also depends on the type of equipment you have available and the speed at which you want to produce parts. If you have a horizontal boring machine, your operator can run a flat table machine and then run the horizontal borer while the CNC is running.



From contributor R:
I have never needed to machine more than just the face of any of my parts. I use dado construction, no dowels. If I do any decorative machining, it has always been just the face.

I have always thought the key to any machining process is the software. The more versatile, the better.



From contributor J:
It is a combination of both. Depends on the product you run - you may only need a flat table machine, or if you have enough Z-clearance, then you can run other parts.

For dado construction, a flat table is perfect. A pod and rail can be a flat table, but also give you the flexibility of running complex custom parts with CNC accuracy. Let's say you are making a sunburst shutter frame and want to drill the holes on the CNC. This could only be completed on a pod and rail. It could be run on a flat table, but then you would need to raise the part and have the C-axis option installed. This comes almost standard on most pod and rail machines.

There are ways to get a flat table to machine anything you want, but the real factor is how much setup time you want to spend. A pod and rail machine is easier to clamp parts with, compared to most flat table machines.



From contributor M:
As a custom shop engineer who bought a machine almost 7 years ago, I can tell you what I'd do different, looking back at all of the custom architectural products we have produced. Nothing. If I could not find money for a 5 axis head, I'd get the same configuration. Flat table router with a grid system for fixturing solids when needed. Large spindle with C axis, drill bank with horizontals, and an independent saw. With this configuration, there won't be much you cannot produce.


From contributor W:
In the same business! Flat table nested here. I have the three head x3 machine, so at a minimum get one similar or an ATC. A single Z machine will frustrate you.


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From contributor E:
I run both a nested (flat) CNC and a pod and rail point to point. Since I do high volume production kitchen cabinetry and high end commercial, it has been useful to have both. I use a panel saw to cut the parts for my production prior to sending them to my point to point. This gives me the ability to do volume with minimal manpower. I run smaller parts that need machining on my nested (flat) router because I can do onion skin cuts to help hold them in place better. I also utilize my nested router for MDF doors and specialty cuts for our desk area (curved, etc.). Software is a good thing to focus on when deciding what type of machine you need. I rely on Routercad for my nested router. It allows me to create DXF files quickly from AutoCAD drawings for specialty items, but I use BiesseWorks for the pod and rail.


From contributor B:
The main question I see is, should you consider nested base manufacturing with a flat table CNC router? The way your shop is set up now, a point-to-point could fit in without much change. You rough cut the parts on the saw, take them to the p-to-p to finish cut, perform top and edge drilling, and go to edgebanding or assembly. If a majority of your parts require a lot of edge work, then a p-to-p with a pod-and-rail setup could offer some advantages. Also, these machines typically have some basic software onboard for cutting and drilling panel parts, so your initial investment in software could be lower.

In a nested base world, all your parts are cut from sheets. No sawing required. The software choice is important because that is where the process starts. Some type of parametric cabinet software will probably be critical. All of your top face machining can be completed. The parts will be automatically nested into sheets based on material type. The machine code is generated automatically and you are ready to start cutting. Sheets on, finished parts off, ready for edgebanding or assembly.

Most nested base machines have an automatic tool changer (ATC) and a drill block. ATC machines usually start at 5 tools and can go up to dozens of tools depending on your requirements and how much money you can allocate to the purchase. A drill block is not essential with an ATC because you can pick drills from your tool selection, but if you do a lot of drilling, it can be very beneficial. Again it is a function of how much you have to spend. A three spindle machine versus a single spindle ATC system might be enough or could be a limitation. Multi-spindle machines are typically faster to the next tool, but setup is more complicated, and adding and maintaining routers can be more costly.

If your budget is small and you want a new machine, you will probably have a better selection of flat table CNC routers. If used is a consideration, you should be able to find a point-to-point or flat table machine to meet your needs.

As your shop grows, you might end up using both processes. Getting started in CNC you need to consider how much time and money you want to invest, and which process will work best in your shop.



From contributor U:
The key component of the original post for me was what would fit into the existing process. In my opinion, for entry level, that would be a pod and rail. If the right machine/control was selected, no additional software would be needed. The existing machinery could be reconfigured in machining clusters or cells to facilitate and enhance flow relatively easy.

That said, the flat table would possibly eliminate some machinery, definitely include additional software, possibly revamp current construction methods, and possibly have an increased learning curve.

Either can be the right decision - it depends on the individual company dynamics and where you want the company to go in the future.



From contributor I:
Another consideration - if you have the volume of business to justify it, you could get a machine like the one we have. It's a hybrid, half flat panel and half pod and rail with an overall capacity of 5' x 20'. Split at the center for two independent 5' x 10' work areas. We have the ability to put bed extenders on the pods when needed to achieve the overall of 20'. We do use it frequently that way. Commonly up to 16' and a few have hit 18'. We also take advantage of both worlds. I would say the split 60% flatbed and 40% pod and rail work.


From contributor V:
The best of both worlds would be a combo machine, sometimes referred to as a convertible CNC. Or what a lot of our customers have, flat table machines at 10 to 12 feet. This type of machine can accept vacuum cups and utilize the last 2 or 4 feet of the table as a pod and rail machine.


From contributor O:
You have to ask yourself what you want to make. Simple and difficult at the same time. We have a 5 axis point to point machine and decided on it because of the flexibility and versatility it has. Flat table is appropriate for panel processing with your set up pins in front of the machine. Typically on a PTP you have references all over the place. I think the real beauty of CNC is moving the part once. That said, going from machine to machine defeats the purpose and wiggles in human error again. We looked at tasks and the time it took. On a PTP all we need to do is surface sides and the machine does the rest. We are making entry doors, so the PTP shines in this realm.


From contributor Y:
We are new to CNC and have a similar setup to you. We went with a nested 5x12 router that came with pods. We nest sheets for cabinets and doors. For smaller parts that would move in the nest, we cut to rough size and then place them on the pods for final shaping. The pods also allow us to do solid wood and profile the edge of solid surface countertops. In my short experience, nesting is all about the right software if you want it to be efficient.


From contributor L:
Whichever you pick, you won't be disappointed. We run a pod and rail and slider combo. We wanted a beam saw, but just no room. We don't have the software in place for the flat table, but anyone can walk up to the slider and check for calibration and cut an end and just about everyone could go to the PTP and load the part and process it. The time savings in assembly alone paid for it, many times over.


From contributor O:
It sounds as though you primarily make case goods. For your current product, a flat table seems like it would work best. In the end it comes down to how you hold the part. What kind of parts you make will determine the machine.


From contributor Q:
We've been running nested for several years - very efficient for panel work. We also have a Schelling panel saw, but unless you are stack cutting, the router wins. 8 minutes to the sheet fully detailed, down the conveyors to the bander, then to the bore and insert machine and case clamp. If you go for a flat table machine, get push off and table cleaning. We do some solid wood on the router, but far more panel. We still have our old slider and it gets used for all sorts of odds and ends.

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