Why Use a CNC for Drilling Dowel Holes?

      Flexibility, accuracy, and speed — the advantages are pretty obvious. August 14, 2007

Question
We cut our boxes on a flat table router and are moving toward doweling to enable us to bid on larger commercial projects where it is required. Back in the day when we were cutting on a pair of sliders, we doweled with a manual gun. Obviously the bore/insertion machines are the way to go, but I fail to see the need for this machine to be CNC driven versus a fixed head machine. Accuracy, speed and cost seem to either be a wash or favor the fixed table, so what are the advantages (or disadvantages) of going CNC with this particular machine?

Forum Responses
(Cabinetmaking Forum)
From contributor B:
You can write your program to set dowels anywhere along the edge, not just on 32mm centers. I place mine 30mm from the front edge and 50mm from the back edge. The back is inset 19mm so the decks have a dowel more or less the same distance from each edge. The rest of the panel is divided up equally with a logic statement that loses or adds dowels as the depth of the cabinet changes. I see CNC as an advantage. Next step is to lose the dowels, glue and case clamp and have the machine drill for comfirmat screws. In my opinion, way better and faster.



From contributor L:
The CNC gives you all that flexibility of making the one off cases that everyone gets into. We are looking into a Biesse FSE or equivalent that is not a CNC but still the borer doweler. This alone will cut our time in half. We presently drill our dowel and confirmat holes on the ptp.

I still haven't made up my mind either, and have not asked any machinery rep as to whether or not we can get the borer dowelers to do the confirmats at the same time.

The most important thing, I was told, was the ability of the CNC to read the barcode of a screen to machine setup that strives for the speed, but you still require the flexibility to move around.



From contributor A:
A CNC dowel inserter has the same advantages of your PTP machine over construction drills. The accuracy, speed, and flexibility of PTP machines over the best construction drills are self-evident. So are the advantages of CNC dowel insertion.

Here are a few advantages that come to mind:

1) Ease of use: you don't need to know where and how many dowels to insert. Program that designs your casework does that for you with very little input. On fixed head machines, you have to engineer your casework with the limitations of the fixed head machine in mind. We use Microvellum and we have to only specify where to insert the first and last dowels and the maximum distance between the rest and the program does the rest.

2) Speed: most CNC dowel inserters can read a barcode on your label and call up the program instantly and bore and insert a dowel every second. Throw the panel on another stop and execute a mirror program with one push of a button.

3) Accuracy: CNC accuracy is apparent. Add to it less likely chance of panel movement, as one hole is drilled at a time instead of up to eight at a time, requiring robust clamping.



From the original questioner:
We use MV also. Do you drill at a consistent distance off the face of the part or do you center the dowel based on the thickness of the part? What dowel machine do you use?


From contributor A:
We have a Gannomat Index Trend. We drill 8mm from the bottom of the panel. This setting works for both 3/4 for case parts and 5/8 material which we use for drawer boxes and also acts as a check just in case a part is flipped by mistake during assembly. The off-center drilling makes the error in assembly very obvious.


From contributor L:
We have a Koch 8' machine that we ordered with an extra horizontal drilling unit so we could run dowels and Confirmat holes at the same time. We also had a vertical drilling unit installed so we could run an 8mm bit for drawer boxes there or change to a bigger bit for KD cams. We got the Z-axis stepper driven so the machine will auto setup when the barcode is read. In our case we don't stack dowel, but if you need to you can get the Z-axis with a high-speed servo unit. These machines can be set up with many different tools, shaping, sawing, miter stops, router motor, etc. The glue system has been very good. Clean the area around the nozzle at end of day and it can sit for days without any problem and start right back shooting glue and dowels. On typical cabinet sides it can process parts about as fast as you can load them. On drawer parts a man can't keep ahead of it because the machine has 4 stop locations. We got the wide machine because we do architectural millwork and store fixtures. For kitchen cabinets it seems like the shorter machine would be fine.

When MV isn't used, you can easily program at the control for a few odd and end parts. We’ve found other uses for the machine also. We do a lot of odd things in store fixtures so we’ve made jigs that allow through boring or to hold parts that have a profiled edge.

We’ve got the timer on the case clamp set at 5 minutes. That serves to set the pace for completing a case. All face boring for panels is done on a Komo, nested.


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From contributor O:
I'm looking at purchasing a CNC dowel borer/inserter. I would prefer to use 5mm dowels on 1/2 drawer box material and 8mm dowels on cabinet parts. For those of you that already have CNC machines, is it easy/quick to change what size dowels the CNC machines run, or would I have to go to 3/4 in material on drawer boxes?


From contributor S:
5mm does not do well with auto insertion. You might want to consider using 3/4 for your fronts and backs.

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