I've been reading a lot on making interior wood doors since a client has asked me to make a few hundred. In terms of equipment, although it's not necessarily meant for it, could a double ended tenoner be used for making the rails?
(Architectural Woodworking Forum)
From contributor L:
"Could a double ended tenoner be used for making the rails?" Sure, but they could do the rails for a few hundred doors in a day, take up a lot of space, cost a lot even for a decent used one, and take twice the tooling of a single end tenoner. The newer tenoners typically have stacked tooling and readouts or CNC and can change from one job to another very quickly. You can also get HSK/tool changer machines that can use the same tooling as your machining center. The same work can be done on a nice shaper. It wonít be done quite as fast, but itís a lot less expensive
You can produce a very large quantity of parts of the same sticking profile in a short time, although not much else.
Downsides include changing to different profiles and it was a very time consuming process. Keeping the machine dialed in was a never-ending job. It would only cope rails down to 9" and anything shorter had to be coped on a shaper or CNC. The operator would spend a lot of time watching parts travel through the machine if they were different lengths as well.
If you are going to be producing 25 plus doors every day of the same size and sticking profile, I would say go for it. Anything short of that I would recommend a shaper with sliding table. One of the DETís we had was a godsend when it came to trimming doors to length before sending them through the widebelt.