I’m hoping to get some insight from some of you all working in production environments about how you would increase the efficiency of making these hanging hammock chairs, seen in pic 1.

Our shop created the design for these and have been making them since 1977. Our production facilities burned down recently in a wildfire (R.I.P. Oliver 299 and many others), and as we’re looking at retooling, we’re wondering if there are aspects of our production process that could be improved.

They’re made of white oak, and currently everything is assembled square, and then shaped by hand on a pedestal mounted drum sander, from 40 grit up to 120. This is a physically taxing process, so we’re hoping to move to more repeatable operations on the shaper to profile everything.

The arms just need a ¼” roundover, so I’m imagining a stack with a roundover cutter at the top and bottom, and a rub collar in the middle.

With the arms fully profiled down their length, that would mean we’d need a matching cove cutter for where the back meets the arms. This would leave a very fine point on the backs that I’m not sure would survive without splintering. Does this seem doable?

Moving on to the beveled curve along the back of the chair. Currently it’s run through a curved fixture on the bandsaw, with the table tilted. Coincidentally, the bevel on the front of the arm runs pretty much the same profile. See pics 2 and 3.

I’m thinking that with a custom cutter matching that profile, we could crosscut the ends of the arms, backed up to avoid blowing it out, and then run the backs through a curved fixture to bevel them. Is this set up feasible? Power feeder is obviously a given in this scenario, although getting the right angle on it seems confusing.

Continuing the roundover profile down the beveled end of the arm seems tricky, worried about tearout there. Could we freehand this on the first cutter mentioned with a large enough cutter diameter to avoid tearout? Maybe climb cut on the router table otherwise?

For rounding the back corner, I would make a template and follow it with a compression bit on the router table, then use the same method as above to add the roundover profile.

Then for finish sanding, is a foam backed ROS the way to go, or are there flap/mop sanders that may make this easier?

This all makes sense in my head, but I don't have any experience with a shaper or how most production shops do things. If you all could sanity check this for me or have other suggestions I’d really appreciate it, and it would make me feel better about trying to pursue it. Thanks!

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A shaper would improve what you are describing but if I was starting to retool completely, I would go the CNC route for this project. It would be able to do most of what you need in one machine without removing the part to change setups. Those who are CNC experts will be better at laying out the process. Myself, even being extremely proficient on a shaper, I know the shaper could do it but lots of work still.

We do alot of work like this. Shaper is not going to do it all. Looks like you need a bunch of router table setups. Let me think about it.

Thank you, I really appreciate you taking the time!

I second a cnc approach. Side legs drill groove profile cut.
Back piece drill, maybe 3d carve with a roughing pass. I am assuming there is a groove on the bottom side for the rope. This would have to include flipping the piece on the table.
Still use the drum sander to blend and finish the 3d carve.
Round over after assembly.

I could see CNC for the arms. I've only ever ran a hobby level machine, but if we were pushing things harder on a pro machine, getting all that done in one step could be big. That could replace the pin router and gang-drill. It's hard to see in the picture, but the holes are countersunk on the inside of the arm to reduce strain on the rope, so the piece would need to be flipped or added some other way.

The holes on the back are 3" deep, would that not be a problem?

The issue I was running into with rounding over with a router after assembly is that inside corner where the arm meets the back. That's what got me thinking about the cove cutter, like how it's done in rail and stile construction. Any suggestions for a solution to that?

I think you are hearing some good suggestions. But what is your budget for equipment? Good routers seem like a good option for a round over, shaper is even better but more expensive up front. For small or light cuts we use several routers, for more dedicated task and larger cuts we go to our shaper. They both cut well and deliver the profiles we need, but using several routers minimizes set up times when switching cuts. However, stacking cutters seems to be something I would only do on my shaper.
Could you utilize a stop and start profile, rather than profiling the full length? That way you have a square edge where your joints meet.

Oh yeah, stop and start does seem like a better solution to that. Thanks!

What is your production rate? A lower end CNC with multiple heads could really put you into quick production. Possibly outsource some of the operations to a CNC shop to get back into production faster.

Oh wow, never knew multi-spindle was an option! That makes it make more sense.

At our peak we were making 1100/yr.

3" deep holes are possible with a cnc with a 8" plus z axis travel. I would set these parts up in multiples on a fixture table to accept accurately dimensioned parts wedged in place. Half the table jigged for on side of the operations - the other half for flipped parts. Toolpathed in 10 -20 parts per table, the process time would likely be about 2 minuts per part total to drill groove, countersink. I still would round over after assembly.
Consider have a shoulder on the side rails to ease the inner corner problems of rounding. I do this with ash with success.
I rout and drill ash components more complex than these by the hundreds per day with simple wedge clamping. I order my stock in D4S with a corner round on all four edges which has improved my production and profit in a big way.

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This is great, you've all got me thinking bigger than when I started. If we increase our frame production time, eventually we'll start bottle necking at finishing.

We've got a spray booth where we finish these off with two coats of marine spar varnish. Is parallelization the only option to increase throughput here? Minimizing worker effort and solvent exposure would go a long ways to making this more feasible, as we've had a harder time filling the finishing position than anything else.

I also wonder about a first coat of CPES. This is outdoor furniture, so increasing it's ability to weather the elements is a big concern. We were spending a lot of time filling checks and finish sanding to a high degree so that they didn't come through in the finish. Might a first coat of epoxy reduce the need for this?

Anyone have experience with the no-VOC versions of CPES? I assume the performance characteristics of these are not as desirable, but if they're acceptable it would make a big difference.

You all are great, thanks so much for helping me think this through!

If you don't want to go the full CNC route, I would also recommend checking out an inline profile shaper. Not the standard spindle shaper that most think about. (I use two old onsrud inline profile shapers) They can be picked up at auction quite cheaply some times and one man could do 1100 of your back "scoops" in a ten hour shift. A double spindle profile shaper could do it even quicker. The long groove in the arms would be the exact same, just a shaped cutter in one of the spindles. Pick up a cheap Cemco or such vertical boring machine to do your holes with and you are off to the races. Both of these things can be had at factory liquidation auctions for around 10k, and I feel pretty confident you could do the wood working side (not finishing or sanding) of 1100 of these things in less than two weeks with a single employee.

I'm not seeing too much online about the operation of the inline profile shaper. Is that like a planer molder without the planing function?

Here are some picture of mine. Some call it a hydraulic spindle shaper as well. Mine is an onsrud W-684 H. Spindle floats in and out of the piece and the 9 foot bed pushes into it. Spindle can be made with any shape or angle of cutter. On bed, a form is made and bolted down to mimic the shape you want, and a wheel on the bottom of the spindle rides against the edge of the form. when you press the foot pedal, the bed moves to the right and the shaper is forced into the form with an air cylinder.

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I realize my explanation and pictures are sub par, so heres a short video link to it in action. This is a curved top rail of a bed.

VIDEO HERE.
https://drive.google.com/file/d/10QZATrebFAsKoCQKUAfcWIcVr6ToSAFH/view?usp=sharing