most ergonomic solution for torquing fixture screws in machine

wheelieking71 · Jan 15, 2018

So, I am building a fixture, that will have 24 3/8-16 (5/16 hex) cap-screws to loosen/tighten every cycle. They will need run down to about 40lb/ft (I think).
It needs to be quick. And it needs to be easy on the operator.
I was originally thinking/picturing something like this hanging on a yo-yo inside the enclosure:

But, I am worried that over time, that might tear a guys wrist up?
Then I was thinking air-ratchet? Might be a little easier on the wrists? But, maybe also more cumbersome inside the cabinet?
I just don't know what direction to head here. All I know is I have a shite-ton of parts to make, and I don't want operators miserable, or worse, quitting.

What say you production guys that have already faced this situation many times? What works?

ewlsey · Jan 15, 2018

How much of a shit ton? Are you in the range where a hydraulic fixture would be justified?

DDoug · Jan 15, 2018

Maybe get rid of screws altogether.

Bimba air cylinders underneath pulling down, with a slotted
quick acting washer/nut on top.

Hodge · Jan 15, 2018

Without seeing a pic of setup it's left to the imagination, however could you make some type of top plate/Gibb that cam locked down with a lever. Possibly taking place of numerous bolts at once. Just a thought

Nami · Jan 15, 2018

Look on ebay for Uyru drivers. Made just for this. Set the torque once and forget it. Also quieter than air ratchets. I use a screwdriver model that's $1500.00 new, got off ebay for $60.00. Tool starts rotating by pushing driver down on/in fastener (no trigger). Does (60) 1/4"-20 shcs in about 2-3 minutes.

MachEng · Jan 15, 2018

ARO Straight Push to Start hanging on balancer. Little to no torque reaction because clutch shut off.
I fixtured one in old Matsuura VMC on a piece of welding curtain track.
The tool hung on a trolley that rode in the track. I even had the track running a slight angle so when the operator was done it would move to the side out of the way on it's own.

converterking · Jan 15, 2018

Wouldn't some type of pallet changer be perfect for this? Change pallets and change parts outside while the machine is running? What is the cycle time?

wheelieking71 · Jan 15, 2018

ewlsey said:
How much of a shit ton? Are you in the range where a hydraulic fixture would be justified?

Yes, I am afraid so. We are not sure yet. But, judging by last year? 40-60 thousand parts this year.
But, I am literally out of money (and credit). And, I need to make parts. I may (probably should) go hydraulic later.
But, I have to run parts now to make money.

wheelieking71 · Jan 15, 2018

converterking said:
Wouldn't some type of pallet changer be perfect for this? Change pallets and change parts outside while the machine is running? What is the cycle time?

I have the parts nested so tight, it would have to be all on one pallet. And, said pallet would be HUGE (heavy).
That is why the fixture is in a machine with a pallet-changer (Brother R650).
Total (educated) WAG on cycle-time is 18 minutes.

wheelieking71 · Jan 15, 2018

Hodge said:
Without seeing a pic of setup it's left to the imagination, however could you make some type of top plate/Gibb that cam locked down with a lever. Possibly taking place of numerous bolts at once. Just a thought

Nope. I am only holding .080" stock. Top/sides needs to be open. The blanks are 1.02" tall.

Test fixture:

Just finished that just now. I have not ran a part on it yet. That is tomorrow. But, it looks promising.

706jim · Jan 15, 2018

Battery operated drillmotor?

At least you wouldn't have an air hose hanging around inside.

Jashley73 · Jan 15, 2018

Those butterfly-impact guns are way, way better than an air-ratchet. Way less torque reaction, and chance of a broken wrist. Not saying they're the best solution, but definitely better than an air-ratchet. (I personally think air-ratchets are the worst air-tool ever...)

Adjust air-pressure with a regulator for a little better control, and use an in-line oiler, so you don't have to worry about changing speeds/torque.

Also, would a cordless drill with clutch work? Probably not too precise in the 40 lb/ft. range...

Tightening won't be a big deal, whatever you use. Un-tightening would probably be the bigger hassle. If you use a power-tool, you don't want to be backing the screws out all together, and then have to re-start them.

What is your plan for loosening all these screws...?

Triaged · Jan 15, 2018

wheelieking71 said:
...cap-screws to loosen/tighten every cycle. They will need run down to about 40lb/ft...

So what is it? Loosen/tighten or run down (what I read as needs to be unthreaded a long ways)

To just tighten a 24" torque wrench wouldn't be too bad depending on how many there are. What you need is something like a thick slotted washer so you don't need to unthread so much.
https://m.grainger.com/mobile/product/GRAINGER-APPROVED-Slot-Washer-1JYF4

DanielG · Jan 16, 2018

A right-angle nutrunner (like the ones Nami suggested) would definitely do the trick, and with a toolbalancer would be pretty easy to use. If you do go with a nutrunner, go with a right-angle version. I wouldn't want to do 40 ft-lb with a screwdriver- (like your original picture) or pistol grip-style,

Since it sounds like you just need something to get you up and running and this isn't a super long term solution, what about a cordless impact wrench? The Milwaukee 12V ones are cheap, light, and put out 37.5 ft-lbs of torque, which is just about what you need.

PeteM · Jan 16, 2018

If you don't care about torque accuracy, an impact wrench will be quick in and out. Operator should wear ear protection.

An air motor with a clutch can help with the reaction torque if you need accurate torque.

Galling of the bolts is an issue over many cycles. You'll want them lubed, but that will also play be a very different torque-tension profile than dry.

If you're planning on doing this a whole bunch you might consider a fixture with two or more spindles (arrange the bolt locations so you can get them in pairs??). This takes away the torque reaction that can eventually cause carpal tunnel and the like.

As others have said, a tool balancer probably makes sense regardless of what you do.

Best if your fixture is designed so that the part is pretty much locked in place for machining forces regardless of variations in torque/tension on the fixture. You mention a really thin part, so maybe that's not possible.

Air tools last longer around chips and coolant than electric tools.

FWIW, the fixture link isn't coming up for me (says "invalid link").

B-Mathews · Jan 16, 2018

A used one of these if you could find it cheap enough would be the cat's ass. I see them advertised as torque limited nut runners but not sure how many foot-pound. The flex arm would take all the torque that your wrist might take with other methods. Tapping Arm - Wapakoneta, Ohio - FlexArm Tapping and Assembly Solutions

EDIT looks like this model will do 50-foot pounds so it would work. Item # RNR2-6, RNR2 Pneumatic Tapping Machines On FlexArm, Inc.

Chances are you have or will have another app. this could be used on too while not using it for this pallet.

SteveBausch · Jan 16, 2018

Milwaukee has a series of cordless 12 volt tools, and thr 1/4” inch inpact is tiny and lightweight.

The M12 FUEL 1/4 in. Hex Impact Driver once again raises the bar for 12V performance with best in class driving speed, power, and size. By focusing on productivity, this Impact Driver gets the job done faster by being over 20% faster in application speed vs. the competition.

This tool outputs over 1,300 in./lbs. of torque that allows the user to get more work done by completing a wide range of fastening.

Measuring only 5.1 in length allows for unmatched access in tight spaces. The POWER-STATE Brushless Motor delivers up to 0-3,300 RPM with constant power output to drive screws faster.

REDLINK PLUS Intelligence is the most advanced electronic system on the market, preventing damage to the tool and battery caused by overloading or overheating. For use with M12 REDLITHIUM Compact Batteries or Extended Capacity Batteries which deliver more work per charge and more work over the life of the pack than competitive batteries on the market. The 4-Mode DRIVE CONTROL provides greater control over output speed and power for greater versatility by delivering 0-1,300 RPM in Mode 1, 0-2,400 RPM in Mode 2 and 0-3,300 RPM in Mode 3. Mode 4 is Self-Tapping Screw Mode which is designed to reduce walking when starting self-tapping screws as well as reduce overdriving, breaking and stripping out screws.

Larry Dickman · Jan 16, 2018

I had some high volume parts a few years back. The butterfly type impact worked awesome. Very light and easy to maneuver. We were using them with 1/2" stripper bolts. A couple suggestions. We put helicoils In the fixtures. With zipping bolts in and out a hundred times a day, they don't hold up. Switched to ez-locks and never had to replace one. Also, the socket heads on the stripper bolts would strip quickly. I machined hex heads onto the bolts to solve that problem.

hanermo · Jan 16, 2018

I suggest an engineered/engineering solution.

Make 60 bolts with cams to tighten them and an offset lever about 6" long - for 1/4 " bolts.
The levers will act as springs and tensioners.

Link all levers together, threaded rod might do - or couplers.
Now You only need to tighten one part, the end of the long lever.

Matt_Maguire · Jan 16, 2018

That’s a lot of clamping, (24) 3/8”x16 screws torqued to 40 ft/lbs works out a bit over 150,000lbs total load. That’s plenty to bow some stuff around? I regularly cut 1/2” keyseats in v-blocks with (4) 1/2”x13 studs with clamp straps @ 120in/lbs (10 ft/lbs) which works out near 5000# total clamping.

I also like the multi-point cam solutions mentioned above if you can.

Matt

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