Plastic roll pin

I want to bid on a part for a floor washing brush. The company made a bunch of PVC tubes 1" ID X 1.375 OD x 12" long. It's covered with a material that looks like carpet...'kinda. It works great until it gets hot then it gets bendy. The company's lab came up with a fix that involves a taking a Derlin tube that's 1.040" OD x .75" ID x 4" long with a .312" slit along the side and pressing it into the middle of the

12" tube to act as a stiffener.

What's the cheapest way to make these? Is there a better solution? They need 10k+ of these. They will supply the Derlin material.

Reply to
Tom Gardner
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I forgot to mention that one end gets a 30 deg chamfer to aid insertion.

Reply to
Tom Gardner

Cheapest = outsource to China/Viet Nam...

Slit the tube first, for that a cheap small table saw with guides on both sides and top of the blade and a narrow fin inline with the blade on the outfeed to keep the cut nice and straight.

Next, modify a cheap lathe. Make an internally tapered collet that gets placed in the jaws or welded in place on the spindle. Tubing gets compressed as it enters the taper until the slot is closed where it exits the collet. Have a stop placed 4" away with a modified live center with a 2" or so pin that is a tight fit in the compressed tube and a sleeve on the outside the same length. Have the tail stock on a pivot so it can on a pivot away from the operator and a position stop when it comes back. Make a chamfer tool and a parting tool. Mount both on pivots with stops.

In use the tubes get slit, then pushed into the "lathe". Quick chamfer on the end. Push through onto the stop set to give you a 4" section. Chamfer first then part off. Part will open but be secured from motion by the internal pin and external sleeve. Operator pivots part and tail stock away while pushing part out of sleeve and off pin into "finished" bin behind the machine. Pull the tail stock back into position, feed in more tube and repeat process.

Basically a home brew chucker screw machine.

Reply to
Steve W.

I see. My first thought was to part and chamfer in one cut then to slit on a router table with an out-feed fin as guide to keep it straight...but I like your set-up. The other thought was to farm out the parting and boring and chamfering and do the slitting in-house.

Reply to
Tom Gardner

Any CNC lathe with a bar feed could knock out the part bore and chamfer with maybe a 30 second cycle time. No need to build a special machine.

My *guess* is pre sltting would not be any easier and would slow down the CNC lathe work.

Karl

Reply to
Karl Townsend

The trade off is slitting 15 4" pieces vs 1 5' piece.

BTW - I found a source for 1" x 3/4" Delrin that prices it at $37 per 5' piece. $2.50 material cost for each 4" piece! 'Course when you're buying 2500', you'll get a better price, I hope.

Bob

Reply to
Bob Engelhardt

A wooden plug?

Reply to
Bob Engelhardt

S/B Delrin, eh? Rather than this kludge, why didn't the labs redesign the brush properly? That seems foolish.

On a CNC lathe/machining center.

Reply to
Larry Jaques

This volume (10k units) is on the edge economically, but Delrin can be injection molded.

Joe Gwinn

Reply to
Joe Gwinn

Cut to length with a standard automatic bandsaw if you have one, otherwise use a table saw with a jig to allow fast cutoff feeding from the presumably long stock.

Make a custom chamfering head that has a bore to match the OD of the tube and a standard insert to cut the chamfer (look for HSS inserts). Incorporate the depth stop in the head so you just push the tube in until it bottoms out on the flat part of the front. Continue a bore and a side port for chip evacuation and surround that with a connection to a shop vac / dust collector. Mount the whole head on a basic motor so you don't tie up any normal machines.

Do the slotting on a cheap table saw, with a holding fixture for the tube. Something with a chamber in the bottom you put the tube into where the tube sits slightly past the bottom of the fixture so you can apply down pressure to keep it from rotating. Position the operator and parts bins so they can pickup a tube, place it in the bottom of the fixture as they slide it over the saw table, run it over the blade between a pair of fences perhaps 2" apart, and as they run it off the end of the table the completed part falls into a bin. Minimal labor and pretty fast.

For insertion do a simple pneumatic press setup where you drop a brush and a tube in the press fixture and hit the button or foot pedal to press in to the preset depth. This could be automated easily with some gates to allow you to just load some feed bins and let the cycle work automatically.

If the quantity was higher or this was to be a regular job, a lot more automation could be applied pretty easily.

Reply to
Pete C.

Their lab tried that size and it's too small.

Reply to
Tom Gardner

Wet environment. I suggested it.

Reply to
Tom Gardner

They did. They don't want to scrap the parts already made. Unless the fix is too expensive.

Reply to
Tom Gardner

I did talk to a guy that make CNC parts for me and he doesn't want to deal with the plastic swarf.

Reply to
Tom Gardner

I've not done 10K parts but I found a shop vac to work real well for plastic swarf. Maybe you don't want to go there, but this might be a good time to buy your first CNC lathe.

Karl

Reply to
Karl Townsend

No, I'm at the stage in my life that it's time to divest rather than buy stuff...except fishing rods and reels and pistols.

Reply to
Tom Gardner

Their lab tried that size and it's too small. [/quote]

So when you say they will supply the Delrin, does that mean they supply tubing with the correct id and od, or what? If the outside is going to need turning to size, use the 1" tubing, do the cut/deburr/slot ops then slide each piece onto a SS tube mandrel (have to experiment a bit on the size) and toss piles of them into an oven at 425F or so for 30-45 minutes. The Delrin will anneal and relax and take up the new ID of the mandrel +/- a bit, so you get your correct od without turning the full length. Two sets of mandrels so while one batch is baking the other is cooled, finished tubes removed, new ones loaded on the mandrels and the mandrels loaded into a crate maybe standing them on pegs or whatever, so the entire oven can be unloaded and reloaded quickly. Anyway, just a suggestion.

----- Regards, Carl Ijames

Reply to
Carl Ijames

They will supply tubing 1.040" UD x .500" ID and want it bored to

11/16". I wonder if their original size of 1" OD x .75" id could be stretched open to provide more holding power? That would eliminate yhe boring op.
Reply to
Tom Gardner

Yeah, with some foaming/expanding glue. Delrin is EXPENSIVE!

Reply to
whit3rd

If you're getting 10,000 or more, ask the plastic supplier to supply it in the lengths you want. For them, it's a simple adjustment.

Reply to
whit3rd

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