On Sat, 12 Jul 2014 11:58:31 -0400, Tom Gardner Mars@Tacks wrote:

On 7/12/2014 5:29 AM, Karl Townsend wrote:
On Sat, 12 Jul 2014 02:56:21 -0400, Tom Gardner Mars@Tacks wrote:

On 7/12/2014 2:33 AM, Steve W. wrote:
Tom Gardner wrote:
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.


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.



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.

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



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

I can see his point. It's extremely statically charged and sticks to
everything. I've slit PVC pipe and don't think I want to try THAT
again.

--
Liberalism is a pathology.