finishing delrin?

Hi guys, IVe been playign with bits of delrin but the surface doesnt look that great. wondering if anybody has ever tried to finish delrin to H****** spool standards and how it can be achieved without spending too much

thanks!!

wet-dry sand paper works well.
File rough cust edges first then polish with wet sand paper.

Mike D

Can you flame pollish delrin?
I have done it on plexiglass.

I haven't tried to flame polish delrin, although I don't see why not, considering that it's a thermoplastic. I always cut my delrin parts out with a laser, which, if you have access to one, is the best way to make sure you get perfectly smooth edges every time.

actualy ive been using a laser... but the edge has some bubbles... and its not usually very smooth.. usually having a slightly slanted edge... hmm..

what kind of a laser do you use?

Ive tried with various types of sandpaper.. but the finishing still leaves a lot to be desired. What is flame polishing?

You can use a propane torch to melt the surface of many plastics. When the surface melts the ridges and parts that stick up melt first and tend to level out.

Practice on some scrap material first and you can quickly learn how much you can do and how to avoid damage to the material.

Gee, I would love to have a laser cutter. Got a spare laying around?

I use a ULS model M-300, which is a 50W CO2 laser head. I use an air assist on the cutting head, at about 50 psi, which helps cool the cut point and keep the flammable vapors down. I also run the laser at 1000 dpi, which gives me a finer cut.

A laser cut will always have a slight kerf on it, meaning that things like cubes/boxes (for things like lens alignment) will need hand finishing. Of course, the thinner the part, the less of a problem this is. For most items, this isn't a problem, and you can usually compensate somewhat by over/undersizing the cut parts. It took me a lot of wasted parts to start judging the "error" in measurements to induce.

If you really have serious bubbling issues with the laser, I suggest reducing the power output and upping the cutting speed. Then just overlay multiple passes, which will give the part time to cool between hits. I find this works REALLY well on softer plastics (like ABS) but delrin might benefit, too, especially thicker parts. As I mentioned above, that air assist nozzle is, for me, a must have.

I made a dive reel by stacking laser cut rings on a core (laminated a stack), and in the last dozen or so dives, I've had no problems with it holding up in some pretty rough Pacific NW waters at fairly chilly temps.

Pipedope: Thanks!! Ill go take out a torch to play .. will see how it goes. Ill go look around.. If i see a laser cutter thing lying around.. Ill let you know.. or maybe I could just lend you my lightsaber... hmm..

Cameron: OOo I forgot about about the air LOL Ive been cutting thin material for so long. When I use the gas it sometimes shifts the smaller pieces away. SO I turned it off. Will go try it out. WHen I try to use multiple passes tho, it doesnt work because the delrin tends to fuse itself together at the edges when the cutting speed is too fast. I need to use a less focussed beam and slower speed. NOw I know its possible tho, Ill go try it out.

I get to play with an Eurolaser M1200 at work. I just made a couple of spools using 2 sheets of delrin and a delrin rod in the middle held by screws. Your idea sounds interesting, so theres a threaded rod down the middle? guess that means that theres no hole through the spool? or is there?

Let me / us know how it turns out with the air assist. With the multiple pass thing, it's really important to either power way down on each pass or speed up with the thicker material. For instance, half inch (0.517" Delrin), I use 10 passes on the 50 watt / 100% power setting at a speed much higher than I thought I'd need.

In order to make sure that things don't fuse back together, I cut a "delay" line between passes of the cutter by retracing the cut with 0.5% power and 0.5% max speed (the slowest speed and lowest power I can set the head). That gives the first pass time to cool off before I repeat the cut again.

FYI - I didn't mention it before, but for whatever reason, Delrin seems to have a bigger kerf than acrylic or lexan. That half inch piece gives me a +/- 0.006" kerf.
Again, not too much of an issue, except when trying to mount multiple lenses in optical alignment.

WRT the reel, I had one of these 150' ratchet dive reels that I used for my SMB. The coldwater handle stripped out of the reel, and there was no good way to get it back in, cleanly, so I fabricated a replacement on the laser cutter. There is a threaded metal rod down the center, and plates on the top and bottom. The plates lock through the plastic with washers/nuts on one side and a circular clip on the other.

I really like Delrin, other than the cost - less brittle than acrylic, and works really well for gears and other parts that take some stress.

ragdoll:

Hi guys, IVe been playign with bits of delrin but the surface doesnt look that great. wondering if anybody has ever tried to finish delrin to H****** spool standards and how it can be achieved without spending too much

thanks!!

Click to expand...

Ragdoll, Howdy!
I noticed you while sending a message to someone else, was intrigued by your posts, but noticed that you have been busy working the site before we've even gotten a chance to say, "Hi!"
So I did.
See ya around.

**Apologies folks, I didn't notice this was an old thread until I looked at the date on the thread that lead me to it. (I didn't post to that one!)

Tom