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Plating sticky stainless

Posted by tray 
Plating sticky stainless
October 11, 2014 09:10AM
I've heard that while stainless is good for a hot end, it's somewhat sticky for hot plastic, particularly PLA. Has anyone experimented with plating the bore with another metal to reduce friction? If so, what would be a good choice? (slippery, and compatible with a nontoxic electrolyte)
Re: Plating sticky stainless
October 11, 2014 10:41AM
Wouldn't it be easier to make the part out of a different metal ?
Re: Plating sticky stainless
October 11, 2014 11:30AM
Are you talking about the tip?
Or the lining of the hotend?

If you are talking about the tip. They make and sell hotends with brass changeable tips.
These are cheap. And you can easily change between nozzle diameters.

If you are talking about the lining of the hotend.
Stainless works well. They also have models with teflon lining.

Its simple to maintain with this rule.

Keep the hotend hot, and the coldend cold.

If the stainless is kept to a reasonable temp. Any friction issue going into the hotend should be less, or not even worried about.

Its my opinion. Tell me if i am wrong.
Re: Plating sticky stainless
October 11, 2014 11:33AM
Perhaps there's a easier material, but stainless presents an attractive design compromise compared to other available metals, so many hot ends use it. Plating might be a simple way to improve that compromise.
Re: Plating sticky stainless
October 11, 2014 04:21PM
Is it a stainless itself is making it more sticky or it's surface quality?
Re: Plating sticky stainless
October 12, 2014 07:04AM
When I hear people say that stainless has higher friction compared to brass as a hotend lining, I assume they mean the material, not the machining.

pushthatbolder, barrel friction is enough of an issue that e3d added a teflon liner in their v6 hot end.
A teflon liner won't work in my case. It will have a very nice surface finish, so that may be enough for some materials.
Re: Plating sticky stainless
October 12, 2014 01:54PM
Stainless has more friction than PTFE, as do all metals, that is the issue, not that is more sticky than other metals.

Stainless is a poor conductor of heat so it is used as an insulator to make the transition zone and that is where friction is an issue. Once the plastic is fully molten there is no friction and that is where brass parts are used.

Re: Plating sticky stainless
October 12, 2014 09:29PM
I'm working on a fused silica (quartz) tube to replace the ss pipe, it should in theory eliminate the friction problems and it is even better insulator than ss. Not cheap though, for testing I ordered 2 pieces at $ 24.00 each already machined to my spects. I have some other parts in production (heater block and cooling block)it will take few weeks for parts starting to arrive but will give feedback once I can put it together.
Re: Plating sticky stainless
October 16, 2014 09:41PM
Not all metals act the same with plastics. For example, mechguru lists steel/PTFE at twice the coeficient of friction as chromimum/PTFE. I haven't yet found data for the materials and temperatures we care about.
Re: Plating sticky stainless
October 16, 2014 10:19PM
Let us know how your quartz tube works out, ggherbaz.

My own pipe dream is to modify a 12 gauge all-stainless glue dispensing tip into a hot end. The inside of the barrel has a mirror finish and comes with a luer lock attached for mounting. Rough idea: Braze the luer lock to the tube, copper fins next to that, and the nozzle inside the tip. Add a thin sodium silicate coating to insulate, wrap in nichrome, dip again, add a small PT1000 for temperature sensing, and wrap in insulation.

It'll probably be a fail in a hundred different ways, but it's an interesting experiment. And on the odd chance it works, it'll be an exceptionally light and quick reacting hot end.

I tried Taulman's old trick of cold rolling the nozzle tip, but that didn't work on such a large tube, even with bearings and annealing. (BTW, stainless magnetizes when cold worked. Very cool.) Thought about hot-forging the tip around a sewing needle, but I don't have the tools to make the die. So it looks like drilling a nozzle. Kind of on the back burner at the moment, as I work through some other issues.
Re: Plating sticky stainless
October 22, 2014 05:55PM
I just got my first printer (Kossel Mini) and can't get the PLA to extrude for more than some seconds and if I stop, it seizes up and I have to tear it apart to clean it out. gah! I haven't even printed anything yet and already I feel like I'm trying to redesign this thing! (that's good and bad)
Anyway, I've concluded that: my fan is too small, and PLA is sticking too easily to the stainless heat break. And I"m pretty sure this is a cheap clone so the inner finish is probably not good.

Anyway, what about chrome plating? Chrome seems popular for mirror and stick-free finish in many cases, I don't know if it is industrial-only process or what.
Re: Plating sticky stainless
October 31, 2014 02:44AM
Chrome plating is a pro job only. The residues are highly toxic.

Note that there are several kinds of stainless.

303 stainless is better for machining, but not easy to find in the tube dimensions I wanted. It has slightly higher thermal conductivity however.

304 is considered nearly un-machinable (although very common) - it is difficult to get a smooth finish, but with careful reaming it can be done. I ran into this with the hot end I built for Raptosaur. We re-machined the tube and reamed it smooth, but still had serious problems with PLA. I think a Teflon liner may be needed for my design.

Machinists have this little (off color) rhyme: "303 she's for me, 304 she's a whore"
Re: Plating sticky stainless
November 01, 2014 09:55AM
Electroplating SS is not advised. At home I've plated a copper strike onto SS but it's not durable, and take a lot of energy. Best to begin with a different base metal. Surface finish is not improved with electroplating, all machining details are faithfully reproduced. Begin with a smooth surface.
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