×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Rubber coating of a shaft

Rubber coating of a shaft

Rubber coating of a shaft

(OP)
What is a simple way to apply a uniform coating of rubber (thickness 0.15-0.35 mm) to a mandrel?
The mandrel is essentially a cylindrical shape and made of aluminium.
The coating is a urethane rubber: https://www.smooth-on.com/products/simpact-60a/

RE: Rubber coating of a shaft

Tricky with it being so thin .

Build a cylindrical female mould that splits in 2. Experiment with release agents and surface prep.

Or maybe paint it on and then turn it down to size on a lathe, if it is a one-off.

If the cylinder is short relative to length then maybe cast a urethane sleeve and slide it over.

Given the absence of info in the OP, the answers are many.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Rubber coating of a shaft

The pot life is only 4 minutes so you have to work fast but dip coating should work for this. You need a bath that fit close to your cylinder so you do not waste a lot. Lower the cylinder into the bath length-wise until fully immersed without splashing or generating bubbles. Then withdraw from the bath at a constant speed. The faster you withdraw the thicker the coating. After withdrawal you let it hang till the coating cures. If there is a problem with drips or sags, turn the cylinder horizontal and rotate it during cure, or withdraw more slowly so the coating is thinner.

RE: Rubber coating of a shaft

(OP)
I actually built a mold, with cavity split in half and a core.
Problem is material didn't cure after closing the mold:



I was looking for alternative techniques, and in fact I considered dip molding.
But the pot life is really short and I don't want to waste material for the bath.

Will try spinning the core / mandrel while pouring material over, sort of like spin coating.

Thanks

RE: Rubber coating of a shaft

Davide Recchia:
Put the cylinder in a lathe and spin it slowly, as you mention above. Add a sharp edged, straight edge (spreader, smoother) bar, .35mm away from the cylinder surface. Might be good if you could rotate the straight edge a bit to become a scrapper/cutter as the rubber starts to set up, to remove excess rubber. The straight edge goes from pointing down 5° to spread the liquid rubber to pointing up 5-6° to kinda shear the firming rubber smooth, and roll excess back onto the straight edge.

RE: Rubber coating of a shaft

What material didn't cure? If it was regular single part silicone, then that's the reason. Two part/catalyzed urethanes cure in molds unless you left out the catalyzer.

RE: Rubber coating of a shaft

Probably wouldn't translate to your application, but this is a common item in the material handling business -

roller sleeve

durabelt

RE: Rubber coating of a shaft

We do custom extruded rubber gaskets sometimes (i.e. make a thin wall tube). You have to order quite a bit of material (1000ft), but its cheap per foot.

RE: Rubber coating of a shaft

Must it be urethane?
How about a heat shrink tube?

RE: Rubber coating of a shaft

One option is to spin it on an axis that's perpendicular to the longitudinal axis, but I think you'd have to slowly rotate along the longitudinal axis, as well. Spinning on the longitudinal axis is probably not going to work, since there's no way to shed the excess material.

Spin coating of silicon wafers with photoresist could achieve 1 um thicknesses with something like ±2% variation

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Rubber coating of a shaft

Admittedly I like MintJulep's suggestion of heat shrink better than this (no seam), but would a self adhesive tape/film work? Mcmaster has a few options in PTFE, UHMW, polyurethane and a few other materials in the thickness range you want. It would have the advantage of being dead simple to replace the cover if it was damaged.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources

Ebook - Mastering Tolerances for Machined Parts
When making CNC machined parts, mastering tolerances can be challenging. Are general tolerances good enough? When does it make sense to call out for tighter tolerances? Do you need a better understanding of fits, datums, or GD&T? Learn about these topics and more in Xometry's new e-book. Download Now
eBook – How to Choose the Correct Corrosion Testing Method
When designing a metal component, engineers have to consider how susceptible certain alloys are to corrosion in the final product’s operating environment. In a recent study by NACE (National Association of Corrosion Engineers), it was estimated that the direct and indirect costs of corrosion in the United States is approximately 6.2% of the GDP. In 2016, that cost exceeded $1 trillion dollars for the first time. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close