Automatic Oil Paint Dispensing Unit

Is curing time your biggest problem? there some paint formulation using photoinitiator (UV curing paint) that maybe you can use. The curing time is a lot faster: almost right away.

Some UV lamps can be bought for as cheap as 300$, it all depends on how much intensity you required and the wavelenght. Mecury lamp provide short-wave application while neon give you a full range but small penetration power...

There is also electon curing paint on the market... much more expensive than the UV curing paint but it could be use in massive production: ink is a perfect product for EB (electron beam) curing for example

Beside aesthetic purpose, do you have special needs, colors, specific electrical resistance etc... for your paint?

Actually curing of the paint on screw is not a problem (it can be anything), but what about the curing of the paint inside the dispensing unit. The time between dispensing varies from 10 min to 30 min & the plant runs for one shift (7 hours) only. As I told you the paint curing time is 4 min, so How to dispense the paint, without it getting clogged inside dispensing unit. Or is there any other easy alternate solution?

That's why you want to use a UV curing paint: as long as you don't have any UV light in the paint pot or dispensing units, the paint will never cure... If it's a drop you can use kind of needle: the same type use in the adhesive industry or you can use a paint curtain for some big screw ( 6 or 10 inch for example),it's only a question of adapting the equipment.

Depending on the size of the screw and the design or your dispensing unit, can you consider using baking enamel paint ( it could be also a baking polyester), once again the paint will never cure: you need heat. I have formulate some low bake polyester paint long time ago, I pretty sure with the new resins we can lower the curing process to 10 mins maybe less...

How about powder paint? Paint doesn't have to be always liquid...

Maybe by seeing your design and getting more details, I can give you a better way of painting or get you the exact paint formulation for your needs.

Some epoxies formulation can give you up to 24 hour pot life.

The purpose of using oil paint is to identify tampering. The paint is applied only on the quarter portion of engagement of the M12 grub screw & it's nut, so that if somebody tries to rotate the screw the paint will peel off revealing the tampering.

If the UV paint is having the same feature then it seems to be a good alternative. How much is the min size of this UV light souce (for mounting on setup), does it require special controller units? I would prefer a compact source which can be mounted on the setup & since there are six of such screws per assy (three on each side. Pls refer the Photo) I would need six of those sources. Can I have a common controller for all sources?

Is switching of UV sources is possible thru PLC? How much time is required for curing (i.e how long the UV light should remain on?)

Generally UV acts as the initiator then the normal curing continues.

I can see some cables being terminated/connected close to the painted nuts. You make sure that the insulation on those cables & the cable ties are UV stabilized.

You don't want to solve one problem & end up with another.

I got a better picture of your problem...

First the UV lights comes in a various size and intensity: think about the one your dentist is using (handheld spotcure system) I got one that is 2 ft long to cure my fiberglass mat.

The following explains (without going too deep) how UV coating/ink works:

"UV Curing" is a photochemical process by which monomers undergo curing (polymerization or cross-linking) upon exposure to ultraviolet radiation. A specially formulated monomer will polymerize when exposed to ultraviolet radiation. This UV "curable" monomer includes a sensitizer which absorbs UV energy and initiates a polymerizing reaction in the monomer.

The rate (speed) of curing will depend on the following factors:

The chemical compound: each monomer react at a different rate, depending of the formulation, type and amount of sensitizer, pigments etc

The thickness of the coating: a thick layer will require longer exposure to UV source.The relation is not proportional. The amount of UV energy inside a layer of coating decreases exponentially with depth. EX: 90% of the UV energy is absorbed in the top 1 mil then 90% of the remainer, or 9% of the initial amount will be absorbed in the second 1 mil.

The amount of UV intensity per unit surface: up to a certain point the curing rate will increase with the amount of UV energy per unit surface. Once again it's not linear. In fact, the curing rate of most monomers, in presence of air rises much faster than the intensity of UV energy. If the amount of UV energy per unit surface is double, the curing speed may be tripled, quadrupled etc... The result of this relation is that 2 UV lamp of a certain power will not affect as fast a cure as 1 lamp having twice the power. Without going deeper I think you got the idea... you will need a reflector that concentrate UV energy on a small surface in order to cure faster ...One thing to remember: the more power you got the shorter the lifetime of your lamp...

The UV spectrum emitted by the source. not all UV sensitizers require the same range of UV wavelengths for proper reaction. It (sensitizer) should absord UV in a range which is not absorb by the nonomer or the pigment. The wavelenght emitted by the UV source should coincide with the wavelenght absorb by the sensitizer. Mercury lamps for example emits a range of UV between 180-400nm. Most of the time they are suitable for commercial application such as wood coating, pinting inks etc..

Switching of UV source thru PLC and common controller for all sources I guess it is possible you will have to talk to a manufacturer sales reps. I have a book giving an ideas on how to build a curing UV system but building one it's way beyond my knowledge & expertise! If you want to try let me know I would like to assist you if I can...

UV ink is probably a solution in your case: it will require less power, cure faster, your set up will be easier...

Do you know a printing company using UV curing ink in your area? You should look for available products, unless you know a chemist close to your company: adjusting formula to equipment require several visits for troubleshooting.

One good source of expertise:

http://www.radtech.org/ is a non-profit trade organisation for manufacturers of ultraviolet and electron beam cured coatings, inks, adhesives and composites and products. I went to several conferences/seminars and it's worthed in my case

I will check my books/documentation, usually in the paint industry we are trying to get the best adhesion possible on the substrate... in you case you don't need this adhesion you want the paint to peel off...

I got several questions regarding your dispensing unit but first I need to check a couple things...

Follow this link to see one of the UV spot lamps talked about above.

Talk to loctite adhesives about their range of products, they cure very fast. Also will lock the threads.