Plugging openings

[BrianP.]

I have some plates to do. They are actually 2 plates dip brazed together with slots through out for a microwave application. In the post braze machining I need to try and keep chips from entering the openings and lodging in the channels. At one place I worked they rigged up air lines and pumped air through the channels while machining. Makes a lot of mist and I would have to create a bunch of fixturing. I was thinking about trying to plug the openings with some kind of wax. The problem is that it needs to be able to be flushed out of the part completely in order for the parts to function the way intended. Stuff in the channels tends to make it so the microwaves do not travel through as intended. Does any one have any experience with anything like this? Any suggestions?

 

Thanks

Brian

 

A small pic of a section of the part. About 70 of theses openings. Only about the size of a pinky fingernail.

Edited May 20, 2016 by BrianP.

[Guest]

Plumbers putty?

[BrianP.]

I did find Rigidax tooling and fixturing wax.

 

 

http://www.machinablewax.com/product.php?product=44

 

The part that scares me though is:

 

"REMOVING RIGIDAX FROM YOUR PART:

When you are finished working with your part and want to remove the Rigidax, you can reheat the part and remove the bulk of the wax.  The wax can be re-used multiple times.  You'll then be left with what looks like a coating of cheap paint on your part that will have to be removed.  You can remove the residual wax by mechanical means, a hot oil dip, or the advanced BioAct 280 cleaner that is shown as a Related Item at the bottom of this page."

 

Plumbers putty may stick to the sides and bottoms of the openings I think. If any is left inside the parts will fail and they are not inexpensive at this point.

[mkd]

tape?

silicone caulk?

epoxy?

[Colin Gilchrist]

What about Thermo Forming a cover? For Thermo Forming, you end up cutting a "male" form out of MDF, or another cheap material, then heating a thin plastic sheet to the point where it is almost melting, then you raise up the male form, and apply a vacuum to the press. This sucks the plastic sheet to the form, and "presto", you've got a cover that would be reusable.

 

A Thermo Forming machine is actually pretty cheap. I used to work for a Mastercam Reseller, and we sold these machines as a side thing. I think they were like $500 bucks. Certainly not cheap for a one-off use, but they are so handy to have in the shop for making trays, covers, and other thin plastic parts. In lieu of getting a machine, you could also find a company that does this work, and just have them make you some covers. Cost would be pretty low, depending on quantity, and if you can supply the male form. Heck, you might even be able to just use the actual part as the form. The heat involved all goes into heating the plastic sheet prior to forming. I think the process is only around 250 F, and the softened sheet would only contact your part under vacuum for a few seconds as it rapidly cools...

[Colin Gilchrist]

http://www.zycon.com/Products/Thermoforming.html

 

There is a list of some companies that do thermoforming. They are many of them, so I'm sure someone could do the job...

[BrianP.]

What about Thermo Forming a cover? For Thermo Forming, you end up cutting a "male" form out of MDF, or another cheap material, then heating a thin plastic sheet to the point where it is almost melting, then you raise up the male form, and apply a vacuum to the press. This sucks the plastic sheet to the form, and "presto", you've got a cover that would be reusable.

 

A Thermo Forming machine is actually pretty cheap. I used to work for a Mastercam Reseller, and we sold these machines as a side thing. I think they were like $500 bucks. Certainly not cheap for a one-off use, but they are so handy to have in the shop for making trays, covers, and other thin plastic parts. In lieu of getting a machine, you could also find a company that does this work, and just have them make you some covers. Cost would be pretty low, depending on quantity, and if you can supply the male form. Heck, you might even be able to just use the actual part as the form. The heat involved all goes into heating the plastic sheet prior to forming. I think the process is only around 250 F, and the softened sheet would only contact your part under vacuum for a few seconds as it rapidly cools...

 

We have to face the top of the part so that's why I am looking for something that could actually be pushed into the openings. If I am understanding the Thermo form correctly it would make a cover that would then be machined through with nothing to hold it in place.

[Colin Gilchrist]

Yes, that's the basic idea. If you've got to face the part, a cover might not be the best solution. What about cutting some blocks of foam? I'm thinking something like the material for those orange foam earplugs. Something you can squish down into the holes, but won't leave a residue...

[BrianP.]

Yes, that's the basic idea. If you've got to face the part, a cover might not be the best solution. What about cutting some blocks of foam? I'm thinking something like the material for those orange foam earplugs. Something you can squish down into the holes, but won't leave a residue...

 

 

That sounds interesting. Will check it out. Was thinking along the lines of JP's idea and going with some type of grease or petroleum jelly that would wash out with hot water. They are not keen on anything that may leave a residue. Foam blocks may fly. Thanks. Much appreciated.