How would you put the final polish on this weldment?

Here's a picture as an example of one of the products we make:



They're for furniture applications, and in general they look very good, but my picky customers really nit pick them. In direct sunlight, the reflection is very hazy, and there is still a slight grain to the finish.

Currently we run the cut parts through a Timesaver wide belt sander starting at 120 grit going up to Trizact A6 (about 4,000 grit), then we weld the pieces together, grind down the welds, and rework the ground areas with a handheld drum sander using the same grits as the Timesaver, then we go over the entire part with a felt disc on a variable speed grinder using white and green buffing compounds, then we use a Nushine polishing paste from Nuvite for the final shine. Like I said, it looks very good in general, but under close inspection just looks sloppy.

Is there another step I should try implementing to get closer to a perfect mirror finish in direct sunlight? Or maybe try a completely new process? Any help on this would be much appreciated, there isn't many resources out there on this process.

And no, electroplating or chrome plating are not valid options as the lead times are too long and the costs are way too high.

Felt disc is probaly your problem in direct sunlight, assuming your removing all the scratches at each grit jump you have to do the final polish in the same direction, discs swirl and even sub micron swirl looks shit to the human eye in reflection with enough light. Change to a peripheral wheel for the final few polishing steps should make the jump your customer is after, it won't be any "shiny er" but it will be a even shiny and look a zillion bucks! Kinda hard to explain, but the shiny is under a microscope near to a brushed stainless finish and we all know how shit brushed is if its not straight and even!

I do similar tricks on a flat surface, i normally use a DA, final polish with a felt pad and compound is also done with a DA and its constant and even and then looks great, polshing with any kinda angle grinder always looks shit IME. DA is as near to rotory as you can get with out hitting this problem and even then it works because it is so evenly random unlike the swirls of a real rotating disc.

While I have always preferred to sell these type of fabrication without grinding down the weld I realize that there are too many customers that do not see things my way. In those cases, like Adama, we use a DA for the final finish.

Obtaining a high polish with no imperfections using hand equipment is next to an impossible task. Selling a uniform DA finish can be done. If you could make up one with a nice even TIG weld showing but cleaned up you might even sell that!

Walter

I've done one polishing job, as kind of a favor and it seemed like a good deal. Polishing 304 stainless tube frames. I had two frames to polish, maybe 4 times the surface area of the parts in your pic. I must have spent over 100 hours polishing them.... I even went in and bought a Metabo Inox grinder, Walter polishing materials.... I will say the Walter QuickStep one-step polish was actually pretty nice, not as fine of a polish as the blue paste but way, way faster than white paste. NIGHTMARE of a job. Nobody at Walter could really help me out, just 'more elbow grease, you'll get there!'. My biggest issue was getting the scratches out to start with. I should have bought pre-polished material for 5 times the cost and saved myself the nightmare and a 57-hour-straight work day before delivery...

I wish I had known to use a DA for polish. I used mine only to sand.

Econdron said:

Or maybe try a completely new process?

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A bead blast finish is what I would do. A nice satin finish that does not show finger prints. Every time I did this myself I was never dissatisfied.
Forget about the nice shiny finish and perfect looking butt joints. Automated robotic welding/grinding could do it. Who cares, a satin or brushed look
is a different look that is just as pleasing to the eye.

DethloffMfg said:

I wish I had known to use a DA for polish. I used mine only to sand.

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Don't worry nor did i till i worked some were that did it that way, dig a bit deeper and you fin d the auto paint crown using the snot out of DA polishing tools for that final amazing finish and most of the steps to get there! I did some round stainless disks circa 4" in diamiter last month for some posh bathroom parts, took std 2mm stainless plate to a real mirror shine, you could see nose hairs in the reflection from 6" away! Gotta love 3000 grit discs and all the ones upto there too,

Pre polished is a must too, its always easier to just spot polish the final weld areas, no way is going from rough tube even remotely sensible. Same for any brackets.