Creating brushed finishes?

[julianf]

I've got a requirement to create some brushed alluminium.

I've seen YouTube vids with people just sanding along the axis of the part using a jig, which does not look too involved...

...but I'll have a number of parts to do, and need the grain to go at right angles to the axis.

Parts will be about 17inches X 7inches, and I need the grain across the short measurement. Cosmetics are vital, so it all has to be spot on, otherwise theres no point in attempting.

Anyone got any ideas? I'd probably be wanting to do about 20-off on the first job, and they're fairly big money parts, so it's worth me putting in effort to be able to knock them out. (Ie I'm looking for repeatability with out too much per-part effort)

Thank you.


PS I know I can buy pre brushed, but I want to be more brutal (quicker) with the machining, and then finish when complete.

 

[MattF]

What type of sander are you going to be using?

 

[gordon stephenson]

Sounds like a job for a flap wheel.

 

[colnerov]

Belt sander.

 

[waddycall]

Why not use pre brushed with vinyl/laserguard. I doubt you’d get a consistent finish over the 17” even with something like a burnishing machine.

 

[julianf]

It's mainly as I do a finishing pass to clean of any burr and the like, but I did a job recently that was to be powder coated. It was just a whole load less stressful -

Basically one mark on the jobs i do put them in the scrap bin. A single scratch etc.

But the powder coat job I could just have at it, go over it with the DA sander at the end to flat it all, and that was that.

Plus the non anodised stock is cheaper.

So I thought that if I could brush the work at the end, then I could cut it, clean it with the DA sander, then add the brushed finish, and print it.

Wonder if a wood working drum sander (the one that's kind of like a thicknesser) would do it. But I think they get used like thicknesses, so may actually thin the job significantly rather than just touch the surface.


How is it done to sheet on a large scale? I was kind of hoping that there might just be a machine that could be bought (or looked at and copied) off the shelf?

 

[julianf]

This was cut yesterday onto brushed then anodised stock -

But this is just onto flat anodised, and more the scale I'm looking to brush -

You can get an idea as to why I'm needing a uniform finish. If the brushing is all wavey, or not at perfect right angle to the side, etc. it would just look a mess.

 

[Wallace]

Is the brushed finish a customer request? I like clear anodised alloy with a heavy etch so the finish is like satin chrome.

 

[gaz_moose]

if its jus for aluminium cant you just use red scotchbrite? buy it on a roll and make a big long drum type sander.

 

[julianf]

I think anodised is a way more sensible finish, be it flat, or over brushing, but, yes, it's customer directed for continuity with pre-existing items.

Both parts in the photos above are rotary engraved, but this job will be pantone matched screen printing partially for scale, but also, again, for continuity with pre existing parts.

With the printing, my greatest per part time sink will be the milling, and if I can speed that up at the expense of finish, and then restore the finish thereafter with brushing (which is, so far as I'm aware, why brushing was ever a "thing") then I can cut the time a fair bit.

 

[julianf]

if its jus for aluminium cant you just use red scotchbrite? buy it on a roll and make a big long drum type sander.

That's kind of what I was thinking before, with my talk of woodwork stuff.

I could make up a drum easy enough, and get it to spin, but, for uniformity, I guess I'd need some sort of stablaised part feed rate?

Or maybe not if the scotchbrite is soft enough that dwell wouldn't create visual anomalies?

Ughh... I can see that before I know it, I'll have some steppers pulling a caridge, but I'd rather not get that involved!

 

[angellonewolf]

wheeler dealers done some thing like this on the deloron cars brushed steel

see about 41 mins in a horse hare and light sanding bits installed

any good if your doing ali should be easyer as softer metal

 

[Paul.]

If you brush ally by hand it will need anodising or some other coating applying afterwards, once you have broken the surface and removed the natural oxide you will get black fingers everytime you touch it.

 

[gaz_moose]

actually I bet you could just stick a length of scotchbrite to a plank of wood and manually move the work piece back and fourth ontop of it.

 

[Shox Dr]

I doubt you will achieve a consistent finish, I’m sure @Paul. will agree, it’s not easy keeping the brush lines in the same direction even on small areas.

Can you not use a radius or chamfer tool in the cnc once the the slots/holes have been cut, or incorporate the bevel into the slotting tool.

 

[Wallace]

actually I bet you could just stick a length of scotchbrite to a plank of wood and manually move the work piece back and fourth ontop of it.

Most of the plate I have brushed in the past has been done this way or a pad across the work. I was thinking the same for larger parts by dragging a weighted pad across the surface on guide runners. Anything rotating eats away at hole and slot edges when passing over them.

 

[julianf]

Can you not use a radius or chamfer tool in the cnc once the the slots/holes have been cut, or incorporate the bevel into the slotting tool.

Hey, if you look at the photos, i can clearly make a clean cut - its just more effort. The stuff in the photos is all anodised - which is not applicable for this job.

But that is also a bit of a red herring - if i buy in pre-brushed (without anodising) then you pretty much only have to sneeze on it to mark it. Even chip ejection from the cutter will probably mark the surface - i mean far worse than just mill finish stock.

Brushed is a horrible material to work with from the start, but that is what is required for the end.

Most of the plate I have brushed in the past has been done this way or a pad across the work. I was thinking the same for larger parts by dragging a weighted pad across the surface on guide runners. Anything rotating eats away at hole and slot edges when passing over them.

Thats a good point with the rotation - i wonder if, for want of a better description, somthing like a desktop covered in abrasive, with a sliding frame over the top would do it. Ie attatch the part, and move it over the abrasive on its jig?

 

[eLuSiVeMiTe]

Hey, if you look at the photos, i can clearly make a clean cut - its just more effort. The stuff in the photos is all anodised - which is not applicable for this job.

But that is also a bit of a red herring - if i buy in pre-brushed (without anodising) then you pretty much only have to sneeze on it to mark it. Even chip ejection from the cutter will probably mark the surface - i mean far worse than just mill finish stock.

Brushed is a horrible material to work with from the start, but that is what is required for the end.



Thats a good point with the rotation - i wonder if, for want of a better description, somthing like a desktop covered in abrasive, with a sliding frame over the top would do it. Ie attatch the part, and move it over the abrasive on its jig?

I'd investigate that option too.
Would suggest the plate laid down on a tacky surfacr and the abrasive surface moved over the top though.
Can make the later strong enough to load evenly. Should be easy to make a runner to suit even moment.
The thin sheet may flex and cause uneven finish.

 

[Tiggy_dorset]

As has been mentioned, you will want to brush it before anodising. If brushing it by hand/hand tools it would probably be a good idea to do it before the profiling of the holes and slots.

It sounds more logical to have the whole lot done profesionally in one hit which would provide a good consistent look. Find a company who can grain it and profile it the same time.
Can you buy aluminium sheet pregrained like you can with stainless? *ahh just re-read your first post*

 

[Wallace]

I have had better results on small parts and badges by doing as @eLuSiVeMiTe says and moving the abrasive over the work as you can see the finish on each pass.