Rigol Bumpers Deteriorating

[xrunner]

I bought a Rigol DM3058E 13 years ago. Have had it on the bench all of the time and not even near a window. I was re-arranging things and happened to look at the bumpers - wow. They are falling apart in thin air. I've seen similar things on equipment a lot older that this, but this seems a little ridiculous.

 

[Filippo52]

It is the plastic undergoes polymerization and, in fact, crumbles.
Thirteen years is neither a short nor a long time.
Keep in mind that the environment plays a major role; as does the use of harsh cleaning agents.
There are protective coatings available, but if the crumbling process has already begun, they can do little to help.

[voltsandjolts]

I find this happens with a lot of modern plastics. The plastic goes brittle or rubber goes sticky. Yet I have stuff from the 1980's where the plastics are still great.

[mawyatt]

I bought a Rigol DM3058E 13 years ago. Have had it on the bench all of the time and not even near a window. I was re-arranging things and happened to look at the bumpers - wow. They are falling apart in thin air. I've seen similar things on equipment a lot older that this, but this seems a little ridiculous.

 

That seems bad for an instrument not subjected to environmental extremes. You could at least 3D print replacements.

Best

[xrunner]

That seems bad for an instrument not subjected to environmental extremes. You could at least 3D print replacements.

Best

I agree!

I really don't need the bumpers because it doesn't "bump" into things around here  . But Geez it sucks for the parts that come with it to get destroyed by just existing in the air.

I pulled all of them off and it would suit me fine like that except of course the nubs that are left behind look bad. So I'll fire up Fusion and come up with a design to stick on them that looks acceptable.

Thank you Rigol.

[xrunner]

Except for the four feet on the bottom the rest will be decorations. I cut the deteriorating rubber to the size I wanted and worked on making a model of it for 3D printing. I printed the prototype and it's close enough to what I want. I don't yet have the holes for mounting in the bottom of the model - will resume tomorrow ...

[mawyatt]

What filament are you going to use, TPU?

Best

[Geoff-AU]

I find this happens with a lot of modern plastics. The plastic goes brittle or rubber goes sticky. Yet I have stuff from the 1980's where the plastics are still great.

Polymerisation/hydrolysis depends on the stabiliser mix (or lack of) in the plastic/rubber compound.  The material is often doomed from the day it's made or completely fine for decades.  Environmental conditions and solvents are a factor but it's inherently a manufacturing materials problem, and it's gross and annoying when a manufacturer skimps like this and wrecks their product over a minor detail.

[xrunner]

What filament are you going to use, TPU?

Best

PLA is all I have right now.

I don't have any TPU at the moment, buying a whole roll for this would be costly, but maybe they have smaller rolls of it like 0.5 kg. Have you used TPU and how did it come out?

[mawyatt]

What filament are you going to use, TPU?

Best

PLA is all I have right now.

I don't have any TPU at the moment, buying a whole roll for this would be costly, but maybe they have smaller rolls of it like 0.5 kg. Have you used TPU and how did it come out?

Haven't used TPU yet, but probably will sometime (like 3D printed feet for the pool Navigator). It's supposed to be more "rubbery" than PLA or PETG, so likely a good candidate for replacement "bumpers". Not sure the cost, but 1/2 kg would be good if you can find it.

Best

[jfiresto]

Does that window have a northern exposure or one of the other quadrants?

I ask because PLA is not UV stable. Sunlight is good for breaking down plastics.

My father has kept in a dark drawer, some plastic coupons from the 1960s. They have gotten rather sticky. His son shall continue the experiment.

[Geoff-AU]

TPU is the material of choice for these kind of bumpers.  I'd choose something stiff like 64D though, 95A is too soft.

[xrunner]

Does that window have a northern exposure or one of the other quadrants?

... Have had it on the bench all of the time and not even near a window.

[xrunner]

TPU is the material of choice for these kind of bumpers.  I'd choose something stiff like 64D though, 95A is too soft.

Well I ordered some TPU last night - I need to expand my capabilities. However it's 95A I had not read your post until this morning. I was able to cancel the order and I will now get the TPU you are recommending. Thank you.

[xrunner]

This is what I have at the moment. They fit but I'm waiting on the TPU filament to finish the exact size I want for the holes. I can't tell without experimentation how snug to make the fit because I expect the TPU to deform a bit and without making a few experimental feet I can't lock it down.

Just an observation - it's a weird combination of holes the designers chose for those rubber bumpers to push on to. I suppose there is a deep meaning to why they designed them that way, but not being a mechanical engineer, it escapes me. 

[xrunner]

I did receive the 64D TPU filament this afternoon. I tried printing some primitives directly from the slicer like a cube and a cylinder just to get a feel for how the TPU would come out - they came out fine. I can squeeze the models but they aren't so flimsy that I can ruin them by squeezing really hard.

I then printed out my latest design pass for the foot, it also came out fine and looks just like the PLA foot so no need for a picture now. I like the fit too, but I want to decrease the diameters of the two circular openings because I think a bit tighter fit is going to work out now. The part will deform just enough to make it fit really tight. I'll post the results ...

[tautech]

Now you should post the design files here:
https://www.eevblog.com/forum/testgear/replacement-knobs-feet-and-fittings-for-test-equipment/

[xrunner]

Yes indeed I will.

[mcinque]

the same situation happened to me here after 12 years of dmm and fg. rigol europe has original spare parts. they cost 16 euros for a set of 4, so for an instrument it takes 2 sets, 32 euros. it's not really cheap

[xrunner]

Nothing is ever easy ...

OK so I got the TPU and printed out a foot to try on. It fits well except I discovered another small thing now. They put a bevel on the front of the meter bezel or face, but not on the back. It's just a few degrees. I never noticed it and to me it adds nothing to the looks of the thing - it simply could have been the same 90 deg as the back. Some designer was being cute that day or their manager had too little to do and they wanted to feel important so in the final design review they told somebody to add it. The rubber foot had enough squishyness to fit OK, but I can't get away with that because you see a gap at the front when my foot is stuck on.

So now I'm having to add a angled bottom to the design, I'm hoping it will print out OK laying that flat down. 

[xrunner]

I decided to solve the problem of the strange small bevel (only on the front) by making the front feet in two parts. I did design one with a bevel added but due to the additional complexity of the area where the pins are (see pics) it resulted in having to have supports added while printing. This was very difficult to pull off and keep the foot in good shape. So I'm going to add the beveled TPU shim to each TPU foot and glue them together, making the final part, using Loctite Vinyl, Plastic, and Fabric Adhesive which is proven to work with TPU. Now I'm waiting on that glue to be delivered.

On a side note, the handle of the DM3058E is of no use to me at the moment and gets in the way of maximum space usage on either side on the shelf. So I removed it and designed two TPU parts to fill the hole where the handle was.