Help me duplicate this stupid part for my stupid microwave

So, our microwave has two of these tab latch things in the door, and one broke, rendering the unit inoperable (silly safety switches ).

I have not been able to find a part number for it, let alone a supplier selling them. It is shown in the door assembly drawing, but no part number. Ebay has some sellers offering similar but not the same used parts for like $20-150 each, lol. But again, they aren't the right part for this unit.

It seems like something that could be fabbed, but what's the best way? I'd really like this to be a one and done exercise. The parts require pretty significant disassembly of the door, and the big plastic bezel parts already cracked a little just from their first disassembly.

Options:

3D print it! (duh)- Would be cool, but I've never created a part file (I did search Thingverse with no hits) and don't have a printer, plus I'm skeptical that typical printable materials would be strong enough. Also, this feels like something that might take a couple or more iterations to get right, and thus using online printing companies will probably be expensive and slow.

Machine (surveying my available tools - ok, whittle) a piece of Delrin or similar - I think this should work, but dimensional accuracy would be tough.

Plastic weld a replacement section back in - What material is compatible with existing part and strong enough that I can forget about it as soon as it's fixed.

Make a metal tab replacement- Not going this route because not really sure what it interfaces with, and I don't want to risk a conductive part poking in the cabinet causing other problems.

Ok, so this is where I ask the hive to point out to me the quick, easy, cheap or free solution that I've overlooked. Whatcha got? 

If it closes with one latch bypass the safety switch and start saving for a new unit.

In the meantime, what about repairing/reinforcing the existing piece with a thin sheet metal layer over the top, with the metal from the hole folded down to locate it and keep it from moving?

Kind of like this, but shaped like your latch instead of a square?

I need to get into desktop injection molding... 

Given the tools at hand, I'd probably try to repair it using JB Plastic Weld.

Oh, and yeah, that's a crappy design for an sure.

I'd take a piece of sheet metal about the thickness of the plastic, and fold it in an L shape. The short part of the L would have the screw for mounting it and the long end would have the d shaped hole. Wouldn't worry about the rest of it, but you could cut it off and glue it to your new metal bracket if needed.

Ain't never gonna break that part again!

This thing trips a micro switch. No need to worry about material from the electrics, but it does see a corrosive environment . It needs to be more corrosion resistant than aluminum or steel. I would make a round brass or bronze wire loop that passes through holes where the previous legs have been amputated. Make the wire long enough to turn up or down after inserting in the plastic body, and epoxy in place. Pay close attention to which edge of the original dick actually pushes the switch before finalizing the design. You may need to dis-assemble the other side far enough to make measurements. My dishwasher has an intermediate floating plastic plate that wears away. Different cure, same symptom.

WonkoTheSane said:

I need to get into desktop injection molding... 

Given the tools at hand, I'd probably try to repair it using JB Plastic Weld.

JB Weld or epoxy resin. Packaging tape (shiny side up) as the backing so it peals off. Some creative engineering for the center part to keep the epoxy in place. When dry file to fit.

I spent a few minutes with Sketchup last night (Doc Brown voice: "this model is not to scale, and I didn't have time to paint it").

The latch tab is 2mm thick and centered in the total height which is 10mm, so I think I could pretty easily make a 3 pc stack with the center being 2mm thick and the other 2 pcs 4mm each. Would just need to bond them together or pin them.

Maybe I should relent on using metal. Brass plate would be pretty easy to work with and is available in the thicknesses I need.

In case you haven't seen them, we have some advice on 3D printing and CNC machining:

• A crash course in 3D printing
• Crash course: How to start CNC machining at home

MyMiatas said:

WonkoTheSane said:

I need to get into desktop injection molding... 

Given the tools at hand, I'd probably try to repair it using JB Plastic Weld.

JB Weld or epoxy resin. Packaging tape (shiny side up) as the backing so it peals off. Some creative engineering for the center part to keep the epoxy in place. When dry file to fit.

This is what I would do. A glob of JB Weld close to the original shape and file to size after it sets. 

What brand and model?

In reply to Toyman! :

I am really skeptical that would last. I actually did super glue the missing piece back on, and it worked great about 3 times then broke off and fell inside the cabinet. 

My experience with superglue and jb weld is that they are pretty vulnerable to shock forces. The repaired area will be striking the latch mechanism each time the door closes, and getting pulled by the latch each time it opens. If it was easy to pop in and out, I'd give it a try. 

In reply to sevenracer :

A little wire reinforcing should help with that. Melt it into the plastic and form it to match the old part. Glob on the epoxy of choice and form to match. The wire should take the shock loads. 

Another option could be a plastic welding kit. The part is probably ABS which is easily heat-formable. 

Spent a few minutes last night. Heated up some safety wire and confirmed that the plastic part melts vs burns.

Made up a possible wire insert. The tab is about 2mm thick, and the wire is about 1mm thick. Not sure how I'd keep the wire hot enough to press it into the plastic. 

HF has a hot air plastic welder, but it's $80.

Wire staple welders are much cheaper, maybe I could make my own staple shape and heat the wire electrically while pressing it into the part.

I have pushed threaded inserts into plastic with an old soldering iron. I don't know if it would work for this. 

There is ABS glue available at hardware stores in the plumbing section. You might also want to look at the plumbing aisle for raw materials. Take a small fitting, whittle off a chunk, and glue it together. 

House door strike/lock plate and a Dremel tool.  

cdowd (Forum Supporter) said:

If it closes with one latch bypass the safety switch and start saving for a new unit.

Too bad it would cost even more to send to Syria or Ukraine for a short but useful life as a dummy SAM site...

Is there 2 micro switches ?

if there is only one , switch the brackets between the  2 of them....

Good Luck

I'll try again.  What brand and model? There's a huge appliance repair place nearby, I can stop in and ask them.

 maybe drill two holes on each side and slide the wire into it. Then epoxy it in place.

Update:

Amazon sent to me a plastic stapler iron. The staples weren't the right shape for my needs, and were very obstinate to be re-formed into what I did need. So, I made my own staples out of 0.030" MIG wire. Basically a metal ring that goes through the broken part and anchors into the back section. A couple of design iterations, and a couple of practice runs to refine the process:

Then moment of truth:

Cut the leads off:

Slather on some plastic filler and shape it a little bit and we have this, ugly but functional?

There was another element to this repair not previously mentioned. The top pin that the door pivots on is a pin with a reduced section that interfaces with a keeper that is just a piece of sheet metal slid onto the plastic snap in trim bezel. A very simple and clever design to retain the pin. Too clever for this wannabe appliance repairman. Thinking the pin was a snap in, snap out deal. I mangled and broke it while trying to remove the door. Of course it is an NLA part. But Amazon to the rescue again with a pin that has the same diameter. A little work on my "lathe" and new pin fabricated:

Much success!

Thank you for the idea for repairing bumpers. Sometimes you don't have the correct staple to do the job.