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Making a heat treatment oven (ibuildit.ca)
44 points by OJFord 5 days ago | hide | past | favorite | 18 comments

A word of warning to those building this same contraption: if the solid state relay you're using is the one pictured in this article and you received it together with the cheap PID temperature control shown, it's almost surely a counterfeit. It will work fine, but nowhere near the specced 25A. Here it is used at about half that, but still I would have bought a real SSR, and ditched the clone. They tend to fail in spectacular ways.

Have you any tips on how to avoid fakes? Is there a supplier or something that can be used to prevent this.

I have zero knowledge of electrics and buy the bits I need then cobble them together. The thought of a “spectacular” failure with a relay or similar makes me twitch a little.

In general try to stick to the larger distributors or suppliers like Mouser, Farnell (or CPC in the UK), RS Components, Digi-Key, etc, or your countries closest equivalent assuming you have good consumer protection laws, if their target market is the business and industrial sector but they still sell to individuals it will likely be a good bet if a little expensive.

Another good choice can be hobbyist or educational sites that have some reputation to uphold, the most talked about online will be US centric like SparkFun or Adafruit but there's many European equivalents for example. One way to find them would be to find an authorised distributor in your country for larger projects like the Raspberry Pi and see if they sell the components you need. Chances are if they're an authorised distributor for a recognisable product then they're probably not going to risk losing their spot on that products website just to sell some fakes or dodgy components.

The key thing is to not buy directly from China or random eBay sellers from abroad if you can help it, return postage to China is prohibitively expensive and Chinese stores or marketplaces like Aliexpress won't always agree that you're entitled to a full refund without returning the item even if that item happens to blown up in your face, and likewise you can't really expect that small random foreign eBay sellers are going to be liable for selling you items that adhere to your countries safety regulations for instance.

> Farnell (or CPC in the UK)

In the UK we have both CPC (~.farnell.com) and Farnell (uk.~.farnell.com; née Element14).

It's not always clear to me which I should be using (optimally for me - to them I think it's clear that CPC is trade/savvy DIY, and E14 is larger electronics buyers) - one or the other can be cheaper on the same product.

Recent examples - that sort of make sense given demographics I mentioned - small volume components cheaper at CPC; (low-end/budget) test equipment cheaper at E14.

Buy stuff that needs to be reliable from reliable sources, i.e. not ebay. RS, Mouser, Digikey, whatever is available in your country.

Great tool, super useful.

For a few extra bucks you can use a programmable temperature controller... search "Programmable Temperature Controller Ramp Soak Heat" at the usual suspects. Allows you to program heating ramp up, ramp down, and soak times - very useful for heat treating various alloys.

Yup, Automation Direct is my go-to "cheap" option for this.

They also make some very low cost PLCs that work pretty well. I built a solar powered DC irrigation pump with proper PID control+SSR to support varying flow rates(most irrigation pumps are on/off only) with their hardware.

I used an off the shelf controller for my pump. About $100 for a 3A VFD not including transducer

Yeah, most pumps are AC and this was DC so I didn't have a off the shelf solution.

With a PLC, analog input for the pressure sensor and SSR to drive the PWM it was fairly straightforward to put together. Hardest part was getting the PID tuning right but even that only took a bit of time.

What PLC did you use? I’m looking to build a load shed controller for another project. I’ve been looking for something simple.

Great project! A heat treatment oven is useful for so many things.

If you're building one of these, you might want to adjust the hinge so that when you open the oven doors, the hot side of the oven door always faces away from you. It will make it much more comfortable to use.

What are some of the things they’re useful for?

Basically, the capability to harden, temper, and anneal steel allows you to do a lot that you couldn't otherwise. It means you can take a single material and rotate it through any of soft and malleable, knife-hard and brittle, and strong and springy.

For example, without a heat treatment oven, it would be very hard to make a new hard cutting tool. What would you cut it with? You basically have only the option of grinding it, which is very difficult especially because if you overheat it at any time you'll destroy the temper.

But if you soften it, you can use other steel tools to sculpt it to any shape you like, and then you can harden it again!

Now you can make bearings, hinges, chisels, files, sawblades, knives, wear surfaces, deadbolts, springs, needles, gears, and all sorts of other things that require a hard material in order to perform or last a long time.

Hardening or softening metal (e.g. to make less easily marred tools, knives) is how I got there, not sure of non-metal-working uses.

I suppose though if you can get it to hold cooler temps too, then it's just an oven, could use for reflowing solder, testing performance of something at higher temperatures, warming bagels..

Making pigments (aka cooking some rocks).

My dad was a plant manager at a heat treating plant and worked there over 30 years. I remember he had me open up a huge furnace just to let all the super hot air blast over me, was pretty cool for a teenager. Not a fun place to work at in the summer though...

I guess (an even) temperature distribution could be a thing you'd want to get right. Also, how closely (fast) can it follow a given temperature profile?

Here's a similar PID controlled one from Black Beard Projects:


The video description has all of the parts.

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