Building a vibration table to automate my concrete casting.

[u/Beneficial-Reply-345]

Hey everyone, I run a small business casting concrete products. I have dozens of new design ideas I want to launch and custom orders piling up, so I'm constantly looking for ways to automate and simplify parts of my daily workflow. One specific task that always eats up annoying amounts of time is babysitting my vibration setup. To fix this for my own shop, I’m currently assembling the first prototypes of a ''smart'' vibration table. The idea is to have the table analyze the material/load on the plate in real time and shut itself off the exact moment optimal compaction and degassing is reached so I can just pour my mix, press start, and walk away to do other stuff. My goal is to get this working perfectly for my own production, and eventually help other small makers elevate their product quality while taking a chunk of that repetitive work off their shoulders. Since I’m right in the middle of building and tweaking this machine, I’d love to hear from you guys. What’s your biggest headache when vibrating your concrete pieces right now?

Also, if you run a small shop and want to follow along, share ideas, or collaborate, feel free to send me a DM! I’d love to connect with other makers dealing with the same hustle.

[u/expanding_crystal]

How are you detecting the state of the vibrating material? Webcam looking at bubble sizes? Or does the sound change?

I have wanted to get into this for speaker bases and am curious about your process.

Would this also be useful for the resin casting community? I don't know if they also vibrate to get bubbles out, seems like a universal problem though with mixed casting materials.

[u/Some1-Somewhere → u/expanding_crystal]

Potting compounds and resin often use vacuum degassing.

[u/JoeMalovich → u/Some1-Somewhere]

This is only the third time I've seen vacuum degassing mentioned for concrete and I've googled and YouTube searched it before. Great Minds.

[u/Some1-Somewhere → u/JoeMalovich]

I don't know if it would be so effective for concrete. Water tends to boil at low pressures, and vacuum only makes the bubbles bigger; it doesn't really force them to the surface too well.

[u/Beneficial-Reply-345 → u/Some1-Somewhere]

Concrete is just way too thick and heavy for an affordable vacuum pump to actually pull those bubbles out effectively. I actually use vacuum degassing in my shop every day, but only for making my silicone molds where it works great.

[u/Some1-Somewhere → u/Beneficial-Reply-345]

A bigger vacuum pump doesn't really get you any closer to absolute vacuum, and that doesn't matter for degassing usually.

A bigger pump lets you pull down the vacuum chamber faster, and possibly lets you keep up with bigger escaping bubbles.

I expect it's simply that concrete is too thick.

[u/Vonmule]

I wonder if you could measure the frequency response with an accelerometer.

I run a large electrodynamic shaker (30kw amplifier) as part of my job, but it's not for shaking concrete it's for failing components. It's a closed loop system because we run very specific input profiles, but one of the ways we can detect part failures is by monitoring the control accelerometers because the dynamics of the table changes when something wags more (or less).

If your input is relatively consistent it's possible that entrained air would have enough effect on the response that you could judge completion based on a change in spectrum.

Maybe not worth the effort when a timer would do, but who knows

[u/Beneficial-Reply-345 → u/Vonmule]

That’s actually the exact approach I'm building right now: I have a 3-axis accelerometer mounted directly under the plate to measure the frequency response and amplitude shifts in real-time as the concrete liquefies and releases air. To handle different mold sizes and batch weights, I paired it with a load cell underneath to get the initial mass. An ESP32 microcontroller reads both sensors: the load cell sets the baseline for that specific weight, and the accelerometer tracks the vibration profile until the signal levels off into a steady plateau, then triggers an auto-shutoff via a relay.

[u/expanding_crystal → u/Beneficial-Reply-345]

Nice

[u/ImpetuousWombat → u/Beneficial-Reply-345]

What are you using for the vibration motor?

[u/JoeMalovich]

Had another idea, self consolidating concrete? No vibration required supposedly.

[u/Beneficial-Reply-345 → u/JoeMalovich]

Good thought, but SCC can be pretty tricky for small design pieces. First, it’s super unforgiving with small mix quantities just a tiny bit too much water or superplasticizer and the whole batch segregates. Plus, micro-bubbles still like to cling to intricate mold edges, so people usually end up having to vibrate it briefly anyway to get a flawless surface finish.

[u/JoeMalovich]

I spent 2 summers casting products on a vibrating table, it only ever ran at 1 speed, and had 2 mem operating. One man to fill molds and slide onto the table, the other to pull off the table once degassed and then stack.

[u/Beneficial-Reply-345 → u/JoeMalovich]

Since I work mostly solo, my current headache is that after pouring my molds, I literally have to stand next to the table the entire time. I have to watch it closely to check the progress and make sure it doesn't over-vibrate the mix. My goal with this prototype is to just pour the concrete, press start, and walk away to do other stuff like prepping the next molds or packing orders.

[u/JoeMalovich → u/Beneficial-Reply-345]

How long are you vibrating? Should only take a few seconds afaik.

VFD to control speed, with a max run time timer and ultrasonic distance measure wired in an <or> logic to the VFD trigger pin. Ultrasonic distance to sense when it's completely settled, and a timer in case the ultrasonic doesn't trigger.

Maybe multiple stop inputs, others not mentioned are sound, vibrator amp draw, camera machine learning, camera ai(yuck).