Why use expensive T-slot extrusion?


New to the forum, but have been receiving email updates on this project. I’m a CNC’er guy and have built my own large’ish CNC router table (4’ x 8’), so I love this kind of project.

My question is - why use expensive extruded aluminum T-slot? I mean, for a CNC router it makes sense because you need sub-millimeter accuracy, but for the Farmbot, it seems like totally overkill (and T-slot is expensive!). Why not use something like simple steel C-channel (which is available at big box hardware stores for something like $10 for 8 feett)?

(EDITED - I mistyped the price of C-channel. it’s about $10 for 8 feet, not 1 foot… sorry)

Just an idea…


Aluminum extrusions are a good choice because

  • They look awesome
  • They’re relatively lightweight for their strength
  • They don’t rust
  • They’re easy to cut with a hack saw
  • They work really well in conjunction with V-wheels and belts
  • You can easily attach stuff anywhere to them such as plates, plastic parts, etc
  • They really aren’t that expensive (~$5/foot for 20x40mm, anodized black from OpenBuilds)

Okay, but…

A) $5/foot for 2cm x 4cm extrusion is expensive to people who don’t know why it is so expensive. To them,it is VERY expensive. Look at the market for the product. It’s a very price sensitive market. Do you want cool looking or do you want wide spread adoption and higher volume?

B) You can buy aluminum C-channel which is just as strong and lightweight and of course, does not rust.

C) C-channel (even steel C-channel) is easy to cut with a hack saw. I’ve done it many times. It’s actually easier to cut than T-slot extrusion.

D) C-channel works fine with regular rollers and belts. No specialized (read: expensive) v-wheels required. Again, do you want something fancy looking or something inexpensive that works just as well. And if you absolutely must use V-wheels (why, I don’t really know), then you can always just use plain angle iron and put it on it’s edge in a “V” orientation and use v-wheels. That would be even CHEAPER.

E) You can attach stuff anywhere on slotted C-channel as well.

F) C-channel can be bought all over the place and is widely stocked… at super low prices.

Look, I’m not trying to be argumentative, but every criticism I’ve seen on the Farmbot is centered on the cost. Do you want it to look fancy or do you want it to be widely adopted? Because at the high price level it’s currently at, you are severely limiting adoption rate. Also, while you and I have an appreciation for the “coolness” of T-slot, I bet the average home/urban farmer wannabe does not have nearly the same amount of appreciation or even differentiation between T-slot and C-channel. I think it’s worth at least asking your potential customer base, since the savings would be in the hundreds of dollars range (if not thousands on larger farmbots).

EDIT: I apologize for mistyping the price of C-channel in my first post (typing too fast without editing… not a good habit). It’s 8 feet for $10. Not 1 foot. I can see why you would think it isn’t better than t-slot at that price… but again, it’s $10 for 8 feet, which is a fraction of what t-slot costs…

Thanks and hope Farmbot is a huge success!


Another option is Super strut:


Again, a fraction of the cost of T-slot, but would do the job just as well (although perhaps powdercoated version would be better for weather resistance).

Just suggestions of course…


Thanks for the thought out response and suggestions Eric.

You’re right that using more basic materials such as C-channel (aluminum or steel) would be less expensive and more readily available. And we do want to lower the cost of the device and achieve widespread adoption. Though right now we want to have a flexible hardware system that is easy to work with and customizable for the DIYer/maker/hacker type folks - something that t-slot extrusions afford us more so than C-channel, strut, or angle iron would. That’s not to say that it can’t be done with those materials, it’s just that that’s not the route we took in our development because the first generation of devices are closer to 3D printers and CNC machines than they are to outdoor gardening/ag equipment.

But of course, anyone is welcome to build (and hopefully share) a FarmBot design with those materials. If they build it the same size as the devices we’re building then they could save up to $120 or so considering the total cost of all the extrusions in the current FarmBot design is about $150 (https://farmbot-genesis.readme.io/docs/extrusions). Perhaps there would be even more savings using regular rollers and belts too, on the order of $50 or $100. The benefits would be greater at larger scales!

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Someday I’d like to take a shot at making a farmbot using stainless steel tube, like the Mostly Printed CNC

I am actually working on making a mpcnc right now, and had that exact same idea about using the same frame for the farmbot. So I am printing parts for both right now, we will see if it works