Aluminium profiles - currently THE material to build your printer, CNC or any other contraption with. Unfortunately lack of clear standards and manufacturers innovation lead to creation of few variants with some distinct pros and cons.

Designs created for One profile may fail when u use different one or you will need to change some components to accommodate features of specific profile type.

Currently in common use (3d printing construction) there are 4 main types of profiles:

  • I -Type
  • B-Type
  • V-Slot
  • 5 Series (Misumi)

 I-Type

Together with B-Type one of most popular profile types available, mainly due to wide availability and profile being adapted by many manufacturers. From all profiles this one is most "rounded" with corners radii at 2mm. Axial hole of 4.3mm allows easy tapping for m5 screws. Its main defining feature is slot width - nominal 5mm (for 2020 profile). 5mm slot width unfortunately means that this profile size is quite challenging for designers and makers due to badly restricted amount of connector and fixing combinations available:

  • Your standard hammer head T-nuts won't fit due to 6mm width.
  • Cast aluminium corner brackets won't fit without modifications - most of them have locator tabs for 6mm slot, and you will need to cut or grind them off.
  • You are restricted to max M4 screws in you want nut in slot
  • T-nuts for this slot are very hard to find, and are considerably more expensive than 6mm slot versions.

At 20x20, 20x40 sizes this profile is best avoided for typical construction purposes. If you end up with this profile, don't despair, there are few tricks to overcome issues.

B-Type

Possibly the most popular Aluminium profile type, widely used in construction of guards, machines and fixtures in production environment. Known also as "Bosch Rexroth" or slot 6 profile. Again its defining feature is 6mm slot width (nominal) - and that in contrast I-type means that there is tons of compatible fixtures and accessories for this slot. From brackets to adjustable angle connectors and sliders. T-nuts and fixings are available from tons of suppliers @ bargain prices (quality dependant). From all listed profile this one has only one drawback - depth of the slot at only 5.5mm. That depth complicates choice of fixings if we need to connect thinner parts to this profile without bottoming out screws in slot . Generally I use 5mm as guide for this slot as this allows me to use M4 8mm or 10mm long screws with t nuts (8mm as last resort). Anything below 3mm will require downsizing to M3 6mm screws as M4's are not normally available in lengths below 8mm. 5.5mm axial hole allows tapping for M6 screws. Bottom of slot has very useful Grove in the centre allowing better drill location when drilling cross holes.

In my opinion this type of profiles is most useful for general construction purposes, mainly due to shear amount of accessories available and average cost of build.

V-Slot

Profile created by Openbuilds forming very popular construction and motion system. V-slot profiles combined with Motion plates and V-Wheels form very popular Linear rail system widely used in inexpensive printers and CNC routers. Most popular machines using those are Ender 3, CR-10 printers and their clones. V-slot profile can be treated as a bit of Hybrid between I and B type profile features with addition of distinctive chamfer along slot profile forming guide for V Wheels.

For most construction situations V-Slot profiles can be treated as B-Type - most accessories will be compatible. One main disadvantage of this profile is limited usability with MGN12 type linear rails - chamfered edges reduce surface available to correctly support rails. Smaller rails like MGN9 would be completely impossible to mount. That's usually not a big problem as generally if you chosen this profile it was to use it with V-Wheels as Rail system - if you want to use MGN style rails you would want to use B-Type profiles 

Misumi 5-Series

I've added this profile to comparison mainly due to popularity of Misumi as source of Profiles and accessories among Makers (mainly US as European Misumi restricts sales to business customers only).  Name of this profile is unfortunately VERY misleading as its slot is 6mm not as name suggests 5. Its cross section is very similar to V-Slot profiles including 4.2 mm axial hole and ~6mm depth of slots. Due to lack of chamfered slot edges its also compatible with MGN rails. If you can use Misumi as your source of components this profile can easily become your go to solution for any construction needs especially when combined with suppliers wide assortment of accessories and options for pre-cutting profiles. Downside is limited availability for makers in Europe without business accounts with Misumi