Large Delta printer build - advice and suggestions welcome

[Reefsider416]

@Reefsider, I'll just offer some small things to think about. Regarding 2 motors vs 1, you've worked with a few industrial machines by the sounds of it, have you ever seen 2 motors driving one belt?......Also, I'd second CA's suggestion of using wheels. A delta that's moving fast, especially in a zig-zag type of way like for infill will have a fair bit of vibration. Linear rails are pretty shoddy at vibration damping, it's one of the reasons subtractive machines tend to use box or V ways instead......

What made me think 2 motors might be better than one is purely from RC cars and boats. It is quite common to use 2 servos for one control. Stepper motors are basically just fancy servos. Also i have a prusa I3 MK3 and it has 2 z steppers and I would say it works better than my first printer which only had one. I think its probably best to use one larger one but its worth considering. Also, if you use separate drivers i believe you can manually control the very fine initial position with the pot on the driver. I could be wrong though, I am trying to build my first printer now. I guess i should say rebuild because its a Mono Price Select Mini V1 but the firmware crashed so I am trying to install an SKR Mini E3 DIP but having some issues. also upgraded the printer substantially. making a post in a minute about that.

Anyways, I think both are probably fine one set up probably would have better acceleration and one might have slightly better accuracy or something but that's all something I can play around with if I get some time.As for the Cable system it is just a random thought. I am building this printer with GT2 stuff but may play with it later and see what i can come up with. I also saw a hydraulic system on youtube that has crazy accuracy and insane speed lol. I'm sure it's too expensive but fun to think about different ideas and set ups.


With the linear rails; You'r probably right about the vibration dampening. I guess the point is to make the printer so rigid there is little to vibrate. I worked briefly for the Canadian distributor of a well known Japanese CNC/EDM machine company and I have seen some pretty crazy subractive CNC mills, lathes and wire EDM machines and i have never seen one with box extrusions or wheels or V slots. These machines are pretty much solid cast iron. When I went to my first install I was surprised by the size of the crane truck that was needed to get it off the mac truck flat bed. They pretty much all had linear rails of some sort. A lot of ceramic bearings and fancy accordion covers and jackets or shrouds etc but never have I seen wheels or guide rods of any kind or extrusions except for the mounting surface for parts so you can use t-slot clamps to hold parts.

Some of the machines didn't even have bearings on the linear rails. They were simply made to such a fine tolerance they slid perfectly on each other. At that point its almost changed from friction to hydrodynamics because of the layer of machine oil on everything and the fine tolerances. This system is used more on lathes than a moving bed situation but same idea, eliminate slop and make it as rigid as possible.

Most of the drive systems were ball drives except for the really fancy stuff that had linear motors (mag lev tech as i call it) which increased speed and accuracy substantially. Rigidity was the name of the game in CNC. It's why all the machines were as much one piece cast iron as possible. Its the only way they can get the accuracy which was insane. One of the machines advertising pamphlet showed it could engrave over 100 Japanese characters on a grain of rice. Also could drill a square grid of 100 holes in a HB pencil lead, on the rounded side/face. That kind of accuracy requires all the moving parts to have a fitment of unbelievable accuracy, rigidity and absolutely no perceivable play.

I'm not saying that's what a 3d printer needs but I think with any machine, rigidity and the least play is going to yield the best results and allow the fastest speeds while maintaining those results. Its kind of like old domestic cars vs old German cars. German cars were built to a higher tolerance which is why they lasted a lot longer and were generally faster. Now the tolerances are less of an issue with cars, mostly because the CNC machines that make the parts and/or moulds/stamps are more accurate as well.

There are ways of isolating vibrations but you cant fix slop. Just my opinion from my experience, I am not an expert and only dealt with one brand of CNC machine so take it for what its worth.