TriPlanar Machine

[Zathras]

Hi Guys,

I'm just kinda obsessed with parallel machines and found this amazing design called a "TriPlanar" from a German University recently.
There's a video with explanation of the motors but in German only. Looks like a 2D linear stepper motor/table. Amazing technology!

http://rtm.upb.de/forschung/triplanar/index.php

Quite a few videos here;
http://rtm.upb.de/forschung/triplanar/multimedia.php

I'm having fantasies of the CNCBrain controlling one of these babies.
Each (lower) leg could be controlled by a small x-y table. Arguably mechanically simpler to build than a "traditional" Hexapod. Only 3 ball type joints at the lower legs and 6 roller bearings at the platform for 6-axis control.
If instead of the XY tables one used a linear actuator, this reduces to 3-axis and would be exactly like the Linapod or "Triaglide" design.
It could operate in any orientation too as you can see.

Always the biggest problem with these PKMs is the control. At first thought it does not look to be trivial.

Any thoughts comments?

Mark

[The Blight]

I have only seen one other machine similar to the one you have linked to, and it's made by Index. http://www.index-werke.de/de/deutsch/546_DEU_HTML.htm

[ironDigit]

i can't grasp the profits over just mounting a x-y table to the ceiling with a z-axis hanging from it and placing the workpiece underneith of this construction.

though i can grasp the profits of a x-y mounted to the ceiling like no coolant in precious places ,gravity taking up some backlash maybe and just looking beautifull.

just the x-y with a mounted z will stay 3-axis wich is no prob for THE BRAIN or any other prog.

can some1 pls explain why it should be better or cheaper building such a triangle construction with roller joints and alikes wich i expect to get somewhat expensive when needing them to be free of any backlash.

this post was posted assuming there is no limit to how stupid a question may be before it is disqualified to being answered.

thx in advance

[Zathras]

Originally Posted by ironDigit i can't grasp the profits over just mounting a x-y table to the ceiling with a z-axis hanging from it and placing the workpiece underneith of this construction. though i can grasp the profits of a x-y mounted to the ceiling like no coolant in precious places ,gravity taking up some backlash maybe and just looking beautifull. just the x-y with a mounted z will stay 3-axis wich is no prob for THE BRAIN or any other prog. can some1 pls explain why it should be better or cheaper building such a triangle construction with roller joints and alikes wich i expect to get somewhat expensive when needing them to be free of any backlash. this post was posted assuming there is no limit to how stupid a question may be before it is disqualified to being answered. thx in advance

Hmmm, interesting. It wasn't really a question I was asking was it? Isn't this about discussion and sharing info? "Stupid question disqualifying itself"?
Yes, how stupid of the guys in this German university to be wasting what must be substantial amounts of money and time in this research.
Why don't you let them know, they may appreciate your input on that.
As a matter of fact, why don't you do some rounds around other universities while you're at it?

Research is just that, exploration into areas previously unknown. It is also partly to see how such devices operate in real life. Hopefully there will be commercial benefits if 2D motors were easy to make anyway.
Perhaps one day no? Or do you want no progress which ever direction that will takes us? Oh,... XY tables that's right.
In other words, people have to TRY ideas.

One of the reasons you don't see too many PKMs is that they expensive. Both the control system and hardware, although the control system is far less of an issue now days.

You're complaining about antibacklash expensive bearings in this design?
What about the backlash in the ballscrews themselves, the ball screw holder, the motor coupler and the linear errors in the guideways? Do you know how errors propagate in this TriPlanar machine design? Are they worse than a cartesian design or some reason?
You know what a Hexapod looks like? How many bearings are used for the end universal joints? Only 2 for each side on this design.

As for the advantage of having this thing on the ceiling, the vids just show it being used in either configuration, on ceiling or floor. It's a research program! They can. They probably find it easier practically speaking to mount it "upside down". Big deal.

The advantage of this configuration as opposed to an XY and Z stuck on a roof? How about 6-axis movement instead of three?

Yes, you surely know how to get at the heart of the discussion.

Mark

[Zathras]

Originally Posted by The Blight I have only seen one other machine similar to the one you have linked to, and it's made by Index. http://www.index-werke.de/de/deutsch/546_DEU_HTML.htm

The Blight,

Thanks for that link. Nice, I hadn't seen this Linapod (Hexaglide) before. Not many of these machines in real products are there?
You can see what a small working volume it has for it's size. Well, it looks quite small to me anyway.

Yet another reason they aren't many of these around. They're really designed for particular applications in mind I suppose.

Mark

[sharpshooter90]

This machine must have been designed for some very specific function. I cannot see the practical advantages of such a machine in the real world. Those 3 moving carriages up top would be hugely expensive to build, and I see no method of moving the Z axis up and down. But if you know the Germans, they have a tendency toward large and highly complex mechanisms. Their WW II tanks were a perfect example- monstrous in size and very complicated leaving them mostly broken down and stuck in the mud while US and Russian tanks were built in the thousands and simply overwhelmed them with reliability and numbers.

[Zathras]

Originally Posted by sharpshooter90 This machine must have been designed for some very specific function. I cannot see the practical advantages of such a machine in the real world. Those 3 moving carriages up top would be hugely expensive to build, and I see no method of moving the Z axis up and down. But if you know the Germans, they have a tendency toward large and highly complex mechanisms. Their WW II tanks were a perfect example- monstrous in size and very complicated leaving them mostly broken down and stuck in the mud while US and Russian tanks were built in the thousands and simply overwhelmed them with reliability and numbers.

Unless someone who can read German can enlighten us, I don't know if it is designed for a specific purpose. It appears to be just a research program for this design. Perhaps to find out what advantages, if any, there are in the real world. Refine and assess control issues. Profs always need poor unfortunate students to do their work for them.
Their may be some specific applications it could excel at.

The 2D motor looks expensive alright. I don't think it's that complex in principle though. No, don't see them rolling off the product line just yet! Just compare the (mechanical) complexity of the Hexapod with this one and I see obvious advantages in the design. Only 1 degree of motion at the top of the delta shaped struts as opposed to 2 for a uni joint on a Hexapod. Isn't a Uni joint more complex than a single bearing? Everything counts to eliminate any errors at the business end.

The Z-Axis movement is simply attained by moving the "pad" all outward or inward. All in the vids.

From what I have read, one of the advantages with PKMs in general is that positioning errors don't add like Cartesian systems.
You don't have "stacking" errors like a Cartesian system. For e.g. a rotary table on top of the XY. The table has some linearity error and the rotary table run-out error.
I'm talking about the inherent mechanical design not any compensation that could be done on an Cart system

Anyway, I think it's interesting although perhaps very far from practical at this time.

Thanks for you comments.

Mark

[Switcher]

Maybe this will help with the translation?




I use the Google translator (works most of the time)

http://translate.google.com/translate_t?hl=en


.

[rk176]

http://www.index-werke.de/de/englisch/546_ENG_HTML.htm

english page

[neilw20]

Unless you are doing extremely high speed cutting with resonant tooling and slow down the feed until you can't see the chatter marks. If its got to be this good, move at 3 M/sec, 1HP feed power, with 5 micron resolution, with 100KG side load on cutter. In their dreams. What a waste of resources.
Great type of mechanism on flight simulators. What's new about this except that it has become fragile and added lots of extra joints for lost travel, and given someone a job for years writing custom software to drive it.
Hitting a golf ball with a cricket bat, I reckon.
Fellas. Put a spindle motor on it and a chunk of metal and discover chatter.

[The Blight]

The machine I linked to is actually a lathe, and it is used. I have never seen it working, but I have some colleagues who have.

You should take a look at some of the other index machines. Some of the multi spindle machines are truely amazing. These machines are also quite expensive, but the quality is supreme.

Sharpshooter: WWII data from the discovery channel?

[sharpshooter90]

Naw- History channel- Discovery is all about fishing in Alaska.