V slot carriage

Just finished my first delta bot build using V slot linear rails and rollers.
[ooznest.co.uk]

I'm currently using carriages very similar to this, [www.thingiverse.com].

Iv noticed if I grab hold of the effector when the motors are stationary i can move it a good 2 or 3mm. All the movement is coming from the carriages flexing under load, and the wheels splaying.
I know this is far from how the carriages are loading in reality, and the forces i am putting on the effector/carriage are huge compared the inertia forces in reality, but it does show a "weakness" in this design.
I say "weakness" because under real operating conditions this design may be more than strong enough for the delta bot application.

Iv only done a couple of slow test prints so far, has anyone noticed any print quality issues when using these carriages at higher speeds?
Also a friend of mine has asked me to look into building a large (+500mm square) printer for him, and id like to use the V slot rails. Does anyone have any experience of using these with cartesian, specifically coreXY or H bot machines?

Using linear guides or almost anything made of metal instead of printed plastic would definitely eliminate the slop caused by splaying of the guide wheels.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Strange, because the carriages on my large Kossel look similar, but when I try to move the effector I find that the carriages are rock steady. The free movement in the effector is 0.3mm, and it is coming from two Traxxas joints that have a little play in them. What material are your carriages printed in?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

The carriages are printed in abs, 50% infill.
It does take a bit of force to move it the 2 or 3mm.
Obviously if you push on anything with engough force it will move, I was just a little surprised how easily I could move the effector.
One simple way I have just noticed the carriage could be improved is to move the point where the diagonal rods attach to it. Currently they attatch right at the top, I guess to maximize z height. This means any load going through the diagonal rods, either from pushing on it or the inertia of the effector, will create a moment about the top v wheel. This moment then pulls the two lower wheels out of the v in the extrusion, resulting in some movement. If the diagonals connected to the carriage in the centre of the wheels you wouldnt have this problem.
May be this is something I need to try at the weekend. I guess I should also work out just what loads are placed on the carriage. I suspect it's actually pretty small!

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willenbrook
One simple way I have just noticed the carriage could be improved is to move the point where the diagonal rods attach to it. Currently they attatch right at the top, I guess to maximize z height. This means any load going through the diagonal rods, either from pushing on it or the inertia of the effector, will create a moment about the top v wheel. This moment then pulls the two lower wheels out of the v in the extrusion, resulting in some movement. If the diagonals connected to the carriage in the centre of the wheels you wouldnt have this problem.
May be this is something I need to try at the weekend. I guess I should also work out just what loads are placed on the carriage. I suspect it's actually pretty small!

You may have a point there. A couple of days ago I replaced my carriages with Robotdigg aluminium ones with belt tension adjusters. The trucks that the wheels and carriages mount on are still ABS. However, the Robotdigg carriages have the rod end mounts in the centre, not at the top as my old plastic carriages had. Perhaps my delta had more play in the effector before I replaced the carriages.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

A little OT, but you might be interested in my version of a delta-carrier without v-slot and rollers:



-Olaf

Hi O lampe

I like the idea of a carriage that works on standard square extrusion.

I think you need to look at adding something to prevent rotation about the left to right axis as shown in your image.

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willenbrook
Hi O lampe

I like the idea of a carriage that works on standard square extrusion.

I think you need to look at adding something to prevent rotation about the left to right axis as shown in your image.

You were right willenbrook,
I changed the design already:


Let´s keep the discussion about it, in my thread.
-Olaf

I'm going a different direction I have a block of delrin that I bought from mcmaster-carr and I'm going to machine a bushing that rides inside the extrusion slot Wish me luck!