Repositioning Endstops (Reprap Air/Prusa's)
May 05, 2013 08:06AM
Hey guys, I have been thinking about some endstop management.

One thing I never quite understood was why the endstops weren't mounted on the X-carriage? You can easily put the X and Z endstops in an X-carriage.

There are three advantages to this:
- Cable management - The cables can be combined with the cables that are already running from the E-motor and the hotend, this will effectively cause that you have even less separate cables to take care off
- The X-endstop can be mounted in a space that is made in the side of the X-carriage, right now, I am using a clamp on the smooth rod of the X-axis and it takes up more space than I would want it too, I bet there are more people feeling the rod-clamps are a pain in the rear
- The Z-endstop can ben greatly improved - My idea is to mount the Z-endstop on a small arm that has the exact same height as the tip of your hotend nozzle. When you are setting the Z-height you flip down the arm, and when printing starts, you can manually put the arm up, out of the way of the printbed. Since the endstop arm is mounted on the X-carriage itself, and pre-calibrated to the height of the nozzle exit, chances of getting the wrong Z-height are highly reduced since the bed is the part that deforms the most under the influence of heat. Flipping an arm down and up is much easier and more fool-proof than having to turn a screw on the side of the machine (thats what I do now) to calibrate the height.

I also had an idea of making a small adjustment to the clamps that hold the smooth rods of the Y-carriage, and that is to incorporate the endstop holder into the clamp, since the carriage can't move beyond the clamp anyway, why not use it as an endstop holder too?

Are there more people thinking of improvements like this? I am not able to create these things yet, since I only know how to design in Sketchup, I don't own Rhino or any other program, however I do know a bit how to work with Rhino.

Is there software that I can use on the Mac to create STL files, besides Sketchup?

- Marinus
Re: Repositioning Endstops (Reprap Air/Prusa's)
May 10, 2013 02:01AM
You can try autodesk in design.
Re: Repositioning Endstops (Reprap Air/Prusa's)
May 15, 2013 06:41PM
I havent had much issue with the wires, to be honest. You just have to wire it once.

But the idea of using hitting bed to calibrate it does sound like a good idea. But getting the same distance is easier said than done..

People have done calibration where it measures the orientation of the bed. Frankly though, bed leveling doesnt seem to be so much of an issue in the first place) 'reprap industrial' has a nice leveling feature, that could be easily be applied to other repraps, though i think most of them have a bit tricky access to those screws..

Slightly tangient I do have an endstop holder for which the idea is to have two endstops at differing height, say one fore drawing and one for FDM. Then you want the higher one to go away easily, in this case it just rotates out of the way. (It rotates on the rod that connects the two Z smooth rods of a reprappro) (Of course the second endstop would go in series with the other z endstop)

I'll probably try it with pen plotting at some point. However, the endstop holder is too wobbly imo. If i 'release' it i kindah want it to be better than this.

My main 'beef' with current designs is that i feel the machines might be more valuable as 'general' x-y-z-e machines, where things can be exchanged for other things. For instance I also have a design for making the E-motor easily removable.(which i havent printed yet, some slic3r problems and there is a thing now i think i want to change) For instance so you can take it off the filament drive and put it on the carriage to move a syringe or pump for instance.

As for what to use, i like openscad and implicitscad. Neither is perfect but i tend in the direction of implicitscad.
Re: Repositioning Endstops (Reprap Air/Prusa's)
October 02, 2013 12:22AM
I just had the same thought about moving the X-Carriage end stop onto the carriage as it saves having another flexible cable from one end of the X track (i.e at a Y carriage).

The only reason I can see for not doing this is the extra weight of the switch (or opto) and the wires, but I can't see this would be a big problem, as the rest of the wires and cable surround going to the X-Carriage are not exactly light weight.

@Ohmarinus did you move you X end stop onto the Carriage?
Re: Repositioning Endstops (Reprap Air/Prusa's)
October 03, 2013 08:25PM
I have a design for a carriage(just there atm, not released edit: i have an earlier version in use) with a sort of small quick fit.. I could try implement the idea on it. Basically think an arm rotating on a screw with a slider which is is controlled by a screw and the end stop goes on there. Main difficulty is probably getting the arm to sit steady at two points well.(with precision mattering in the down position, of course) The slider might be as the one in that endstop holder i mentioned before. By the feel of that thing, it is too wobbly.

Could also go with the endstop fixed to the carriage and the arm swiveling under it both as 'going into action' and as indicating a touch, then only the arm rotation matters. A screw for adjusting the height could double by being the thing that touched the bed.

Anyway even if i did, I dont know how to get the data out, nor how to make the slicer subsequently use it, though. Probably would have to mess with the arduino software to make any use of it other than what is already done in the normal setup. So i dont see much use in doing the one if you dont do the other. Also, it is calibrated, and doesnt seem to go out of calibration, so it isnt very pointful. Well, maybe you might want to add a use of it as a 'touch scanner' or something.(Measure height at different points)

Edited 1 time(s). Last edit at 10/03/2013 08:27PM by Jasper1984.
open | download - car-csg.png (8.3 KB)
Re: Repositioning Endstops (Reprap Air/Prusa's)
October 16, 2013 05:14AM

I moved my X endstop micro switch onto the X Carriage.

I designed a simple T shaped support for the microswitch and then "glued" the support to the carriage using a bit of ABS juice.

See attached photo.

One minor problem I had, is that I have an all metal hot end, and my X Carriage has a fan glued on the same end as the end stop, so I had to bend the lever arm on the microswitch as fan was colliding with the end stop post (the one that slides on the x carriage rod / rail).

I'll need to modify the existing end stop, so that a bit of it sticks out, and then I can bend the lever back to its more normal angle.

The wires for the X endstop microswitch now go inside the cable loom with the existing wires on the X Carriage

BTW. In case anyone wonders why the underside of the carriage is covered in Kaptop tape. Its because I found that the air flow from the fan was causing my prints to warp, and I found the only way to stop this happening is to make a duct for the air out of Kaptop.
I have longer term plans to make the duct out of thin aluminium sheet


open | download - IMG_5279.jpg (319.6 KB)
Re: Repositioning Endstops (Reprap Air/Prusa's)
January 03, 2014 09:48PM
Nice to see you all working on this, I have my MendelMax finished now and didn't make a final place for my endstop yet because the X-axis is way too wide grinning smiley Haha, so it's tie-ripped to the smooth rod for now...
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