Changing Prusa i3 Z-axis threaded rods to 8mm in SCAD

Hi guys, I am trying to find where I can change the M5 threaded rod for the Z-axis to M8.

I have already created custom bearing settings so my X-ends have a 10mm hole without a split side to accomodate the pushfit linear bushings I have, but I just can't figure out where the nut holes can be changed to accomodate an M8 nut and rod.

I found the file called 'nuts_and_bolts.scad' and I have been looking into 'x-end.scad' and 'x-end-motor.scad' and 'x-end-idler.scad' but I just can't find out how to make it work with M8 nut and rod.

All I need is to print the X-end motor and idler so I can finally start printing out the last few pieces for my kit.

Would be great if someone could help me to find the correct value to change. I did try the nut-trap but that only changed the size of the outside of the nut-trap.

All files can be found here:
[github.com]

Hi guys, I still haven't found out where to change the nut-trap and threaded rod size, would be awesome if someone could point me out where I can change this. I think in the file it's a M6 for the Prusa i3 X-ends, but when I compare the values in the size-table, and then later check back into the file, I can't really find the correct values.

It was changed to M6 to reduce Z wobbles. Why do you want to go back to M8?

Assuming single plate....


open 'x-end.scad' , goto "module x_end_holes()", nut trap is the last part of this module.............

// Nut trap
translate(v=[0,-17,-1]) cylinder(h = 10, r=2.45);
translate(v=[0,-17,3]) rotate([0,0,30]) cylinder(h = 5, r=7.5, $fn = 6);


1st bold is the small hole
2nd bold is the hex nut trap.

(my numbers may be differnet because I've been potchin)

Ok, so you mean that M6 has less wobble?

I had just bought some very expensive M8 couplers and also some stainless steel M8 rod....

So I was thinking of changing the M6 to M8, but as you say, it can also just be done with M6 because it reduces wobble?
Any good way of attaching the M6 rod to my 5mm thick stepper-motor shaft?


Masnachu, thanks for your help also!





DanMoto Wrote:
-------------------------------------------------------
> It was changed to M6 to reduce Z wobbles. Why do
> you want to go back to M8?

DanMoto Wrote:
-------------------------------------------------------
> It was changed to M6 to reduce Z wobbles.

M6? I thought they were M5...

why change?

you might aswell go for a good lead screw if you change, the moto is don't change nothing that aint broken lol

you may think that i'm against your idea but i'm not i'm just finding out what improvements would gain changing the z rod to m8 as its bulkier and no rod is true rod unless its a good lead screw so i suppose the weight and mass of a m8 if not perfectly straight would be worse then having a m5 with the same issue

---

Check my rubbish blog for my prusa i3

up and running
[3dimetech.blogspot.co.uk]

SheldonE Wrote:
-------------------------------------------------------
> DanMoto Wrote:
> --------------------------------------------------
> -----
> > It was changed to M6 to reduce Z wobbles.
>
> M6? I thought they were M5...


Are you sure?
I just ordered replacement 5mm to M6 couplers hahaha.. Argh.





chris33 Wrote:
-------------------------------------------------------
> why change?
>
> you might aswell go for a good lead screw if you
> change, the moto is don't change nothing that aint
> broken lol
>
> you may think that i'm against your idea but i'm
> not i'm just finding out what improvements would
> gain changing the z rod to m8 as its bulkier and
> no rod is true rod unless its a good lead screw so
> i suppose the weight and mass of a m8 if not
> perfectly straight would be worse then having a m5
> with the same issue


Why change? I have been putting together all different kind of parts to use in my MendelMax 1.5 the machine originally has a horizontal X-axis and I want to try out building in a Vertical one with Bowden system. I have already finished most of my parts, but the X-ends were the last to create. However, it needs some tweaking since the distance between the leadscrew and the Z-rod seem to be different.

What is lol about that moto? (it's motto btw). I don't mind making a bit of an effort to change some things, because for example I had already ordered the leadscrew M8 and I had already ordered the Z-motor couplers. Since this is the second machine I am building, I can assure you that I have meanwhile developed a talent for detecting the straightest rod from a batch, so no worries about Z-wobble.

The 5mm to M8 couplers I have are very good ones, however, they require me to grind a flat side on my Z-motor and I haven't had the time yet to do that because I need to do it in someone else's workshop. The 5mm to M6 couplings I have ordered now, work without any special adjustments, so I will try those first.

In my experience the weight and mass of an M8 rod are no problem. I have them in my current machine and it works perfectly fine, I don't know where you read that information.

Edited 1 time(s). Last edit at 07/19/2013 05:21AM by Ohmarinus.

It's definitely M5, and the rods were indeed made smaller to help with wobble issues.

Yep M5. In addition to less wobble the thread pitch allows for more variations of appropriate layer heights.

Edited 1 time(s). Last edit at 07/19/2013 09:58PM by vegasloki.

Okay, well I just bought an M6 rod and an M6 coupler to 5mm, would M6 also be ok? I am really not into getting all the threaded stuff for the third time. Also, yesterday I have perfected the tolerance for the M6 nut on the X-ends

Opps, I think M5 is correct and not M6. The size is not that important as long as it is smaller than your smooth rod.

Hi all,

Yes it is M5 Z-rod.
I have done some experimenting with the z-rod and the "easy-made-coupling" of water tube (aquarium tube).
All you need is approx 50mm of clear tube with an inside dia of 4mm. This fits snug onto your 5mm stepper shaft and the M5 rod can be threaded in as well without too much of an issue.
Now the "secret" is to make sure the rod does not touch the stepper shaft. Leave about 1 to 2mm clearance between the two metal parts so that the tube can pick up any wobble that may occur.
Another important thing is to handle your M5 rods with extreme care. Depending on the lenght you buy them in they need to be kept straight at all time. They bend very easily as they are after all just M5 rods. Very careful when cutting it to lenght. If you bend it, throw it out as it becomes useless.
Have attached a photo of my setup on the i3.

Regards
Jan

I thought the Z axis smooth rods that sit parrallel to the z-axis threaded rods eliminate most of the z-wobble .... no ?

I ahve had problems using tube for coupling the threaded rod to the motor shaft. often the tube slips... you really have to pay close attention. I suggest marking the tube & rod with a slip marking. this will allow you to actually see if the tube is slipping. Many users prefer to use aluminium
couplings. ( available on e-bay.. but double check when purchasing the correct coupling diameters )

I've seen some solutions where people used a couple of tie-rips to secure the tubes even more to both the stepper shaft and the threaded rod.

I guess when you've got yourself a good quality of tubing and a very clean grease-free surface, it should work fine. The plastic will set onto the stepper-motor shaft and adding a tie-rip will only make it better.

I will start working on the machine again this week. It's been absolute hell to sit inside for the last couple of days because my country had a genuine heatwave since this weekend and I've been doing nothing else but spend my time on the beach surfing.

Also waiting for my aluminum couplings for the M6 rod, because I have managed to get the most perfect M6 nutholder imaginable. The nut doesn't get stuck in the hole, but it slides in and sets in a perfect fit



Mickman Wrote:
-------------------------------------------------------
> I thought the Z axis smooth rods that sit
> parrallel to the z-axis threaded rods eliminate
> most of the z-wobble .... no ?
>
> I ahve had problems using tube for coupling the
> threaded rod to the motor shaft. often the tube
> slips... you really have to pay close attention. I
> suggest marking the tube & rod with a slip
> marking. this will allow you to actually see if
> the tube is slipping. Many users prefer to use
> aluminium
> couplings. ( available on e-bay.. but double
> check when purchasing the correct coupling
> diameters )

Ohmarinus Wrote:
-------------------------------------------------------
> I've seen some solutions where people used a
> couple of tie-rips to secure the tubes even more
> to both the stepper shaft and the threaded rod.

Yes, the use of zip-ties to secure it to the shaft and m5 rod is a good idea. I used that as well but have not had any issues after removing them.
Have not used the aluminium couplings on my machines but I am sure they are ok.
Used to use them on some CNC engravers in a company I used to work for many years ago.
I am just always looking for a simpler and cheaper solution which is available to all, hopefully all over the world as well.
The tube costs $1.30 per meter and can be bought at any lenght (100mm if you want) at hardware stores.
It works fantastic.
Marking the tube and shaft/rod is a good idea as well.

Regards
Jan

Hi Jan, I got myself the straightest M5 rod imaginable, it was stainless steel btw. And I added the tubes you recommended. I found translucent green tubing in an Animal shop, where they sell it for fish-tanks for the water pumps. At the hardware store it didn't go below 6mm ID.

It looks great, also tightened both ends of the tube with a tie rip, and I will mark it. I didn't clean the parts with acetone before attaching the tube, so if they ever move, cleaning with acetone might fix the problem.

Now reversing the design of the X-ends back to M5 nuts and getting it ready to print.

Image of the tube connection included!

Edited 1 time(s). Last edit at 07/24/2013 01:02PM by Ohmarinus.

Ohmarinus Wrote:
-------------------------------------------------------
> Hi Jan, I got myself the straightest M5 rod
> imaginable, it was stainless steel btw. And I
> added the tubes you recommended. I found
> translucent green tubing in an Animal shop, where
> they sell it for fish-tanks for the water pumps.
> At the hardware store it didn't go below 6mm ID.
>
> It looks great, also tightened both ends of the
> tube with a tie rip, and I will mark it. I didn't
> clean the parts with acetone before attaching the
> tube, so if they ever move, cleaning with acetone
> might fix the problem.
>
> Now reversing the design of the X-ends back to M5
> nuts and getting it ready to print.
>
> Image of the tube connection included!

That looks good
Same as mine without the zip ties, mine has done 1200m of 1,75 ABS without any issues. And stainless is a good choice (found it to have a much better thread then zincalume etc)

Regards
Jan

Okay, I have managed to now make the X-ends into ones that are usable on the MendelMax with 8mm smooth rods and M5 threaded rods, with custom bushing holes that are ready for push-fit and the distance between the M5 and the 8mm smooth rod is now also implemented.

I have beefed up the block that holds the M5-nut because the distance between threaded rod and smooth rod is much bigger on the MendelMax compared to the Prusa i3.

This is probably not of any use to other people, but still I will post my files here in case anyone else is going the exact same way as me.

Thanks for the help so far
- Marinus


ps I got a hold on Teflon/PTFE spray to use as lubricant on both of my printers, I have heard it is 'the shit' so will report back on this later if it really is

Edited 1 time(s). Last edit at 07/26/2013 12:47PM by Ohmarinus.

Thanks everyone for the help, in this topic: [forums.reprap.org] there are pictures of the machine and how it turned out.

Now waiting for new belts (the ones I currently have are too short... Argh. So can't finish the machine yet. Also, the hotend didn't arrive yet. I hope it comes this week.
- Marinus

I have been hoping to do this so that I can make use of my steppers with lead screws built in
but mine have m8-8 acme thread so I have no need for a coupler or any of that

but I had not been able to do that until I found this thread
thank you very much