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Printrbot Z Axis 5mm threaded rod upgrade

by RedJoe, published

Printrbot Z Axis 5mm threaded rod upgrade by RedJoe May 31, 2013
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Summary

I was unhappy with the 5/16 threaded rod that the Printrbot comes with and the Z-ribbing artifacts. The problem is the stepper motors have an uneven amount of steps with the 5/16 rod. When you print something with the 5/16 rod, your layer heights will be off every x number of layers unless you choose very specific layer heights. By going to 5mm threaded rod(mine cost $15 shipped from McMastercarr) you can change your steps from 2267.72 to an even 4000 steps. This gives a nice even layer height all the way through your print. Also, by adding dual nuts and a spring, any backlash is excluded. The other issue is the 5/16 rod coupled to the 5mm motor shaft is a poor design, by using 5mm threaded rod and some tubing, you get an even coupler and no z wobble.

This is hands down the best upgrade I have done on my printrbot, it improved my prints by a huge amount, if you do any upgrades, this is the one to do, best $15 bucks you will spend.

Instructions

Print off the parts, one for each side, they will fit perfectly into the stock Printrbot Plus V2.

Cut the threaded rod to length and install nuts with spring in-between into the new part. Couple the threaded rod to the motor shafts with a short piece of tubing and zip ties from your local hardware store.

Adjust your Printrboard firmware in Repitier from the 2267.72 to 4000 steps on the Z-Axis and print!!!

Also, if you want the best, purchase brass 5mm nuts, however they only come in quantities of 100 from McMasterCarr for $15 so I didn't do this to mine, however, if you want the best possible setup, go with the brass instead of Stainless nuts.

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Will this work on a 1405?

Not sure what spring to buy. Any P/N's you can recommend from McMaster? Thanks so much for this by the way.

Not really sure. I went to harbor freight and purchased their assorted box of springs, contains like a hundred springs of various sizes for like $5.

What springs are you using? 7mm diameter sound about right? Are they absolutely necessary? Could you explain the function they carry out?

I've got my rod and brass nuts, just no springs.

got the rods springs and nuts...Printed the piece out and the nut hole is a little small...is there some clean up needed or is my print off.

Search for a different outer diameter nut, the ones I had didn't worked, they where too big, so I bought some smaller ones and fitted perfectly.

I used the stainless nuts I got from McMasterCarr. I never even thought to measure them, it's a nice snug fit in the part, but my guess is there is a wide variety of nuts available all with different measurements. I'm not sure what to say other than take the part down to the hardware store and find one that fits. In the future, I'll be sure to measure the hardware I use so people can match things up better.

Hi there, I had the same issue, just went to the shop again and bought slimmer ones.

You mentioned that the steps will change to 4000, is there a way or tutorial on how to correctly set all the steps on my firmware?

And if you are kind enough can you share your firmware settings so I can try them out?

I am having some issues with my calibration.

Thank you.

If you do enough googling, you can figure it out. But here's the basics.
If you look at the Reprap docs for printrborad here.
http://reprap.org/wiki/Printrboardhttp://reprap.org/wiki/Printrb...

You will see that the board performs 1/16 microstepping.

What is happening is your stepper motor for Z axis turns 200 steps per revolution which is also 1.8 degrees per step (200 x 1.8 = 360 degrees). The drivers on the Printrboard further refine the steps using microstepping by dividing each 1.8 degree step into 16 microsteps.

Using a 5mm threaded rod with a 0.8 mm thread pitch means in one revolution of the threaded rod, the height will increase 0.8 mm. Which means in 200 steps or 3200 microsteps the height will increase 0.8 mm. If you divide 0.8mm by 3200 you will see that for each microstep, the height increases 0.00025 mm. We need to know how many microsteps at 0.00025mm will equal 1mm( which is what the firmware controls inside Repetier want to know). Simple algreba tells us that microsteps needed for 1mm will equal (1mm / 0.00025) which is an even 4000 microsteps.

4000 microsteps with 0.8 mm threaded rod will equal 1mm in height. 4000 is a nice even number and makes your layer height selection work well without messed up layers in the middle of your print like you will get with 5/16 threaded rod. The reason for 5mm and not 6 or 8 is that the mass of the rod is less so there is less likelihood it will move your printer from side to side(wobble) and also 5mm matches the exact shaft diameter of your stepper motor so you get a nice clean coupler between rod and shaft of motor.

I hope that clears it up.

Excuse my ignorance, what is the "pitch" of the threaded rod? What do I have to meassure?

I just went to my local shop and asked for 5mm threaded rods and they only had stainless steel ones, so I took them ( looked everywhere and that was the only shop that make those).

The pitch is just the distance between the threads. You need a pitch gauge to measure it, but you can probably measure with a caliper too or just screw a nut that you know the correct pitch of and see if it screws on ok.

I made this yesterday and got it all set up but it through my z all at of whack. I got the same rod but in regular steel and set my steps to 4000. Am I missing another setting? When I run 100mm it goes about 130mm. I haven't had time to do a z calibration test piece. I have a Printrbot LC V2, I was actually getting pretty awesome results with everything stock. Any help would be appreciated.

Are you positive you got .8 pitch threaded rod? If you have a different pitch, you will have to use a different amount of steps. Almost sounds like you got a pitch of 1.0

Any trick for that calculation?

Try a nut you know that is a pitch of .8 and see if it screws on the thread, if so, you know it's correct. Or use a pitch gauge from your hardware store.

I was told where I bought it that it was. Looking at McMaster Carr and Grainger that is the only pitch they sell as well.

If it is indeed a .8 pitch, then you should be getting 100mm height when testing for 100mm, if not, then I'm not quite sure at this point what it would be. You might have to post over at the printrbot forums and see if you can get some assistance. It should be 100mm right on the money, it's extremely accurate if things are working correctly.

Thanks for the help. I will check. Bye the way were does 4000 steps come from? Also if I put my M92 4000 calibration in repetier I should be correct right?

I got the threaded rods and nuts, but I just realized this is for Printrbot V2, will this work with my version 1 Printrbot?

The place where the printed part has to be looks a lot like the one on my printer.

I'm not positive, but most likely it should fit, from what I heard there isn't much difference in the printer pieces, rather just longer rods and such.

It wont fit my V1 Printrbot Plus. The laser cut part where the threded rod goes is rounded and wont let this piece up enough to reach the nutkeeper. I made a version for V1 HERE: http://www.thingiverse.com/thing:118354http://www.thingiverse.com/thi...

Printrbot Plus (V1) Z Axis 5mm threaded rod upgrade
by soke

what is the X axis upgrade you have printed in the last picture? That has me curious if it is worth checking out also. Thank you for doing all the leg work on this one for the rest of us! Its on the top of my list of upgrades

Just a replacement for the stock front plate, really doesn't do too much, I did it to fix an issue with my X axis being out of square with the frame of the bot, however this might not be the case with other bots.

Out of curiosity, what were the specific layer heights that were appropriate for the 5/16th rod?

I personally wouldn't use stainless nuts with stainless rod. Tends to destroy the threads

I totally agree, and would recommend brass nuts if you can find them.

ditto on the brass nuts. I can't find it now but I remember reading, maybe in a machinists magazine, that same or similar metals tend to "stick" together. so if you use a steel rod and brass nut it will be smoother.

will this work with the printrbot jr?

what metric size is the 5mm rod. is it M6 or M7 or M8 and what pitch did you select. 1mm or 1.5mm

It's M5 - type 316 rod with .8 pitch. Here's the exact part number I used at McMastercarr -> 94185A150

Where did you find a matching brass nut for the rod? The only one at mcmaster, that I can find, is $15 and sold in packs of 100.

Perfect thanks. I ordered my rods. Thanks again.

Did this same upgrade with my solidoodle. Single best upgrade you can do! Hopefully, the printer makers will get the hint and start incorporating these into their printer designs. Great item. I am sure you will help a ton of people with this.

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