Before you begin the MK2/S to 2.5S upgrade - some tips and caveats
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Before you begin the MK2/S to 2.5S upgrade - some tips and caveats  

Active Member
Before you begin the MK2/S to 2.5S upgrade - some tips and caveats

I hope this will help someone avoid some of the mistakes I made. Most of it is common sense but hindsight is 20/20.

The original MK2/S was also a kit but be warned that my experience is limited to these two builds: the original and this upgrade.

The kits:

- MK2/S to MK2.5 upgrade with self printed parts (some parts printed, not installed)

- MK2.5 to MK2.5S upgrade with pre-printed parts

Duration: ~12 hours. This includes time for:

- setting up the work area, prepare the kits contents, storage bins etc.

- lunch, dinner (with some cooking time) and bathroom breaks

- firmware upgrade, wizard calibration and first layer print with passable results

- light cursing at times (but enjoyable overall)

Below are a few tips which are better known up front, before you start the upgrade.

- BEFORE you take the printer apart, purge as much filament as possible if you plan to also change the nozzle at this time.

- If you need to print some parts, print them with whatever black PETG you already have dialed in. Save some calibration time. If you don't already have any, calibrate for the filament you'll use. It's worth the time. Make sure you have all parts for whatever kit you have.

- While the printer is disassembled and after the old parts are removed, take time to re-tighten all nuts & bolts using the tools provided. This is part of the regular maintenance but it's easier now than with everything assembled e.g the printer has better balance and you have more space for tools. Turn the printer on its power supply and work your way through all accessible nuts & bolts.

- While the extruder is disassembled change the nozzle. You have better grip on the heating block and less risk of damaging the wires.

- Dust the PTFE tube housing while it's completely exposed. I wish I'd remembered.

- If the print fan doesn't fit when mounting, loosen the other two parts and thighten them back after the fan is in position. This is pretty generic advice but wort mentioning as the plastic is frail and can break/crack easily.

- When a square nut fails to insert cleanly into a printed part slot you can use a tool that looks like a steel needle bent to 90 degrees to carefully scrape the corners of the hole from inside out a few times until the inside has less rounded corners. If you don't have such a tool try to inprovise one using a very thin nail or a bent needle. A blade won't work though.

Then use a flat electrical screwdriver tip (bigger than the included one) to push the nut. There is a size which is almost perfect, you'll find it if you already have some tips.

Remember that the printed parts can break so grab them on the strongest/thickest volumes when doing this operation.

- When inserting the pin for the Bondtech secondary, if the fit is too tight, don't force it! You'll break the printed part. Instead use a smaller diameter drill bit held between the fingers to SLOWLY enlarge the holes. Or if you have a conical needle file use that but rotate it instead of using linear motions.

ATTENTION! Both of these techniques will produce holes which are irregular and NOT cylindrical. Proceed slowly and measure often. Stop while some effort is still needed to push the rod through. When using a file this operation will enlarge each hole's exterior more than the inside. Keep in mind that the rod will always encounter the smaller diameter when hitting the second hole. Don't enlarge too much.

- When working on the X-axis belt (after you cut it to the proper length) if you struggle to push it into the X-carrier slots, unscrew the motor and rotate it as you did when installing the belt. An untensioned belt is easier to push. Rotate it back and tighten after the belt is in.

- When you adjust the pulley on the X-axis motor to center the belt, move the extruder SLOWLY so it doesn't generate power which will power up the electronics (you'll see the LCD screen light up). This is documented in some other place but it's worth mentioning in this context. You can use a flat screwdriver to push the pulley away from the motor in small increments.

- Both kits include a plastic piece used to zip tie the cables as they exit the X carriage. The second kit include a bigger piece with a different design not yet in the manual (Jun 24, 2019). The first kit piece you have to print yourself.

If you use the second kit piece, rotate its top sligthly to the left when tightening the screw. It will allow the X end stop to make contact. Probably a newer, slightly longer end stop piece is needed.

Also keep the last two ties' "heads" (the ones around the heater and thermistor cables) under the cable bundle as they will scrape against the electronics box while th Z-axis moves up and down in the X-zero position. Make sure they're both higher than the extruder's lowest part so they don't drag through your fresh print.

- Use the screw pulling technique to insert (4) hexagonal nuts into the new electronics box you printed - where the cable bundles are entering - but do it BEFORE you assemble and mount the box or electronics(PCB). Use longer (20mm) screws if the 10mm can't reach the nut or if you forgot to do this before mounting.

If the extruder bundle doesn't close completely or you struggle even when you have the correct part, use longer (20mm) screws instead of the recommended 10mm.

- Ground yourself every time when you come back to work on the electronics. Avoid ESD.

- Probably mounting the upper hinge and the door of the electronics box is better left off until all cables are plugged in. You'll have much better visibility.

- Using a zip tie for PINDA positioning (as recommended in the Preflight check Step 3 PINDA adjustment) was too much for me. Two business cards were still on the plus side. Using just one is probably to little but if PINDA calibration should be done without the steel bed, pay extra attention so you don't drive the extruder into the bed.

- Do NOT install any steel sheet on the heated bed until after the firmware is updated and the wizard asks you to do so.

Good luck!

Posted : 24/06/2019 3:32 pm
New Member
RE: Before you begin the MK2/S to 2.5S upgrade - some tips and caveats

I need some guidance.  I have a 2s and was attempting to change the nozzle.  Unfortunately, I messed up and, as a result, broke the little plastic piece the pinda was on as well as breaking the wires to the hotend and pinda.  So, I went to the Prusa site to order replacement parts.  I started up a chat and along the way, the 2.5s upgrade came up.  I figured, why not go ahead, bite the bullet and do the upgrade.  I asked specifically if it had everything I needed to replace and was told it did.  Well, imagine my surprise when I got the kit today and see that the first step is to print some parts.  Obviously, I can't print them since the reason I ordered my upgrade was because my printer won't print.  I'm going back to support to see what they say the best way to address this is; however, I figured I would get the real scoop from those who have done this.  So, my first question is, does the upgrade kit actually have everything I need to fix my printer (I think all I need is the hot end or new wiring to support the existing hotend/thermistor, new support for the Pinda).  My second question is how do I get the parts I'm supposed to print?  If I interpret the initial post correctly, it appears this was an option.  


Posted : 12/07/2019 7:41 pm
Active Member
Topic starter answered:
RE: Before you begin the MK2/S to 2.5S upgrade - some tips and caveats

Sorry it didn't work out for you, I'm not thrilled about the nozzle changing procedure either.

I don't want to confuse you even more but I can tell you what I started with:
- a functional printer - MK2S
- an upgrade kit from MK2S to MK2.5 (no S here) with self-printed parts
- an upgrade kit from MK2.5 (no S here) to MK2.5S with pre-printed parts (by Prusa)
This is not the ideal or the shortest upgrade path! Lemons, lemonade.

I printed:
- rambo base
- rambo doors
- rambo hinge
- rambo extruder cable clip
- rambo heatbed cable clip
- extruder cable holder (only to find out he second kit had a pre-printed improved version, with its own problems)

In your case I'd recommend the "MK2S to MK2.5S upgrade kit with pre-printed parts" but it DOESN'T exist.

They offer only the "Original Prusa i3 MK2/S to MK2.5S upgrade kit", Reference: UPG-MK2-MK2.5S-BLK-PEI
@ $199
- Printed parts are NOT included! Please print them before you disassemble your MK2/S!
-The ABS fan nozzle shroud IS included though.

Maybe you could ask them to print all the needed parts for you, but in addition to the above you'd also need the extruder and X-carriage parts.
I guess you'll still pay for and receive the filament for the parts as the kit content is fixed.

Posted : 12/07/2019 11:39 pm
Noble Member
RE: Before you begin the MK2/S to 2.5S upgrade - some tips and caveats

Thermistor and heater are not part of the upgrade. So if you damaged the wires, you need to get this parts separately. The list of included items can be seen here:

If you damaged something which is not in that list, then you need to buy it separately.

If you gonna buy this parts from the Prusa shop, you can also order the extruder plastic parts.


Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram

Posted : 13/07/2019 12:20 am
New Member
RE: Before you begin the MK2/S to 2.5S upgrade - some tips and caveats

Thanks. I think I've ordered the correct parts to get it back working

Posted : 13/07/2019 1:31 am
Trusted Member
RE: Before you begin the MK2/S to 2.5S upgrade - some tips and caveats

If you get stuck , I could print them for you - I am in the UK?




Posted : 19/07/2019 2:02 pm
New Member
RE: Before you begin the MK2/S to 2.5S upgrade - some tips and caveats

Thanks.  I appreciate it.  (Have my fingers crossed that I can patch things up enough to get the parts printed).

Posted : 19/07/2019 3:46 pm
New Member
RE: Before you begin the MK2/S to 2.5S upgrade - some tips and caveats

ok, got the printed parts; however, it's clear that these are an updated version.  My extruder body parts are marked as R4.  There is no slot for the filament detector, and the piece for the pulley is different.  I think the pulley will be fine, but I am struggling with the mounting on the PCB for the filament sensor. Anyone else run into this? Thanks

Posted : 09/08/2019 7:26 pm