Best way to shorten hot end assembly by 1mm?

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09-18-2021, 04:59 AM
Titan

Best way to shorten hot end assembly by 1mm?

I've got a couple Monoprice 3D Printers, an MP10 and an MP10 Mini that I picked up pretty cheap. They're kinda quirky in some respects and display some odd behaviours (software is a little buggy etc.), but can both provide great quality prints when working correctly, which isn't currently the case for the larger MP10.

The nozzle blocked up mid-print so I had to remove the bowden tube and disassemble the hot end assembly to clear it out. At this stage I thought I'd replace the nozzle so, after a little research into sizing, I purchased a new nozzle. Here's where the issue I'm having began.

It seems the 'standard' sizing for similar nozzles is M6 thread, 12.5mm long total; basically, copies of the E3D 0.4mm Brass nozzles. But Monoprice decided to use a 11.5mm nozzle instead (the thread section is shorter, otherwise they're the same as the E3D ones). This creates a problem as, due to the weird monoprice design, the bowden coupler at the top of the hot end assembly can't be moved up or down at all (its held in by a lug nut, not screwed in), and that sits bang up against the throat, which sits butt up against the nozzle. The nozzle has to sit within a specific tolerance of the auto level probe and all the replacement 12.5mm long nozzles means that tolerance is out by 1mm. Ridiculously it's not possible to adjust the value in the operating system for distance of the sensor from the bed enough to allow for the 1mm height difference. The MP10 won't go further than '0' and to create the necessary distance the value would need to be in minus figures. Not only that but the sensor isn't good quality, so even when it' physically 1mm higher than its original position it misbehaves, failing to register the heat bed and diving the nozzle into the print bed when homing before a print.

So I think I need to do one of the following:
Reduce the height of the throat by 1mm
Reduce the height of the nozzle by 1mm (buying from Monoprice would solve this but the nozzles are 30 time the price of cheap ones available everywhere, so I'd prefer not to)
Lower the height of the sensor by 1mmm which is tricky due to the stupid design of the sensor

Any suggestions how to solve the issue (preferably not, "get shot of the printer" lol)!? Thanks.
09-18-2021, 11:37 AM
NHSA_Rainer

If it is brass then take a file and file it down. Should be done in less then 10 minutes. Clean it up well afterwards ...
09-19-2021, 04:04 AM
Titan

Quote:

Originally Posted by NHSA_Rainer

If it is brass then take a file and file it down. Should be done in less then 10 minutes. Clean it up well afterwards ...

The heat break's made from a polished steel. To be honest I was hoping there'd be a simple solution that I was missing, but having done more research it seems Monoprice have just created an annoying and fiddly issue using non-standard sized parts. Even getting a compatible replacement heat break is proving a problem, and I'd like to buy a spare so I can return the machine to standard if necessary (GigDigit sell them but only deliver to the US and Canada, and I'm in UK). I think filing away the top/entry section of the metal throat is the best solution as it's the only part that doesn't 100% need a perfect seal.
09-20-2021, 02:38 PM
Titan

Monoprice really don't make getting parts in the UK easy and a heat break is only available from the US store for a cost of £9 plus £14 postage! So I adjusted the position of the sensor by lowering it 1mm. Happily the problem's solved and I can now use standard 12.5mm long nozzles.
09-22-2021, 05:13 AM
Titan

2 Attachment(s)

Quote:

Originally Posted by Larry337

So you just have to adjust the machine to fix the problem? cool.

Yeah, bit of a bodge to be fair. It turned out the easiest fix (by far) was to forcibly push the part cooling fan, which has the bed level sensor attached to it, down closer to the bed. The part cooling fan is just held into place within the hot end assembly body by friction (no screws or anything!). It's held in surprisingly tight, so I just carefully pushed it downward by 1mm to compensate for the extra 1mm length of the nozzle.Hopefully the basic diagram of the MP10 hot and assembly I threw together and the attached photo helps better explain. :-)I highlighted the extra 1mm gap by circling it in red on the photo. Simple fix in the end.
09-27-2021, 08:11 AM
curious aardvark

filing the nozzle down would have been the simplest and quickest.
Any pound shop will sell you a file capable of doing the job, if you don't already have some.

And don't be so sure it's NOT a standard nozzle.
I've currently got three totally different sized 'standard' nozzles.
You have to read the descriptions really carefully before ordering, and even then there's no guarentee that a new 'mk8' nozzle will match the old 'mk8' nozzle.
Other 'mk's' are available and all just as likely to be random sized :-)

But other than that - just shave 1mm off the brass thread.
09-27-2021, 08:50 AM
Titan

Quote:

Originally Posted by curious aardvark

filing the nozzle down would have been the simplest and quickest.

Thanks, that's true, but I wanted a better solution that didn't require shaving 1mm off the end of every nozzle ever installed. Also if the nozzle isn't filed perfectly smooth it has the potential to affect the flow and adhesion of every single print. Lowering the sensor was the best option.