- November 20, 2017 at 5:22 am #48112
I ordered one of the all-metal hotends to replace the throat on a Prusa clone’s MK8 extruder.
Everything installed fine, but I didn’t notice until after install how much shorter the micro-swiss throat is compared to the stock one. I need to figure out how to raise my bed up almost 10 mm, or lower my extruder assembly.
Any ideas on easiest way to do this?November 20, 2017 at 6:57 am #48116
I think I just answered my own question.
It looks like the gap is about the thickness of my 10mm wrench. I’ll just make some metal spacers the same thickness and put them between the roller tubes and the bottom of the metal plate that the heated bed mounts to.
That way none of my X axis geometry and Z gantry has to be modified.
Time to run to Lowe’s for some aluminum plate and longer bolts.November 20, 2017 at 8:21 am #48118
What printer is that? Almost looks like you could flip the axis over to get the lead screw nut on top like a standard prusa clone.November 20, 2017 at 9:02 am #48124
It’s the Geeetech Aluminum.
It’s a rather cheap printer. The threaded rods are a little bent, so the brass bushings aren’t actually tightened down. The screws are just tight enough to hold them in place. it allows the bushings to wobble a little inside the metal holder.
My prints aren’t perfect, but I don’t have the time/money to perfect the printer. Everything I’ve designed has been useable and that’s all I care about. Honestly, all it really needs are some new straight lead screws. When I first got it, I did a lot of work on it including replacing all the bent soft steel rods with hardened steel ones.
I also replace the cheap controller with the RADDs board. That was probably the most costly upgrade.
The printer has been rock solid since I did that. It’s coming up on a year old and with the exception of the Extruder steepper cable, I’ve only had to replace nozzles and the PTFE tube in the throat. Oh. there was the extruder fan I had to replace, but that’s because I stuck a screw driver in the stock one while it was spinning.
I love that the entire frame is aluminum/steel. There’s zero flex in it and I don’t have to worry about any parts melting in an enclosure. I have a few PLA parts on it for fan guards, thumbscrews, etc… as soon as I get the all-metal hotend working I plan on reprinting all of those parts in PETG. I also plan on printing some filament guides for inside the extruder to try to print with NinjaFlex.November 20, 2017 at 9:20 am #48127
Looks like you’ve got a lot of the parts needed for an MP3DP 😉 .
After seeing the geeetech page, I can now see exactly what’s in your profile pic.
Seems like raising the heater and the bed would work. I like Ryan’s idea of flipping the X too, you’d get an extra 10mm of Z that way (although I’ve never gotten close to my max Z).November 20, 2017 at 5:52 pm #48158
I took a look at flipping the Z. I don’t think moving the brass bushing on top of the bracket will work. The big problem is the head on the bolt is the same thickness as the brass bushing, so whether it’s above or below the bracket won’t matter.
The brass bushing also isn’t thick enough to make up the difference I need.
I have a long piece of steel strapping that’s thick enough. I’ll cut some spacers from that and put it between the rollers and the bottom plate. I just need to get some longer bolts and spend a little time in the garage… probably this weekend.November 20, 2017 at 11:07 pm #48170
Not just the bushing, the entire axis. If you have a look at the prusa and most of the clones, even the MP3DP. The entire x/z axis is flipped over. On yours it would put the x axis motor on the other side though.November 21, 2017 at 1:30 pm #48217
I see what you’re saying. I think that would cause the Z axis switch to not hit correctly.
The other issue is the extruder mount is actually in the middle of the gantry that goes back and forth. Flipping it over would still have the bracket be in the middle of the gantry.November 28, 2017 at 6:40 am #48653
I got the heatbed lifted up. Now the hotend reaches it again.
I tried my first print. Everything started off OK, but then the filament jammed. I tried again, and it did it again. When it jams, I can push the filament through by hand, but it is very hard until you feel something give.
Is there something I’m missing? Do the all-metal hotends need to run at a higher temp for the same filament?November 28, 2017 at 6:44 am #48654
Maybe you’re getting too much heat?November 28, 2017 at 7:24 am #48655
I’ve noticed on this print that the printer slows down after the first few layers. I think I have the slicer set to slow down if the layer takes less then X number of seconds.
I’m wondering if it’s an issue with the lower speed.
I can try lowering the heat as well. Right now I’m printing the PLA at 210*C. This is the same temperature I used with the old hotend.November 28, 2017 at 8:04 am #48656
I would do some test prints with bridging and overhangs, as that really does sound too hot. I haven’t had any PLA issues but I print at 196? That could all depend on the filament brand. I bet you could easily drop 5-10 degrees off that and be in a much better place.
The other important part is to get it as far into the heatsink as possible, you want the temp to drop as close to the nozzle as you can. Maybe you hung it out really far to try and take up the gap you had? Kinda rough that the printer was at it’s absolute minimum you could have had a free 100mm of Z. ..I have an updated printer almost ready to go if you are getting sick of that one, you can probably swap most of the parts right over….November 28, 2017 at 8:05 am #48657
Actually looking at your pictures it does seem to be hanging out really far and you might want to swing your heater block towards the fan, you don’t want to cook that naked bearing.November 28, 2017 at 8:06 am #48658
I have a Regular longer PTFE throat if you want to swap back to what you had.November 28, 2017 at 8:13 am #48663
The temps for some PLA recommends 230 (makergeeks) so I think it’s pretty hard to tell across brands.
I also have a working theory that every thermistor is different, so when you first start, you mess with the temps, get something that works well, and then swap out the hot end or filament or just the thermistor, and you’re off the ideal temp by 10 degrees again. The actual number doesn’t matter because 215C on my wanhao seems very similar to 195C on my MP3DP. But it does seem to be pretty consistently working at those temps on those machines.
I haven’t dealt with heat buildup AFAIK, I just suggested it because of the Canuck thread with a similar sounding issue.November 28, 2017 at 8:25 am #48666
The regular MK8’s have the throat almost directly into the heatsink. I have some that don’t even fit the tension nut on the outside and have them on the inside. Looking at Davids pics the throat is in the air for a long distance and then it goes into some silver riser block or something and then into the heatsink it it even goes in that far. I have a feeling the throat is almost as hot as the nozzle after 5 minutes of printing like that.
If you can see the last three pics on the assembly of it in the link below vs. Davids pics I think it will stand out.November 28, 2017 at 9:13 am #48675
The metal riser is how the MK8 is mounted to the gantry.
If I screw the hotend any farther into the heatsink, then the nozzle won’t clear the bottom of the gantry. I guess I need to figure out how to lower the MK8 instead of raising the heated bed.
The metal riser gets a little warm, so it’s acting as part of the heatsink too.
I’m sure I’ll figure something out.December 29, 2017 at 4:55 am #50181
I took this week off from work and spent a good amount of yesterday working on the printer. I was finally able to get it to print by doing the following:
- Lowered the print head: I removed the X gantry from the printer and modified it so that I could move the mounting bracket for the extruder to the bottom of the gantry instead of in the middle. All it required was drilling two holes for the lower bearing holder
- Extended the Z-axis end stop: The screw that’s used to trigger the z-axis end point was too short. I had printed a bunch of M3 threaded risers a while back. I glued about 5 of those together and made an extension for the screw.
- Removed the print bed risers: This lowered the print bed back to stock height
- Print new Parts Cooler: Since the hotend isn’t as long, I’m having to design/print a new parts cooler. I’m printing my third iteration now, but this should be my last. The one that’s currently on the printer just barely grazes the top of the last layer printed… Little too close for my comfort.
By doing the above, I was able to screw the hotend all the way into the extruder until it just comes out of the top of the block it screws into.
While taking everything apart, I also discovered that I had filament oozing from out from under the nozzle and up through the threads of the hotend. It looks like I didn’t have the hotend far enough into the heat block and the nozzle wasn’t wedged up against it. In the end, this could have been the smoking gun to my issues all along and the rest were just red herrings.
Today will be the real test. I plan on pushing some petG through the printer as soon as this latest print is done.
Here’s some pics of the mods:
December 29, 2017 at 8:41 am #50186
- Pic 1 Shows how the extruder is lower on the X Gantry
- Pic 2 Shows what the hotend looks like (might be blurry is in middle of print)
- Pic 3 is the Z Axis end stop extension. Looks GhettoFabulous
That will do it, nozzle not properly seated with the throat is a sure fail.
Bright side, you tuned up you printer, should work perfect now.December 29, 2017 at 5:26 pm #50217
Works ‘perfect’… as long as I stick to PLA or ABS. I still can’t seem to keep PETG from jamming in the nozzle when trying to use it to print. Will need to do more research on how to get PETG to print correctly.December 29, 2017 at 5:33 pm #50218
The only thing I can think of would be to try and print faster and/or cooler, with the smallest retractions possible.January 2, 2018 at 7:21 am #50345
Yeah. the next full day I get, I plan on trying to print a bunch of test cubes until I get it right. I really want to get some of the MK8 inserts printed in petg so I can start playing with flexible filaments.January 2, 2018 at 7:25 am #50346
I found that petg was just much more fickle than pla. The temperature envelope was smaller and so was the extrusion multiplier. When you over extrude, it gums up, which makes big problems.
You must be logged in to reply to this topic.