1 Topic by op7ical

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Topic: J-Head Mk V-BV on Lawsy's Mk 4

I got my J-Head Mk V-BV from hotends.com in the mail the other day, and I am thinking to put it on my Lawsy Mk 4 nozzle mount today.  I know a few other people on the forum have looked into this and I just wanted to see if there were any quirks when using it.

-What temperature setpoint is best for extrusion now? (Since the thermistor is in a different location)
-Does aluminum foil wrapping work well to improve heat transfer for the resistor? (I saw this in a couple other places)
-Do we have to change the firmware thermistor code?

Thanks in advance!

2 Reply by newq

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Re: J-Head Mk V-BV on Lawsy's Mk 4

I also received my J-Head Mk V Hotends some days ago and want to put it in Lawsy's MK 4.

I used the aluminum foil wrapping instead of thermal paste wenn I replaced a broken resistor in the Solidoodle hot end. It continues to work well. But that resistor was concave so the aluminum foil around the center filled that space very well. The resistors I have for the J-Heads are more convex so I'm a bit unsure and bought some thermal paste to fill any gaps around the edges.

Only thing I'm missing at the moment are PTFE heat shrink sleeves for the resistor leads. They were not included and I have to order them first (crazy expensive! ~10 EUR / 1,1 m). I might try wrapping the leads in kapton tape but I'm not sure I like that. Did hotends.com include sleeves for the resistor leads? (I didn't buy from them)

I'd be interested in temperature recommendations for ABS and PLA as well. If necessary I'll just start testing with PLA and turn the heat up until i think / know it is at the right temperature to print. Knowing the difference of Solidoodle and J-Head I'd start experimenting with ABS.

Good luck with your upgrade! smile

3 Reply by IanJohnson

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Re: J-Head Mk V-BV on Lawsy's Mk 4

I use 230C for ABS with mine.  I found it was starting to have trouble extruding at 220.  For PLA, I've have good luck at 185-190.  The thermistor table will depend on what thermistor was shipped by your supplier.  I think the one I got from hotends.com needed to be changed to 5.  It works well, gets up to temperature in a minute or less.

I have mine in a Mk3, which I tweaked a little in Tinkercad because the groovemount is slightly different from the SDs.  I think I would have been fine filing the original instead.  I need to get around to printing the MK4 hot end.

4 Reply by newq

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Re: J-Head Mk V-BV on Lawsy's Mk 4

Do you happen to know what type the Solidoodle thermistor is? Hotends.com say they now ship with a Type 1 thermistor.

I'm printing the MK4 in ABS right now ... only had it in PLA but I'm too worried with it's low melting point. I'll report back if I get it printed and working with the J-Head. By the way: the J-Head fits perfectly in the PLA printed one.

5 Reply by op7ical (edited by op7ical 2013-03-02 23:44:28)

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Re: J-Head Mk V-BV on Lawsy's Mk 4

The thermistor table will depend on what thermistor was shipped by your supplier.  I think the one I got from hotends.com needed to be changed to 5

Indeed, it looks to me like they shipped the Semitech 104GT-2 thermistor, which is supposed to be #5 in the table.

Edit: Originally in this post I asked how to change the thermistor code, but I figured it out now, so it's not an issue.

6 Reply by lawsy

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Re: J-Head Mk V-BV on Lawsy's Mk 4

Please confirm if the J-head fits in the stock design. If so, that is very fortunate. If not, if someone can measure the PEEK part accurately with vernier calipers, I'll modify the design and add a second version to Thingiverse.

lawsy's Website

7 Reply by timp610

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Re: J-Head Mk V-BV on Lawsy's Mk 4

I have a ceramic hotend that's similar to the  jhead ones that I ordered.  Is it possible to.change the  themistor tables via gcode and then use the m500 command or whatever it is to save to the eeprom?

8 Reply by lawsy

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Re: J-Head Mk V-BV on Lawsy's Mk 4

You can only set the PID tuning via gcode. The thermistor table will need to be changed so that it is compiled with the firmware.

lawsy's Website

9 Reply by enginuitor

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Re: J-Head Mk V-BV on Lawsy's Mk 4

Wow, what timing.

Just last night I put together my new J-Head and was trying to work out how best to mount it. I have Lawsy's Mk.3 extruder body, and the J-Head barrel would fit into the mounting slot, but it wasn't particularly secure and had some fairly substantial wobble in the YZ plane.
My solution was to draw up a pair of inserts for the Mk.3 that seat in the groove on the barrel and clamp it from the front and back. The result is very secure, but it does sacrifice the use of the accessory posts.

I've uploaded a print-ready model here: thingiverse.com/thing:56507

It's too bad I hadn't found out about the Mk.4 extruder before starting this project. I really like the idea of having the whole filament path visible and accessible right up to the barrel. I'm personally not a fan of not fully constraining the barrel, but maybe I'll rework my front retainer piece to fit the Mk.4. Only 4 hours of runtime on this new setup and I'm already thinking about rebuilding it again...

10 Reply by newq (edited by newq 2013-03-03 02:10:13)

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Re: J-Head Mk V-BV on Lawsy's Mk 4

I have the ABS mk4 on my Solidoodle now and the J-Head fits perfectly. The fit is just the tiniest bit tighter than the original Solidoodle hot end. I don't think there's anything you need to change, lawsy!

Thanks for your work on this! smile

Edit: My J-Head MK-V is not from hotends.com though. I got it from Reprap-UK on ebay. I wonder if there might be tiny differences between my j-head and those from hotends.com. I'm still waiting for my digital calipers so I can't give you measurements right now.

Sorry about my thermistor confusion by the way, I somehow had "Type 1" in my head.

11 Reply by op7ical

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Re: J-Head Mk V-BV on Lawsy's Mk 4

I have the ABS mk4 on my Solidoodle now and the J-Head fits perfectly. The fit is just the tiniest bit tighter than the original Solidoodle hot end. I don't think there's anything you need to change, lawsy!

I agree, the design seems to work well as-is for the J-Head nozzle.  My printer is happily whirring away on a torture test print, and everything looks great so far!

The print temperature I'm using is 228C.  Thanks to Ian for figuring out the optimal temperature range! 

I do, however, have to figure out a better method for connecting my thermistor/heater wires.  I ended up just soldering a bunch of joints until wires were long enough and things held together.

12 Reply by newq

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Re: J-Head Mk V-BV on Lawsy's Mk 4

I finally put the J-Head together after playing around with the original hot end in the mk4 mount. I got the Type 1 thermistor with mine and user aluminum foil as well as thermal paste to mount the resistor. It heats up incredible quick and holds the temperature perfectly.

After all the hassles I had printing the mount in ABS I decided I'll use my first J-Head for PLA.

For me PLA prints perfectly at 195C, 180C - 190C was too low in my case. I could extrude in the air but couldn't get a print started.

I'm just finishing a test print and it might be my imagination but for me the J-Head seems to have better quality when printing.

13 Reply by IanJohnson

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Re: J-Head Mk V-BV on Lawsy's Mk 4

I do, however, have to figure out a better method for connecting my thermistor/heater wires.  I ended up just soldering a bunch of joints until wires were long enough and things held together.

I originally just soldered the resistor legs to the wires that go to the connector, and the joints failed pretty quickly.  There needs to be a solid crimp of some kind there.  I took some crimps I had for fan connectors, and clipped off the end that locks into the connector.  The part that normally folds over the insulation, I crimped onto the resistor leg, and the other end went on the conductor of the wire.  Then I drowned the whole thing in solder and shrink wrapped it.