Start Sequence: leak PLA strikes bed

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eeyore
Posts: 125
Joined: Tue Oct 16, 2012 8:09 pm

Start Sequence: leak PLA strikes bed

Postby eeyore » Sun Feb 09, 2014 9:40 am

I've noticed that most of the time after a completed print, when the hotend is turned off, some PLA will leak out as it cools. Then when you go to print next time, the first thing that happens is commands are sent to tell the hotend to go to home and Z is also homed. With the extra material that has leaked out this causes the hotend to strike the print bed. Sometimes I can easily break off the material that has leaked out other times the hotend needs to heat up before I can clean it off.

Possible Solution: Change the order of the gcode start commands.

Have the hotend heat up first, then have it home

concerns: The printer will not know what position the hotend is end when until it homes. So if the hotend is touching or close to the print bed when it heats up it could damage the bed.

Mitigations: The closing geode tells the hotend to go to the front middle and it will be the distance of the last print from the print bed. There could be a issue if you where leveling the bed and left it touching the bed.

I'm concerned about the constant hotend strikes, I can hear the PLA break (the material that has leaked out) often, and see the bed get depressed (luckily it has springs so has some give).

Has anyone else noticed this ? if so please share any start gcode you have modified. I've started to customize the start gcode. If I get something working i will share it.

Joe

jd_3d
Posts: 629
Joined: Fri Nov 09, 2012 12:30 pm

Re: Start Sequence: leak PLA strikes bed

Postby jd_3d » Sun Feb 09, 2014 3:36 pm

Hey Joe,

Check this thread out:

viewtopic.php?f=1&t=526&hilit=epiphany

I basically brought up the same thing back in July 2013. My solution has been to remove the homing command from the start gcode. I don't recommend it for everyone but it works well for me and I can always manually home if I feel like something has skipped steps, etc. It keeps my z-height much more consistent too.

eeyore
Posts: 125
Joined: Tue Oct 16, 2012 8:09 pm

Re: Start Sequence: leak PLA strikes bed

Postby eeyore » Mon Feb 10, 2014 6:19 am

jd_3d wrote:Hey Joe,

Check this thread out:

viewtopic.php?f=1&t=526&hilit=epiphany

I basically brought up the same thing back in July 2013. My solution has been to remove the homing command from the start gcode. I don't recommend it for everyone but it works well for me and I can always manually home if I feel like something has skipped steps, etc. It keeps my z-height much more consistent too.


Thanks ! this is exactly the same issue. It looked like "Rodwagner" had come up with a nice solution. He heated up and extruded some material before zero'ing everything. Be great if he could post the start gcode that he created.

Joe

eeyore
Posts: 125
Joined: Tue Oct 16, 2012 8:09 pm

Re: Start Sequence: leak PLA strikes bed

Postby eeyore » Mon Feb 10, 2014 6:38 am

All,

I'm not very good with gcode :D

This is what is currently in the start sequence

G28 ; home all
G1 Z5 F5000 ; lift nozzle

This is the mod I'm thinking about making. Want to do some more reading before testing it

M104 S185 ; set temp
M109 S185 ; wait to get to temp

G28 ; home all
G1 Z5 F5000 ; lift nozzle

If this works that way I think, then the "dripped/leaked" material will be hot so when it goes to home
it will not be cold and "strike" the print bed.

Joe

jd_3d
Posts: 629
Joined: Fri Nov 09, 2012 12:30 pm

Re: Start Sequence: leak PLA strikes bed

Postby jd_3d » Mon Feb 10, 2014 9:28 am

You don't need both an M104 and M109. Simply specifying an M109 will set and wait for the temp. Should work fine otherwise so try it out.

eeyore
Posts: 125
Joined: Tue Oct 16, 2012 8:09 pm

Re: Start Sequence: leak PLA strikes bed

Postby eeyore » Mon Feb 10, 2014 10:02 am

jd_3d wrote:You don't need both an M104 and M109. Simply specifying an M109 will set and wait for the temp. Should work fine otherwise so try it out.


This start gcode did the trick. Per "jd_3d" I could probably remove the M104 line. I tested this and it worked fine. The result is the hotend is heated before homing x/y/z, which often caused bed strikes due to cooled material that had leaked form previous print.

Evert thing is the same except for the third line (M109). This makes the printer wait until that temp before going to next command.

;Standard Profile for Series 1. Single Extruder
M104 S185
M109 S[temperature]
M301 P24.72 I0.88 D231.1
G28
G1 X120 Y115 Z15 F10000
G92 E0
G1 Y5 Z15 F5000
M109 S185
G1 F100 E50
G92 E0
G1 X50 Z0.3 F10000

Elijah
Site Admin
Posts: 767
Joined: Wed Oct 10, 2012 6:33 pm

Re: Start Sequence: leak PLA strikes bed

Postby Elijah » Mon Feb 10, 2014 3:47 pm

eeyore wrote:
jd_3d wrote:You don't need both an M104 and M109. Simply specifying an M109 will set and wait for the temp. Should work fine otherwise so try it out.


This start gcode did the trick. Per "jd_3d" I could probably remove the M104 line. I tested this and it worked fine. The result is the hotend is heated before homing x/y/z, which often caused bed strikes due to cooled material that had leaked form previous print.

Evert thing is the same except for the third line (M109). This makes the printer wait until that temp before going to next command.

;Standard Profile for Series 1. Single Extruder
M104 S185
M109 S[temperature]
M301 P24.72 I0.88 D231.1
G28
G1 X120 Y115 Z15 F10000
G92 E0
G1 Y5 Z15 F5000
M109 S185
G1 F100 E50
G92 E0
G1 X50 Z0.3 F10000


If this worries you, how about this, which I adapted from the above:

Code: Select all

G91 ; relative coordinates
G1 Z10 ; force move Z ten more than it is.
G90 ; back to absolute
M109 S[temperature]
M301 P24.72 I0.88 D231.1
G28
G1 X120 Y115 Z15 F10000
G92 E0
G1 Y5 Z15 F5000
M109 S185 ; redundant
G1 E50 F100 ; E first than F is convention
G92 E0 ; very important
G4 P500; hold for hold for 500ms to give you enough reaction time to swipe PLA away from the hot end with tweezers. This is my personal flare which you can try.
G1 X50 Z0.3 F10000 ; you can consider slowing the feedrate if you want.
Elijah Post
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