2 Process prints with a raft

[JSField]

So, I have 2 processes, the first one stops and raises the Z axis, so I can insert a part in to the print. I use the 'Stop printing at height'. After loading the insert, I manually lower the Z the same amount, and start the 2nd process with the 'Start printing at height' set. I have a 'G90 ; absolute mode' in the Start Up script of the second process. This works fine, but I wanted to add a raft to the 1st process, which prints fine, but the 2nd process dives the head into the part. What do I have to do differently for a raft? (I'm using Vicky's method: http://tgaw.com/wp/?p=359 )

Thanks,
Jeff

[d_barnette]

+1
This has to be a bug in the way Simplify works . Whether I have two processes running sequentially or two gcodes that have a natural stop height that coincides with the start height of the second gcode, the result is the same... the head knocks the print off the raft.

In the picture above, each of these parts being built is the same, a cylinder that is 50.8mm tall. The cylinder on the left starts at 0 (on top of a raft which is 25.4mm tall for clarity) and ends at 30mm. The cylinder on the right starts at 30mm, and ends at 50.8mm. The problem is that the raft height in the second process is ignored, and the part starts at 30mm from the build table. Except for the first process starting at z=0 and stopping at z=30mm, and the second process starting at z=30mm and going to the z=end, the processes are exactly the same (both include a raft). This is just an illustration of the problem.

Where the problem comes in is if you have a single part to be made that needs a substantial raft and requires two separate gcode sets. For example the first gcode set prints the raft and the model to a certain height so an insert can be added, and then the second gcode set has the ending z value from the first gcode set as its starting height. For some reason Simplify ignores the raft and starts the z height as measured from the build platform, not the raft, which guarantees that the head will crash into the part.

I know this procedure works fine when neither gcode set has a raft included. So why the height offset issue with the raft?

Darrel

[CompoundCarl]

There's a few things you need to know. First, you can't use a raft for a process that starts up in the air. So if you are only printing one process that starts at z=5mm for example, it can't have a raft, which makes sense since it isn't anywhere near the surface of the bed. The other thing to keep in mind is that when you use multiple processes in a single print, the software is smart enough to adjust other processes if it needs to (such as raising the second process if the one below it is using a raft). But it won't know to do this if you print the second process by itself.

So what you're seeing looks normal. If you want it to raise that second process, you would need to print both processes at the same time. You can't print just the second process only.

That being said, there's another easy way to do this which probably makes more sense based on what you are doing. It's explained in more detail here: viewtopic.php?f=8&t=5420#p23421

I've used this many times to do the same thing. If you use this method, then you also only need one single process which makes it a bit easier too!

[dkightley]

Isn't there a simple workaround for this scenario?

Why not work out the z offset created by the raft in the first print.....and then apply that offset to the second print process.

I'd use the value of the second layer in the print LESS one layer thickness. The first layer will be laid artificially high due to raft separation.

[JSField]

That makes sense CompoundCarl, about the second process, and printing it by itself. So, from your other topic you linked to: Could I raise the Z and send the pause ('M0') command in the End script of the first process, then in the second process start script, have the Z lower back the same amount and continue with the second process. I would run both processes when I start the print then. I will have to try this.

Thanks,

[d_barnette]

CompoundCarl,
Does the method you linked to work when printing from an SD card? How would I restart the print after the pause command. Or is that taken care of in the Viki2 hardware already?

One reason I use two separate gcode sets is that I don't have to count layers. I just specify the start and end height in mm for the first part of the model to be printed, and save that gcode to SD. Then I edit the original process file to now start at the ending value of the first gcode and print to the end, and save this gcode as a separate file also on the SD card. This worked fine for me until I started using a multiple layer raft to help nylon prints stick to the bed.

It seems easiest to me if S3D would let ME select or deselect the raft for the second gcode. If selected, then zero from the top of the raft, and if not selected, zero from the bed. I don't see a downside to this added functionality.

[CompoundCarl]

The M0 command works on some firmwares, but not all. If you want to find out, just try putting an M0 command in a simple gcode file and print it from the SD card to see if it pauses.

[JSField]

Ok, so here's what I did:
I have a single process, with a raft. I have my normal Start and End scripts.
On the Scripts Tab in the 'Additional terminal tabs for post processing, I put this:

{REPLACE "; layer 18," "M106 S0\nG91\nG1 Z100\nM0\n; layer 18,"}

On layer 18:
M106 S0 turns off the cooling fan
G91 Z100 raises the Z 100 mm so I have room to put in the insert
M0 pauses the print, a window pops up in S3D that says to press Resume to continue the print

I then load the insert, then manually jog the Z down 100mm and press Resume.
The only strange thing is then the Z moves up 100mm again, then back down 100mm and continues the print. Not sure why this happens?


Thanks,
Jeff

[Heutinck]

Forget what I said you need two processes, I was thinking of something else

"Could you not just make this one process and use the pause at layer setting to pause the print while you insert your object into it and then press the resume?"