Tool 1 can not reach print bed



  • Hi I just installed a second tool on my printer. T0 is used to home and level the bed. T1 has a positive offset compared to T0. The problem now is that T1 can not reach the print bed since the minimum of the Z axis is defined to be at 0.0 and it wold need to go lower to reach T1.

    What is the best way to solve that? Any experience?

    Best regards
    TC



  • M208 X0 Y0 Z0 S1 ; set axis minima

    you can set negative values for z.
    try that.

    are both hotends on the same carriage?



  • @Veti no its a tool changer. but if I set a negative value T0 will be able to crash into the bed... is there no way to include the offset into the mininum?



  • @TC it seems like such an obviose problem...



  • @TC Well if you've got 2 tools with different heights, then there will always be a danger that the lowest one will crash into the bed if the z height is set for the highest tool.



  • @deckingman not if you are using a tool changer.



  • @TC said in Tool 1 can not reach print bed:

    @deckingman not if you are using a tool changer.

    You said quote "but if I set a negative value T0 will be able to crash into the bed". So it doesn't matter whether it's a tool changer or not. You could set Z zero for tool zero, then you won't have need to make Z min negative. But when you change tool you'll have to lower the bed for the other tool. Then when you change back to tool 0, it will crash into the bed unless you change the change the Z height to suit that tool.

    Z0 is just a datum point. It's zero relative to something which can be anywhere in space. Whether you only allow travel in the positive direction or whether you allow travel either side of that datum point is irrelevant.

    In a nutshell, if you have tools that are different heights, and thus have different offsets with respect to each other and/or a Z probe, then whenever you change tools, you'll have to adjust the bed height to suit the offset for that particular tool. Whether the machine is a tool changer, or whether you allow the travel below Z min is irrelevant.



  • @deckingman thanks. So would the best way to do it be to include an M208 in the tpost script?



  • @TC said in Tool 1 can not reach print bed:

    @deckingman thanks. So would the best way to do it be to include an M208 in the tpost script?

    No, I wouldn't do that. It's generally best to set the axis limits in one place and not mess with them. All you need to do is use G10 to set the tool offset(s). There are a number of ways of achieving the same thing but what I would do is use the tool with the largest offset between the probe and the nozzle as the datum and use this tool to home the printer (with the axis minimum set to zero). Then set the Z offset on the other tool(s) with respect to that datum. So supposing tool A has a probe to nozzle offset of 5mm and tool B has a probe to nozzle offset of 4mm. I would home using tool A then use G10 to set the Z offset for tool B to +1mm.



  • @deckingman But what if tools are modified from time to time and the offset can change? Which one is the lowest might change...



  • @TC said in Tool 1 can not reach print bed:

    @deckingman But what if tools are modified from time to time and the offset can change? Which one is the lowest might change...

    If you have to modify tools and the offset changes, then you have to "tell" the firmware what the new offset is. There really isn't any way to get around that. But there is nothing to stop you using any offset value for any tool. You don't need one of them to be zero - that is just one way to do it. But you could pick any datum point and use positive or negative offsets for each and every tool with reference to that datum point.



  • @deckingman ok thanks I am gonna try that


  • Moderator

    I'm not a tool changer user but from what I gather on the E3D tool changer the head has an endstop switch to set the bed position relative to the head and then the tools each have an offset from that point which is set in the tool change macro at pickup. Again, I could be totally wrong about that because I have only used one myself very very briefly.


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