Reduce max. Acceleration and Speed

smoki3 · 18 Jul 2020, 05:56

Hi,

I have a useful feature request for the tool changers. Especially if you have different tools with different weight.

For different tools you may need different max. acceleration speeds and max. travel speeds.

To do not hard code this in every tpost script would be nice if this could be done in subject to the config.g.

Config:

 M203 X35000 Y35000 Z500
M201 X6000 Y6000 Z100

tpost.g

 M203 X0.6 Y0.6 Z1.0
M201 X0.8 Y0.8 Z1.0

This means that you use for this specific tool just 60%/80% of the acceleration/speeds.

deckingman · 18 Jul 2020, 10:32

@smoki3

I'm struggling to understand the benefit. In your example, you have M201 defined as M201 X6000 Y6000 Z100 in config.g and in tpost.g you have M201 X0.8 Y0.8 Z1.0 in order to set that acceleration as a percentage. Why not simple use M201 X4800 Y4800 Z100 in tpost.g?

It strikes me that the only thing your proposal will do is save you the 1 or 2 seconds it takes to multiple 6000 by 0.8 (in that example).

If one has a heavy tool, one would want to set the acceleration such that it can be achieved by the motor torque available, or some other limiting factor. Which means that one would need to calculate the acceleration to use as a determinate value. Which, if your suggestion was adopted, would then need to be converted to a percentage of the maximum as configured in config.g.

smoki3 · 18 Jul 2020, 10:51

@deckingman it's exactly the same as for the M913 motor current reduction. Its to avoid that you have to edit every home script file.

So if I declare a M201 X1 Y1 at the end of the tfree script then the machine jumps automatically back to the in config defined speeds.

I have four tools. When I for whatever reason (e.g. changing the mass of the tool changer) have to slow down the acceleration in general I have to edit config.g tpost0,1,2,3 and tfree0,1,2,3. These are 9 files.

With this feature request I just have to edit config and finished

deckingman · 18 Jul 2020, 11:11

@smoki3 TBH, I think M913 is a waste of time. You can either use M913 Xnn Ynn Znn or M906 Xnn Ynn Znn. It's just two commands that do exactly the same thing and the only thing it saves is a the time it takes to find the percentage of a number. As far as your files are concerned, you have to enter M210 Xnn Ynn Znn regardless.

smoki3 · 18 Jul 2020, 11:23

@deckingman you personal opinion.

it's very useful. You can define the maximum current in the config and on all home script just minimize to the right value. For example when I use sensor less homing and so on.

I know that slot of people are using it.

If you have only one printer and you now all your values it's not a problem. But if you have 10 different printer you always have to check which value is in the config, for which axis and so on that you know which values you have to place in the other scripts.

fcwilt · 18 Jul 2020, 11:55

@smoki3 said in Reduce max. Acceleration and Speed:

I have four tools. When I for whatever reason (e.g. changing the mass of the tool changer) have to slow down the acceleration in general I have to edit config.g tpost0,1,2,3 and tfree0,1,2,3. These are 9 files.

With this feature request I just have to edit config and finished

So you are saying that the percentages for each tool never change?

Frederick

smoki3 · 18 Jul 2020, 12:51

@fcwilt it depends on which tool is mounted. For direct drive I have to reduce the speed, for Bowden tools I can use the max

A Former User · 18 Jul 2020, 13:14

Maybe I'm missing something, but if you have to work out what percentage to use - then you might as well apply the absolute value?

To restore to nominal power you could either execute config.g or separate that section to its own config file and call it both from config.g and as needed.

I.e. try to work with what you have instead of against it?

deckingman · 18 Jul 2020, 13:53

@bearer said in Reduce max. Acceleration and Speed:

Maybe I'm missing something, but if you have to work out what percentage to use - then you might as well apply the absolute value?

My thoughts exactly. This proposal will only mean that users can replace numbers with different numbers in order to achieve what is already possible.

I don't know enough about coding to say if a single command could interpret values as meaning a) absolute values if they are integers >1, else b) restore to full (configured) current if the value ==1, else c) set percentage current if it's a non integer<1. If not, then additional gcode commands would be required, just as M913 is required in addition to M906 to achieve the same thing.

And if this gets implemented, then it will only be a matter of time before some user or other wants it to be expanded for M204, M566, and goodness knows what else. Which leads to a whole raft of additional gcode commands, essentially duplicating what is already possible.

Of course, that's just the opinion of an old fart as I'm sometimes reminded.........

fcwilt · 18 Jul 2020, 15:19

@deckingman said in Reduce max. Acceleration and Speed:

@bearer said in Reduce max. Acceleration and Speed:
I don't know enough about coding to say if a single command could interpret values...

If would be simple enough to allow the presence of the % symbol to indicate mode thus no need for multiple commands.

One issue might be insuring that prior to any use of a percentage of a value that the absolute value had been set.

deckingman · 18 Jul 2020, 15:21

@fcwilt Why didn't DC do that with M906 instead of introducing a new M913 gcode?

fcwilt · 18 Jul 2020, 15:22

@smoki3 said in Reduce max. Acceleration and Speed:

@fcwilt it depends on which tool is mounted. For direct drive I have to reduce the speed, for Bowden tools I can use the max

Sorry but I'm confused. You said that with the ability to set a percentage in the "tool" change bit of code you would only have to change config.g to deal with a different tool.

I took from this that the different tools had unchanging values that were all fixed percentages of the "master" values in config.g

Can you clarify what these different "tool" change files are doing?

Thanks.

Frederick

smoki3 · 19 Jul 2020, 07:45

@fcwilt the tool files are handling the tool change on Reprap firmware.

Drive to the dock, grab the tool, apply offsets, park the tool and so on. They are hard coded in rep rap firmware.

smoki3 · 19 Jul 2020, 07:50

@bearer said in Reduce max. Acceleration and Speed:

Maybe I'm missing something, but if you have to work out what percentage to use - then you might as well apply the absolute value?

To restore to nominal power you could either execute config.g or separate that section to its own config file and call it both from config.g and as needed.

I.e. try to work with what you have instead of against it?

Yes the procedure to work out the percentages is the same as if I work out the absolute value.

But for example I put a raspberry on the tool head (not on the tool) then the mass gets higher for all 4 tools because the raspberry is carried all the time. So I have to reduce the acceleration from 6000 to 5000 to avoid ringing. Then I have to change all the tpost, tfree script and the config.

If I had percentages then I just edit the config and the values of the single tools get adjusted automatically.

And this is the same behavior for the motor current with: You put a motor on you printer and figure out the max. motor current once and define it in the config. In some cases you need to reduce the current (e.g. idle, homing). Then for example you have to replace this motor because of a defective and the new motor need a different current. With absolute values you have to edit all files which have absolute motor currents. With relative currents you just edit the config.

deckingman · 19 Jul 2020, 08:02

@smoki3 Ahh. So you are saying that on a regular basis, you are changing the mass of the entire gantry which in turn changes the mass of all tools that are attached to that gantry, yes?

Your opening post stated "............if you have different tools with different weight." But changing the mass of the gantry to which the tools are attached is an entirely different thing.

That being the case, and if you genuinely change the carriage mass on a regular basis, then I can see the benefit of your proposal.

smoki3 · 19 Jul 2020, 08:05

@deckingman

Yes this is exactly what I mean. Sorry may my initial post was not clear enough.

deckingman · 19 Jul 2020, 09:56

@smoki3 Oh course, changing the maximum print speed (M203) won't really help because most moves generated by the slicer will be at feed rates which are a lot less than this maximum. So you will need to re-slice anything you print whenever you change the carriage mass, in order to change the feed rates used for print moves. And if you want to have percentages of accelerations, then you will also need to apply your proposal to M204 as well as M201. The instantaneous speed change (M205 jerk) will likely also need to be different depending on carriage mass, so that would need to changed to allow percentages as well. I would imagine that's quite a lot of work.

smoki3 · 19 Jul 2020, 10:01

@deckingman In the slicer I use 600mm/s as travel speed. So don't have to reslice everything. For printing moves it doesnt make any difference. There mainly the accelerations play some role.

I did different tests, but jerk doesn't have much influence on the print quality.

deckingman · 19 Jul 2020, 10:16

@smoki3 said in Reduce max. Acceleration and Speed:

@deckingman In the slicer I use 600mm/s as travel speed. So don't have to reslice everything

In you opening post, you stated quote "For different tools you may need different max. acceleration speeds and max. travel speeds". I take that as meaning you want to use different speeds for different tools. If not, why not (given that the mass is what you say you are regularly changing)? If so, then because the feedrates for print moves are governed by the slicer commands, then you need to re-slice in order to change those print speeds.

smoki3 · 19 Jul 2020, 10:43

@deckingman said in Reduce max. Acceleration and Speed:

@smoki3 said in Reduce max. Acceleration and Speed:

@deckingman In the slicer I use 600mm/s as travel speed. So don't have to reslice everything

In you opening post, you stated quote "For different tools you may need different max. acceleration speeds and max. travel speeds". I take that as meaning you want to use different speeds for different tools. If not, why not (given that the mass is what you say you are regularly changing)? If so, then because the feedrates for print moves are governed by the slicer commands, then you need to re-slice in order to change those print speeds.

Yes but if the slicer request 10000mm/s and you limit the firmware to just use 500mm/s then the printer is just moving with 500mm/s. So the travel speed in the slicer is always the same for every tool. But it will be limited by the firmware.

And I am not talking about print speeds I am talking about the travel moves. The print speed are so low that the printer can easy handle this for all tools no matter which mass.