SOLVED Dimensions in Cura vs final printed part

[schemer 3]

I have used Cura in the past and never noticed any issues with dimensions but now I have printed a few small parts with the latest version and have noticed some issues. I am not an expert but it seems strange when I open an stl file that is 2mm thick and slice it and print it, it measures 0.045 inch instead of 0.0787 and if scale it in Cura, it still comes out incorrect. I tried another part at 5mm thick and it too is way undersize in the thickness. Any ideas? Using a CR10S with a 0.4mm nozzle and PLA.

Thanks,

schemer

[GregValiant 1,344]

Z steps/mm

Z Axis binding

The screws holding the Z axis rod into the coupler and onto the stepper motor shaft are loose (popular problem).

[DivingDuck 105]

What do the gcode say as last Z height?

[schemer 3]

1 hour ago, GregValiant said:

Z steps/mm

Z Axis binding

The screws holding the Z axis rod into the coupler and onto the stepper motor shaft are loose (popular problem).

I was hoping you were right but I got the allen wrench and checked and the couplers are both tight. I can run the z axis up and down without any binding. And the print looks fine other than being thinner than it should be. What do you mean ny "Z steps/mm"?

[schemer 3]

1 hour ago, DivingDuck said:

What do the gcode say as last Z height?

I am going to make a new one and from DesignSpark Mechanical make it the thickness I want so I won't have to scale it. And then I will report back.

Thanks.

[schemer 3]

I fixed it. 😁 When I was checking the steppers and couplings for tightness and free turning, I chose disconnect steppers from the control panel so I could turn them. That is when I realized the right z axis stepper was not connected. Funny thing is I had noticed the cable with the connector for that stepper hanging off of the table but thought it was the unused connector for the filament sensor. It's printing fine now after re-leveling etc.

[gr5 2,224]

You don't need to disconnect cables to rotate the steppers.  Worst case you can turn off the printer but usually that's not necessary.

 

[GregValiant 1,344]

Perfect...a cheap fix.

 

Don't tell your buddies that you missed that lose connector.  You'll never hear the end of it.

[schemer 3]

1 hour ago, gr5 said:

You don't need to disconnect cables to rotate the steppers.  Worst case you can turn off the printer but usually that's not necessary.

 

There is a selection to disable the steppers on the CR10S. I thought when the unit is powered on that the steppers are locked into their current step position so disabling them would allow for me to push the bed etc. But, on the older printers you could supposedly back feed voltage into the controller board by pushing the table or the hot end too fast and ruin the board. I guess it would be hard to turn the z axis too fast but I was just being careful. I didn't remove the cable(s) to rotate the stepper but when I was rotating it, I noticed the plug was unplugged causing my whole issue. Don't know when it happened, but it did. 🙂

Edited October 10, 2020 by schemer

[schemer 3]

34 minutes ago, GregValiant said:

Perfect...a cheap fix.

 

Don't tell your buddies that you missed that lose connector.  You'll never hear the end of it.

I know. 😬 I am glad that is all it was and I will always check all of my connections in the future when I have a weird problem.

[Longtoke 25]

6 hours ago, schemer said:

Don't know when it happened, but it did. 🙂

 

Heads up, the connectors for both of the z-axis steppers is perilously close to the movement of the print bed. If there is a bit of slack on the cable it can get caught by the print bed as it moves, and bingo, you're down the rabbit hole. Make  sure the plug is seated firmly into the stepper motor then make sure to push the excess cable into the adjacent hole cleanly, this takes it out of the path of the print bed permanently. 

 

Another thing I'd recommend is linking the 2 z-axis steppers with a closed loop GT2 belt ( 748mm is perfect, 760mm will do but you will need to print a tensioner too ) and a couple of 20T 8mm bore GT2 gears. The right side Z-axis tends to sag a little when it's powered down, throwing the print head gantry off. While bed leveling will compensate for this to  a degree, you're better off linking the axis' and be down with it all. 

 

13 hours ago, GregValiant said:

The screws holding the Z axis rod into the coupler and onto the stepper motor shaft are loose (popular problem).

 

Learn something new every day ! ( and cheers ;D )

 

Props to you also schemer, most people wouldn't admit to it lol. 

Edited October 11, 2020 by Longtoke

[DivingDuck 105]

Errors happen and this gave a little lesson to learn. There a not a lot of people who speak about own mistakes.

Glad you found and solve the problem. 👍

[schemer 3]

On 10/10/2020 at 9:17 AM, DivingDuck said:

What do the gcode say as last Z height?

Exactly what line or what is the gcode for the last Z height?  I looked in Notepad++ . Is it the line with the largest number in the "Z" like the 6.2 in this line:

G0 F300 X150.07 Y116.084 Z6.2

The reason I think it may be that is when I did the preview it has 30 steps (if I remember correctly) and I was printing in 0.2 mm resolution. so 62./0.2 = 31

 

11 hours ago, DivingDuck said:

Errors happen and this gave a little lesson to learn. There a not a lot of people who speak about own mistakes.

Glad you found and solve the problem. 👍

 Thanks for your support everyone.😇

[schemer 3]

15 hours ago, Longtoke said:

 

Heads up, the connectors for both of the z-axis steppers is perilously close to the movement of the print bed. If there is a bit of slack on the cable it can get caught by the print bed as it moves, and bingo, you're down the rabbit hole. Make  sure the plug is seated firmly into the stepper motor then make sure to push the excess cable into the adjacent hole cleanly, this takes it out of the path of the print bed permanently. 

 

Another thing I'd recommend is linking the 2 z-axis steppers with a closed loop GT2 belt ( 748mm is perfect, 760mm will do but you will need to print a tensioner too ) and a couple of 20T 8mm bore GT2 gears. The right side Z-axis tends to sag a little when it's powered down, throwing the print head gantry off. While bed leveling will compensate for this to  a degree, you're better off linking the axis' and be down with it all. 

 

 

Learn something new every day ! ( and cheers ;D )

 

Props to you also schemer, most people wouldn't admit to it lol. 

 

Thanks for your support Longtoke. I have a question on your linking of the twin z axis with a belt. Do you have any pics of that after it is complete? I can't picture it with the threaded rods in the mix. Maybe a project for later.

Thanks

[DivingDuck 105]

G0 F300 X150.07 Y116.084 Z6.2

Correct. Z is the axis you need to look at. The value is in mm. Regarding the layer count calculated, the count starts with layer 0 not with 1.  🙂

 

 

[schemer 3]

1 hour ago, DivingDuck said:

G0 F300 X150.07 Y116.084 Z6.2

Correct. Z is the axis you need to look at. The value is in mm. Regarding the layer count calculated, the count starts with layer 0 not with 1.  🙂

 Well that is good. I should have known that as I used to program years ago and remember something about certain things starting from 0 vs 1.

[Longtoke 25]

4 hours ago, schemer said:

Do you have any pics of that after it is complete?

 ask and thou shall receive !!!

 

As far as the threaded rods go, the 20 tooth GT2 timing gear has an 8mm hole bored in it and a couple of small grub screws. The gear slips straight onto the the threaded rod, you then tighten the grub screws. It's essentially the same as attachment method as used for the stepper motors and the gear wheel for you belts, just a bigger hole in the gear wheel for the threaded rod size. 

 

You can find the toothed gear pulley wheels ( and the GT2 closed loop belts ) just about anywhere, just make sure to include the "GT2" in your searches. Was going to provide a link, but it seems the web site here  blocks it / I don't have the right authority. 

 

Edited October 11, 2020 by Longtoke

[schemer 3]

Thanks for the pics. Makes sense now. Any potential issues by doing that? If the right stepper goes out will it still work like a jack-shaft? And just because I need to know...why does the right stepper drop a little lower and make the gantry off by a little?

Edited October 11, 2020 by schemer

[Longtoke 25]

2 minutes ago, schemer said:

Thanks for the pics.

My pleasure.

 

2 minutes ago, schemer said:

Any potential issues by doing that?

 

None what so ever. If you go take a look at the recently released CR6-SE, this is a "mod"  that they have included with the design. It's an outright improvement with no down sides. 

 

4 minutes ago, schemer said:

If the right stepper goes out will it still work like a jack-shaft?

 

Pretty much. The steppers on the Z-axis' are capable of driving both if one goes down ( I did test it when I did the mod by unplugging one of the two z-axis motors ). The only time I'd see an issue arising is if one of the steppers catastrophically failed and physically jammed,  at which point the noises of belts jumping is probably better than the twisting metal noises you'd get otherwise. 

 

8 minutes ago, schemer said:

And just because I need to know...why does the right stepper drop a little lower and make the gantry off by a little?

 

Don't worry, I too have OCD lol.  

 

It's because the whole gantry design itself is not symmetrical ( and thus not balanced in weight terms ) and to a lesser extent the v-rollers design that Creality uses. That said, even a printer with linear rails will have sag on one side of the hot end end gantry without having a dual z-axis, and if those axis' aren't bound, you will need to align them fairly frequently. 

 

That's all this mod does - bind the z-axis' primarily for when there's no power to the steppers, because that's when they  shift freely the most. It has practically no effect while the printer is powered. 

[schemer 3]

Thank you for the most excellent detailed reply to my questions. I will look into getting parts to do this mod with confidence that it is a very useful mod. I appreciate the info. 👍

schemer