Stretched prints with FEP VAT

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Joined: Sun Sep 20, 2015 1:19 am

Stretched prints with FEP VAT

Postby Floreum » Wed Jan 10, 2018 2:13 am

Hello, sometime ago I got the LittleRP from the original kickstarter and never quite got to use it until now, I bought a FEP VAT (flexvat) when i decided to finally start learning how to use the thing. I bought FunToDo Snow White resin and added red pigment. My prints are coming out beautifully except they are stretched along the Z Axis only.

I am using Creation Workshop and I've tried tons of different exposure settings and messed around with the lift speeds, even changed the FEP film thinking that was the case and it doesn't seem like it is. I've tried different approached to adding supports to my test model and it doesn't seem like it's making any differences. I have noticed that every time the build plate lifts, the FEP gets pulled a little but I can't seem to be able to get it to stop doing that, so I'm not sure if that's what's stretching my prints. Ultimately can't figure out what the problem is.

If I were to guess it must be a Z stepping issue, but I haven't got much of a clue how to fix that. I let a stretched print finish and it stretched so much it hit the limit of what the machine is capable and started crashing at the top of the machine. In Creation Workshop it shows the model shouldn't be anywhere close to the top.

Here's a gallery of my settings/prints if that helps at all (I probably shouldn't have printed some of these so big when testing)

Posts: 236
Joined: Sat Mar 29, 2014 6:16 pm

Re: Stretched prints with FEP VAT

Postby goopyplastic » Thu Jan 18, 2018 7:54 pm

Sorry for the delay in answering this, things have been pretty nuts here with fires and floods. The steps per mm are likely incorrect in grbl. You can either increase the microstepping by adding an extra jumper, or change the steps per mm value.

Can you take a pic of your controller board and what steps per mm grbl is using for z? You can connect to the arduino with a program like pronterface @ 9600 baud on the comport of the usb serial. If you type $ it will dump your values.

Posts: 2
Joined: Sun Sep 20, 2015 1:19 am

Re: Stretched prints with FEP VAT

Postby Floreum » Mon Jan 22, 2018 9:16 pm

I decided to try NanoDLP thinking it was a bug with Creation Workshop, and was still getting stretched prints. So that's when I decided to try doing 20microns instead of 50. A perfect un-stretched print came out. But I don't always want to be doing 20microns as some models may not need the fine detail

Here's an image of the Arduino

And here are the values from Pronterface
Grbl 0.8a
Printer is now online.
'$' to dump current settings
error: Unsupported statement
>>> $
[WARNING] raw G-Code line "$" could not be parsed
$0 = 10.00 (steps/mm x)
$1 = 1600.00 (steps/mm y)
$2 = 400.00 (steps/mm z)
$3 = 30 (microseconds step pulse)
$4 = 200.00 (mm/min default feed rate)
$5 = 60.00 (mm/min default seek rate)
$6 = 0.10 (mm/arc segment)
$7 = 160 (step port invert mask. binary = 10100000)
$8 = 55.00 (acceleration in mm/sec^2)
$9 = 0.05 (cornering junction deviation in mm)
'$x=value' to set parameter or just '$' to dump current settings

So I compared my grbl values to the ones listed on the official site and have changed them to reflect what's there. I'm gonna do a test and will report back if there's any success/failure.