Welcome to the SeeMeCNC Community

Hey guys,

So I've been printing for around a year, no issues

Went to print an item today, looked good, go to fit it and it's too small! Said item has a 67.5mm hole, I checked it with the calipers and it's come out at 65mm. Item for reference can be seen here - http://i.imgur.com/NBikAqE.png it's the long square hole on the left. As you can see, can't really be from an extrusion issue.

Quite odd I thought, so I figured I'd print a 20mm Calibration cube - sure enough - Z is good at 10.05mm (as it should be), but X and Y are around 19.6mm, perfectly equal I might add.

I was speaking in #reprap who suggested try changing my extrusion width (I run it in auto so it's .48 on my .4 Jhead), so dropped it down to .4 so it's a 1:1.

At that nozzle extrusion width it's coming out a consistent 19.47mm. I've tried 2 filaments as I thought maybe I was having shrinkage or something (it's PLA), but apparently not.

My steps per mm is at the default 80, horizontal radius seems fine, so I'm not sure what else it could be? Running stock arms with astrosyn dampers on the steppers.

Any help much appreciated, this is the first time it's been out of size, and I have no clue what to do as it's all set correctly!

It's also not my slicer software - I've tried both MattherControl and Simplify3D - both produce the same results (exactly 19.47mm on a .4mm extrusion width).

In terms of my actual filament extrusion - again this is fine - the layers look good, no gaps on 100% as it should be and no obvious issues. Again, it's weird as nothing has changed, so not sure what could have caused it.

Thanks,

Matt

The bandaid fix is to change the diagonal rod length, which will fix the scaling issue. I don't know what would actually cause this, but that's a reliable fix which works on X-Y issues where Z is fine.

(Observed size / Specified size) * Current arm length setting = New arm length should get you a working arm length.

Keep playing with it till you're right on.

Xenocrates wrote:The bandaid fix is to change the diagonal rod length, which will fix the scaling issue. I don't know what would actually cause this, but that's a reliable fix which works on X-Y issues where Z is fine.

(Observed size / Specified size) * Current arm length setting = New arm length should get you a working arm length.

Keep playing with it till you're right on.

Thanks I will try that

As for the issue itself - any ideas?

Actually, that's not a bandaid fix, it is THE way to configure X-Y scaling on a delta printer. There is going to be a little manufacturing variability in the delta arms, effector, carriages, etc. On any new printer you should set up carefully, print a calibration cube and then tweak the arm length to address scaling.

In your case, your cube is too small. That means your arm length is configured too long in firmware. Use this formula to calculate the arm length and do another test print:

actual diagonal length = 290.8 (current length in EEPROM) * 19.47mm / 20.00 mm

Note that longer arm length decreases the X-Y scaling of the print.

If previous parts were dimensional, it would be some mechanical change. I don't know what mods you've put on yours, or how dimensional it was in the first place. it might even be wear in bearing covers for your cheapskates, or some other bit of slowly accumulating error, or it might have been that it simply didn't match in the first place and you never noticed because other things had more dimensional slop.

All I know is some printers that seem mechanically identical will want slightly different H-radius's and sometimes arm lengths to print parts.

I called it a bandaid fix since you indicated you'd been running the printer fine for a period of time, and I figured the scale issue was newish, but unless it's wear or some other mod you've done recently, it's probably been there the whole time.

Ah true - it used to be accurate - only mod done is elastic bands on the arms (top and bottom) to reduce the slack - I imagine if they are too tight, they will indeed slightly reduce the arm length

Mystery solved I think

Redid my arm length last night, finalized that by recalibrating horizontal radius and it's printing perfect again

I wonder how long it's been like that and I haven't noticed lol, it's been a good few months since I put the elastic bands on

Good job in solving the problem!

hey whats up,

i have the same problem..it just started happening like a week ago but i haven't done anything to my machine since i put my MAX V2 together over a year ago and it has always printed superbly..

my diagonal rod length is 269

please tell me how to re-calibrate the arm length like you have done...my parts aren't fitting as well...the ID and OD are both off plus the 20mm cube is off by .45 give or take 3 to 4 tenths but for each print it is equal as is yours...or should i say "yours was"

thanks,
jim

jstone33065 wrote:hey whats up,

i have the same problem..it just started happening like a week ago but i haven't done anything to my machine since i put my MAX V2 together over a year ago and it has always printed superbly..

my diagonal rod length is 269

please tell me how to re-calibrate the arm length like you have done...my parts aren't fitting as well...the ID and OD are both off plus the 20mm cube is off by .45 give or take 3 to 4 tenths but for each print it is equal as is yours...or should i say "yours was"

thanks,
jim

See this link: http://forum.seemecnc.com/viewtopic.php?f=54&t=1622 Towards the bottom it talks about Diagonal rod and it is in Configuration.h where you change those values and re-upload the firmware.
If you still have questions after reading the given link, please send another message.

Eaglezsoar,

i read thru the thread after clicking the link and with no luck. i wasnt able to find anything resembling configuration H.

maybe i over read the thread...i read thru both pages...

but i do want to thank you in advance for the help. i am currently trying to print out a couple different prints to figure out what the exact difference in size is down the the hundredth just to have exact numbers until the main problem is fixed plus i am going to print up a bearing case that was printed correctly before the problem started to see if the problem is across the board..

thanks again Eaglezsoar,

jim

jstone33065 wrote:Eaglezsoar,

i read thru the thread after clicking the link and with no luck. i wasnt able to find anything resembling configuration H.

maybe i over read the thread...i read thru both pages...

but i do want to thank you in advance for the help. i am currently trying to print out a couple different prints to figure out what the exact difference in size is down the the hundredth just to have exact numbers until the main problem is fixed plus i am going to print up a bearing case that was printed correctly before the problem started to see if the problem is across the board..

thanks again Eaglezsoar,

jim

config h is part of the firmware you installed with the arduino software.

Barry is correct, if you look at your repetier firmware folder, somewhere in there is a configuration.h
That is the file that contains all of the settings within your firmware.
If a value needs changing, you open up configuration.h with a text editor such as notepad, find what it is that needs changed, change it, save the file
then upload the firmware again using arduino software.

Eaglezsoar wrote:If a value needs changing, you open up configuration.h with a text editor such as notepad, find what it is that needs changed, change it, save the file
then upload the firmware again using arduino software.

Well, why not modifying the file with Arduino software in the first place, so that you can modify and load with a single software ....

I think it is easier, even though arduino is far from being the best code editor I've seen around....

enggmaug wrote:

Eaglezsoar wrote:If a value needs changing, you open up configuration.h with a text editor such as notepad, find what it is that needs changed, change it, save the file
then upload the firmware again using arduino software.

Well, why not modifying the file with Arduino software in the first place, so that you can modify and load with a single software ....

I think it is easier, even though arduino is far from being the best code editor I've seen around....

That works too.

oh...lol
thanks...i totally forgot when i first installed the printer and to upload the eeprom the whole configuration H script was actually an editable controller like a css layout file or a config file for a network site install but for the printer...wow i havent done websites in 5 years since i got sick and all that info just came rushing back in when Barry talked about arduino not being the best editor around and that made me think of dreamweaver...
thank you guys i will definitely try that...i did how ever figure out the perfect temp fix by adjusting the numbers to print a good fitting piece in the meantime and with that i can finish off the rest of my print by using the adjusted part to model the rest of parts around

thank you..