Uneven Scaling Issue

[SlartiBartFast]

Hopefully, someone can point me to an existing post on this. I'm surprised that I can't find anything.

On Rostock V2, I'm getting great prints. Everything is fine, except...
- all parts are scaled up in the XY plane (the bed) by 5%
- all parts are scaled up in the Z direction (vertical height) by 29%

It took me a while to figure this out. I'm using Pro/Engineer to make PLA parts. I'm slicing with Cura. There are no dimensional issues with the STL files.
I wonder if other people have seen this? It may be that printing out single items you might not even notice it. Obviously, I'd like to have more accurate parts, but the stretching in the Z is a particular problem. I'm making larger parts that I'm having to print individually and in different axes. When I try and put them together, there are major mis-matches. It was only when I printed out a simple cube that I realized that the problem is confined to the machine setup and not my process.

Update:
Good news:) I made a mistake with my maths. Z scaling is ~15%. Not 29%. However, my parts still don't go together:(
No responses yet, so I've added some pics to try and stimulate debate/ridicule. I've tried using Slic3r: same deal. I've tried using different layer heights: same deal.

non-constant scaling is super evident when component parts are built in different directions. The central 2 part go fine together since they were built in the same direction. The outer (wings) were built at 90 deg and therefore don't fit:(

these are the 25mm thingies that I'm building to evaluate different parameters

Any ideas anyone?
Thanks
Colin

[Eaglezsoar]

Hi Colin! Welcome to the Forum.
I apologize that no one has responded.
The best way to get an answer is to search the forum and this is best done by typing the following into your browser:

site:forum.seemecnc.com scaling

This will find every occurrence of the word scaling and there are quite a few.
One of the results from the search should be able to help you.
Again welcome to the forum and hopefully your future posts will be answered much quicker.

[JFettig]

Are your steps per mm correct? Then delta arm length and horizontal radius?

[SlartiBartFast]

You were right, JFettig. Thanks! I eventually figured this out through a process of elimination. I hadn't considered this initially because it's not something I ever messed with and changing it is not part of the assembly instructions.
Dimensions are fine now. Interesting that the machine can be setup and calibrated so that everything appears to work fine but the steps/mm is totally wrong. Because of the delta arm geometry, actual dimensions are all off but they get stretched in the Z dimension. I made some spherical xmas tree ornaments that ended up being egg shaped:)

Incidentally, JFettig, aren't you the CEO at Whirlpool?

[JFettig]

lol nope, not me, I am the CEO of JFettig Machines LLC

With the proper steps/mm(80 I think it is), you will get 1:1 scaling in Z direction and 1:1 scaling in x and y but if you're off a specific length in x and y, your delta arm can be lengthened or shortened to correct that. I was always small by .020" no matter what size until I figured that one out.