# Specific 3D Printers, Scanners, & Hardware > QiDi 3D Printer Forum >  Scaling problem with slicer software

## TFilbert

First post!   I am new to 3d printing at home, My wife bought me an I-mate S for Christmas, and I'm using the QIDI slicer software that came with the printer.  Upon installation of the slicer software, I was immediately prompted to download the newest version, which I think is 5.6.12?  My problem:The QIDI slicer software is not properly scaling my parts.  I intend to use this to print precision tolerance parts for prototyping purposes prior to having parts milled or laser cut out of steel.   So If I model a part to the thousandth of an inch, I need the print to come out to the thousandth of an inch.To test print and learn the software, I created a 2" diameter x 7" tall cylinder with .125" wall thickness.   The part was modeled in AutoCAD "Inventor" software, since that's what I have available at work.   I exported the part in several formats not being sure what the slicer software will be happy with.     When I open the part in the QIDI slicer, each file type opened up at a different size.  None seemed to keep the original dimensions.    I noticed that the part loaded with metric dimensions and not inches.  I found a button to click that said "Scale inches to MM"   When I clicked that, the part exploded and went from way too small to way too big.   All the manuals and instructions are very poorly translated to English and offer very little help.What is the secret to modeling a precise part, and opening it in the slicer software so that it maintains the precise dimensions?  Picture 1 shows how the part imports at different sizes based on file type.   one is .stl  the other is "3d part file"  (I can't see the extension type)   Both file types were exported from Inventor from the same part model.Picture 2 shows how the dimensions seem random.  it says 5mm x 5mm x 18.08mm   (Keep in mind, it was modeled to be a 2" diameter, 7" tall cylinder.)Picture 3 shows what happens when I click "Scale inches to mm" and it blows up so big it wont fit in the print space.What gives!?  How do I print exactly the size I modeled without having to do guess n check work?!

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## TFilbert

Nobody has any input?   Am I in unchartered territory?

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## fred_dot_u

Even though I have a QIDI X-Max, I don't use their slicer, which I understand is based on Cura's program. For 3D printing, one uses .STL format files, which are unit-less, but defaults to millimeter. It's always safer to build your models in millimeters.

7" is 177.8 mm, which is "close" to the 18.08 number you've referenced but not close enough for me to think it's a decimal point error. Same thing with your 5 mm reference, as 2" is 50.8 mm, although that's somewhat closer to a decimal point shift.

Consider to attach your STL file for others (including myself) to examine, process and expound.

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## TFilbert

Thanks for the input.  It could be the wall thickness of the bottom of the cylinder, which I think I modeled at 1/8"   7.125 = 180.975mm  But, What I don't understand is why the shift at all in the decimal?   The dimensions in the photograph are the dimensions the part imported with, which shows mm, not cm.   If it was in cm I would have been less confused.   And I didn't understand what was happening when I "scaled inches to mm" and the part exploded in size.  What slicer program should I look into?  I wasn't sure if I could use any slicer, or if I need to use theirs because it's modeled for the print bed/space of their printer.Attached is the .stl

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## fred_dot_u

Thanks for posting the file. The cylinder imports as 5.08 mm diameter, off by a factor of ten. This points to the creation/export aspect of the program. It also presents as 181 mm tall, but that's the overall height/length. This also points to the creation/export. I'm unfamiliar with Inventor and therefore cannot offer hints.

I don't think it's your slicer, as three programs I've used to check the dimensions all agree. Is a step file (.STP) an option for your export? I suspect the results could be the same. Perhaps there's a settings reference within the program to make appropriate adjustments?

On another note (G-Flat, F-Sharp, etc.), you'll be surprised at the work involved to get the tolerances you've described in your post. Layer thickness on a filament printer can get as low as 0.100 mm. My math says 1 mm = 40 thousands approximately, 1/10 mm comes to about four thousandths. That's in the Z-direction, X and Y get a lot looser, depending on the tuning of the machine. Add elephant's foot to the equation, or maybe a bit of post processing and you'll have your hands full.

Even in resin printers, with a 0.050 layer capability (default in most cases), the X/Y is dependent on tuning the exposures for a specific resin. It appears that you have sufficient motivation to pursue tuning to the point of meeting your requirements, and I applaud that attitude, if true.

I purchased a license for Simplify3D and wish I had pursued other options in my slicer choice, but it's been working for me. I'm transitioning to PrusaSlicer lately, as they've improved the interface and ease of use by a huge factor. Their instructional videos are fast paced, but quite clear and easy to understand. You aren't so deep into the muck with your existing slicer that you'd have to re-learn too much. Getting a printer profile tuned for your machine, if it's not available, would present the bigger challenge. 

I'd love to have a profile in PrusaSlicer for my BCN3D Sigma R16 IDEX, especially with the multi-color support in PrusaSlicer as it is now.

Spend a couple dollars for Maker's Muse Clearance and Tolerance test model which will allow you to determine (and improve?) your printers capability, specifically in the X/Y direction.

If you are experienced with Inventor, it's a bit of a stretch to move to another creation program. I understand that the workflow for Inventor and SolidWorks is quite different from that for Onshape, Fusion360, etc. If you have a logical mind between your ears and are comfortable with a bit of coding, check out OpenSCAD. It's a text programming package that works great parametrically and is virtually made for things like your model. Plus, it's free and multi-platform

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## TFilbert

Well, I agree, I'm being ambitious when I say .001" tolerance.   I think I'd be happy with .01 tolerance honestly.  Possibly even .05    I'm not going to be prototyping engine pieces.  Mostly mounting brackets and whatnot.  

I have experience with solidworks and inventor, but I'm not a pro at either one.  I can do some basic stuff, but I'm not at the level of being able to model intricate, complicated parts.   I would like to find a solid 3d modeling program that's similar to inventor or solidworks for use at home, that's not super expensive.  Solidworks was what I used at school, and autodesk inventor is what my employer has available.   

I'm new to 3d printing at home.  Previously I would just email the stl file to a tech center and they would print it for me.    I will have to learn a lot about tuning.  I didn't realize there were things you could do to tune/adjust the tolerance capability of the printer.   I'm more familiar with things like encoders/servo motors which there's not really any "tuning" to do with them.   you install the servo/encoder into the robot joint and plug it into the wire harness.

I'd upload the step file, but it's rejecting as an invalid file type

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## curious aardvark

try exporting the model using millimetres. 
Inventor will do that.

Almost no current software is particularly happy with inches.
 Pretty much only used in the united states and most software is written elsewhere. 

Some slicers do offer the ability to change the default settings to inches, but then it'll probably just confuse the printer as that only works in millimetres.

You can keep mucking about with inches, but you'll find life a lot easier if you just use millimetres for 3d printing.

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## fred_dot_u

For not-super-expensive, you can't go wrong the hobbyist version of Fusion 360. It's a one year subscription, free although it has to be renewed each year. There's tons of features in the free version and at least that many tons of tutorials how to use it. Product Design Online is a YouTube creator with a great series of tutorials, easy to follow, really clear to understand.

With respect to the difficulty with the file, usually turning it into a zip file will let it squeak by the filtes.

I agree with the curious aardvark about doing the work in millimeters. The math is so much easier and the programs behave far better.

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## TFilbert

Thanks.  I'll look into the fusion 360.I created a new part (something to hopefully print a little faster and use less material.  a 1" square cube to do some test printing with.   I created it in inches, then converted the document to metric.   I'll give these a try tonight when I get home.

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## TFilbert

inches cube

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## fred_dot_u

Both of the cubes are 1/10th the "real" size. Instead of 25.4 mm, both are 2.54 mm. Something is amiss in the software, I believe.

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## TFilbert

That's so strange.   I've made 3d parts before, exported a dxf file and had stuff laser cut out of steel and the shop who received the dxf had no problem at all with scaling being off by a factor of 10.   

I'll ask a co-worker who has a lot more experience with autodesk inventor.

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## TFilbert

Alright...How about this file?    --I found an "options" button in the pop up window to save the export stp file.  In the options, the units were set to centimeters.  I changed that to millimeters

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## fred_dot_u

that one is 2.54 cm / 25.4 mm / one inch!!!

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## TFilbert

So weird, but glad I figured it out.   Looks like I can do my modeling in inches, change the units in document settings to mm, then make sure that the units of the stl file is set to mm.

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## fred_dot_u

STL files are unit-less, usually interpreted by slicers and the like as millimeters. What you did in the last file resolved the confusion.

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## TFilbert

Printed my cube last night.   Overall, I'm pretty happy with how it turned out.   I used minimal fill inside the cube.   X and Y axis was within .005 of nominal, one was higher, the other was lower.  Z axis was off by about .040"

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## curious aardvark

dxf files are NOT solid 3d models. 
they are 2 dimensional vector graphics. 

So most likely using a different conversion algorithm to a proper 3d model. 

you can usually 'fix' z-axis issues by making sure that the print layer height is an actual factor of the actual height of the model. 

I use 0.25mm layer height a lot if I'm making something that uses whole MM. 

If the model height is not divisible exactly by the layer height then the slicer has to fudge one or  more of the layers to try and get the correct height. 

It does depend on how critical a few hundredths of a mm are to the design. 

It's also worth bearing in mind for x& y as well.

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## TFilbert

Thanks.  I am aware of what .dxf files are for.   I did not say I was trying to 3d print a .dxf   I said that I have exported .dxf files from the same software to have things laser cut out of steel plate, and that there were no scaling problems with those parts.  But thanks for your input, especially about the filament sizing and how it can affect the finished dimensions/tolerances of the printed part.   That is something I had not considered yet.      (That the printer can only print a whole filament diameter, and has to + or - a layer if the dimensions of the part are not a whole factor of the filament diameter)

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## fred_dot_u

Not a multiple of filament diameter, a multiple of layer height. I have both 2.85 mm and 1.75 mm filament printers, but use 0.20 mm layer heights, rarely 0.10 mm layer heights. Those are the numbers for managing a "clean" slice.

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## TFilbert

That's what I meant.  When I said "filament diameter'  I didn't mean the size of the material on the spool, I meant the diameter of the thread of melted plastic that comes out of the extruder.     Still working on proper vocabulary...

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