I've had a lot of problems doing things like this, and the only way I was successful was by getting a digital protractor and using that to set up my miter saw. Although I was getting close with normal speed square, etc. it wasn't really truly 30 degrees or 45 degrees or whatever, it was always off a bit. But with the digital protractor, you can set up your miter saw perfectly, and check each cut, and if you have to adjust the cut you can easily do that on a belt sander with just a tiny amount of effort. It's really made things much easier for me.
That one sucks long term. The body is plastic. The electronics stopped working after 8 months.
Recently got this one: GemRed 82305 2in1 Angle Finder Ruler (200mm) https://www.amazon.com/dp/B00W395R5E Works better, haven't had it long enough to know how long it will last. I wish one side was thicker like the General Tools version above. But I have recently been using it a lot and finding it to be accurate.
This has been sitting on my tool buy list for a while, but I've yet to have a practical reason to own one.
Wedgie sled plus a cheap digital protractor to set any angle. (E.g. https://www.amazon.com/dp/B00W395R5E/ .)
Second this. Make sure the frame is square. These are the angles I would try to get as close as possible to 90 degree. I used a digital angle finder but you could do a carpenter square too.
Another major important thing is to get the X gantry to have the same measurements on both of its sides compared to the base on the printer. There's lots of tutorials about this and you can use a digital caliper to get the distance as close as possible to be the same on both sides (see second image). This will take some time to get right because you have to continually take out the gantry, adjust, put it back and test again. But once you get it right you might not need to touch it for quite some time.
GemRed 82305 Digital Angle Finder Protractor (Stainless steel, 7inch/200mm) https://www.amazon.com/dp/B00W395R5E/ref=cm_sw_r_apan_glt_i_CW9155FR31PJRGP56MYM?_encoding=UTF8&psc=1
Worth every penny.
Thanks for the write up. I think I’ll go with this one
GemRed 82305 Digital Angle Finder Protractor (Stainless steel, 7inch/200mm) https://www.amazon.com/dp/B00W395R5E/ref=cm_sw_r_cp_api_glt_fabc_X4SRZR4VXT1HWG4W6CPZ?_encoding=UTF8&psc=1
GemRed Digital Angle Finder Protractor (Stainless steel, 7inch/200mm) https://www.amazon.com/dp/B00W395R5E/ref=cm_sw_r_cp_api_i_EzHMFb1W42ANB
Similar thing. Get an angle gauge.
GemRed 82305 Digital Angle Finder 7-Inch Protractor (200mm Stainless Steel Angle Finder Ruler) https://www.amazon.com/dp/B00W395R5E/ref=cm_sw_r_cp_api_9UY6BbXHHE7ZT
> https://www.amazon.com/dp/B00W395R5E
Good to know... I may pick one of these up as a replacement if I have issues with mine. Thanks!