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CH35C0

anet a8 y belt tensioner

by CH35C0 Mar 3, 2017
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Is there a way that i get the .ipt?

I don't even know what that is... I made it with illustrator and tinkercad...

It work very nice. Thanks for sharing this idea.

that's another version but It looks really good!
nice work

made this and took gregs advice. Printed at 0.1 resolution and but for the screw i scaled down the X and Y to 95% and kept the Z 100% works perfect. only thing i wish for would be a recess area for the nut otherwise working perfectly on my printer

FOR THOSE WHO ARE HAVING SCREW/PLATE FIT ISSUES
scale down the X and Y to 95% and keep Z at 100% of the screw.
This will keep the thread spacing the same as the plate and will solve the fit issues.

I am in the process of printing a Moveo Robotic Arm with my Anet A8. I was having difficulty with attaining the quality I needed for the various holes. They just were not round enough and recessed nut holes were just not clean enough. I decided to try this y-belt tensioner and I am impressed with the results. Gear teeth are "sharp and crisp" and holes actually look round.
However, to attain a decent print of the tensioner bracket I needed rotate it so that it stood on its four legs. Using Cura I simply rotated the bracket and saved the gcode.
Thanks for the work you did creating this helpful upgrade.

I'm glad that it was useful for you.
That way of printing it is another one that works. I just printed it flat because at that moment I couldn't achieve nice prints if they were too tall.

I used this object as my first print on my new Anet A8, after 3 attempts I was successful, the 1st attempt didn't stick down, so I purchased some Borosilicate glass for my hot bed, washed it in soapy water and wiped with white vinegar before starting the print, 2nd print I released I would need supports, 3rd print was awesome, thank you! I wasn't sure of my print speeds though so went 35 mm/s on the print, 50 mm/s on the infill and 100 mm/s on the travel, it all worked out okay. (I then came back here to comment and noticed you had advised supports in your info)

really glad it works and that you're happy with it!

Really inaccurate at least for me, i had a really hard time with it. Anyways thanks for the base model, its fine now

Sorry to read that.
I've read that there are several versions of Anet A8 with variations such as materials for the frame or dimensions (my remix was done because from the one I got the plate and screw didn't fit mine). I'd recommend you to use a caliper to get the correct size and remix it if you like.
It seems it also depends on the kind of filament used and if the printed is well tuned or not, slicer settings, etc.

Plase, which type of THREAD is there used?
I want make my own screew and i dont know type and size...
Thank you
FOndra

as aforementioned in the description, the screw and plate are from a desiggn that is no longer available. I only designed the arms part, so I don't know its size. I'd recomend to modify the plate to your needs

Just a simple THANK YOU!
Nicely done...

Lil'Joe in Conroe

Really glad to see it worked!

sorry, as I don't own an A6 I cannot be sure...

Hi!

This definetly has been some awesome work. The 2018 model of the Anet A8 (or is it a clone?) with wooden parts, needs some adjustments to the roll holder. This part is too wide for the cheap A8s from eBay germany. The width needed for the wooden A8 is 18mm. All other measurements are 100% correct :-)

Depending on your time you want to spend, either drill a hole beside the other ones and use a file, mill the part or change the measurements. I'll print a corrected holder together with the X tensioner about TONIGHT :D

Cudos to the builder!

If its wooden, its likely a CTC copy of the A8, thus a clone. Any adjustments needed to work with that would be a good idea for a remix. Its a shame that CTC didn't keep its native Y belt tensioner as in last year's model. It also included an X tensioner. Everything else was pretty dodgy, but I like that they were trying to include things people were likely to add.

Watch my thing lol

https://www.thingiverse.com/thing:3128253

works flawlessly. I've got this printed lying on the side, too. So it won't break when pulling.

anet a8 y belt tensioner (revised for wooden anet a8)
by do4amf

NOOB Warning! DON'T print all the pieces together like I did! The bracket needs supports no matter what orientation you print it. The plate and screw, however, do not. I printed everything together with supports the first time and it added a big mess of supports in the threads of both the plate and the screw that ended up fusing to the print and ruining it. I then printed the plate and screw separately without supports and everything worked fine. The screw and plate are tight and you have to work them back and forth a bit to get it all the way through the first time but after that it's no problem. My only problem is that, since the idler bearing is mounted higher than the point where the screw contacts the frame, the tension from the belt pushes down on the whole assembly, forcing the lower two prongs out further than the upper two, making everything angle downward. Time to work on a fix or find a new style assembly. :(

depending on what slicer you use you can add supports to only specified objects.
This model is designed using the original anet a8 Y belt piece that came with my printer, so it works with mine. Maybe yours is a newer model and has some changes.

I printed almost everything in the files but why 3 screws when you need one? Just curious

Hi my Y Belt tensioner ist broken. Would someone from Germay print it for me. Payment via paypal?

There is a problem with screw, because probably after cuting hole in plate you scaled down screw in all 3 axis. You should do this only in 2 axis. Now it is possible to connect all parts, but you need to use force to do this.

As I have mentioned in the description and repeatedly in the comments, I only designed the arms part. The screw and plate are from a design that it's no longer available (from elfco). The only thing I did was make the screw longer (copying and pasting) for people that asked for it.
Most people have no issues so I'm guessing you need to tweak it a little before printing. In my case I only needed to screw and screw carefully a few times to make it work.

Hope it works

This tensioner works flawlessly. I did have a problem with the screw breaking when printed at 20% infill, but at 95% it fit well and was very sturdy.

Perfect, printed at 0.2mm layer height.
had to drill the holes up to fit my m3screws though (anet a8's roller for belt was m3 sized hole)

hi,
Many thanks for sharing your job.
Well...; very nice fitting on my machine. make a really great job and improve my print.
Thanks again
Kisscool
Chris

Hey, i wanted to print this part to keep my belt nice and tight.
Everything printed very well but the screw doesn't screw all the way into the plate. Ik printed 3 different sized screws and two different sized plates but they still don't fit right.
Can someone help me of do you have any tips,
Thanks.

what do you mean with "all the way into the plate"? like it was too hard to screw or that the screw is too long? if the former then it depends on your printer's tolerances, you need to screw and screw carefully a few times because it is a tight fit or change parameters.
If the later, that's not a problem

Hope it helps

(maybe a pic would help)

I mean the screw is too tight to screw normally ( it gets stuck when it almost reaches the end and than I cannot screw it any further.)
I printed the screw at 95% but it still does not screw all the way trough, I also added some oil but it doesn't help.
Here are some photos
Thanks and sorry for bad English I am from Belgium and 14 years old :)

I’d say that you only need to screw and screw slowly a couple of times, ‘cos it looks that it will fit to me.
I printed everything together and didn’t have any problem (only screw and unscrew a few times) and seeing that it did screw a little that’s what I’d try.

Hope it works

how ca i set the resolution in simplify3d ?

If you mean the layer height so that it is smoother or harsher you need to edit the process settings and in "layer" there's "Primary Layer Height".
the lower you go the smoother it will be and longer it will take to print, and the opposite when going higher.

hi, i mean the Resolution setting because in the Thing Details it is written, to set the Resolution to 0,1. It is possible thats the Primary Layer setting. i will test it today. thanks

yes, that's layer height. Higher resolution means lower layer height and more layers so it's smoother.
Think of a photo in a screen or printed. it's not the same with 72dpi (few big squares) or with 254dpi (lots of small ones).

yes yes i know, but i havent know it before thats the primary layer height is like the dpi on a normal printer. its printed fine. thanks

Glad to know.
We've all been there so no problem!

I printed these parts and all was fine apart from one thing

The main part of the tensioner didn't print correctly. It printed on its side and it started printing the upper part if the bracket the surface was a mess, uneven and not correctly formed.

How do I fix this during printing? I Added some photos. Thanks for the help

looks like you didn't use supports and that's why it got like that.
Try printing it again with supports ONLY on the arms.

Ah ok. I'm using cura. How do I add supports?

Sorry I'm still very new to all this

Thx

Don't worry. we've all been there.
For starters If you don't have the Support window visible you have to go to any other of the settings and click the gear that I've circled in the supports1 picture.
Then check Generate Support and tweak the settings.

Hope is useful

I made one of these, worked and fit great.

In the photo you have a front frame for you printer. Do you mind to share where i can get it?

Anet A8 Front Frame Brace
by Leo_N

Hey guys, can you please specify printing condition more detailed? I made them and tried to assemble, but I failed. The screw was too tight and then finally broken. I'm using PLA only. Please let me know how to adjust conditions.

I printed it in PET-G and at first had the same problem, so I printed just the screw a 2nd time, but with 75% infill to make it nice and sturdy. After trying to insert the screw, again too tight. But here's the trick:
rub some olive oil on the screw thread and use a lighter to heat it up (do not melt!) then screw it in a piece and back out, always until you feel it's getting too tight. Repeat until you can srew it in without too much friction.

The olive oil is only there to spread the heat from the lighter without harming the plastic (no problem for PET, but PLA reacts badly with non-plant oil). After you're done, clean of the oil to avoid a sticky smelly screw and thread.

This trick helps with all screws and threads, they are just about perfect after the procedure.

Hi, as said in the message below:
"Hi and welcome! I printed the screw and the plate flat down and with a high resolution (0.1) with 4 or 5 wall perimeters (around 2mm in cura I believe) for strength without supports and the arms as in the picture with supports (this can be done with a lower resolution, such as 0.2)"
maybe your printed isn't well callibrated or you should check your tolerances.
Mine is also PLA and it's been over a year and still works great
The screw is a tight fit because its original designer nade it that way, but if you screw and unscrew a few times it should work fine, but some people added lube to it.

be sure to use high resolution for screw and plate and no supports

I am pretty new to the game and I have a question that has been bugging me. Should I print these as they lie in Cura and the image files? I know about adding supports, but is that the best for the screw? Maybe printed this way is best for strength. Also the threaded plate, is shown on its side.

Hi and welcome! I printed the screw and the plate flat down and with a high resolution (0.1) with 4 or 5 wall perimeters (around 2mm in cura I believe) for strength without supports and the arms as in the picture with supports (this can be done with a lower resolution, such as 0.2)

Hello ! First thank you for the design, im new in 3D printing and i am amazed by the posibility of printing threaded holes/screws. I just printed it and it work perfectly, however when i tried to screw, it worked, but it was extremly hard, and the screw unfortunaltely broke. Any advice ? Some printing parameters to change ? Some lubricant needed ? Thank you !

Welcome to 3d printing. You’ll be hooked in no time. I think he best options are to increase the walls perimeter count (I think I used 4or5) and the infill (I used 20% but at 50% it should be more than enough). With that it should be strong enough for what it’s meant to do. I don’t know about lubricants but they should work. Maybe would damage the printing depending of what filament you’re using.
Please let me know if you’ve still got issues.

This was one of the first things I printed when I got my A8 back in Aug - Sept. Been running strong, however I did just observe one issue that may be causing my prints to come out a bit jittery. The holes where the 3mm bolt goes through to hold the idler pulley has gotten a bit loose. I can actually move the idler pully a little bit by pushing the screw-head and this can't be good for the outcome of my prints. It's just from wear-and-tear - the PLA has stretched a bit. (countless hours spent watching beavis and butthead as a child is making me want to laugh at everything i just said... loose stretched holes and screw heads and, oh nevermind...)

I think maybe 100% infill with a metal washer melted into each side would keep this from happening. I'm going to print up another one of these and try that out.

maybe just a few more perimeter walls would suffice, or use PLA+ or another material as ABS, nylon, PETG. I printed it with pla a year ago and it still works fine (don't know how long will it last) but I think I used 5 walls or 2mm with the original 0.4nozzle.
The metal washer insert might be a good idea. Let me know how well it fares.

Really impressed printed this on it's side as in model photo with support.

Came out beautifully.

Thank you for your work.

Grey PLA (bed 60, head 210 seemed to need the heat)

glad you liked it!

Printed and all worked great. However one observation. Would you be able to make the screw about a 1/3 longer. I don’t have a huge amount of play on the belt and it’s almost screwed in all the way. The other version has a much longer screw. Otherwise much better idea to use a plate like you have.

just uploaded a larger screw. Hope it works

OK Im afraid it seems you have increased the size of the whole screw so the thread is much bigger now so won't fit in the plate. I only meant for you to increase the length of the thread so it had more capacity. Perhaps you could do another but just increase the length of the thread. Having said that the actually thumb wheel being much larger is easier to turn, your is quite small so can hurt the fingers to turn.

I don't know why it exported wrong... for peace of mind I've done it again (the thumb wheel is the same as the original one, and as mentioned in the description, the plate and screw design are not mine, but I also agree that it is not the best design, maybe I'll make another one some day...)
I think the thread is long enough now

Thanks, worked perfectly this time :-)

Glad to read that.
I don't know what I did wrong to export it that big, but next time I'll double an triple check before uploading XD.

Top Man, thanks very much, ill print tonight once I have fitted my Anicubic Ultrabase and tightened the Grub screws that came loose on the extruder last night !!!!!

Printed once (plate without supports and screw1.stl), but screw wouldn't screw in the plate.
Printed screw2.stl, and plate with supports, and it worked! I had to screw it in and out many times, slowly, until it went through all the way. Some bruised skin... but atleast my Y-Belt is now perfect tension :)

I printed it the first time with the bearing holder with a vertical orientation. it worked for several days but snapped when i pulled the y belt too hard. i also realize that this is probably the weakest way to print because of layer separation. I reprinted horizontally but the screw would not work....very sloppy print probably due to untensioned y belt because i had to use the stock holder. ...anyway thanks for the model works great now. Printed @ 50 ms, PLA 190/60 with supports, .1 layer height for the screw and plate, 50% infil, .2 mm layer height for bracket 100% infill

prints are now a lot better

sorry to read that.
I've been using mine for almost a year and no problem. It must be due to the untensioned belt or underextrusion maybe.
I printed the screw and the plate vertically with supports and the arms laying flat (you can see the lines in the pics).
Have you tried to add more perimeter shells? I believe I used 5.

Yeah model works fine. I just printed it the wrong orientation. I new to 3d printing and shouldn't have expected it to hold tension with the force apply to the layers that bond. I ended up printing horizontally and it worked for the bracket. But new screw and plate had very dirty threads. So I reused the older plate and screw and I'm up and running. Problem definitely came from under tensioned belt. I would have tried to tighten it with the original clamps but printer is bolted down.
Thanks again

Comments deleted.

glad to read that!

As a workaround (bolt/screw not fitting in plate) i just cut a M10 thread in/on both parts.
Not nice but i didn't want to print the parts a third time and do experiments with scaling.

Thanx for your work anyway!

as said in the description, the plate and screw designs are not mine. this is a remix. I did the arms and used the plate and screw from the original which arms didn't fit my anet. In my case it worked at first try screwing and unscrewing a couple times.
Sorry it didn't work for you, but nice fix

Polecam . Działa super

I had issues with the screw and plate as well.... printed both 2 times.
Finally I figured out it helped to print the plate standing. no idea why it helped but its maybe a solution .

I printed it flat and (despite being tight at first) it was perfect.
at that moment, printing it standing would have been worse.

Glad it worked!

Thank you for this post. It really works and fits well on my A8. I no longer have a tension problem.

happy to read that!

Printed it several Times with differten settings, even shrinkt the Screw by 10%. Won't work. Can't be the Printer, must be the design. The other Tensioner came out fine the first Time.
Also the screw is not very stabel. Top broke away with 20, 50 and 100% infill.

sorry to read that, but I printed mine almost a year ago and it worked from the beginning, so my guess is that you did something wrong.
many other people has been succesful (many other not).
And the screw design (as I've been repeating over and over) is not mine. My guess about it breaking would be bad filament, wrong temperature/layer or not enough walls.

I made it too, but how come that the top layer is open and not fillet

I don't get what you mean by "open".
If you're talking about the arms design, I made it really fast in tinkercad and prioritised that everything worked.
If you're talking about the screw and/or plate, as I said in the details those are not mine.

Works perfectly without touching the setup ! Nice design, if there was one thing to improve I would make the screw a little bit shorter, no need for that much length

glad it worked for you!
I think if it was shorter it would make it difficult to turn....

I made one but the screw doesn't fit with the plate

Many people had the same issue.
I printed it at the same time and it worked. A bit tight at the begining but screw nd unscrew it a few times and it will work.
If not try with different settings.

Little tabs broke on me under tension after a couple weeks.

Reprinting at 100% infill to see if it happens again.

sorry to read that.
I haven't had any problem so far.
have you tried printing it in any other direction?

Do the vibrations loosen it over time?

I don't think they do. I've only re-tightened it when I've moved the printer and had to adjust it everywhere

this screws does not fit holes, broke both of them hm!

the screw and plate design are not mine (I did design the support) but it did work for me at the first try. many other people also got it to work. I guess there's something wrong with your callibration, printer or how you printed.
I used PLA and for over 8 months it's still working.

Try making some adjustments to infill for example.

I have reprinted the screw with 0.9 scale, now its ok!

Made for my Anet A8. Just need a bit of sanding into the screw and thread. Perfect !!

that is a problem for lots of people. Guess its due to the original designer (I used his screw system and made the arms myself).
I also had to screw and unscrew a few times to sand it but it works great.
Glad it worked!

thanks, dude, this is absolutely amazing. my y belt was loose AF and now it sounds like a guitar when I tap it... and I'm going to need a front brace too, that front acrylic plate is bending like a yoga master

I'm sure this has been figured out, but i just reamed the inside of the plate screw threads with an xacto knife and all fit well as printed. Thank you for the design.

I just screwed in and out mine a few times and it was good to go, but yours looks like a nice way too

I'm at 90% scale now and the screw still does not fit into the plate.

What's curious however, is the fact that many have no issues with the print, and many do have issues. Why is that?

maybe it has something to do with the material used. I used PLA and printed everything together.
From what I've read, ABS shrinks so maybe that's your problem.
If not maybe the settings of the printer.
All I can say is that it fitted me perfectly printed together in PLA.

My printer is pretty well tuned. I printed this in ABS and this material does in fact shrink, so I think you are correct about shrinkage (with a nod to Jerry Seinfeld).

It would be very interesting to take a poll of everyone here. What material and printer specs were used? Doing this might reveal why some have problems with this piece and some don't. In fact, it should be standard practice to list your settings for the model.

that would be the best for sure.
I think a few used petg and someone nylon. Those are what I want to try sometime (not a big fan of ABS for the troubles I've read it gives.
Maybe PLA+ if I find it locally.

Mine is quite tuned (I'll have to change the belts for reinforced ones but the rest is almost perfect).

my settings are as I said, 0,1z, 20% fast hexacomb infill, supports for the tensioner printed as in the 3d image

Printed the Screw @98% Scale, still noch fitting the Plate printed in 100%. :-( Any recommendations?

I printed everything together and it worked for me at the first attempt.
That's the only thing I can think of, sorry

Printed the "original" Tensioner, worked out fine! Hmmmmmmm... :(

Same here. Print twice this version but the screw does not fit the plate hole. I printed this version (https://www.thingiverse.com/thing:2588902) which have a thinner screw and it worked

Anet A8 Y Belt Tensioner
by vezzfra

what can I say guys, I remixed one that is no longer available made by elfco (used his plate and screw which I had already printed together) and my arms because his didn't fit. It's a tight fit, you need to screw and unscrew a few times, if not maybe there's some setting wrong, but In a year I've been using it I hadn't had a problem, and I was a total newbie a year ago..

I tried forcing to screw and unscrew with this model and 20% of infill and the screw broke ^^ I retried with 100% infill did not broke but did not success to screw completely (even forcing alot).

I also had to force to screw and unscrew with the model in the link (infill 100%) I gave but there was lot less resistance.

This information is just for people who have the same problem than me :)

yeah, I mean no ill will either. Just saying that that part is not mine (remix) and that I was lucky to get it right at my first attempt.
glad the other one works for you! ;)

Any chance you could make the end of the bolt (thumb and finger side) a bit thicker where it mates with the screw thread? Even on 100% in fill after a few turns to "prime" the hole after it was first printed, the top of the screw snapped off. Maybe a thick collar or something? If I can remix this when I get time I will :) Other than that, awesome part. Thank you!

try printing the screw with 4 walls an 20%, my screw is mega tough

I've uploaded a new screw. Hope it works for you. In my case the first one was perfect and is still working.

Just to let you know, if you stand the pulley bracket on its legs and use a Raft with 85% infill it sticks really well and can be printed without supports. (y_belt_tensioner)

That is so awesome (and quick), thank you so much! I think the tolerances on my printer may be smaller as I really had to force the thread through the hole and it was at that point it broke. I printed screw2 and the first screw and both work fine now the bar part is threaded. Thanks once again :)

thanks. I didn't try but it would be better for wasting less filament.
your're welcome. I didn't have any trouble with the original one, but as you said, it could be the tolerances.

What frame brace did you use?

Anet A8 Front Frame Brace
by Leo_N

you're welcome

How should I print the actual tensioner piece? I printed it in the orientation as it is in the stl file that was provided but as I was removing the supports it came into 2 pieces cleanly. Idk if It was designed that way or what. Please help. The screw and plate work awesome! No screw scaling needed!

Sorry to read that!
I printed it as in the picture, with its face down to the bed and had no problem. Maybe you're using too much support infill, try lowering it (I think I used about 15% or so).

Okay, thanks! I will try it out hopefully later today.

I think my problem was there was too much moisture in my filament I was using. I recently switched to a new roll of filament and completed my dry box. The difference is unreal.

happy to read that! I'll have to make one myself too. Thankfully I've not had that issue (yet) but better to be safe than sorry as is said..

I still haven't purchased a 3d printer so I wouldn't know about this, but why do you need a belt tensioner? And how do you know if the tension is correct?

If you've seen the assembly videos you'll see that the belts need to be quite tensed. If they're not or they are too much the printer wont move correctly and the print will fail. By tensing the belts manually under the frame it can be quite difficult and tedious so this helps doing it without having to move the printer or even reassemble it.

Hope it helps you.

I have printed 3 Y belt tensioners, This will be the fourth... (I am waiting for my glass enforced belts and a couple other things before I rip apart my print bed)... As the old saying goes.... "I Think We Have A Winner"...

so far it works for me so I hope it does for you too.

I printed the screw and plate a few times now, on the last print, I scaled the screw to 98% on the X and Y, but it was still too much tolerance for the way my printer is printing. Going to try 95% next, hopefully that will be able to turn in the plate.

Edit: Nope, 95 was no good either.

I printed the screw with matter control with a layer height of .1 mm and 20% infill with generate raft and support material both on. It printed successfully With no scaling. (I printed the screw sideways like it is in the stl file) I used the blue clipper tools that I got with the printer to clear away the support material. I did the exact same thing to the plate. Hopefully this helps you out!

sorry to read that.
When I printed it I didn't have to scale anything, just put it all together on the bed and it came out fine (only needed to screw and unscrew a few times to loosen it)

Ya, I got to try and scale it down cause its not able to turn in the threads. Too tight on the tolerances or maybe the threads are messed up, not sure. The first one I did broke off in the plate so hoping when I get a chance to print it again, 90% will work, but so far no luck.

great work! this is the first mode for my Anet a8.
thanks

glad you like it!
I just remixed it because the other one didn't work for me due to different dimmensions.

In what position did you print the tensioner body? My print choked when it got to the upper arms

I printed it rotated 90º so that the "faces" would be on top and bottom, with supports between arms and a honeycomb infill if I remember

Excellent , thanks, nice design , works well . Had to scale the thread down slightly for a nice fit , but that was to be expected with thread tolerances & various printer settings & different filament materials .

Glad it worked for you! I didn't have to scale it when printing at 0.1, only had to screw in and out completely a few times to make it smooth
I used PLA but maybe with ABS or nylon would be more resistant

I printed it in ABS & I always find ABS holes seem to shrink 8-10% , so i was ex­pecting to have to scale it a little ,but it all worked nice .
I just modded my A8 to take a 200 x 300 hotbed , which is working well.

looks great! what did you do to enlarge it? did you modify firmware or only hardware?

Yes, it was fairly involved , Had to mod everything . Firmware needed changing for all the new parameters for bed & axis movement , Auto bed leveling co-ordinates & lots of mods to the startup G code, & then tune it all. Hardware took a month to build & accumulate all the necessary parts , like the larger bed , new bigger power supply , mosfets , wiring etc, & the hardware . Needed new M8 joining rods , linear shafts & then had to design & print parts like a frame extension , cable duct , & also fabricate a new aluminium table base etc.
Once i had everything done it only took an evening to convert it all, but many hours of prep . Happy with the result , much more versatile machine now but a fairly complex upgrade .

that sure is a lot of work but it's worth it! now you can print larger objects without having to slice and glue them so much and that great!!
really..good job!

Yep , already printed some 300mm long parts , so worth tbe effort.☺

I typical newbie question...... Anet A8 - hotbed plate 220 x220 on the diagonal it should fit . Cura scales it down to around 176mm and I have not found a way to re-scale it and turn it 45 degrees on the diagonal. Slicr Also seems to start it at 176 and scalling x125 give more or less the right dimensions - in theory... but its will cut off on one end or the other ! So how do I get to print it fit the frame?

I'm a newbie too so don't worry. what frame are you trying to print? the same one I have in my pictures? if you open it in cura it says that it's been scaled to 74%. click on the object and go to the SCALE button on the left and then insteadd of the 74,41% that you should have put 100%. Then click the button under it and rotate 45º. after that move it manually (auto center doesn't work for this model so don't even bother trying it) and done.

Hope it helps

Can you give 123 file or make arms 6.7 mm thick instead of 7.7? With about 10.2mm distance between them?

I can't give that file since I made it using illustrator and tinkercad...
I don't know if this is what you asked for, but I made it using the measurements you gave me.
https://we.tl/CiiRVaYJD0