Hello, I'm trying to build a 3D printer for BIo-Medical application.

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(Athul S Nair) #1

Hello,
I’m trying to build a 3D printer for BIo-Medical application. It should be precise. Whats’ you guys opinion about using something like this for X & Y axes https://www.aliexpress.com/item/Free-Shipping-oem-low-price-40mm-wide-linear-guide-rail-with-motor-and-ball-screw-for/32607755602.html?spm=2114.search0604.3.8.2ba070f976eHAY&s=p&ws_ab_test=searchweb0_0,searchweb201602_4_10065_10068_10059_10696_100031_5017615_10084_10083_10103_451_5017515_452_10618_10307_5017415_5017715,searchweb201603_54,ppcSwitch_2&algo_expid=3220a35f-ec02-4854-862b-b1f201b8ab47-4&algo_pvid=3220a35f-ec02-4854-862b-b1f201b8ab47&priceBeautifyAB=0
along with closed loop stepper motors and drivers
https://www.omc-stepperonline.com/closed-loop-stepper-motor/
https://www.omc-stepperonline.com/closed-loop-stepper-driver/closed-loop-stepper-driver-0-70a-24-48vdc-for-nema-17-23-24-stepper-motor-cl57t.html

Also I need a help selecting linear guide way too.

https://www.hiwin.com/linear-guideways.html

My build volume is 400x300x250

My plan is, Similar to Ultimaker, bed mounted on Z axis. X axis will carry th Extuder and X axis mounted on Y axis

Similar to this, but not CoreXY belt arrangement

d55174e78c008c6ab4a48c5167881837.jpeg

(Ulrich Baer) #2

50µm per 300mm should be ok, but can’t find a rating for the linear rails. (25µm per step)

(Athul S Nair) #3

@Ulrich_Baer 50µm is for full step right ?? for 10 mm lead ball screw. But this decreases with micro stepping?? What I’m worried about the Ball screw mechanism is Motor overheating.

(Ulrich Baer) #4

50µm/300mm is the accuracy class C7 of the ball screw. The <500mm lead is 5mm with 200steps so you get 25µm full step or 50µm for the 10mm lead.
Motor overheating only happens if your load is too high or your speed.

(Ryan Carlyle) #5

Stepper heating with typical constant-current driver chips in 3D printers is totally independent of motor load. At low speeds there’s no difference in heat generation. They will run cooler the faster they spin.

(Ulrich Baer) #6

@Ryan_Carlyle intresting, so they always use the same amount of energy independend from load? … wonder why some on my printer are warm and some are not, any idea? Maybe differnce between holding current and moving.

(Ryan Carlyle) #7

@Ulrich_Baer more advanced drivers may have standstill current reduction for idle motors. That reduces heating a lot.

The motors consume more energy from the PSU under load, but that’s direct from electrical to mechanical. At standstill the motor consumes P = I ^2 * R with all power going to heat. (Ignoring high frequency driver switching hysteresis losses which should be small on 12/24v systems at typical driver chopping frequencies.) The driver might be running at 10% duty cycle so the PSU only supplies 10% of what you would think the motor is drawing from the current and supply voltage. Then when running under forward-driving load, the back-emf voltage waveform opposes the PSU voltage and the driver uses a higher duty cycle (up to 100%) to get current up against the back-emf… and the PSU thus supplies more power. But that power goes to motion not heat.

(Athul S Nair) #8

@Ulrich_Baer
Also any recommendations for linear guide way. https://www.aliexpress.com/item/HIWIN-MGN12-Linear-Guide-Rail-400mm-500mm-300m-200mm-150mm-with-MGN12H-MGN12C-Slide-Block-for/32961904736.html?spm=2114.search0104.3.74.418a1a1bf9RrPy&ws_ab_test=searchweb0_0,searchweb201602_7_10065_10068_319_10059_10884_317_10887_10696_321_322_10084_453_10083_454_10103_10618_10307_537_536_10902,searchweb201603_59,ppcSwitch_0&algo_expid=4f942dec-bb21-4186-9380-a2ee9304a4f9-10&algo_pvid=4f942dec-bb21-4186-9380-a2ee9304a4f9

MGN12C or MGN12H

(Ulrich Baer) #9

depending on your mechanism the outer (static) rails can be HG20 - with a quad ball guide. I also like the new CG Series. There are also some nice linear systems from IGUS (drylin) - very lightweight and maintanance free.


(Mano Biletsky (Open MAKER)) #10

The frame of this printer is sturdy. I can only comment on the printer itself though.

It is precise and once setup, it is ready to print without having to calibrate anything.

Though…

When the printer is powered down, and you put a little pressure on the bed, you are able to push it down. Since there are 2 Z motors, one can be pushed down more than the other and your bed will hang skew.

So don’t touch the bed when it is not powered.

Allthough it’s a cheap printer, it is quite a good quality of printer and prints.

(Athul S Nair) #11

@Mano_Biletsky_Open_M That’s because it uses a lead screw with a lead of 8 mm. Use 1.25mm pitch screw or 2mm pitch screw. I have printer of 500x500 with M8 screws
Is there nay vibrations, what is your print speed
???

(Athul S Nair) #12

@Ulrich_Baer Which has more accuracy C7 ball screw with linear guide way or Normal GT2 belt pulley.
if C7(50 micron) is more accurate then how come Ultimaker which uses belt has 12.5, 12.5, 2.5 micron resolution.

Also would vibration increase if I use ball screw assembly given in the link for X & Y axis.??

(Ulrich Baer) #13

longer ball screw have a higher mass so your stepper need to be able to slow and accelerate this mass in time. The accuracy is for 300mm - not for positioning (keep in mind if this gets hot metall will expand). your positioning accuracy is dependent on how accurate you turn or meassure the rotation of the ball screw.

(Ulrich Baer) #14

maybe a good start before building a printer is to read a book about this https://plus.google.com/114722716901025057698/posts/U5VeS37mDZM

(Mano Biletsky (Open MAKER)) #15

@Athul_S_Nair i actually don’t know what speed i’m printing at. I always print of uSD card and use a standard profile in simplify3d.

I probably won’t change out the lead screw, but i know what you mean. I am happy with how it works and if it ain’t broke, don’t fix it😉

(Tom L) #16

What sort of biomedical application would actually be best suited by FDM printing? Have you used other FDM 3d printers in the past, or are you jumping in to building a big one?

(Athul S Nair) #17

@Tom_L I have a 20x20x20 3d printer and I have also build a 3d printer using Openbuild profiles. It can be used for Bio gels or ceramics & Plastic. I actually have a Auger based extruder for printing Clay and I hope I can use it for printing gel as well.