Posts made by Philn

Hello everyone,

Following my previous post, I decided to use one of my two Duets (2 Wifi) to build a CoreXY printer with a triple-z set-up.

Which means I am going to need to add a 6th driver.

I just finished reading:
https://duet3d.dozuki.com/Wiki/Using_external_stepper_motor_drivers

And got some questions:

1. Can I use the 5 on-board drivers for Z-Z-Z+X+Y and use the additional 6th driver for the extruder? (my goal with this is, all 5 axis movements will end up using the same driver model)

2. Can I use a TMC2209 as the extruder driver or would you recommend another type, say 2100 or even DRV8825? (I got TMC2209 and a DRV at hand, so would make it simpler)

3. I admit, that article went a bit over my head. Are there any gotcha's or something you'd in particular advise me to pay attention to?

I have ordered a break out board, the same in the article:

Thank you for your help

P.S. I apologise if General Discussion is not the right place for this thread. I thought about posting under Duet Hardware but since the expansion will consist of external hardware, I wasn't too sure.

Thanks so much everyone for your valuable input.

Following your advice, I decided to upgrade the bed slinger I'd built with somewhat better components for a relatively low cost, and build a CoreXY machine using the rest, which is going to be my 1st.

Cheers

Hello,

To some this may come across as a no-brainer but I am kind of lost. To be honest I suck at making such decisions and your help is much appreciated.

I have 3 printers. I want to upgrade / convert them and 2 good ones.

I had one Duet board and got another one.
2 Beds I have are 1 prusa mini bed + 1 regular prusa 3 magnetic bed and 1 low quality aluminium heat bed.

Also have enough stepper motors. And got some additional Stepper Online ones (the "good stuff", apparently).

If I were to get some additional parts, such as 2020 / 2040 extrusions, I could build 2 Core XY style machines.

But is it really worth it, compared to bed slingers?

That's what I'd like to know.

I'd seriously appreciate your thoughts and input.
Many thanks

@sebkritikel

Hello,

I feel humbled that you have taken time to explain all this. Thank you very much. This is some truly important information that I need to learn.

However I am OK with the XZ motion and my question is regarding the Y axis / bed movement.

I attached an immage to my above reply.

Do you mind taking a look?

There is no reduction at all. I just want to use 60 Teeth 38mm pulley / idler instead of a 20 teeth 16mm diameter one and due to the larger diameter, I am afraid my motor won't be able to move the same amount of mass.

So I would like to figure out if I need to get a more powerful motor or if its good enough.

Does that make sense?

Once again, thank you and I will study the things you shared and the links you provided. Cheers

@deckingman

I apologise for the confusion. I was so convinced that it was all clear

Here is a picture demonstrating what I would have liked to explain:'

Current Y axis is a "typical" setup.
Nema 17 with 16mm pulley with matching idler.

I want to use instead a 38mm pulley with matching 38mm idler.

My issue is, I assume, I will lose force / torque when moving the bed?

P.S.
Saving space is linked to the enclosure. If I use larger pulley / idler combo, I will be able to position things differently and run the belt around the rail on which the bed will be riding. Eitherway I am very curious
about learning these torque, force etc. Most common printers from China, even Prusa use 20 teeth pulleys and I wonder what would happen with a larger set.

Good evening,

I am working on a CoreXZ bed-slinger powered by Duet. So far I managed to make good progress on CoreXZ mechanics.

On the Y axis however, I'd love to be able to use 60 teeth pulley & idler for design purposes. This would allow me to save space and box things up nicely.

From what I figure:

• 20 teeth pulley has an outer diameter of ~16 mms.
• 60 teeth pulley stands at 38 mms.
• And I can estimate the weight of my bed assembly + the weight it should be able to carry

This translates to a 2.4x distance increase from the shaft. And this is where I get lost as my knowledge in physics and torque calculation is limited.

1st) Could you please help me with the following?

• How can I figure out the torque value I should be looking for when buying a motor so that I can safely use 60T 2GT pulleys in order to drive the Y axis?

2nd) Is my calculation below correct (excluding friction, which is sort of OK I hope for this application)?

1. Using a 40 N-cm stepper, I get a torque rating of 4.5 kg-cm.
2. At 8mms from the shaft (16mm OD 20 T pulley), the value jumps to 5.6 kgs (4.5 * 10)/8=5.6)
3. However at 19 mms from the shaft (38mm 60 T pulley), this would go down to 2.36 kgs (4.5 * 10)/19=2.36)

Therefore the motor would be limited to safely moving ~2kg

Thanks in advance for your help and reminding me physics.

One picture's worth a thousand words demo:

Many thanks @fcwilt

This is great to know it will help a lot in the future I bet. The one I have is not the better version it seems though which is bit of a sad news.

Do you mind if I ask what is your usecase for these motors? Are you doing a CoreXZ or similar?

@Veti
Backlash

What I'd really like to know now is why they haven't used bigger motors with higher torque. I feel bad wasting their time with my questions though. They are already doing so much and I feel like abusing their kindness.

Hi! Thank you for the extremely rapid response. I couldn't believe my eyes.

I read the 1st thread. I understand that compensation is a no-go.

And I get your point regarding the 2nd question. Even if backlash wasn't an issue, things become slower..

Do you mind if I trouble with you with a 3rd question?

Bed-slinger printers are usually quite slow as far as I can tell if you want to get a decent print.

If I was printing, say at around 60mm/s on avarage, would reducing the gear be an issue?

Understanding acceleration/jerk vs speed was hard enough, when combined with torque I have no idea where to begin just to get the numbers.

Good afternoon,

I started working on building a CoreXZ printer called Voron Switchwire.

This printer uses a counterweight (via a retractable keychain) to lift up the X assembly since the motors driving the CoreXZ system are not able to maintain the weight.

Although unrelated, I know that Duet has advanced features such as pressure advance.

To simplify the setup, I am thinking about using a stepper motor with integrated planetary gear reduction mechanism (5-to-1) and forgo the retractable keychain.

From the specs sheet, however, I see that these mechanisms come wikth a "less than 1 degree" backlash.

I do not understand how does this backlash could effect the movement of the axes.

I guess my question is two folds;

1st) Can duet make up for this backlash the same way it magically handles pressure advance?

2nd) If I used the 5:1 geared motors to drive the axes, what kind of an affect could they have on the prints with their less-than-1-degree-backlash specs?

I know many will say just build the the printer as specced but I was very excited to learn about the planetary gear system and I would love to have an actual understanding about these things.

Thank you for your time, I am looking forward to learning about this.

Cheers

P.S.

This is my first message on the Duet boards. I apologise in advance for any possible mistakes. I am posting this under General discussion. Please feel free to let me know or just move the thread to the appropriate board if it should belong elsewhere. Thanks again