Zasquatch's CoreXY Design/Build

Had a productive night yesterday.

I cleaned the rails and carriages with WD40 to loosen up the old grease, then applied a healthy dose of fresh lithium grease.. The hiwin carriages were NOS from automation-overstock so had been sitting in a box for 10+ years. The difference in motion was noticeable, everything is nice and smooth, yet tight and controlled. This thing is rock solid.

I set my xy accel values to 500 each. Is there a method for dialing in accel? I have noticed the machine actually responds better to higher values to a certain extent but don't want to get too crazy

Same question with stepper current- I have swapped out my defective "stepperonline" steppers with LDO 59 Ncm units, 2A max current. For testing I have them set to 1.5A. Is it trial and error to see how low you can go before they start to stall?

My endstop terminals arrive today, so I'd like to do a "draw-bot" pencil test this evening. Are there any tricks to doing this? Or just slice as normal and stop after layer 1? Will the board be confused there isn't a z axis hooked up?

Edited 2 time(s). Last edit at 08/30/2017 08:08AM by Zasquatch.

Unless the stepper motors are getting hot, I suggest you leave them set at 1.5A. The drivers on your Duet WiFi will remain well below the warning temperature at that current without a cooling fan, and the firmware will reduce the current (to 30% by default) when the printer is idle anyway.

I am surprised you had trouble with the motors from stepperonline. I've found them OK. Definitely worth asking them for a refund or replacements IMO.

Edited 1 time(s). Last edit at 08/30/2017 06:50AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Yes I was also surprised! They are giving me a refund without any hassle. The rear screws were loose on arrival, and threads stripped so they couldn't be tightened. As a result the motor housing was able to rotate a degree or two when mounted. Not good! I may look into seeing if there is a way to repair them since they don't need me to send them back...maybe with a helicoil? Can you just take apart a stepper like that or do you need precision alignment tooling?

I will keep current at 1.5A to start... but my question is really how low can you go? Is there a benefit to going as low as possible or if it is working at 1.5A should I stop monkeying with it?

Edited 1 time(s). Last edit at 08/30/2017 08:06AM by Zasquatch.

Higher currents give you more precise positioning and more accurate microstepping, make the motor more likely to ride over a temporary obstruction without skipping steps, and provide more torque for acceleration until you hit the speed limit for the driver supply voltage you use. Lower currents keep the motors and drivers cooler. So the best current setting to use is a compromise between these factors. 70% to 80% of rated motor current is typically used in 3D printers.

Edited 1 time(s). Last edit at 09/01/2017 01:27AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Do you have issues with flexing with your Hiwin AG20's on the x carriage? They're significantly smaller rails than what the digital dentist is using. I'm planning to do a similar build and am looking at the EG20's.

Can't say for sure yet but I don't think so. My rails are 20mm wide by about 16mm thick. I believe the dentist used "slim" rails that were 24mm x 8mm thick.

D

Edited 1 time(s). Last edit at 08/31/2017 09:27PM by Zasquatch.

Draw test went well. Pen used had some play in it but overall everything is square and good,

Couple updates today.

Got the frame all cut and started assembly, need to wait for screws to come in from McMaster to finish. I have a variety of corner brackets that I'll mess with to see what results in the most solid configuration. Don't think I can get away with thru-bolts since I didn't use a mill to cut everything... miter saw!!



Had a good and bad news story with the hot end... I drilled out the threads with a 7mm drill bit- and the kracken style heatbreak fit perfectly!! I drilled a hole ffor a grub screw and the chinesium tap snapped half way through the hole now I am trying to figure out how to back it out. Worst case I drill a second hole and leave the f-up there to forever remind me...

Very nice! What are plates are you you using for your y axis? I notice that you don't have any extrusion underneath it for support.

Thanks! 1/2" MIC-6 aluminum.

So do you think a 12mm lead screw is thick enough since most of the load will be on the linear guides? Specs say they can handle hundreds of pounds axially but it seems small to me. Thoughts? Motor will be on top so screw will be in tension, not compression.

Edited 1 time(s). Last edit at 09/05/2017 07:04PM by Zasquatch.

I bought 20mm lead screws for my 400x400x744mm build. However, with some calculations on the column strength, 10mm should be sufficient for my application (if mounted properly). The reason I went with 20mm is because it costs about the same as 10mm or 12mm lead screws and I was more concerned about the lead screws getting bent on the way to me than anything else. This answer probably didn't help much but just my 2 cents.

A question about how you mounted your x axis linear rail to the aluminium tubing. Did you drill an extra hole? Also, any issues on the x axis linear rail flexing?

Thanks. I have a sample coming today for a 16x2 screw. I am leaning towards that with an igus plastic nut, or a 1605 ballscrew from zyltech. German quality lead screw vs higher quality chinesium ball screw....

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nkewong
A question about how you mounted your x axis linear rail to the aluminium tubing. Did you drill an extra hole? Also, any issues on the x axis linear rail flexing?

Yes, I drilled a thru hole where the existing threaded hole was, and another one next to it through the whole rail. No issues so far, but not sure how to test it aside from pushing on it.

Took a break for a little while, turns out newborns are very distracting!

Got back into it this weekend, and as a result my z-axis is taking shape. Continuing on the theme of overkill.... zero noticeable play in any direction - and weighs a ton.

Beefy!

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

All that aluminum, and only 6mm belts? Or are they bigger due to scale :p

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prot0typ1cal
All that aluminum, and only 6mm belts? Or are they bigger due to scale :p

9mm

Because your profile is so beefy, you probably could have got away with just one spar sticking out in the middle, maybe with the smaller one you have at the front at the back, forming the T shape.

I just noticed in the earlier picture, the X axis guide rail has no mounting holes! What sort of rail is that? How did you drill it?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

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the_digital_dentist
I just noticed in the earlier picture, the X axis guide rail has no mounting holes! What sort of rail is that? How did you drill it?

Looks like a sheet metal cover. Some linear guides have a stainless strip to cover the bolt holes...

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MechaBits
Because your profile is so beefy, you probably could have got away with just one spar sticking out in the middle, maybe with the smaller one you have at the front at the back, forming the T shape.

That was actually one of my initial design iterations... which I abondoned. I am doing 3 point leveling, and didn’t want any adjustments way at the back of the machine. So the single beam would need multiple support arms for the build plate. I was worried about robustness and alignment so I ended up where I ended up. In the end it is solid as a rock and should be ok with my 1605 ball screw. If needed I will get a geared stepper but have a feeling I’ll be fine with std NEMA 17 high torque stepper.

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the_digital_dentist
I just noticed in the earlier picture, the X axis guide rail has no mounting holes! What sort of rail is that? How did you drill it?

It is a bottom-mount hiwin rail. The top is solid and smooth and the back has tapped holes. I use 3d printed drill guides throughout to ensure accurate holes and it’s worked out great. Low speed, nice sharp bit, with lots of cutting oil on my drill press, no problem drilling the rail at all..... except for a considerable amount of stress leading up to it lol

Edited 1 time(s). Last edit at 11/15/2017 01:00PM by Zasquatch.

I wouldnt have been too bothered by 2 screws at the back(one could be reference) & one at front) though I suppose once the head is in there it could be restricted, but your machine, your solution, you know why your at where your at, that's all that matters.

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MechaBits
I wouldnt have been too bothered by 2 screws at the back(one could be reference) & one at front) though I suppose once the head is in there it could be restricted, but your machine, your solution, you know why your at where your at, that's all that matters.

Is that the polite way of saying “you’re crazy”?!?! Lol the nice thing about using aluminum extrusion is that if this design doesn’t work out I can always reconfigure using the same material. We will see!

I also did feel challenged to use as much of the 200lbs of aluminum as I could....doing prettty well so far, just a few scraps left!

Got the build plate mounted this morning, seems to work very well. The springs are very stiff so the whole thing is very stable. I am pretty happy with the result.

How are the leveling screws anchored to the support plate? I used teflon blocks that grip the screws tightly so they can't wobble and so the bed plate can't move laterally.

Is the bed heated?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

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the_digital_dentist
How are the leveling screws anchored to the support plate? I used teflon blocks that grip the screws tightly so they can't wobble and so the bed plate can't move laterally.

Is the bed heated?

I did read that in your thread, very clever! I just used a M8 thru tap in the .5” mic6 plate. The spring rate is 10.5lbs/mm so they are exerting a considerable amount of force on the threads. I can yank the corner of the plate and there is no noticeable wobble. It seems very solid.

Yes bed will be heated by an 1800W 550mm x 550mm keenovo silicone heater. It’s on the slow boat from China, probably a few weeks out. Will use 120v direct, and a SSR to control via Duet WiFi.

Next consideration is bed glass- I hate to start a borosilicate vs window glass debate, so I will likely try the $20 option before I spring for a $200 plate of the “good stuff”. Any thoughts on that?