My coreXY design is progressing to the build stage

The best 'hairy lion' I've seen yet!

Dr. Digi-Dent,

Now, that you've had a chance to print for a while, have you noticed any issues with x axis bed-roll/wobble/tilt?

With the new z axis shaft design, it looks like it's now perfectly oriented to add in a third belt/pulley/linear rail/mount point. (Not to mention the further reduction of stretch under load...)

On a side note, Maybe it's time to rename the printer to:Ms. Kitty's MegaMax Dominator (now with improved feline pre-warming bed technology)

Edited 1 time(s). Last edit at 06/22/2017 07:48AM by Dees.

No issues at all. It is rock solid. It really doesn't need a third guide/belt. Stretch is already so low it doesn't matter.

I'm trying to get the front doors finished up and then run some tests to see of I need a heater for ABS or if the bed heater will do the job. It will probably need additional heat. I also have some higher powered UV LEDs coming from China that I'll be installing in place of the LED strips that are in there now. I'm going to beef up the print cooling, too. The little fan I have on there seems to be OK for thin, narrow layers, but I'm planning to use a 0.8mm nozzle to run 0.5 mm layers with 1 mm line width most of the time and it's going to take a lot more air to make sure that the print has cooled before the nozzle comes around again for the next layer.

And then there's the electronics- something has to be done about the way it looks.

Edited 1 time(s). Last edit at 06/22/2017 09:17AM by the_digital_dentist.

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

Have you considered putting them on the backside of the printer in a mini cabinet?

The back side won't work - I have to transport the machine laying on its back in my car- that's why the electronics were placed on the top, and x and Y motors are on the front side. I am also tall, and getting old, and don't want to have to bend over to access things if I don't have too. Electronics on top puts them at eye level while I'm standing.

Edited 1 time(s). Last edit at 06/22/2017 11:59AM by the_digital_dentist.

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

Minor progress- I picked through the cut-off rack at Midland Plastics yesterday and found a piece of 6mm Makrolon AR (abrasion resistant) polycarbonate for $5 and used it to make the upper front cover. I cut notches for the A and B motor mounts and belts and it drops right into the slots in the frame.



I'd like to make the lower front cover from the same material because I like the abrasion resistance, but that stuff is crazy expensive. I'll probably just go with plain old 1/8" PC and attach it with magnetic tape.

I picked up a few small blocks of Teflon for $5 while I was at Midland, too. You never know when you'll need a few small pieces of Teflon- maybe for bed levelers in another printer...

Edited 1 time(s). Last edit at 06/24/2017 10:13AM by the_digital_dentist.

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

Hey digital dentist nice build! I really like your z axis an would like to implement it on a bot i'm building, do you think something like this would work instead of the RINO worm gear? no specs on it though it might be not very precise :/

[www.robotdigg.com]

They are pretty similar, however the price difference is not that much,

It looks like a pretty good deal, but they don't provide much in the way of specs on the motor. I like the 11 mm output - beefy!

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

Currently im on a Anet A8 and am getting realy fed up with its poor quality. After realising i would have to replace the whole printer to get decent quality im now planning to go all the way, a "digital-dentist-style" printer would propably satisfy my thirst for better quality, it seems realy awesome!

I only need 200mm^3 build volume, but i think lots of lessons from your printer projects still apply. After finding good sources for all materials i need im now starting to plan the build, but im limited by one thing: I dont have access to a mill. Now im looking for ways to fabricate parts like those rectangular aluminium tube pieces, i assume using a triangle ruler wouldnt provide the required accuracy. I have access to a drillpress, but im not sure how i could utilise it the best way. Any suggestions?

I am building this with a drill press. It's still a work in progress. I use higher quality digital calipers and a starret center punch to lay everything out, then I drill the holes. You need high quality drill bits and taps. When I made my measurements I made them from an uncut side so they would be the most accurate. I spent $60 on some taps and $90 on some drill bits for this project and they have been worth it. You need a vice. A higher quality x-y vice would be a good choice... You can cut the aluminum on a wood table saw with a blade for cutting aluminum. Just keep in mind this might shorten the life of table saw because the motor isn't protected from aluminum shavings... also, there is a fire hazard if your saw is full of saw dust....

Overall I am happy with the direction my printer is going. Buy extra metal

"Poor mans digital dentist build" on the forums here if you want to take a look.

Edited 1 time(s). Last edit at 07/03/2017 04:46PM by Qdeathstar.

The rectangular tubes that hold the pulleys really don't require extreme precision. When you drill the holes for the pulley's axles, as long as the tube is clamped so the top and bottom surfaces are perpendicular to the drill bit, and you drill all the way through both the top and bottom, the pulleys will be oriented correctly. The belt paths are critical so the locations of the holes for mounting the rectangular tubes on the bearing blocks are likewise critical, unless you oversize them slightly to allow for some minor adjustment of the positions before tightening the screws.

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

The Digital Dentist, how did you tension the Z-axis? You described the method for the previous design with all the pulleys.. but not for the current design. Thanks!

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

Leave the drive pulleys free to rotate on the drive shaft, pull up on the plates with the pulleys at the top of the Z axis, tighten them down, then tighten the grub screws on the drive pulleys with the bed support sitting at the bottom of the mechanism.

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

Ah, I understand now. I am going to have do some thinking then, my design is different so i can't pull up on the top pully or down on the drive pulley. I may need to do some redesign.Thanks!

Quote
Qdeathstar
I am building this with a drill press. It's still a work in progress. I use higher quality digital calipers and a starret center punch to lay everything out, then I drill the holes. You need high quality drill bits and taps. When I made my measurements I made them from an uncut side so they would be the most accurate. I spent $60 on some taps and $90 on some drill bits for this project and they have been worth it. You need a vice. A higher quality x-y vice would be a good choice... You can cut the aluminum on a wood table saw with a blade for cutting aluminum. Just keep in mind this might shorten the life of table saw because the motor isn't protected from aluminum shavings... also, there is a fire hazard if your saw is full of saw dust....

Overall I am happy with the direction my printer is going. Buy extra metal

"Poor mans digital dentist build" on the forums here if you want to take a look.

Do you have any brand recommendation for the vise?

I attempted an ABS print yesterday after closing the front opening off with a piece of cardboard. The dual layer PC side panels and foamed PVC top panel are good insulators, and the bed was up at the top of the machine for most of the print, and warm air rises, so things got super toasty in there. I didn't put a thermometer in, but after yesterday's run, I'm going to just set it all up with a thermometer and see how high the temperature gets. I think it was well above 50C.

The part I was trying to print was a fan duct for a blower that will circulate the air in the enclosed printer. It will suck air from the top and blow it down to the bottom of the printer. The print failed- the duct consisted of thin material in long runs that delaminated in spite of the high temperature in the enclosure. I'll see about scoring and folding some thin plastic to do the job.

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

It's interesting I've never had a problem with ABS delaminating even without an enclosure, just warping... thin walled abs should be even less susceptible to delamination since there is less chance for differential cooling.. I even add a small amount of cooling (like for printing pla) when I'm printing something small or with a large top shell....

Edited 1 time(s). Last edit at 07/05/2017 01:07PM by Qdeathstar.

I got this hazard fraught

[m.harborfreight.com]

But I know there are better ones out there

Im not sure which railwidth i should choose for the linear rails. I will propably order from Misumi, the ones i would need arent much more expensive than good used ones on ebay (which is so flooded by chinese shit its hard to find something else). It boils down to the decision between 12mm and 15mm width, they are 38,50€/41,37€ for about 350mm. Now the question is, which ones to choose for the X-axis? 12mm is lighter, so better to move around while 15mm is more rigid and maybe i could get away without mounting it to an extrusion and thus save more wheight.

What about the other rails? Since those will be mounted on milled aluminium plates (found a cheap souce) and the forces are low it propably doesnt matter at all, does it?

Im also currently stuck on my heatbed design, i cant figure out a secure way of mounting without using your more complicated milled holes. Since my heatbed will be smaller (200mm+200mm) and ill only print PLA/PETG the heat expansion will be limited to about 0,3mm, maybe i could get away with a more simple design.

If you go too small on the X axis rail, it may become too flexible, so you have to add weight back in by mounting the rail on a piece of t-slot or a tube to stiffen it up. It might be better to just use a bigger, stiffer rail. A smaller rail has a smaller bearing block so it may get tricky to mount things on it. OTOH, smaller is lighter, and as long as things are rigid enough, lighter is better.

The Y axis rail width doesn't really matter, but again, the narrower rails have smaller bearing blocks. It's lighter, which is good, but you have to mount pulleys on those blocks, and it might get difficult if the blocks are too small.

The design of the bed mounting system can be changed easily enough. My other printer's bed has a more conventional springs on screws (springs have since been replaced with nuts because the leveling doesn't need readjustment) arrangement and it works reliably even though the bed is larger and gets heated up to print ABS. See: [www.instructables.com]

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

Which acceleration are you using now on the X/Y axis? I remember you had to reduce it to 1500m/s back when using a pen, how did that change when mounting the extruder? Im asking because i could use that number to calculate the actual flexing of the linear rails.

Why do you screw your levelingscrews into teflon blocks? Those are realy hard to find.

Teflon is easy to machine and resists the high temperature that the leveling screws will reach because they are in contact with the heated bed. ABS and PLA will definitely not be suitable materials for that purpose. Teflon can be found in small pieces on ebay or from industrial plastics suppliers. I just picked up enough to make about 8 of those blocks from a local Midland Plastics cutoff rack for $7. You can saw it to size, drill it easily, and you don't need to tap the leveling screw holes- just drill a slightly undersized hole and let the screw roll its own threads into the plastic.

One of the three blocks in the new printer is made of Torlon, a very high temperature plastic similar to PEEK, that I tried as an experiment. That stuff is very hard to machine, so I don't recommend it. The drill bit got very hot, and I couldn't just drive a screw into a slightly undersized hole. I had to tap it and it was not easy. It's pretty hard to find and quite expensive when you do. Someone at the makerspace uses it where he works and he brought me a bag of small cut-off pieces that would have otherwise gone into the trash.

The accelerations are currently set to 1000 mm/sec^2 for XY and Z, and junction deviation is set to 0.1 mm. I haven't actually played with it to see how high I can push it. I do get some ringing in the prints, mainly on surfaces parallel to the Y axis, but I don't find it too objectionable. The slic3r profile is set for non print movement speeds of 150 mm/sec, and it has never shifted layers, so I can probably push the acceleration a little higher.

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

I'm running another ABS print with the printer closed up. This time the parts have some bulk and infill and so far they're holding together just fine. I put a thermometer inside the enclosure and at 45 minutes, it was up to 42C. It's been running for about 1:17 and the temperature at the XY mechanism is up to 43C. The bed is set to 105C.

Update: The print finished nicely- no delamination at all- and the temperature inside the box stabilized at 45C, and 20C above ambient. I'm sure that the lower end of the enclosure was much cooler, and when I install a fan to circulate the air the overall temperature will end up too low for reliable ABS printing, so I will be adding an enclosure heater.

Edited 1 time(s). Last edit at 07/09/2017 08:54PM by the_digital_dentist.

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

You mentioned on page 3 that you are using printed bushings for the larger bearings, which have a 17mm bore. Knowing that you dislike using printed parts in important structural parts i wonder how those hold up to the load. Which material did you use to print them?

The few parts that are printed in this and my other printer are all ABS. The parts you mention are only reducing the inner diameter of the bearing from 17 to 8 mm so they fit on the 8 mm bolts. There's nothing critical about them. They don't rotate and they don't contact the belt. They were printed solid, so they hold up just fine.

I used nylon washers to position the bearings in the tubular rectangular pulley mounts. At some point I'll probably replace those with aluminum spacers and I'll replace the printed bushings at the same time.

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

Is there a specific reason you used nylon washers instead of normal ones or were those simply the ones at hand?

My concern regarding the printed bushings is that they have to carry the belt tension, so i would expect them to creep. This would lower the belt tension over time...

I used nylon washers because I had them, they were light weight, and when stacked they filled the space exactly as much as was needed.

It's possible all the nylon washers and ABS bushings will creep, especially when subjected to heat and belt tension, so I'll be replacing them. In the meantime, if the belt tension decreases, I'll tighten them up again.

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

Can't seem to find any 17mm aluminum stock. Are you planning to turn some down on a lathe.... or are you going to try steel( I could find 17mm tool steel)? I imagine that will be harder to machine.

Edited 1 time(s). Last edit at 07/12/2017 11:47AM by Qdeathstar.

I'll use aluminum and turn it on a lathe at the makerspace.

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