Will this use MatterControl with auto leveling?

 

OK, I guess I didn't figure out what was new/old. I see about 4 versions. Can u tell me which is newest and why. I am trying not to have moving pieces hanging outside frame.
I am also trying to do this with 2 screws on either side instead of 3. Any advice to that scheme?
thx

 

well, maybe a pic is best. I have modeled this in sketchup in 5 versions. Now I have the idlers facing front, one Z motor, 2 and all motors in the rear - XY, Bowden motors, and the Z is near the back. I may have to use a counterweight! lol. I figure 2 wheels on each corner and the screws on each side would work but I am thinking about 3 screws as it would be more stable. Just not sure how much more. I guess I could figure something to allow some adjustment if needed. Probably only talking 1mm or so and I could do that on the platform X bars, but not easily. I think I have all axis giving approx 305mm but I am still working on the endstop locations before committing to the modifications. It doesn't change the amount of rails needed but might reduce the Z height if I cut 3 screws from a 1m screw. The footprint is about 530x530x570 if u include the motors hanging off the back. That reduces the width by about 40mm and increases the height by about 100mm to give me the approx. 12"x12"x12" build area. I may change my mind about the height if I go with 3 screws. I may opt to reduce it 100mm instead of buying more screws.
Do u see any issues?

 

thx for that Carl.
1 of my ver has 2 motors. I have an extra 1 but am concerned about driving them in parallel. Some strong opinions posted about that. I thought about driving 1 directly. I didn't like how high the belt was but it is an option I guess. I like the fact that my idler runs on the back side of the belt. I also have a tensioner from an AIO printer I would like to use, but it should work either way. 1 direct would require it to be on the front side. The current setup gives me about the max tooth engagement I can get.

I don't follow this "If you're set on a front back lead 2 screw setup then I'd go with my or NickM axis setup but move your leadscrews.". As shown they r on the sides - where would u move them to?

I don't know how many times I looked at the pics and the BOM to figure out if that piece was a 20x40 or 20x20. Is the front base also a 20x20? No 20x20 is listed on the BOM.

I would like to have the spools mount on the frame. I just haven't figured that out yet. I am thinking an angle iron on the back sides. I may have to bolt the front down to the table with all the weight on the back, lol.

I guess it is time for ver 6 to look at 3 screws. I need to figure this out soon as all my parts at OB will be in stock next week so I can make 1 order.

 

I have been following along here for a bit with plans to build one of these. But this latest talk about build platform wobble got me concerned about my plans. I was wanting to make a 12x12x? build area. Not sure how tall I will be able to go with a 500mm lead screw. Is the base design with the two lead screws sturdy enough to support this size of platform or should I look more at what Adam has done and go with 3 lead screws connected with a belt?

 

Personally I wouldn't cantilever more then 6"of Y travel. Carl has proven results with his bot with a 8" Y. Nick ran into issues with a 12" Y cantilever, even with the 60mm Z slider bar.

@ruggb If your looking to enclose your bot, there are a few places that panels can be mounted on standoffs to allow sliding parts. The main issue with your design, as I see it, is getting repeatable tension all along your total travel height. You are relying in the frame being perfectly square and having zero flex. The top of that particular frame rectangle is mated with a printed plastic part, the bottom can be anchored with a few aluminum parts. With Carl's design you are clamping opposing wheels onto a single extrusion.

I am planning a cross member at that point, under the sliders on the right and left side of my frame. I have ordered some low profile screws to mount the wheels, hopefully that will allow clearance. I am also planning on only using two, or possibly three, wheels per side as I should have no torsion.

 

Sounds like I might be better off sticking with an 8x12 build area then.

 

I can appreciate the multi-step process for sure. But I believe in using experience - just so happens I really like ur design so I am using ur experience and trying to minimize the total footprint while getting 12x12 (or close to it). I have no idea why I need that but the cost differential is minimal. Just trying to minimize buying parts I can't use, or buying more after the fact. My current issue trying to implement 3 screws with 1 direct drive and pulley drives is getting a belt pulley and a motor-2-screw coupling onto the motor shaft and keeping the belt low. I have about 8mm left on the shaft with the pulley in place. I don't know if that will be enough for a coupling. I may have to keep what I have and/or just add another screw. I think I will model that. Ver 7 coming up.
It is a testament to ur design that this discussion is so active. Ur help and opinions are much appreciated.

 

Moving the back build plate mounts onto the Z bar, wouldn't move a lot or weight, where they are no is reasonably close to the Z bar anyway, so most of the weight is expressed in sheer pressure. The ones at the front are give more of a twist force on the Z bar.

A counter weight is a good idea, but it would increase the weight the Z motors have to list, also I want to avoid building a teeter totter.

I had a good look at what was happening with it today, and it seems the flex isn't coming from where the build plate supports mount onto the Z bar, these are rock solid. All the flex is coming from the wheels, bolts holding the wheels and the plastic holding the wheels to the Z bar.

I was able to reduce the flex a bit by using a clamp to compress the wheels into the rails before tightening the bolts, it seems the rest is in the plastic and twisting in the bolts. It isn't much flex, but a small amount on the Z bar equate to a big amount at the front of the build plate.

 

No idea why it doesn't bounce back to the same spot, I guess it only takes a small difference on the Z bar's wheel to make a big difference on the front of the build plate.

 

Never thought about the possible flexing of the legs. I guess I could add a strap across the middle on the outside. Or possibly rotate the wheels 90° so they r pushing on the 40mm width. Then again how much is a 20x40x500mm rail going to flex on the amt of pressure that can be applied to those wheels??? It seems like the amount of force needed would destroy the plastic or the wheels or both. I am thinking of using this to give me some adjustment.

 

I didn't mean the extrusion would flex. With your configuration, the wheels on the inside only of the legs, the force will be applied outward to maintain tension with the wheels. The frame section that you have chosen is essentially only a U shape, and not a rectangle. This is discounting the connection made by printed plastic parts, the idlers and motor mounts. As your Z platform rises to the top of the machine the potential for the rectangle to become a trapezoid. If I recall your Z height was around 500mm, which is close to mine, I was surprised at how much flexing I am getting. I will try to grab a video of the deflection.

the red arrow is the spreading force on the frame. The green line is the planned location for a crossmember on my bot, 20x20, hopefully using low profile screws will allow clearance for the Z wheels. If your design hinges on the inboard wheels only, you may want to consider using only 4 wheels. Keeping the wheels inline with the build plate plane, will be a little more forgiving to being slightly out of sync.

 

All the corners r attached by plastic so I don't even have a U. More like a bunch of I's. What u r talking about is what all boxes do without a cross member unless maybe the corners r welded together. I would secure it with an 2-3" 1/8 piece of masonite. But it needs to be secured with at least 2 screws on each side. The farther apart the screws r the better the support. Basically u r forming an X across the sides. U will need to do it on at least 2 adjacent sides because it can move in both X and Y directions. U could make the piece 500mm wide and call it an enclosure.
Diagonal wires would work but that may be more difficult to implement than a 2" board - but it may work better also.
I don't think wheels on both sides of a rail does much to eliminate this issue. They just r not tight enough on the rail and they move.
I was thinking about that but I believe I just talked myself into it - especially if u r seeing the issue. Now to figure out how to do it.

 

this should make it very ridgid with 1/8"-1/4" hard masonite or ply

 

I wish i could model like that in sketchup.

have you decided to go three leadscrews on a belt? If so, should really consider removing the one horizontal set of wheels, and only use 4. with the 8 wheels spread out in your render, if the leadscrews become out of sync you will get some binding in the respective corner, which will lead so some sore of artifact on your print. With that bracing your frame will go nowhere, using 1 inboard wheel per corner should be sufficient to maintain location, and if one screw gets slightly out of sync you will bind much less. Using three leadscrews will completely isolate the build platform in the Z axis, leaving the linear ways to only handle the XY motion.

 

I'm a nooby at this - it is my first project - but I am starting to figure SU out. If SU would behave I would like it a lot better.
I have ordered the belt for the 2 screws so I guess I will set that up first. I just need to cut the 1m screw into 3 pieces for the future upgrade which will cost a little height but I have no idea what I would use 12" for anyway.
otherwise I have to buy more - well it would only be $20. so maybe I will go for the 500mm extra piece. Trying to only order once. BUT then if I do 2, I need an extra 4 wheels which will pay for the screw, so I guess I have ordered the belt too soon. Sorry, just thinking out loud.

OK, I started with 16 wheels, then got down to 8, now u say with three screws I only need 4. Interesting. I understand that logic but could u explain this a little more -- "Using three leadscrews will completely isolate the build platform in the Z axis, leaving the linear ways to only handle the XY motion." I'm not following that.

How would u suggest syncing the lead screws?? I guess the idea is to get the platform square with the legs, assuming the whole thing is sq with itself.

 

OK, I started with 16 wheels, then got down to 8, now u say with three screws I only need 4. Interesting. .I understand that logic but could u explain this a little more -- "Using three leadscrews will completely isolate the build platform in the Z axis, leaving the linear ways to only handle the XY motion." I'm not following that

3 lead screws, properly synced will raise and lower perfectly in the Z axis, the purpose of the linear ways would be to keep the platform steady, across the horizontal. with a cantilever setup, the linear ways will keep the build platform constrained in all three axis, as the slides are preventing any motion in the vertical plane( rotation of the HBP), as well as the horizontal. Using multiple planes of wheels( lets say 8, in your design) could be over constrained as now you have two items keeping control of the same direction. The 8 wheels will need the plate to move perfectly vertical, some binding will occur if those 8 wheels get out of vertical, dropping the wheel count in your design down to 4 will be a lttle more forgiving

How would u suggest syncing the lead screws?? I guess the idea is to get the platform square with the legs, assuming the whole thing is sq with itself.

In my setup, the leadscrews are on round shafts and the motor has a flat. I can just loosen the set screw for my 36T pulley set the bed correctly and then re-tighten. If you have flats on your leadscrew / pulley interface they you will sync the screws by slipping teeth, this will give you 2mm adjustments.


Maybe we should take all this 3 screw talk to my thread and not hi-jack Carls

 

Did you see this? http://www.openbuilds.com/threads/h-bot-corexy-cube.788/ uses your z setup. You could easily adapt to a single motor belt combo. I just posted up some stl's you might want for motor and lead screw mount

 

Haven't had time to read the whole thread yet but I've talked myself into building this. Already have most of the components from my Mini Kossel which will be disassembled after the plastic pieces are printed. Problem right now is nothing is in stock!

I'm also not clear on the Z nut block. The BOM calls for a block:

http://openbuildspartstore.com/nut-block-for-8mm-metric-acme-lead-screw/

while the pictures show a round brass type. Is this a revision? Acme block holder stl looks like it could mount the square block style I posted above....

This is the threaded rod I assume:

http://openbuildspartstore.com/8mm-metric-acme-lead-screw/

For stock C-Bot build height should I go for the 250mm or 500mm? Reason I ask is because it says something about actual length being 285mm for the 250mm variant.

Here are the links to the rest of my shopping list here at openbuilds just for confirmation before I order.

http://openbuildspartstore.com/v-slot-20mm-x-40mm-linear-rail/ (1000mm x 7)

http://openbuildspartstore.com/delrin-mini-v-wheel-kit/ (x 20)

http://openbuildspartstore.com/aluminum-spacers/ (1/4" x 12)

http://openbuildspartstore.com/tee-nuts-25-pack/ (x 7)

http://openbuildspartstore.com/5mm-8mm-flexible-coupling/ (x 2)

http://openbuildspartstore.com/cast-corner-bracket/ (x 10)

http://openbuildspartstore.com/90-degree-joining-plate/ (x 8)


Thanks and awesome design!

 

@ruggb inspired me to learn a bit more CAD

Puting the bar ends into fusion was a fun experiment. I added a little more plastic in the insticde of the LED groove, render is a not quite finished version, I still have to add the endstop pad. I have yet to model the xy motor mounts and the XY idlers, saved the best for last I guess.

 

Thanks Carl. I plan to start with the stock setup since it's a massive step up over mine but may end up rebuilding it to print 25-40" in size for car parts ect but for now I'm just looking to get it built and figure out how well it will print. I could probably get away with 250-285mm on the Z height so as long as I can source the rest of the parts I'll be good.

To start I might try printing most of the parts out of stock at openbuilds, plus I like the idea of getting off cheap to start. Did you use 4 plastic plates(2 upper & 2 lower) to mount the two print bed extrusions to the linear Z axis extrusion? Just wondering if I can cheap out here for now too.

Love how cheap this thing is gonna be for such a monster print size!

 

Forgot to ask if there was a reason you didn't go with the V wheels? I kinda wanna try them over the regular delrin mini wheels as they seem to be more versatile since you can use them with the V slot on the extrusion or with the OpenRail linear rail giving more options for experimenting plus I think they would offer more material for locking in linear movement but I may be missing something commonly known about the design?

This mounting method seems like it would be solid for the Z axis although not as clean:

http://cdn1.bigcommerce.com/server2...ed_images/v-slot-connections.jpg?t=1398725710

Hate to spend $65 and regret not going with one or the other. Really want igus T linear rails but they would be even more money plus a wait from China...maybe later.

 

I did some reading and it seems like the smaller wheels are considered better under heavier loads than the standard V wheels so I'll go with those to stay as close to stock as possible initially since I'll have enough work on my hands. Never cut any extrusion myself before so I'm gonna also need a miter saw.

Glad to see you use 123D as it's the cad program I'm most familiar with (only made a few simple parts so far).

If I order the 250mm linear rods from Openbuilds:

http://openbuildspartstore.com/8mm-metric-acme-lead-screw/

With your stock dimensions do you think I will have a problem with the build plate being high enough to reach the extruder(Genuine J-head)? Their specs say 250mm ~ 285mm which I assume means it's actually 285mm so I figure 15mm wouldn't be a show stopper but I wanted to get your opinion or see if anyone else has tried them yet. Sure would be nice if Openbuilds would send you new products to test with your obviously popular designs

Already got the parts coming from Mcmaster ($62.57 in bolts, nuts and washers!) so that just leaves ordering another Kysan stepper for the second Z threaded rod and 20 F623ZZ bearings which were really hard to find in the US. Hopefully I didn't miss anything crucial. Planning to print the plastic parts in Sainsmart fluorescein green PLA at 0.1 layer height with black extrusion so it should be a good looking rig.

 

hax0red
u might want to chk MrMetric for fasteners. Their M5x10 socket screw (as example) is $0.05/100 vs $0.0965/100 and shipping is $6.00 flat rate and free over $75. I don't know what Mc M charges for shipping.

 

Wow wish I knew about these guys before. I just checked and it would be about $26 shipped for everything with shipping...almost 3 times cheaper and the site is much easier to navigate. Going to email Mcmaster and try to cancel. Thanks for the tip.

I also got a reply from Openbuilds about the 8mm Acme threaded rod. They are indeed 285mm so I'm going with them instead of sourcing from ebay since most sources at a decent price are outside the US. Worst case I'll double up on bed leveling springs and use longer bolts to make up the othert 15mm but I doubt it will be necessary.