Increased Build Volume Concerns

What considerations should I take into account if I would like to build a TAZ-style printer using the openrail design from piercet instead of smooth rods on the x and y-axis but on a larger scale. Basically instead of the 300mm glass bed I was going to go with 480mm. I have sourced the glass and silicon heater @ 120v using a solid state relay. My plan was to increase the length of the extrusion on the x and y axis by adding 180mm. The aluminum bed plate I can have cut on a laser but I will need to modify the drawing. Should I scale the y-axis end plate to compensate for the larger print bed? How bad of an idea is this?

Where did you find your silicone heater and glass?

Also, have you determined the aluminum extrusion and V-Slot lengths required for your build?

You should be ok at that length. The Y axis you will want a couple of extra middle support pieces. You might also consider drilling holes for 6 wheels rather than just 4 to support the larger bed, but see how it runs with 4 first. You’ll need longer cables for the bed, etc but that shouldn’t be a problem. I’m working on a cable chain anchor design to go with those anyways. Since you have access to a laser, you could widen the front and rear plates and move the holes out if you wanted, but you should be ok without going that route.

For the X axis, you shouldn’t run into any droop at that length. If you were going longer than that, you might want to start looking at the C beam openbuilds extrusion instead, but even double that length you shouldn’t see much if any droop. Scaling up the gantry structure you may want to reinforce the frame corners with 8020 aluminum corner plates instead of the stock acrylic ones, and potentially a different Y axis frame to gantry frame connection just to stiffen things up at that join.

As long as you aren’t adding a huge amount of mass to the X carriage, it should be plenty stiff. You may run into some additional flex on the X end plates that might manifest as something close to minor Z wobble at either side of the part in the X direction for extremely large parts, but you could also put a stiffer or thicker plate there to counteract that. The Anti wobble Z nut mount won’t help that specific circumstance.

Overall it should work fine. Let me know if you need a specific part altered for your design.

X-axis droop should not be a problem, I am only seeing ~10microns/lb droop across an 875mm V-Slot extrusion. In hindsight, I am not sure C-Beam really offers much advantage, since the vertically oriented span will take most of the load. Narrowing the distance between V-Slot wheels might actually be a significant disadvantage of C-Beam.

Cutting aluminum extrusions to length turned out to be one my biggest problems. So far, the only tool I have found will make quality cuts is a mitre saw with an expensive blade and lots of heavy cutting fluid. Hence, why I asked about the extrusion lengths.

I use either a manual hacksaw, or my little $30 craftsman mitre saw with a metal cutting blade. The hacksaw usually does a better job if I am not in a hurry. Whenever possible I just design to the available extrusion length. I definitly need a better mitre saw though

Interesting. I found it difficult to control hacksaw cuts to achieve flatness better than ~2mm across a 40mm*40mm surface.

Craftsman’s 10" mitre saw is excellent though, at only ~$100.

I use a really nice mitre box with the hacksaw and a fine tooth hacksaw blade with minimal rip teeth.

Ahh, thanks for the information. Wish I had known that worked well enough sooner, might have saved on the saw (though it has bought itself back since then).

For the glass, I got a quote from Cincinnati Gasket & Industrial Glass. $110 including shipping for a 1/8" thick 19"x19" borosilicate glass cut and swiped edge.

The silicone heater I was considering is on EBay. I emailed the seller and they said they could install a NTC100k at no additional charge.

The lengths of 20x20 extrusion, I am thinking would be current BOM length + 180mm. According to the Mangrove BOM X-axis would be 510 + my additional 180mm = 690mm x 4 pieces. Y-axis would be 500mm + 180mm = 680mm x 2 pieces.

As for the openrail … yeah, no idea. I wanted to put it all together then order the openrail after I see how the new carriages on the Z-axis are going to work.

I’m planning to use a band saw. Something similar to this:


I’m still upset you won the musical instrument challenge on reddit, my bongo drums were awesome-ish. Just sayin’. I think Lulzbot made out like a bandit since you have been lighting up the forums with your new projects. Props.

FYI, I’m not modifying an existing TAZ, I will be building this one with existing knowledge of owning a TAZ 3 a while ago. Unfortunately, I sold it and am trying to get back in the large build volume arena.

I do have some existing parts, like Lulzbot stepper motors, the z-axis parts, heat inserts, extruders, hotends, etc.

I’ll probably go ahead and have those holes cut in while it’s on the laser in the event I do need them.

I think I want to widen the front and rear plates, just to be sure.

Long story … I had some made out of 3/16 stainless a few months ago :slight_smile:

I’m plan on using the same x-carriage as you, right? I also have some x-end plates cut out of 3/16 stainless … same long story. However I wanted to see how the new carriages from Mangrove were going to work. I don’t see an x-end plate anymore.

I may take you up on this.

Cool, thanks for the information. FYI though, you might get straighter cuts with a miter saw like this one.

Those were some nice looking bongos! They were one of the designs I was really worried about. How wide are you thinking for the y rails.

The bed plate size I came up with is 510mm to match my 480mm glass/heat pad. I redrew the Mangrove bedplate to match the 510mm size. I added a 2nd set of slots for zip ties. There are to 20mm circles on the left edge of the plate, one in the middle for cables and another towards the rear. What goes in that circle? You can see it in this picture, it has a sliver top:

Also, there is a 20mm circle in the middle of the plate (not on the edge). What goes there? Cables?

I still need to add the fillets on the corners and figure out how many and where to put the rollers. Any tips/suggestions?
510mm Bed Plate (15.8 KB)

The magic silver button is apparently an endstop, and is possibly part of the nozzle cleaning thingy.

The further out the bearing wheels are towards the edge of the bed, the better they should perform, though at the same time you want them in 2 or 3 inches from the edge or so to prevent the corner mounts from influencing things.

I created a larger y-axis end plate today. It’s 322mm wide and I am planning to use 20x20 at the bottom like a stock taz, and 40x40 at the top where three holes are on both sides for a span of 690mm long extrusion. If I use 40x40 for a span with a load of ~10 lbs it looks to have less deflection than the 300mm x 10mm smooth rod with ~5 lbs of load. Then I will drop some holes in the build plate to match either side of the 40x40 for wheels. Thoughts?

Are you going with Openrails for the 40mm section? they come in 20mm x 40mm sections, unless you double up two of them with interconnects somehow. Looks like it should work. Be aware there is a different hole spacing for the front and back plates for the stock lulzbot motor mount and idler pulley mount. You might also want to go with the Project Mangrove parts for that. The main difference is the Z max and Z min endstop instead of just the one.

Looks like they have some 40x40 here:

Definaltey going with mangrove parts and I believe the y-axis plates are identical now and they modified the y-idler and y-motor mount to the same spacing.

Oh neat, those must be new! Yeah for that long and large of a bed, no reason not to go with the larger ones.

That makes sense, Good thing I have a spare plate.

Is the belt drive still a good idea for a build plate this size and stock TAZ motors?