by B Cantin | Jun 21, 2015 | Gemini 3D Printer
The latest test build of the second revision of the Gemini 3D printer is coming along well. Shown in this photo (sorry for the bad lighting) is the mounting of the fans (only one shown) along with the 24v power supply, motors and of course the Smoothieboard.
The print bed is not actually mount yet in this photo, it’s merely resting on the Z axis platform to ensure the design of the assembly is capable of supporting it’s weight – which it is.
One addition to note is the inclusion of the Z axis endstop switch at the top of the machine, beside the Z axis drive motor and the spring loaded adjustment screw on the moving platform. This will allow for easy fine-tuning of the print bed height.
I am looking at revising the parts that hold the Z axis smooth rods – there is a slight bit of wiggle room with the current design which has had the unintended result of causing some misalignment of the two 12mm rods. The result of this is that the platform is skewed at a slight angle. Additionally, getting the smooth rods in proper alignment with the drive motor is trickier than I would like.
I am looking into creating a single central part at the top of the Z axis with which to mount the Z motor, endstop and rods with side-clamping of the rods which should provide precise mounting of the rods.
There are a few more parts that need to be designed for mounting of the front power switch as well, so the next build picture have an improved and simpler to assemble Z axis, better wiring management and power controls.
Stay tuned for later this week!
by B Cantin | Jun 16, 2015 | Gemini 3D Printer
I have been working hard at the 2nd revision of the Gemini 3D printer prototype. The new version has a sturdier frame assembly which is easier to put together and more straight forward in it’s construction. This is a work-in-progress of the new design:
The Z axis has now been re-designed as a cantilever style platform which eliminates the binding and levelling issues found with the first prototype that used a dual drive configuration. This platform eliminates two 12mm smooth rods and one Z motor from the build as well.
This new Z portion is still under testing but so far looks like it should do the trick. I am considering changing it to use all four smooth rods if the completed assembly ends up having issues with keeping the platform level on just the two rods.
In progress as I write this is a set of parts for mounting the 24v power supply to the frame. Not pictured are two panels for the rear of the printer which will hold 120mm fans for cooling the electronics. All motors are now mounted at the top-rear of the printer and the extruder motors are located beside the gantry drive motors.
There will be enclosing panels which will protect the electronics and create a pair of airflow channels from the 120mm fans which will cool the motors, PSU and stepper drivers and exhaust out of the top of the machine away from the print area.
There are a few small details to work out for mounting the end-stop microswitches for all three axis as well as attaching the voltage conversion and Smoothieboard to the frame at the back. Once those parts are designed and then printed I will be doing a rebuild of the above photographed assembly.
The Z motor mount needs to be flipped to allow for clearance of the heads of the mounting bolts and gain a few more millimetres of print height.
For mounting the panelling there will be small snap-fit parts that will form mounting points – the idea is to use some double-sided tape to hold the clip-on parts in place.
Once the final assembly is built-up the final parts to be designed will be the hotend mounts and a new filament pusher design. I hope to have all of that completed within the next week and then start running some test prints in late June to see how this all works out.
One final set of changes involving the electronics will be done in July – there are two 120mm fans, one 40mm fan and a 50mm blower fan that currently I am running with a 12v voltage converter because I only had 12v models of these fans. I have placed an order for these four fans in 24v models, once they have arrived I will upgrade the fans from the test build and bypass the 12v converter circuit that drives them. The LM7812 on the converter board will be replaced with a LM7805 to produce 5v from the PSU and that will power the Smoothie board itself, allowing the machine to be fully self-contained and not powered from USB.
One final consideration is what the user-interface will be like on the machine itself. Running a full-LCD display such as the RepRapDiscount Graphic Controller was the original concept, however I am also considering connecting an Arduino nano to the Smoothieboard to drive a different LCD display as well as serve as a secondary watchdog for internal temperatures.
For initial testing the machine will be accessible via the network as well as USB for direct control.
by B Cantin | May 30, 2015 | Gemini 3D Printer
As per my posts over the previous days, there is a new gantry in the works for the Gemini 3D printer.
Last night the motor mounts were printed and attached to the frame. These have a lot more strength than the previous version and have slotted holes for the for M3 bolts that attach the NEMA17 stepper motors. This will allow for tensioning the belt once it’s clamped to the x-carriage, which is the next part that will be designed and printed.
Since the photo was taken I have also printed a revision of the X-end/y-carriage mounting part which corrects the belt alignment and allows for adjustment of the x-axis – I will detail that assembly in another post.
Note that the belt path is not correct in relation to the x-carriage in this photo, it will run straight like it should once the part with the belt clamps is assembled.
by B Cantin | May 29, 2015 | Gemini 3D Printer
Things are progressing fairly well with the second revision of the Gemini 3D printer’s CoreXY gantry. The new corner pieces assembled well the first time and the resultant frame is quite strong and rigid.
The former corner bracing scheme was fraught with issues of warping and it was a chore to get things completely square – this is not an issue with the new design.
A large part of why this is working is a twofold change with how the parts are designed – I have increased the thickness from 3mm to 5mm and added 1mm thick guide ridges that fit into the slots of the aluminum extrusion frame.
No photos for this post, but I should have an update later today – the motor mounts are being printed off as I write this. These new motor mounts should be much tougher than the previous ones which I anticipate should eliminate the warping issues found in the original prototype.
Getting the object models to be manifold from Sketchup turned out to be a problem, however Netfabb’s mesh repair made short work of correcting the issue. Potentially I could have spent a lot of time trying to fix up the models in Sketchup, but due to the complexity of some of the details on the part it seemed to be a fools-errand. Some things are just out of the STL export plugin’s realm of capabilities and these parts fall into that category.
The new motor mounts will bolt to the frame on two inner faces as well as the lower side of the rear span. This might be a bit of over-designing on my part, but I wanted to ensure that there was little chance for the mounts to come loose from vibrations and heat.
A small revision is necessary for the X axis configuration. I need to re-introduce the previous design’s slotted mounting system for the support beam.
The reason for this is that although the design is very accurate, the reality of mounting the parts to the linear carriages is that there is a small amount of wiggle room required to get things squared away nicely.
Currently the assembly is off by a fraction of a millimetre which prevents it from sitting perfectly even between the two sides of the frame. The result of that is excessive pressure on the Y carriages causing them to come out of alignment. This should be a fairly easy fix by slotting the four-point mounting holes on the aluminum flat bar and slotting the rail mount holes on the X-ends.
by B Cantin | May 28, 2015 | Gemini 3D Printer
As part of the redesign and strengthening of the Gemini 3D, working towards a more production-like model instead of the flimsy proof-of-concept prototype I have printed and assembled one of the new top idler corners.
This is made as a two piece assembly in order to keep the part strong along the print layering. The gantry itself will form a box frame which will then be lowered onto the four vertical corner posts of the frame.
Initial testing is indicating that this corner is a snug fit and very strong. The idlers align well with the idlers on the new flat-bar X axis, so everything is coming together nicely for the new design.
Below is the corner with it’s two extrusions inserted.
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