3D printed thorn

Progress is unstoppable. CNC equipment is becoming more and more accessible to hobbyist home workshops. Although Russian manufacturers regularly delight the domestic consumer with their own developments, the emergence of new domestic products in the field of Hi-tech is of interest and increased attention. And that's why it was extremely interesting for me, as that same amateur enthusiast, to get on my desktop so far the only instance (prototype) of a 3D printer in the world, with which a new Russian manufacturer plans to enter the market soon. I will not disclose the name of the enterprise yet. The pre-production printer was provided to me for testing and evaluation from both an engineer's and user's perspective. And, "taking the opportunity" (c) and the approval of the owner, I post a review of this printer for the #competitionCreality. The printer is clearly still damp, but it is already possible and necessary to note its merits, well, everything that needs to be improved there. nine0006

So, I present to everyone's attention 3D printer "Praktika" - the youngest printer in a family of three models that are planned for production.

Concept

This is an FDM printer designed to teach the basics of 3D printing. It is planned to ship assembled and ready to print, which can be significant for many beginners. Immediately for practical application, so to speak. Hence the name of the model. Built on the traditional i3 Prusa kinematics with a movable table, but having some peculiarities in implementation. nine0006

Housing

The base of the printer is a non-separable rigid box-shaped frame assembled from a cut-out milled composite sheet. The assembly uses tongue-and-groove joints and adhesive seams. There are no metal unique components in the design. Elements (corners, brackets, etc.) made by printing are used. The body is painted in assembled form in silver color with black details.

Thanks to the box structure, the frame has unprecedented rigidity and strength, which is a serious advantage for the "Pryusha" as a kinematics with a heavy sliding table. The box made it possible to hide almost all the mechanical and electronic components inside the case, as a result of which the printer does not look like a Christmas tree hung with toys. Outside, nothing superfluous, only design. The exception is the display in a swivel case, mounted on the upper crossbar of the frame and a spool with filament on the side. The user is protected from the danger of demolishing or damaging something with an awkward movement. At the same time, access for maintenance and repair is provided in the design. nine0006

Composite sheets are milled in a special way to give them smooth curves, which also has a positive effect on the aesthetics of the machine - the developers were able to get away from rectangular "brick" forms. An excellent solution was the idea of ​​​​organizing an “engine room” and a “trunk” in the printer case. Developing the concept of the box to the end, the designers placed two compartments with opening lids in the massive lower part of the frame. One contains all the electronics, the second compartment is a spacious box for useful little things - tools, parts, stash ...

Sliding engine room cover. The lid of the box is hinged. This is a bit confusing. A couple of times, having opened the box and admiring the pleasant emptiness in it, out of habit I pulled up the lid of the filling compartment, almost breaking it. Then I realized that it needs to be moved. But this is not critical. You don't have to go there at all. A photo of this compartment will be in the "Electronics and Electrical" section.

At the bottom of the case there is a niche for three stepper motors - two for the Z axis and one for the Y axis. At the top of the case there is a slot for the cable harness and a Teflon tube with filament. All axle mechanics are hidden inside the box. Cable laying is neat: everything is laid, fixed, tightened. On the side there is a coil holder (printed), an overlay on the body that protects the coil from friction against the body. It's good. nine0006

The legs are non-adjustable and imprinted in hard plastic, meaning they won't protect against vibration. Better fix it.

The body as a whole is really very strong and rigid. The printer can be carried simply by the top of the frame, like a suitcase. The design is elaborate and well thought out. In some places, you can see the results of painstaking manual work on accurate gluing of small parts. This causes respect, and on the other hand, the question of the repeatability of such an assembly in mass production. It is clear that I have the first prototype, where they tried especially. Everything is fitted, assembled and painted neatly, the seams are tight, nothing dangles. At the moment, my body is 5 points .

Electronics and electrical.

"Brains-and-", - stretched out the zombie ... checking the fit of the radiators on the drivers. A sandwich of Arduino Mega 2560 and RAMPS 1.4 was found in the engine room.

When asked about this, the developer answered that "it was in stock." In the future, they plan to equip with more modern controllers, but also 8-bit ones. Drivers installed A4988. The power supply unit is a simple unnamed 12V at 180W. It is clear that this is an entry-level printer. Fan 80mm for blowing down heated air. On the side wall there is a cold air intake grille. There is also a power socket, a switch. The wires in the compartment are partially laid, partially in the form of spaghetti. But everything is available, everything is distributed, everything is serviceable. Practical minimalism. nine0006

Firmware - Russified Marlin 1.1.9 without any sophisticated settings. You can reflash the printer yourself if you wish, which I did by setting the PID, thereby removing the temperature sinusoid on the hot end, and correcting some crookedly translated menu lines to more ... competent ones.

The printer is controlled from a computer via USB or standalone from the display. The popular RepRap Full Graphic 12864 with encoder and "Reset" button is mounted in a convenient swivel housing. The display case is printed, post-processed and painted. The paint on the body lies evenly, but it is clear that the plastic was sanded by hand. Not critical, but more suitable in terms of performance style for a good home amateur production, rather than an industrial one. But still a plus. Moreover, now the case for the display is going to be produced by casting. The location of the display is convenient, rotates smoothly, fixed in any position. For display my 4 points . Or even 5 , given the planned casting.

Someone must have noticed the item about the Power Supply. Why 180W? It turns out that the printer does not have a heated table. To my surprised question, the developer explained that the printer is planned to be produced in different configurations. In the basic version, a heated table is not provided. It will go as an option when ordering a printer. Explanations accepted, I won’t put a minus, although I’m surprised - by today’s standards, a heated table is not a luxury, but a means of achieving ... Well, of course, a prototype, but I’m not used to typing on a cold table ... Okay, I’ll practice. And the built-in LED backlight, mounted on the frame crossbar, will help me a little. She is a plus. But rather weak - I would make the tape longer. And it turns on together with the printer, there is no separate inclusion. These are small cons, but fixable. nine0006

For the electronic part of the machine with electrics, I will put together 4 points . Minus a point for an archaic sandwich. Let's hope for the installation of normal controllers in the future.

Table. A very unexpected design has been introduced as a table at Praktika. The table does not have a traditional leveling system - table suspension on screws with springs. As there is no auto-calibration of the nozzle gap. The table is leveled and rigidly fixed during assembly. This was achieved by an original method. When assembled, the printer prints 4 table supports on itself, which ensures its self-alignment relative to the axes. Glass is placed and fixed on these supports. The idea is interesting, and what came out of it “in practice”, I will tell below. nine0006

The glass I got on the printer is not just any, but Ultrabase 220x220 mm. But in the absence of heating, it makes no sense. Well, the Ultrabase does not work "on the cold". Yes, and the glass was not original - it was immediately scratched.

We discussed this with the manufacturer, and decided that the non-heated versions will be equipped with ordinary glass 200x200 mm, while the Ultrabase will go in the heated version. Reasonable.

The print area was measured by me and after running the head in all axes was: 195 in X, 190 in Y and 145 in Z. Modest, but within the standard. The weight of the printer is small - exactly 10 kilograms. Overall dimensions allow you to place on a small table.

As a result, the table still turned out to be skewed on both axes. Along the X axis, the height difference was 0.4 mm. And along the Y axis more than 1 mm. And this is no good. That is, the idea with self-alignment was interesting, but “in practice” (c) ... Shrinkage of the structure after assembly, shrinkage of printed supports, microdeformations of elements of everything and everything, shrinkage, shaking ... And the departure of unregulated dimensional chains was not long in coming. I also leveled the X axis by tightening one of the Z screws, but everything is bad along the Y axis. I calibrated the nozzle in the center of the table. It is possible to print only within a square of 70x70mm. Closer - the nozzle clings to the table, further - the plastic prints in the air. The Z tightening has obviously created tension in the structure, now the Z movement is coming with a loud bang. So the self-alignment idea didn't work. Reported to the developer, provided photos and videos. Behind the table hard 2 points . Even a genuine Ultrabase, which only interferes here, would not have saved. A manual or automatic leveling system is needed.

Head.

Head carriage is a printed closed design. Also post-processing and painting. Packed inside is the popular direct version MK8 extruder with a surprisingly large 40mm NEMA17 motor. In my opinion, heavy and overly powerful. It is better to replace with 34 mm or even 22 mm.

One-sided blowing of the print area. Hotend is covered in a silicone shirt and wrapped in a fur coat with kapton. It will not work to get burned - I tried, everything is quite safe. But replacing the elements of the hot end will be difficult. The nozzle is set to 0.4mm, the fans are all hidden under the housing grilles. The design of the head is visually thought out well, it looks great. The head is simple, reliable, protected. Dismantled and serviced if necessary.

Head flaws: Printed bearings. And not nylon. They will wear out quickly. But spare parts are included with the printer, and they are easy to change, which, of course, is good. Replacing the filament: The MK8 lever is supported by a very tight spring. Pressing it is simply impossible. Therefore, all operations for loading and replacing the filament are only through commands to the extruder. The extruder itself is closed with overlays and it will not work to manually help the rod into the channel. This complicates the procedure, but you can get used to it. And more about blowing the print area. In general, blowing done unsuccessfully. A small, only 25mm fan works. He pushes weakly. The blower nozzle is directed horizontally and looks directly at the hot end nozzle and they are separated by only 4mm. nine0006

Tests have shown the inefficiency of such blowing, which will be shown below in more detail when analyzing the tests. As a result, for the head as a whole 4 points , for the process of replacing the filament 3 points , for blowing 3 points .

Mechanics.

Everything is traditional. Everything is designed neatly and aesthetically. Steel shafts 8 mm. Screws Z - T8 trapezoid, are connected to the engines through aluminum split compensating couplings. Nuts Z are spring loaded. Belts GT2 6mm. Everything is fine, except that printed bearings bring a fly in the ointment. nine0006

All 4401 motors. For the Z axis and for the extruder, they are clearly redundant. For some reason, the engine is sewn into the casing along the X axis. He would have to cool, and he was insulated for the sake of design and security. Nozzle gap adjustment in Z is convenient. There is a belt tension system. According to X, the tension is also done conveniently - there is an adjusting screw. And along Y, the tensioning belt must be rearranged in toothed clamps in 2mm steps, which is almost unrealistic. The belt doesn't stretch. Discussed with the developer, they also promised to replace it with a tension screw. In general, the mechanics are almost 5… With minus . With the promised improvements.

"Practice" in practice. We print tests.

I have only had the printer for a few days, or rather short evenings after work. Therefore, I cannot boast of extruding tens of kilograms of plastic. It was printed:

Several XYZ cubes in different plastics and in different modes, overhang angle tests, bridge printing tests, a pair of 3DBenchy boats, a pair of Dorus dragons, three left Boots, an OK hand. All attempts to print dimensional parts failed - the skewed table affected. Also, 200 photos were taken, a couple of hours of video filming, two reports were written - for the competition and for the manufacturer, a lot of correspondence and online video chats with developers were conducted. What happened in the tests, now I'll tell you. nine0006

The printer is working and printing. From the box. He came to me assembled and configured, as promised by the manufacturer. Home delivery, no instructions, no box. But with two coils of plastic for tests. I add a couple more of my own from the bins, and open the XYZ cube in Kure. Printing on the “Practice” is best done with PLA plastic. Printing with PETG is also successful, but I did not devote much time to it. It was more interesting to try ABS, which surprisingly turned out to be quite edible if the part does not have a large contact area with the table. On a cold table, the bottom layers of ABS cool instantly, and the corners of a large print come off the table due to shrinkage. You can vary with rafts, borders, heating the table with a hair dryer, smearing the first layer, covering the printer with cellophane ... But time is short. It was quite possible to defeat ABS using the head-on method - a lot of glue on the table and just printing, without blowing, smearing the first layer into the glue. ABS plastic blue from GREG laid down evenly and printed without whims - no sticking, no delamination. Printing with all plastics was carried out on a thick layer of adhesive stick "Komus". nine0006

According to the results of test printing. I printed XYZ cubes in the size 40 * 40 * 40 - so the printer has more opportunity to accelerate, for the effects of printing at speed to appear. Printed cubes from PLA and ABS. Layer 0.2, walls in 2 lines, no filling and no roof. The Z roof was then printed separately. Here are 2 samples. The first printed at 60 mm/sec, the second at 90 mm/sec.

First. 60mm/sec. What do we have.

The sides of the print are perfectly sized. Wall thickness when printing in 2 lines of 0.4 and 94% flow is exactly 0.79-0.81 at various points. No complaints. Everything is fine. But a strong echo everywhere, especially along the Y axis. Tightened the belt along the X - the echo decreased. It was not possible to tighten the belt along Y, so from here on there is an echo along Y. But it became clear that a strongly hanging head is not a source of an echo. The layers lay flat. The corners are clear and even. The separately printed cover Z looks normal, everything lay flat and tight, the edges are even. Hatching with walls is fused normally. I printed several cubes on slightly different modes and different grades of PLA. At some speeds, on different cubes, a slight constant vertical even ripple appears with a step of a couple of mm. Most likely, some kind of stepper is junk. nine0206 Medium quality on flat surfaces with edges.

Second cube. 90mm/sec.

The quality is gone. Strong echo, especially along the Y axis. Layers are uneven. The corners are swollen, the edges of the embossed letters are clumsy - the cooling is no longer in time. The separately printed cover Z contains plastic bulges, gaps - as if under extrusion. In general, 90mm/sec is not for this printer in its current state. 60 mm / sec - while its ceiling for high-quality printing. It is necessary to look at what is there in the mechanics, why it is a problem with laying layers and refine the cooling. nine0206 Failed.

Print test of model with increasing overhang angle from 50 to 85deg. PLA plastic from H-T-P. The part is printed completely, nothing hangs from it. Despite the design flaws, blowing coped well. But this is rather a consequence of the low print speed, small model and the use of PLA plastic. But, nevertheless, passed the test .

Bridge printing test. PLA plastic from H-T-P. The length of the bridges on the model increases from 40 mm at the bottom to 100 mm at the very top. Print speed 80mm/sec. Everything is stretched, everything is stretched, nothing sags. One thread doesn't count. In general, it works fine. nine0206 5 points .

Boat 3DBenchy. PLA plastic from REC. Layer 0.2mm, walls in 3 lines, infill 16%, inner walls at 60mm/sec, outer walls at 40mm/sec. The ship is printed, all the elements are in place. The layers are laid flat. Arches and bridges are in order. Retracts worked cleanly. Of the defects: Echo from the hole, barely noticeable ripples along X and Y, A couple of bubbles from wet plastic - clicked periodically. Test passed by 5 minus .

Boot. A well-known test for the accuracy of printing small elements. Printed 2 times. The plastic is purple PLA from REC and gray from H-T-P. Layer 0.1 mm, 2 walls, infill 18%, bottom and roof 5 layers. Speed ​​30mm/sec. In my opinion, printed well for this printer. The boot in both cases visually looks monolithic and neat. Layers are almost invisible. The buckles on the belts are clear. The imperfection of the print becomes visible only under strong magnification, but this was also printed with a 0.4mm nozzle. I will assume that test passed on 5 . But blue ABS with a layer of 0.1 and a speed of 30 printed really badly. Airflow is needed.

Switching to PETG. Red filament from GREG is involved. Printing the test "Dorus the Little Dragon". It is not as popular as a boat, but it is also quite complicated for a printer. Here and a small area of ​​support with letters on the sole, and overhanging expanding surfaces and numerous retracts with transitions. I love this test. And the dragon is cute. Hotend 240deg, table 20deg, layer 0.24mm, wall in 2 lines, speed 40mm/sec, airflow 40%. PETG sticks perfectly to the table with glue, the layers of red plastic lay down beautifully, evenly, there is no hairiness at the transitions - the retracts are ideal. Everything went fine until a strong expansion of the wall from the neck to the head began. And then the seal broke. In this place, part of the part was constantly under the blowing nozzle and was not cooled. And as a result, the plastic just dripped there. In the photo where I specially printed this section of the model, everything is visible. nine0006

Several attempts to repeat the printing of this particular fragment of the model consistently showed the same result - there is no airflow, the plastic flows down. This is where the design flaw of this system came into play. It is necessary to move the airflow nozzle further from the hot end nozzle and direct the flow not horizontally, but at an angle from top to bottom - into the print area and a little around it. Discussed with the developer. They will think. And so the test showed the inefficiency of the blowing system. Failed.

This is what happens when the blower does not work well.

Further ABS. I repeat the dragon Dorus, since ABS formally does not need to be blown at all, especially on an open Pryusha. Hotend 245deg, table 20deg, wall in 2 lines, speed 40mm/sec, airflow 0%. In general, printing is more successful, but there are also sagging and damaged wall on the extension of the model from the neck to the head. A little blowing in the heat chamber will still not interfere with this dragon ... In general, the test was passed, especially since it was possible to completely print with ABS on a cold table. The print quality is excellent, the layers are even, the retracts are worked out. nine0006

Next, I got bolder and printed the following models with ABS: an enlarged “OK” hand to assess the overall print quality and the likelihood of ABS delamination in an open printer, an XYZ cube to see the angles at the separation from the table, another Boot with layer 0, one. Everything prints successfully, there is no delamination, the quality is good, on small details and overhangs it is better to turn on a little airflow, but here I did not do this. ABS is still outdoors.

You can sum up the review of the printer "Practice". The printer is interesting. A little unusual in design, the main advantage is a rigid body, on the basis of which you can bring the rest to mind. With the elimination of identified shortcomings - promising. It may well find demand among those who find it difficult to independently carry out operations to assemble and configure the printer. While the device is clearly damp. Something like Beta version. Everything that is listed here from the seen advantages and disadvantages is transferred to the developer. Print quality can be assessed as good at medium-low speeds. Slower = better. Small models with fine detail at low speeds print great. In this scenario, this printer asks for a 0.3 or 0.25 nozzle, and print highly detailed models on layers of 0.

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