I would like to get your opinion on my second printer design that included

3D Printing
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I would like to get your opinion on my second printer design that included lead screws for all 3 axis.
My lead screw design used 20/20 lead screws on X,Y-axis to increase the speed. The motors will be mounted on the axis. Therefore Y-axis motor will move itself (Nema23) + X-axis screw 20/20 + extruder with Nema17 + Nema23 for X-axis drive. I thought Nema23’s 2.2Nm torque would be enough to move all these on a 20/20 lead screw. Do you think this printer would reach printing speeds of 200mm on X-Y axis?

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I’m certainly no design expert, but that sounds like a LOT of weight to be slinging around at 200mm/sec. The structure required for all that would probably add another significant amount of weight. With any reasonable acceleration settings, you’d probably have to anchor the printer to something to avoid it shaking.
Again, I have never designed a printer, so this is just my gut talking. I’d still like to see this (or any) design come to life.

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On Stratasys Dimension machines the x motor (i believe a nema 23) is mounted on the x axis frame with its mounting frame and drive pulleys. The extruder head is also quite heavy (essentially a hollow 4 x 5 x 4 aluminum box with two small DC motors and the heater block). The machine does not have near the acceleration I could run on my Reprap nor is the maximum speed (printing or rapid) that my Reprap can run. As it is, the machine gets pretty loud when doing narrow infill. If the machine didn’t weigh 282 pounds there is no doubt it would require some sort of anchoring. What I’m trying to say is I agree with @Carlton_Dodd .

You can also do some basics physics math energy, mass, velocity, acceleration, and forces to see what you are dealing with. It’s also a good way to determine whether the acceleration you are aiming for will cause excessive deflection in your frame.

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Thank you all for your reply. 200mm is a high speed. For a 100m speed my design requires Nema motor to run at 300RPM. (300/60=5 rev per sec; 5 X 20 (screw pitch) = 100 mm/sec
This looks reasonable for me. Given Nema17 motor has 0.5Nm vs Nema23 motor has 2.2Nm. The weight of the axis will be balanced by chrome rods. Therefore there will be almost no weight on the lead screw.

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Your comment in regard to chrome rods prompted me to explain a little more. I’m not sure what your specific lay out is, but generally the concern is about how much mass you are accelerating and decelerating in the x/y plane not so much about weight (vertical forces). Horizontal acceleration causes your rods to deflect horizontally and causes your frame to bend left/right & forward/backward. Until you get to large format printing weight causing vertical deflection is not generally a major concern because the spans are typically small.

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If I change the design to something like Ultimaker. Is that every axis is composed of 1 lead screw driven directly by a stepper and across that a chrome rod. These 2 are connected by a second rod like letter “H”. As a result the weight of the displaced object would be lowered down to extruder mainly, which is around 500g with the stepper.
Additionally how this would effect the system, changing lead screw from 20/20 to 16/16? Other than the lower speed.

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I’m not sure I follow you about the Ultimaker design, I would need to see a diagram.Changing to a screw with a lead of 16 in 20 will lower the maximum acceleration and speeds, it will also reduce the torque required to drive which may allow you to use smaller motors. However stepper motor torque decreases as its speed increases.

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@Ben_Malcheski here is Ultimaker’s X-Y design http://wiki.ultimaker.com/Ultimaker_rev.4_assembly:_X-Y_axes. I am planning to use a stepper with 2.2 or 3Nm torque. Therefore I guess 20/20 is a better choice. It will mainly add weight to the design other than that, it will increase the speed without increasing the revolution.

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I understand how the Ultimaker mechanics work. Are you going to run your lead screws through the x-carriage along with smooth rods? If so you will definitely want to make sure you do not over constrain the lead screws which could cause issues.

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The lead screw will be on one side and across there will be a smooth rod. They will be connected by another smooth rod to form an “H”. I understand that I shouldn’t increase the speed too much. How about 300 RPM. Can the system work on this speed for hours?