Introduction and a small problem.

Hi All,

First post and very new to 3D printing, so please be gentle. Any replies should be phrased so a 6 month old chimp could understand!

I spent a long time reading up on the wiki and other places, fascinated by the fact that you could "grow" plastic items at home. I finally decided on building a Prusa Mendel i2 as it looked the easiest. I had no problems with the mechanics of the build, despite having to adapt some parts and manufacture replacements for printed items that broke during assembly (ebay seller). Electronics and soft/firm ware aren't my area of excellence, so I opted for a "kit" from Gadgets3D, which I found to be of excellent quality.

Having assembled the printer I was amazed that it worked first time with very few adjustments and produced surprisingly respectable prints (although I'm sure there's room for much improvement) ... all credit to the information on the wiki and in this forum.

Having printed quite a few items it occurred to me that prints were coming out mirrored on the X axis, so after a bit of research I altered the X direction of travel in the firmware and, not wanting to physically move the end stop with associated rewiring, changed the MAX / MIN settings instead.

I'm using a ramps 1.4 board with an Arduino Mega2560 Rev3 and Marlin firmware and the printer is set up to "home" to a point rear left of the print bed, i.e. X axis to the far left and Y axis fully forward.

Results are somewhat puzzling ...

Changing the motor direction ... #define INVERT_X_DIR (to true in my case) works fine, but it tries to home to the right.

So, changing #define X_HOME_DIR ( to 1) makes the carriage home to the left, but appears to disable the endstop.

The end stops, from G3D, are mechanical switches on a small pcb with three wires which I believe to be supply, high and low. These worked fine in the old configuration. Is there some other setting I've missed?

Additionally, having got the motor direction, presumibably orientated correctly for the print, the "jog" controls in both Cura and Pronterface fro the X axis are now reversed ... is this something I'll have to live with or again have I missed something obvious.

Appreciate any help, but as I said at the outset, replies really need to be in Noddy-speak please!

Thanks in anticipation,
Julian

Sounds like your problem is on the Y axis. At home position, the bed should be fully to the rear. This places the print head fully to the front which is what you want.

Many thanks for the reply.

I wasn't sure where the correct home position should be, there seemed to be conflicting views in the mass of information available. The way I had it set up, seemed the most logical ... to me at least. So home point on the bed should be front, left?

But is that the cause of my problem? If I mirror the X axis in Cura, it prints correctly, so surely the problem lies on the X axis?

Welcome to the Third Dimension!

The coordinate system is relative to the position of the print head. So when the bed goes one way, the head goes the other way relatively speaking. You have to imagine the bed is stationary, and the print head moving. It takes a while for this mental flip to take place.

This often causes people to set up the printer the wrong way, and the effect is that the print appears mirrored in the X axis. If you flip the X before printing, the effect of two flips cancels out but results in a rotation, so you would have to rotate the printer 180 deg to get the jog to work correctly. You would then find the home switches are in the correct relative positions!

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OK, thanks. I'll reinstate the X axis as was and alter the Y.

Any ideas why changing the max/min setting of the end stop appeared to disable it? Just concerned that I'll have the same issue on the Y axis.

Switching the endstop will cause the firmware to look for the endstop signal on a different pin max instead of min of vice versa. So switching the endstop in firmware and not putting it in the max endstop location on the board would be why it was ignored.

I tried mirroring the an item about the Y direction and that too printed correctly ... a mystery I've yet to fully comprehend as bobc suggested, but many thanks to those who did and apologies for doubting you! All down to complete ignorance on my part.

Plan of action will be to reverse the direction of travel on the Y axis (although Marlin is set up as commented with "INVERT_Y_DIR true"). Just thinking as I type ... I built the machine with the Y motor at the front, is that correct, I've seen pictures showing them both back and front. If it were at the back then the direction would obviously be reversed.

I'll then physically move the Y end stop to the back of the machine. If I do this will I need to reverse the max/min bit again?

Edited 1 time(s). Last edit at 02/07/2014 11:59AM by jjulian.

The motor on front or back would not make a difference, it rotates the same way. Facing it left or right, would change the that.

The way my brackets have been printed would have resulted in the direction being reversed.

For the sake of completeness, if anyone has a similar problem ... it's all sorted and printing things in the correct orientation.

I moved the Y end stop to the rear of the machine and reversed the direction of Y travel in Marlin and all is good with the world. As a point of interest the notes in Marlin suggest that the motor direction should be the opposite to the way it's now configured, so I guess I must have the arrangement of the motor bottom about face.

Anyway, many thanks for the helpful replies, I look forward to the time when I have sufficient experience to assist others in the same way.