homemade ormerod?

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rayhicks
because it might scrape up some of the print? - mind you a large diameter ball-bearing constrained in a tube, and pushing on the the switch wouldn't...

Ray

Haha! So that's why! I've been air printing for too long while playing around with the Ultrasound.

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RS Components Reprap Ormerod No. 481

For small parts only. How do you prevent switch striking againt part?? It's need to be lower than nozzle!
Yes I think about short acting cooler under ultrasonic sensor but I afraid that wind will influence to the readings.

Quote
Radian
Haha! So that's why! I've been air printing for too long while playing around with the Ultrasound.

Yeah it's funny how you kinda forget why you started once you get stuck into a project isn't it - I've had similar EUREKA moments more often than I'd wish

Good work on the ultrasound by the way! - I would've tested one of your circuits, but didn't have the parts or skillz

Cheers

Ray

Thanks for the encouragement Ray... I've gotten into the habit of doing rather than thinking since I noticed my thinking was slowing with age. One advantage I've noticed is that unexpected results sometimes provide pointers to better solutions. Sometimes it just results in a face palm. I just put a new post in the Ultrasound thread for you karabas: [forums.reprap.org]

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RS Components Reprap Ormerod No. 481

A microswitch that can be flipped or slid up out of the way or clipped/unclipped should work. After all, it is only needed before you start the print. Ok, so it would not be fully automatic, but the manual effort is minimal.

Dave
(#106)

I tried servo with microswitch. Illusion of work. Readings vary within 0.3mm. Nonrepeatable.

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karabas
I tried servo with microswitch. Illusion of work. Readings vary within 0.3mm. Nonrepeatable.

Perhaps a better tolerance microswitch would have worked?

Dave
(#106)

I never see such specs to switches. How to choose?

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karabas
I never see such specs to switches. How to choose?

Trial & error perhaps. A simple pushbutton switch might have better repeatability than a microswitch. I have seen a video of a microswitch being used that way, so I guess they are available.

Dave
(#106)

If microswitches are that variable, how are all the Mendels getting an accurate Z-axis zero?

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vonTugboat
If microswitches are that variable, how are all the Mendels getting an accurate Z-axis zero?

My Prusa i3 goes down until it detects the switch, reverses until the switch releases, then goes down again until it detects the switch again - I suppose it's a 'best of 3'-type thing?

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VortyZA

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vonTugboat
If microswitches are that variable, how are all the Mendels getting an accurate Z-axis zero?

My Prusa i3 goes down until it detects the switch, reverses until the switch releases, then goes down again until it detects the switch again - I suppose it's a 'best of 3'-type thing?

I suspect that the first time it goes down at fairly high speed until the switch trips, then backs off and goes down again at a much slower speed. If the speed is slow to start with it could take a long time to hit the zero position if you started with Z high, but a fast speed may overshoot because of a delay in the mechanical switch making contact or the contact being detected in software, so the first descent is to get a rough position fast, and the second to get an accurate position.

Dave

My firmware fork detects when the probe is approaching the bed and then slows down the descent, so that it can use a higher initial speed without needing two goes at it. That is the advantage of using a Z probe with an analog output.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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dc42
My firmware fork detects when the probe is approaching the bed and then slows down the descent, so that it can use a higher initial speed without needing two goes at it. That is the advantage of using a Z probe with an analog output.

If the CPU/firmware is fast enough you would not need to slow down for a non-mechanical switch so long as it trips high enough from the bed to allow for deceleration. The firmware could just note the step where the non-mechanical switch trips or reaches the set threshold.

Dave

One possibility for a mechanical switch arrangement for Z height would be to mount a switch at the front (+X side) of the hotend and have the lowest point of the switch slightly higher than the nozzle. The bed could then be probed with X at its home position, where the nozzle is off the bed and so can descend a little lower than the bed height while the switch is over the bed. The trip point would then be used to set a negative Z value. A similar arrangement would be to have the probe behind the nozzle and probe at maximum possible X position, where the nozzle is also off the bed area. Or have a switch in both locations and you could probe near the 4 corners of the bed.

Kim's arrangement looks good also, where the switch operates horizontally off the X-arm when the hotend tilts after the Z axis is lowered beyond the point where the nozzle is resting on the bed.

Dave

I actually played arround with homing both x and z with the same ms. [www.thingiverse.com]

This design is what i use to home my printer - and it works every time!
The nozzle needs to be relatively clean prior to homing, and the print surface has to be plane glass of something the nozzle can slide a bit on. (im printing pla on glas wiped down with vinegar).

\\Aagaard