Z-Axis in centimeters
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Upon testing, I now have the right heights in mm. Thanks for the help!
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I have never known a 8mm diameter Acme thread to have a pitch of 1.25 I am more likely to think it will be a TR8x8 which would give you a steps of 400.
Every TR8 lead screw that is a multi start I have ever come across have a pitch of 2mm so yours with 4 starts would have a lead of 8mm.
HTH
Doug
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Very interesting. Despite the fact of me figuring out my problem for the most part, My prints are appearing to be very stretched in the Z direction. I might want to consider changing it to a TR8x8. Thanks for the help.
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I know that this is a bit redundant, but I reset my steps per millimeter to 400, and this time, I've finally got it. I would like to thank you all in this thread for making my printer the best it can be. And so, thank you all again for the amount of help you've given me.
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To summarize, I set my Z steps per mm to 400.
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That's a cool benchy though you gotta admit.
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@Super_Sonic_7036 said in Z-Axis in centimeters:
To summarize, I set my Z steps per mm to 400.
Which means that the lead of your screw is 4mm not 5mm. If it's a 4 start thread, then the pitch is 1mm not 1.25mm.
For info, it's generally a good idea not to rely on microstepping for positional accuracy. 400 (mico( steps per mm means that 1 full step will be 0.04mm so use layer heights which are multiples of that. So 0.2 or 0.4 but avoid 0.3 for example. -
@Super_Sonic_7036 I found this the other day on the Printbot forums about the 'Z Lead screw 4 start Upgrade', but didn't post it because you said you had it fixed. https://www.printrbottalk.com/forum/viewtopic.php?f=80&t=11294#p72399
The steps/mm setting is (200 steps/rev * 16 microsteps/step) / (8mm/rev) or 3200/8.
3200 / 8 = 400
FYI an 'ACME' thread is the shape of the thread, not the pitch. I thought it meant it was an imperial/inch thread, but not so.
Ian
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@droftarts said in Z-Axis in centimeters:
I thought it meant it was an imperial/inch thread, but not so.
think you're right about that, the metric counterpart are just called trapezoidal and have a 30 degree angle instead of the 29 for the Acme.
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To be pedantic, "trapezoidal" refers to the thread form (essentially the peaks and troughs have the pointy bit chopped off which helps to alleviate binding), so ACME threads are also trapezoidal. There is an ISO standard for metric lead screws but it's seldom followed. Tr denotes that the thread form is trapezoidal. The number after the Tr is the nominal diameter. This is followed by "X nn" which is the lead. For a single start thread, this is also the pitch. For multi start threads, the pitch should be shown in parenthesis e.g. (P2) but this is often omitted. So a TR8 x 8 means a lead screw of 8mm diameter and 8mm lead. Technically it should be referred to as a TR8 x 8 (P2) where P2 means it has a 2mm pitch and so therefore we can deduce that it is a 4 start thread. What we often see is Tr8x 8 screws with the (Pn) omitted and being referred to as having 8mm pitch which is absolutely not true.
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Yeah, an Acme thread is a trapezoidal thread, but a metric TR8 is not an acme thread.
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@bearer said in Z-Axis in centimeters:
Yeah, an Acme thread is a trapezoidal thread, but a metric TR8 is not an acme thread.
Exactly so. Also the word "Acme" is from the Greek and means the highest point or peak. Which is ironic for something which has it's peaks chopped off.
It's also a myth that the first Acme threads were used by Wile E Coyote.
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I still have my stretched benchy
