Shapeoko & Cold Climates: Is it a concern?

(Andrew Pell) #1

Hello everyone. I’m considering getting a shapeoko 3, but I’m concerned about how it will hold up with cold conditions in the winter. I live in Michigan, and it will be below freezing for a majority of the winter season. I was planning on keeping it in my garage. Does anyone have any experience or wisdom to share on that topic?

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(William Adams) #2

People do this.

The belts are rated for a temperature range of -34°C to +85°C (-30°F to +185°F) (per https://www.amazon.com/Timing-Rubber-500mm-Closed-Printer/dp/B01IR3RGJ4 and http://www.large-gears.com/site/wp-content/upload/2012/01/polychaindesignmanual17595.pdf ) — the electronics, esp. the power supply likely have a narrower temperature range for operation.

The concern has been condensation on the metal parts, esp. the electronics and loss of squareness from differing thermal coefficients.

At least two users did leave theirs in garages (~0 C for one) and used them a fair bit: http://www.shapeoko.com/forum/viewtopic.php?f=7&t=1956#p14930 and http://www.shapeoko.com/forum/viewtopic.php?f=7&t=2612#p19783

One suggestion was to treat the electronics: http://www.rcparts.eu/waterproofing-your-rc-car-esc-servo-and-receiver-with-corrosionx.html

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(Andrew Pell) #3

Thank you for the links. It looks like I should be fine. I like the idea of putting the waterproofing on the electronics. from my thinking, I only really need to put it on the control board, since the stepper motors are NEMA rated correct?

The other thing I’m keeping in mind is the thermal expansion/contraction of the aluminum extrusions as well as the metal.

Lets say I build this thing next month, when its 10 degrees outside. Anyone who knows Michigan knows that it can be snowing one day and 65 the next. Lets go for the extreme and say that the temperature fluctuates 60 degrees in one day.

assuming the extrusions are 6061 T651 alloy, and using the engineering toolbox:
http://www.engineeringtoolbox.com/thermal-expansion-metals-d_859.html

The extrusions (approx 3 feet long or 36 inches) will expand 13 (micro inches/degreeinch)(60 degrees)(36 inches)=.028 inches or 28 thousandths of an inch.
Similarly assuming a low carbon steel, will expand about 6 (micro inches/degree
inch)(60 degrees)(36 inches)=.013 inches or 13 thousandths of an inch.

These numbers seem acceptable as far as stresses go, but how will this affect the homing/accuracy of the machine. If I start a job while it is cold, and 20 minutes later, the machine has warmed up… will I be 30 thousandths off my start. That could make a job look like junk.

Thoughts?

Am I crazy?

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(Richard Cournoyer) #4

I love the calculations Andrew, you did well, and yes theoretically the cold start verses the warm finish dimensions of your part will be different. Machinist will typically (or the machine builder) will write a warm up CNC program that moves the machine up/down, left/right for 10, 20, 30 minutes until the machine reaches temperature.

OR

A temporary cold weather (5 sided) enclosure (even a foam and cardboard one) with an old fashion (incandescent) 60 watt light bulb will do wonders in increasing the temperature 20-40 degrees above ambient.

PS I worked on some large Aluminum Fixtures that grew over 1/4" during their temperature range.

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(William Adams) #5

Note that if you have an XL the inner cardboard box bottom fits perfectly over the machine (except for the controller) — I use mine as a dust cover, and will eventually make a cut out / bump out of cardboard to cover it.

If you have an XXL, then probably you could combine the two box halves together.

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(Andrew Pell) #6

That is a great idea. Create a heated enclosure! It would also double as my sound barrier/chip shield. I could use an arduino to monitor/maintain temperatures inside! I could have a couple light bulbs in there to heat it up initially, and they could dim/turn off as the temperature rises from the spindle and electronics working. I could set it up so that I go in and flip a switch to turn on a warm up routine an hour or so before I start my project.

Side thought, what about belt tension? Will 0.030 expansion/contraction cause any issues with belt tension? I suppose so long as i set the belt tension at the warm or working temperature, and always warm up to that point before starting work, it wouldn’t be an issue.

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(Andrew Pell) #7

I bit the bullet. I ordered my XXL on black Friday. Thanks for the help everyone. I’ll post progress as I go on my enclosure.

AP

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