1. #1
    Hi guys,

    I have a small wooden work shop which is well insulated. I have my cnc router and pc in there. The temp inside was 5C (outside -2C). I put the heater on and the temp rose to about 11C. I started cutting shapes out of 18mm mdf. I do this in 3 passes x 6mm. I noticed that the 1st pass seemed okay but the 2nd pass was not quite following the same path as the 1st pass and the 3rd pass was different again from 1st and 2nd.
    I bought the machine in April this year and have had no issues at all. The last time I cut prior to tonight was last weekend (wasn't as cold) and had no problems. I wondered if the temp had something to do with it. I have had to bring the pc into the house when I am not using it as I found out the operating temp is +10C. If not the temp is it something else?

    cheers Steven

  2. #2
    About 142 miles North of me, my shed got to 8C (outside -2) but I have a dehumidified going to keep my timber stock at the right moisture level.
    I read somewhere that aluminium expands about twice as much as steel for the same temperature rise. Also what type of heater are you using ? if gas then this puts out a lot of water and might be affecting the MDF which is like a sponge. I'm trying to imagine the expansion of a cnc machine and it's like the expanding universe, where is the centre of expansion ? and how does this affect the tool position. I would not have thought the 6 degree rise would have given a visible difference but I suppose local heating will be greater as the stepper motors and spindle motor heat up so maybe you should run some random G code for a while just to heat things up before starting to cut.

  3. The Following User Says Thank You to EddyCurrent For This Useful Post:

  4. #3
    Yes the Cold can affect machine in a negative way and it's always a good idea to run a warm up routine when first turned on.

    Now I'm not saying your problem is the Cold but can affect machine with binding components which can cause missed steps.

  5. #4
    Eddy and Jazz. Thanks for the feedback. I use an oil filled heater. I think even though the air temp was 11c the controller was stone cold. I have now brought the controller inside the house and will try again tomorrow morning. I will get the temp in the workshop up to at least 15c before bringing the pc and controller out. Will also run a warm up routine before cutting
    If this doesn't work it maybe something else

    Thanks Steven

  6. #5
    You say the passes did not follow each other so for example say you were cutting a circle, would the subsequent passes be outside, inside, or offset in one or more axes from the first ?
    I have a wood burning stove in the shed and today it was a toasty 19C but I don't start doing anything other than getting the MP3 player going until it reaches 14C
    Last edited by EddyCurrent; 22-11-2013 at 09:27 PM.

  7. #6
    The passes would be okay for say 80% of the previous passes but then would step out slightly

  8. #7
    I'm thinking that the direction of offset from one pass to the other might indicate where the problem lies.

  9. #8
    Quote Originally Posted by EddyCurrent View Post
    I'm thinking that the direction of offset from one pass to the other might indicate where the problem lies.
    Hi Eddy, Good call! While I was going through the warm up routine without cutting I could see there was jerkiness on the X axis. When I checked the coupling there was a fracture. Once replaced it ran okay

    thanks for pointing me in the right direction


  10. #9
    That's an excellent result.

  11. #10
    An old trick for machines in cold shops overnight is to cover them with a tarp and stick a 15W light somewhere underneath that doesn't pose a fire hazard (you can do a safe, earthed installation in a biscuit tin if you're enthusiastic), it will keep all your components well above the dew point preventing condensation when you start to warm the workshop up,

    - Nick

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