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Messages - dphens

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1
General Mach Discussion / Re: Speed for cast acrylic
« on: September 15, 2010, 05:12:09 AM »
Hey Jeff,

Check the following links:

http://www.onsrud.com/xdoc/FeedSpeeds

http://www.onsrud.com/xdoc/ChipHardPlastic

http://www.onsrud.com/xdoc/ChipSoftPlastic

These numbers are obviously for their bits, but it still may help. Honestly, I don't know if acrylic falls into the hard or soft plastic category, so hopefully someone else will speak up. You may also want to look into getting bits designed for cutting acrylic. Onsrud and Precise Bits are two I know of.

If you're seeing melting, then you need to either slow your rpm's or increase your feed rate. On my machine I set up a small test where I cut a straight line at the desired depth a few inches long. Check the results and then adjust your settings as needed and test again. I think you need to be prepared to waste a little material to determine the most optimal settings for your machine (that is unless someone here can give you numbers from their experience). I've also broken a couple small bits in testing!  :(  Stings, but I consider it the cost of learning.

Once you've dialed in your settings a little, try cutting a few circles and see how they come out. That should tell you real quick how those settings will work. If your settings aren't right, the machine could lose steps and your cuts/parts will not be accurate. If that happens, then back off the feed rate some.

All that applies for any material really, so with your balsa and plywood, run the same tests to determine the best settings for your machine. And make notes for each bit you test in case your ever need to reconfigure your machine or you lose your config somehow.

I'm no expert myself and all this is from my own experience in learning how to cut materials on my machine, so don't take this a gospel, but I hope that helps!  :)

Dave

2
General Mach Discussion / Re: BobCad w/ Mach ?
« on: September 04, 2010, 10:26:41 AM »
Quote
BobCAD/CAM
The world leader in powerful and affordable CAD-CAM software.

I am sure this quote comes straight from BobCAD.  >:D

3
General Mach Discussion / Re: BobCad w/ Mach ?
« on: September 03, 2010, 01:02:38 PM »
I purchased a version last year, but quickly found it not to my liking. Compared to other programs I've used/demo'ed, it took more steps to accomplish the same tasks. Unless they've improved it tremendously, it was not user friendly when I used it.

Also, the salesman used some very deceptive tactics on me. While discussing the software with him on the phone, I told him I had reseverations based on comments I'd read on the software. I asked him if I purchased the software and it "did not work out", could I get a refund. He said "no problem". However, his literal meaning was "if you buy it and it does not work, we'll get it working for you" - the fact that I was not happy/satisfied with it, did not concern them. They refused to give me a refund.

Based on my experience, I would strongly recommned you look at other options, even if it costs a little more. Should have followed my gut. If the retail price is $2000 and then they offer you a deal at $500 with this and that, something's not right.

Good luck whatever you choose.  :)

4
General Mach Discussion / Re: Backlash comp help
« on: September 01, 2010, 06:49:35 AM »
Rich,

The crate the machine was shipped was jarred fairly hard at least once and was broken in a couple places. As far as the machine, more than half the bolts had worked loose (vibration during shipping I guess). Because of this, the Z axis assembly had worked loose and was moving freely a couple inches along the Y axis. Also, the linear slides on the Z assembly were coming into contact with the cross members of the Y axis. I was able to loosen up the assembly and get it back into the proper position, so I think this was also related to the machine be jarred during shipping. There was nothing else visible, but given that, maybe something else was damaged too.

Thanks for the advice! I'll take all of that to heart for future tests.

Dave

5
General Mach Discussion / Re: Backlash comp help
« on: September 01, 2010, 06:39:59 AM »
Thanks Al! I'll give that a try.

I am in communication with the vendor right now to verify my settings and that I've got no other issues. Hopefully he'll be able to determine if something is either configured incorrectly or if maybe there was more damage during shipping than first appeared.

6
General Mach Discussion / Re: Backlash comp help
« on: August 31, 2010, 08:38:55 AM »
Sorry everyone, was tired last night (long day) and the old noggin was not at 100%.  ;D

You're correct Sage - the reading after moving .25 was .2318.

I performed the test a little differently and had similar results. This time I moved into the indicator until it registered movement, zero'd it out and then kept moving in that direction (X-) at .001 increments seven times. Mach3 showed .007 in the DRO while the indicator only showed .0066. Then I moved in the X+ direction at .001 increments until the indicator registered movement. I reached .012 in the mach DRO before the indicator changed. Ran this twice with results of .018 and .019, so something is really off.

I think I've done as much as I can to mechanically eliminate any slop, but I'll go over it again. There was some minor damage from shipping when I received the machine, so it's possible there's something wrong that I have not found.

I've contacted the vendor too for his input and he agreed that these numbers are way out of range. I'll see what he recommends.

Thanks for all the help! I'll post back with an update when I have one.

Dave




7
General Mach Discussion / Re: Backlash comp help
« on: August 30, 2010, 09:19:32 PM »
Sorry that was not clear. Those numbers are the errors. So I had Mach3 move the machine .25, but the dial indicated that it only moved .02318, a difference of .0182 in that case. I added up all the errors then divided by five for the average.

My indicator has a range of only .5". Is there a minimum distance I should move to accurately test this?

8
General Mach Discussion / Backlash comp help
« on: August 30, 2010, 07:50:35 PM »
So I've read a couple different methods of testing for backlash and after trying a couple, I've come up with some numbers. I'd like some feedback on whether my test method and results appear accurate.

I set up a digital dial indicator for both the X and Y axis. For each axis I moved into (negative X) the indicator about .4in, zero'd the indicator and then used mach3 to move it .25" (positive X) and recorded the indicator reading. I repeated this five times.

So, for the X axis i have .0182, .0170, .0175, .0178, and .0170. I added those and then divided by 5 for an amount of .0175. Did the same thing for Y and got .0105.

Should these number reflect the amount of backlash on my machine or did I not perform the tests correctly?

Thanks!  :)

9
General Mach Discussion / Re: Backlash or something else??
« on: August 26, 2010, 02:37:08 PM »
OK, thanks! I'll try that too.

10
General Mach Discussion / Re: Backlash or something else??
« on: August 26, 2010, 01:41:47 PM »
I am sure I could always use it somewhere else! :D

I have not tested flex as I was not sure how to do that. I'll try it the way you've described. I do need to get a more accurate and reliable indicator though. My current one is cheap and not very good. I'll report back once I've tested this.

Thanks for the help!

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