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View Full Version : Belt stretch causing parts not to fit?



Joe Hillmann
12-17-2012, 11:15 AM
I posted about a month ago about engraving on pear for an inlay. I ran a sample piece and cut a piece of wood for it to fit into. It fit perfectly. After seeing that it worked I ran the same file that I used for the sample on a new piece of pearl and the instrument. Once I ran it on the mandolin it didn't fit. The pearl was about 1/64 to short length wise and about .012 to short height wise (These numbers are estimates from the person who installed the pearl so I don't know how accurate his numbers are). The only difference was the pearl was engraved in the upper left hand corner of the bed and the instrument was engraved in the upper right corner of the bed.


I have done quite a bit of inlay with wood and have never had this problem. Although usually I cut the inlay and the piece it fits into in the same general area on the laser bed.

At this point I think the problem is either caused by belt stretch or by the pearl heating up when being cut and then cooling and shrinking. But Since the sample fit I doubt it is caused by expanding and contracting of the pearl. I also kind of doubt it was caused by belt stretch because I make quite a few items that have box joints where the layout of the piece takes up most of the bed and the parts fit each other no matter where they were cut on the bed. I also don't think that I stretched the parts in coreldraw before I sent them to the laser.

Can anyone think of what may have caused the part not to fit?

Joe Hillmann
12-17-2012, 12:03 PM
There was no kerf. I rastored both the pearl and wood. And it isn't that each letter didn't fit and it had slop, that wouldn't have been a problem it could have been hidden with filler. It is more like the wood was engraved with a 40 point font and the pearl ended up at a 39 point font (I am just using the point sizes as examples, I don't know what size they actually are). Over all they are to small and when the letters were cut apart the individual letters were also to small and when they were forced in they cracked. The customer says he will be able to cover the cracks but I want to figure out what the problem is before I do any more for him.

Mike Null
12-17-2012, 12:07 PM
Sorry Joe, I don't quite understand the job.

Joe Hillmann
12-17-2012, 12:23 PM
I was cutting a piece of pearl to inlay into a neck of a mandolin and I was also cutting into the mandolin itself for the pearl to fit into. When I did a sample with a piece of pearl and a chunk of wood I had laying around the shop it fit. But when I engraved the same file into another piece of pearl and the mandolin it didn't fit. Over all the piece of pearl was to short lengthwise and heightwise to fit into the engraving in the mandolin So the customer cut each letter apart from the other letters and was able to force them into the cut out on the mandolin but the individual letters of pearl were also too small in both directions to fit.

And when I cut the pearl I didn't vector cut it instead I rastored away all of the pearl that wasn't part of the inlay. Because if I vectored it the pearl became to brittle.

Joe Hillmann
12-17-2012, 12:47 PM
I think I found out the problem. Had a bearing on the laser head lock up on me today and since the pearl was the last job I did with that laser I assume the bearing was slowly getting tighter and MAY account for the problem with the pearl not fitting.

Mike Null
12-17-2012, 2:00 PM
Aha! That is why I used multiple passes vectoring with low power.