Need some advice, badly!

Need some advice, badly!

Postby Longknife » Mon Apr 06, 2015 4:20 am

I'm quite new to this stuff, but I have been able to turn out some decent v-carved projects.

I'm starting to get frustrated with the work coming off my machine though and am looking for some advice.

First off, the machine is a fairly rudimentary Chinese model (from a now defunct company) running a 1/4" router (trimmer). When I first started playing with it I (stupidly) didn't realise it didn't have any limit swtiches and drove it into it's ends more than a couple of times by accident before I programed in some soft stops in Mach 3. I'm sure this didn't do it any good, but I've check square, level, and it seems to travel around smoothly enough.

As I said, I've manage a few decent projects but I'm getting some really crappy results from time to time.

These are an example from today I did in some MDF with a 1" v bit. Bottoms not cleaning out nicely, circles not meeting up perfectly, messy lines, etc.

I've had these problems a few times, but others it doesn't seem to be so apparently. I did a large (42" x 20") profile cut out of a cursive word yesterday in some MDF and some lines and curves were perfect, others were quite obviously off from one pass to another. It actually seemed to be worst after the 1rst pass and then line up more or less from there. (I did 8 passes in .75" MDF with a 1/4" end mill, probably overkill).

The second set of pictures is from another sign that came out very poorly. Same types of problems.

I've had many other examples but I attack them with the dremel to clean them up right away because I'm so frustrated I don't want to look at it anymore. It's getting to the point I'm not going to use it anymore as the follow on finish work is just too much.

Is this a result of a sloppy machine? Calibrations of some sort? Bad tool data? Messed up vectors?

I sincerely appreciate any advice.

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Last edited by Longknife on Mon Apr 06, 2015 4:45 am, edited 1 time in total.
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Re: Need some advice, badly!

Postby signmarketingman » Mon Apr 06, 2015 4:41 am

looks to me like the router head is deflecting during cuts.
Have you tried taking smaller cuts?
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Re: Need some advice, badly!

Postby Longknife » Mon Apr 06, 2015 1:24 pm

These are pretty small cuts into MDF (the lower case letters are not bigger than an inch) so I don't think it's router head deflection?
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Re: Need some advice, badly!

Postby Leo » Mon Apr 06, 2015 5:24 pm

Looks like "something" is loose.

I would not rule out "anything"

You should go around the machine and check ALL the nuts and bolts and screws and drive rails and antibacklash nuts.

Check EVERYTHING
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Re: Need some advice, badly!

Postby martin54 » Mon Apr 06, 2015 5:32 pm

To be honest there is a whole bunch of things that could be causing problems so you will need to do a bit of work eliminating some things. Tool deflection as mentioned is one thing you would need to check as a lot of theses cheap chinese machines aren't very rigid.
Have you checked the table is flat & trammed the spindle to ensure it is square to the table. How do you set your z zero as these things are critical to good vcarving. Moving on to tools have you checked the angle of the bits you are using? Don't take it as read that they are the angle they claim to be. The actual bit you are using will make a difference as well, brand, number of flutes etc. MDF tends to blunt tools very quickly from what I have read, haven't machined much of it so can't say from personal experience.
Vectors, are you using the bitmap trace for any of these jobs as it doesn't do a great job with text generally. If you have typed a font out & have problems then it still could be down to the vectors because a lot of the fonts you can get free on download sites have odd loops & messy crossed corners that you won't see unless you zoom in really close.
Years ago one of the reasons why dedicated signmaking fonts were more expensive was because they had been produced/optimised to cut perfectly on a plotter at any size.

Probably a few other things to consider as well but that should get you started lol, there is a lot to think about with some of this stuff so the learning curve can be a bit steep so just takes a bit of time to get there.
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Re: Need some advice, badly!

Postby dhellew2 » Tue Apr 07, 2015 3:33 am

I had a similar problem once and it turned out to be two problems.. the y-axis was pinion was slipping ever so slight on the shaft .. the z-axis thrust bearing was allowing the router to lift a tiny bit.
When the pinion slips on the shaft just a tiny bit is is really hard to see.
The z-axis is not noticeable when in use. The only way to tell is to lift up on the router and see if it moves up and down.

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