Accuracy help?

[Jimmy Walker]

Guys:
I am in the car audio custom fabrication business. I have recently aquired a Shopbot and love it. But I am having a problem with making parts that flush into one another.

I know the fit is not going to be perfect, but what can i do or check to improve my machine?

Any help would be appreciated.

Jimmy Walker.

[rfitzgerald1@nc.rr.com]

What thickness and type of material are you cutting?
What type of bit are you using?
Are you using a Porter Cable-type router or spindle?
Are you cutting in one pass or multiple passes?
What is your cutting speed?

[erik_f]

I have spent a fair amount of time getting my shopbot as accurate as I've wanted it to be...and alot if the problems I had were with the rails for the Y car and the hold down bearins for the y car...if things aren't just right with the Y rails it will cause the y car to ride up on one side or the the other...also at one point I had the Y hold down bearings adjusted too tight...and this also caused the y car to ride up and also binde in some areas giving me variations in my design. If I could trouble shoot all over...I would start with your Y car, rails and hold downs...the damn holddowns gave me tons of trouble...and to be honest...I haven't been using them.

Erik

[Jimmy Walker]

bullseyemillwork:

You asked....

What thickness and type of material are you cutting?
3/4" MDF

What type of bit are you using?
3 flute 1/2" end mill

Are you using a Porter Cable-type router or spindle?
Porter Cable. (saving up for a spindle.)

Are you cutting in one pass or multiple passes?
Multiple passes in 1/4" steps.

What is your cutting speed?
Router speed is set to 13,000 RPM. Movement speed is 1.5" sec.

Thanks
Jimmy Walker
MDF Engineering.

[kerrazy]

Adjust your rpm up to 16 or 19000 and reduce your move speed to 1.25
Dale

[Brady Watson]

Jimmy,
Check your X and Y rails for parallel. Also check them for square.

There are several threads on this board decribing how to square them up. Do a search and I am sure that you will find what you are looking for. It is IMPERATIVE that your X and Y cars are in square with each other...Otherwise everything is going to be off exponentially.

You should be able to cut perfect parts that fit into each other with the exception of inside corners that will have a filet (a function of your bit diameter)

When setting up your toolpath (assuming you are using part wizard), be sure to note the value for tolerance in the toolpath dialog box. The value tells the toolpath how closely to follow the vectors to be machined. It can go down to a value of 0.0001". This parameter can be changed to let's say .01 to do a rough profile...and then increased in tolerance to 0.0001 to clean it up.

Hope that helps,
-Brady

[Jimmy Walker]

Brady Watson & Dale Kerr:


Thank you very much. I will work on that tonight.
I will let you know how it turns out.

Jimmy Walker.
MDF Engineering.