Learned an interesting thing today

Community Discussion šŸ§  New Wisdom
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I have been searching for a way to do double sided milling using Fusion for some time. I did not want to use the dowel method because that is only suitable for an occasional project (IMHO). If you have many different work pieces and each has dowel holes in different places, you soon have Swiss cheese as your spoil board unless you use a secondary spoil board every time. I decided that this was not practical and would likely take extra time during the job. I was certain that there must be a way to do this without dowels and eventually I did find the secret sauce.

I use dog holes on my spoil board and I used 3D printed dogs for a super precise fit. These were used to locate the jobs to the same x/y position. I used eccentrics to lock the work piece in place. I ran into an issue with registration between the two sides and I had a hard time figuring out why this was.

Today, the light came on ā€¦ā€¦ when the job is clamped this way, it moves slightly! The dogs either deform (I am currently printing solid dogs as a trial) or they shift ever so slightly when clamping force is applied. The net result is a shift between the two sides of the job. I think the error is additive as well so if the registration is off by 0.5 mm on either side, there will be a 1 mm position error between sides.

I thought it would be worthwhile to post this issue because on occasion there are posts about double sided prints not registering correctly.

As I said, I will try solid plastic dogs next (I donā€™t like the idea of steel dogs next to my milling cutters) but it might be time to screw a solid fence onto the spoil board any time a double sided job is planned.

2 Likes
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Brainstormingā€¦

If your spoilboard already has a grid of dog holes, could you use them with a long ā€œdogā€ instead of drilling traditional 1/4" dowels?

Also, instead of cam clamping, which shifts the workpiece slightly, maybe try an F style clamp that clamps down vertically?

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I donā€™t think it makes sense to use ā€˜longā€™ dogs ā€¦ having the long dog position pre-determined by the spoil board will likely waste extra stock.

Re the vertical clamps - yes, that was one option that I wanted to explore.

As it turns out, the solid 3D printed dogs are much more solid. I also used PLA rather than my normal PETG which makes things more rigid. Lastly, I am more careful about how much clamping pressure I apply and so far the results seem to be quite acceptable.

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Iā€™ve done my 2-sided experiments with a project-specific spoil board that I clamp to my machineā€™s ā€œGOAT styleā€ spoilboard. I can then set my X0/Y0 to the spoilboardā€™s corner referenceā€¦

This prevents either dowel holes or cut-thrus from making swiss cheese :slight_smile:

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That seems like a good alternative method.