Parts, materials and finishes
Rework a printed part or print it again
It comes out wrong. You can finish it on the mill and accept it, or discard it and start again. The criterion I use is not purely functional, and I think function should be even less of the sole deciding factor.
You print a part and it does not come out quite right. A defective face, a tight dimension, an area with a damaged finish.
You have two options: recover it — machine away whatever went wrong — or reprint it and lose the hours of the first attempt.
It looks like an economic decision, and some people resolve it that way: if rework costs less than reprinting, rework it. But that calculation leaves out what matters most.
My criterion, in one sentence
If the rework will not be visible and the part remains functional, rework it. If the rework will show or will not look right, reprint it.
It is not a cost rule. It is a finish rule.
Before that sounds like a whim, it is worth explaining why finish still matters on an industrial part — one inside a machine, not in a shop window, and probably seen by nobody except maintenance.
Why finish matters even when nobody looks
It sounds odd for industrial work. I have thought about it often and reached the opposite conclusion: it is not odd; almost nobody says it.
Because finish communicates how everything else was done. A part with a clumsy repair on one face tells the installer that its maker did not care. And if they did not care about that, what else did they not care about? The unseen tolerance. The unchecked material. Sometimes that judgement is unfair, but everyone makes it, in two seconds.
Because parts that look well made are treated better. A cared-for part is installed carefully, stored properly and replaced when due. One that looks like a makeshift fix is treated as one and ends up becoming one.
Because the buyer cannot judge what they cannot see. Your customer will not measure your tolerances or check your machining strategy. What they can judge, and do judge, is what is in front of them. Finish is the part of your work they know how to read.
And because, honestly, it is the job. If a part can look right and you leave it unfinished, you have decided it does not matter. Making that decision repeatedly is exactly the difference between one workshop and another.
How it works in practice
Once the rule is clear, the decision takes thirty seconds looking at two things.
Where is the defect?
If it is on an internal face, a hidden support or an area against another part — rework it. Nobody will ever see it, the function is unchanged and the printing hours are retained.
If it is on a visible face, an edge or a surface the operator will see — reprint it.
What will the rework look like?
Machining a printed part leaves a different mark. Layer texture and a milled surface do not look alike, and the boundary always shows. In a hidden area that does not matter. In a visible area it stands out.
There is a trap here: sometimes rework starts small, and making it uniform means machining the whole face. At that point you are no longer recovering a printed part: you are machining a part you also printed. If you reach that point, reprinting would almost always have been better.
What this is not
It is not perfectionism. A reworked hidden part gets no more attention. There is no value in polishing what nobody will see — that would be a whim.
It is not wastefulness. Quite the opposite: recovering parts when possible avoids repeating work. The rule does not say “always reprint”; it says where the line is.
And it is not slow. It is a thirty-second decision in front of the part. What is slow is hesitating every time because you have no criterion.
One check before deciding
If a part fails twice in the same place, stop choosing between rework and reprinting: the problem is not that part. It is the orientation, supports, material or design.
Recovering the second one postpones the problem to the third.
At 7Axis Industrial we manufacture parts and short runs, combining 3D printing and machining according to each part's needs. Finish is part of the job, not an extra.