Though the 3-D-printing industry remains a white-hot niche sector in the stock market, it's a "bubble" showing no clear path to profitability even at one of its flagship companies, Voxeljet, CNBC's Jim Cramer said Tuesday.
"Why do I mention this?" he said on "Squawk on the Street." "The 3-D printing space has been so hot that I'm just calling it a bubble. I was calling it a cult, but now I'm calling it a bubble."
(Read more: Cramer: 'There's bubbling everywhere')
Last week, Cramer identified Voxejet as one of several stocks that were part of "bubbling" across niche sectors, including organic food, cloud computing and 3-D printing. Cramer reiterated his position Tuesday.
"Three-D printers are insane," Cramer said. "Now I am going to be attacked … on Twitter because I said these stocks were expensive. But I want to say, everyone has a right to overpay. I would never get in the way of people's right to overpay.
"When Voxeljet becomes an earnings story, I am willing to listen. But right now they are the poster boy for overvalue," he added.
In contrast, Cramer cited Workday, a provider of human resources software, as a pricey stock worth buying.
"This is the most expensive stock I follow, and I think it's going to go higher," Cramer said. "Go long Workday and short Oracle, I think that's a great pair trade, as they call them in the game."
Cramer's charitable trust does not own shares in either Voxeljet, Workday or Oracle.